Ahamed, R, Ferdaus, MM & Li, Y 2016, 'Advancement in energy harvesting magneto-rheological fluid damper: A review', Korea-Australia Rheology Journal, vol. 28, no. 4, pp. 355-379.
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In this paper, a comprehensive review of the present literature on energy generated magnetorheological (MR) fluid based damper, modeling and applications of the MR damper are presented. The review starts with an introduction of the basic of MR fluid and their different modes, consequences with different types of MR fluids based devices, and their relevant applications. Besides, various forms of MR damper and its applications are presented. Following this, the modeling of the MR fluids and the modeling of the MR fluid based damper are deliberated according to arrangement and configurations. Finally, the review ends with the design and advancement issues, performance analysis matters, and analytical modeling of energy generated magnetorheological fluid damper systems.
Alengaram, UJ, Mohottige, NHW, Wu, C, Jumaat, MZ, Poh, YS & Wang, Z 2016, 'Response of oil palm shell concrete slabs subjected to quasi-static and blast loads', Construction and Building Materials, vol. 116, pp. 391-402.
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Askari, M, Li, J & Samali, B 2016, 'Application of Kalman Filtering Methods to Online Real-Time Structural Identification: A Comparison Study', International Journal of Structural Stability and Dynamics, vol. 16, no. 06, pp. 1550016-1550016.
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System identification refers to the process of building or improving mathematical models of dynamical systems from the observed experimental input–output data. In the area of civil engineering, the estimation of the integrity of a structure under dynamic loadings and during service condition has become a challenge for the engineering community. Therefore, there has been a great deal of attention paid to online and real-time structural identification, especially when input–output measurement data are contaminated by high-level noise. Among real-time identification methods, one of the most successful and widely used algorithms for estimation of system states and parameters is the Kalman filter and its various nonlinear extensions such as extended Kalman filter (EKF), Iterated EKF (IEKF), the recently developed unscented Kalman filter (UKF) and Iterated UKF (IUKF). In this paper, an investigation has been carried out on the aforementioned techniques for their effectiveness and efficiencies through a highly nonlinear single degree of freedom (SDOF) structure as well as a two-storey linear structure. Although IEKF is an improved version of EKF, results show that IUKF generally produces better results in terms of structural parameters and state estimation than UKF and IEKF. Also IUKF is more robust to noise levels compared to the other approaches.
Askari, M, Li, J & Samali, B 2016, 'Semi-active control of smart building-MR damper systems using novel TSK-Inv and max-min algorithms', Smart Structures and Systems, vol. 18, no. 5, pp. 1005-1028.
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Aung, TH, Khabbaz, H & Fatahi, B 2016, 'Parametric Study of Applied Stresses on Infiltration Modular Cells Installed under Roads', Procedia Engineering, vol. 143, pp. 1325-1332.
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© 2016 The Authors. Published by Elsevier B.V. Modular geocellular units are applicable for the prevention and minimisation of stormwater runoff and flooding as a sustainable and cost-effective solution of road applications for drainage. The integrated units buried are exposed to the dead loads and live loads emerging from the surrounding soil pressure, pore water pressure and surcharge. Thus, a computer program using MATLAB is developed for the assessment of the total vertical and lateral earth pressure exerting on the modules complying with the Australian Standards AS 4678 (2002) and AS 5100.2(2004). Lateral earth pressure concept based on Rankine's theory is adopted in this model as the analytical approach. Closed-form solutions based on the fundamental soil mechanics are applied in the analytical calculation steps made. The model also considers different guidelines such as AASHTO LRFD Bridge Design Specifications (2010) for the stress distribution of vehicular loads according to the selected axle type. In consideration of the interaction of the moving vehicle and the bridge, the dynamic load allowance is also applied in terms of the static equivalent of the dynamic and vibratory effect as prescribed in AS 5100.2 (2004). Based on the results obtained, the numerical and theoretical results generated by the program provide considerable and influential factors in regarding to the parametric study and sensitivity analysis presented in this paper.
Aung, Y, Khabbaz, H & Fatahi, B 2016, 'Review on Thermo-mechanical Approach in the Modelling of Geo-materials Incorporating Non-associated Flow Rules', Procedia Engineering, vol. 143, pp. 331-338.
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© 2016 The Authors. Published by Elsevier B.V. Recently, there has been a burgeoning interest in developing constitutive soil models from the laws of thermodynamics, mainly due to the benefits that these models automatically obey them and the approach provides a well-established structure and reduces the need for 'ad hoc' postulates. A thermodynamic framework, also known as thermo-mechanical framework, has the capability to predict the behaviour of geotechnical materials, which requires the anticipated incorporation of non-associated flow rules. As it is very challenging to achieve acceptable accuracy in plasticity modelling of granular materials, this paper aims to review this framework not only to discuss the details of the major components but also to highlight the capability of generating non-associated flow rules in a natural way from thermo-mechanical principles. This approach introduces the use of internal variables to develop the two thermodynamic potentials (the free energy and the rate of dissipation functions), sufficient to derive the corresponding yield function, flow rule, isotropic and kinematic hardening rules as well as the basic elasticity law. It is shown that the non-associated flow rule can be derived naturally from the postulated stress-dependent dissipation increment function. Comparison has been made with stress-independent dissipation to demonstrate that the approach can also successfully explain the behaviour of standard materials with associated flow rules. The basic steps for the thermo-mechanical formulation for developing a constitutive model are also reviewed and summarised. Furthermore, the power of conventional mathematical technique, Legendre transformation, in the derivation of constitutive equations has been highlighted.
Azari, B, Fatahi, B & Khabbaz, H 2016, 'Assessment of the Elastic-Viscoplastic Behavior of Soft Soils Improved with Vertical Drains Capturing Reduced Shear Strength of a Disturbed Zone', International Journal of Geomechanics, vol. 16, no. 1, pp. B4014001-B4014001.
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© 2015 American Society of Civil Engineers. Soil disturbance induced by the installation of vertical drains reduces the horizontal soil permeability and shear strength in the disturbed zone. Thus, the soil disturbance contributes to the reduced overconsolidation ratio (OCR) of the soil in the vicinity of drains, influencing soil deformation. Although a significant amount of research has been conducted on the effect of permeability variations in the smear zone, the influence of the reduced shear strength in the smear zone on the ground behavior has not been investigated. In this study, a numerical solution adopting an elastic-viscoplastic model with nonlinear creep function in combination with the consolidation equations has been developed. Moreover, the effects of shear strength variation in the disturbed zone on the time-dependent behavior of soft soil deposits improved with vertical drains and preloading have been studied. The applied elastic-viscoplastic model is based on the framework of the modified Cam-clay model, capturing soil creep during excess pore-water pressure dissipation. Furthermore, nonlinear variations of the creep coefficient with stress and time as well as the permeability variations during the consolidation process are considered. The predicted results have been compared with available field measurements. According to the results, the OCR profile of the disturbed zone influences the viscoplastic strain rate, the creep strain limit, and consequently the soil deformation.
Biabani, MM, Indraratna, B & Nimbalkar, S 2016, 'Assessment of Interface Shear Behaviour of Sub-ballast with Geosynthetics by Large-scale Direct Shear Test', Procedia Engineering, vol. 143, pp. 1007-1015.
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© 2016 The Authors. Published by Elsevier B.V.A series of large-scale direct shear test were conducted to study the interface shear strength of subballast reinforced with different types of geomembranes and geogrids. The impact of normal stress (σn), shearing rate (SR), relative density (DR) and open area (OA%) on the behaviour of granular material was investigated in unreinforced and reinforced condition. The results revealed that the performance of material was markedly influenced by σn and OA. The results also showed that geogrids provided a greater value of passive resistance owing to have transverse ribs, but the mobilised passive resistance became smaller with increase in OA. The triaxial grids offered more passive resistance than biaxial geogrid.
Chen, Q, Indraratna, B, Carter, JP & Nimbalkar, S 2016, 'Isotropic–kinematic hardening model for coarse granular soils capturing particle breakage and cyclic loading under triaxial stress space', Canadian Geotechnical Journal, vol. 53, no. 4, pp. 646-658.
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In this paper, a simple but comprehensive cyclic stress–strain model that incorporates particle breakage for granular soils including ballast and rockfill has been proposed on the basis of bounding surface plasticity theory within a critical state framework. Particle breakage and its effects are captured by a critical state line that is translated in voids ratio–stress space according to the dissipated energy (plastic work), through a hyperbolic function. A comprehensive equation related to particle breakage is proposed for the stress–dilatancy relationship to capture the complex dilatancy of granular soils. By extending Masing’s rule to bounding surface plasticity theory and introducing a generalized homological centre, a combined isotropic–kinematic hardening rule and a mapping rule have been established to simulate more realistically the response of gravelly soils under cyclic loading. The applicability and accuracy of this model are demonstrated by comparing its predictions with experimental results for different types of granular soils, including rockfill, under both monotonic and cyclic loading conditions. This study shows that the model can capture the characteristic features of coarse granular soils under complex loading paths.
Chen, X, Li, J, Li, Y & Gu, X 2016, 'Lyapunov-based Semi-active Control of Adaptive Base Isolation System employing Magnetorheological Elastomer base isolators', Earthquakes and Structures, vol. 11, no. 6, pp. 1077-1099.
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© 2016 Techno-Press, Ltd. One of the main shortcomings in the current passive base isolation system is lack of adaptability. The recent research and development of a novel adaptive seismic isolator based on magnetorheological elastomer (MRE) material has created an opportunity to add adaptability to base isolation systems for civil structures. The new MRE based base isolator is able to significantly alter its shear modulus or lateral stiffness with the applied magnetic field or electric current, which makes it a competitive candidate to develop an adaptive base isolation system. This paper aims at exploring suitable control algorithms for such adaptive base isolation system by developing a close-loop semi-active control system for a building structure equipped with MRE base isolators. The MRE base isolator is simulated by a numerical model derived from experimental characterization based on the Bouc-Wen Model, which is able to describe the forcedisplacement response of the device accurately. The parameters of Bouc-Wen Model such as the stiffness and the damping coefficients are described as functions of the applied current. The state-space model is built by analyzing the dynamic property of the structure embedded with MRE base isolators. A Lyapunov-based controller is designed to adaptively vary the current applied to MRE base isolator to suppress the quakeinduced vibrations. The proposed control method is applied to a widely used benchmark base-isolated structure by numerical simulation. The performance of the adaptive base isolation system was evaluated through comparison with optimal passive base isolation system and a passive base isolation system with optimized base shear. It is concluded that the adaptive base isolation system with proposed Lyapunov-based semi-active control surpasses the performance of other two passive systems in protecting the civil structures under seismic events.
Chua, L, Head, K, Thomas, P & Stuart, B 2016, 'Micro-characterisation of the colour palette of ceremonial objects from the Papua New Guinea Highlands: Transition from natural to synthetic pigments', Microchemical Journal, vol. 124, pp. 547-558.
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Chua, L, Maynard-Casely, HE, Thomas, PS, Head, K & Stuart, BH 2016, 'Characterisation of blue pigments from ceremonial objects of the Southern Highlands in Papua New Guinea using vibrational spectroscopy and X-ray diffraction', Vibrational Spectroscopy, vol. 85, pp. 43-47.
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Dackermann, U, Elsener, R, Li, J & Crews, K 2016, 'A comparative study of using static and ultrasonic material testing methods to determine the anisotropic material properties of wood', CONSTRUCTION AND BUILDING MATERIALS, vol. 102, no. 2, pp. 963-976.
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© 2015 Elsevier Ltd. This paper presents a comparative study using static and ultrasonic testing for the determination of the full set of orthotropic material properties of wood. In the literature, material properties are typically only available in the longitudinal direction, and most international standards do not provide details on the testing of the other two secondary directions (radial and tangential). This work provides a comprehensive study and discussions on the determination of all twelve orthotropic material properties of two hardwood species using static testing and an alternative testing approach based on ultrasonic waves. Recommendations are given on the execution of the tests and the interpretation and calibration of the results.
Dackermann, U, Li, J, Rijal, R & Crews, K 2016, 'A dynamic-based method for the assessment of connection systems of timber composite structures', CONSTRUCTION AND BUILDING MATERIALS, vol. 102, pp. 999-1008.
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© 2015 Elsevier Ltd. This paper presents a dynamic-based method for the evaluation of connection systems of timber composite structures. The good bonding of the composite elements is crucial for the proper functioning of timber composite structures, as the design capacity and performance of the system cannot be achieved unless an adequate connection condition can be assured. The proposed dynamic method provides an alternative to traditional static load testing and uses vibration measurements to derive a Loss of Composite Action Index, based on an expanded Damage Index method, indicating the reduction in composite action due to the failure of shear connectors. The proposed method is validated on experimental and numerical models of a timber composite beam structure and a timber-concrete composite flooring system. The results demonstrate the effectiveness of the proposed dynamic-based approach that can achieve a good agreement between statically and dynamically derived composite action indicators.
Dang, LC, Fatahi, B & Khabbaz, H 2016, 'Behaviour of Expansive Soils Stabilized with Hydrated Lime and Bagasse Fibres', ADVANCES IN TRANSPORTATION GEOTECHNICS III, vol. 143, pp. 658-665.
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© 2016 The Authors. Published by Elsevier B.V. Soil stabilization is the most common ground improvement technique adopted to improve problematic soil properties. This investigation exhibits a series of laboratory tests conducted to evaluate the influences of bagasse fibres and hydrated lime addition on the engineering properties and shrink-swell behaviour of stabilised expansive soils. Bagasse fibre is industrial waste by-product left after the crushing of sugar cane for juice extraction that was used in this study as reinforcing component for expansive soil stabilization. The expansive soils used in this investigation were collected from Queensland, Australia. In order to investigate the influences of bagasse fibres on the engineering behaviour of expansive soil, varying proportions of randomly distributed bagasse fibres of 0.5%, 1.0%, and 2.0% were added to expansive soil and hydrated lime-expansive soils mixed with different bagasse fibre proportions were also investigated. Although, an array of experimental tests have been undertaken on untreated and treated expansive soil samples, merely the outcomes of linear shrinkage, unconfined compressive strength (UCS) tests after various curing periods of 3, 7 and 28 days are presented in this paper. Other test results have been identified as follow up research. The findings of this experimental investigation indicate that bagasse fibre reinforcement blended with hydrated lime increased the compressive strength of expansive soil with increase in curing time and additives contents, whereas the linear shrinkage of stabilised expansive soils decreased with increasing hydrated lime and bagasse fibre proportions and curing periods. Based on the reasonable laboratory test results, it can be noted that the expansive soils can be successfully stabilized by combination of hydrated lime and bagasse fibres.
Dang, LC, Hasan, H, Fatahi, B, Jones, R & Khabbaz, H 2016, 'Enhancing the engineering properties of expansive soil using bagasse ash and hydrated lime', International Journal of GEOMATE, vol. 11, no. 3, pp. 2447-2454.
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The main objective of this paper is to investigate the influence of hydrated lime and bagasse ash on engineering properties of expansive soil obtained from an array of laboratory tests. Bagasse ash is a readily available waste by-product of the sugar-cane refining industry posing risks to environment. Bagasse ash is considered in this investigation in order to evaluate the potential benefits of its pozzolanic material for stabilisation of expansive soil. The preparation of stabilised soil specimens was conducted by changing the bagasse ash contents from 0 to 25% by dry weight of expansive soil along with an increase in hydrated lime. The bearing capacity and shrinkage properties of stabilised expansive soil were examined through a series of experimental tests including linear shrinkage and California bearing ratio (CBR) after various curing periods of 3, 7 and 28 days. The results reveal that the additions of hydrated lime and bagasse ash improved the strength and bearing capacity of stabilised expansive soil remarkably, and meanwhile significantly reduced the linear shrinkage of treated expansive soil. Hence, the application of hydrated lime and bagasse ash as reinforcing material can not only enhance the engineering properties of expansive soil, but also facilitate sustainable development by using sugarcane waste by-product to improve unusable clay material in road construction.
Dias, A, Skinner, J, Crews, K & Tannert, T 2016, 'Timber-concrete-composites increasing the use of timber in construction', European Journal of Wood and Wood Products, vol. 74, no. 3, pp. 443-451.
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Ding, G & Forsythe, P 2016, 'A comparative study of floor construction on sloping sites: an analysis of cumulative energy demand and greenhouse gas emissions', Construction Economics and Building, vol. 16, no. 1, pp. 33-49.
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In order to make environmentally aware decisions, there is growing interest in the comparative energy and greenhouse gas (GHG) performance of competing construction methods. Little research has been done concerning competing ground floor construction methods, especially given different site variables, such as slope and soil type. A life cycle assessment approach was adopted to analyse environmental impacts, including cumulative energy demand and GHG emissions for detached housing construction in Australia. Data was drawn from 24 case study housing projects, including 12 reinforced concrete and 12 suspended timber floor projects. The data presented in the paper compares cumulative energy demand, GHG and the constituent parts of competing construction methods. The findings indicate that the timber floors use/create significantly less cumulative energy demand and GHG emissions than concrete floors—approximately 2.1 to 2.7 times less energy and 2.3 to 2.9 times less GHG. These findings are limited to the site slope and foundation soil types identified in the paper. The main application of the work is in guidance concerning the lowest environmental impact options for detached housing construction.
Erkmen, RE, Saleh, A & Afnani, A 2016, 'INCORPORATING LOCAL EFFECTS IN THE PREDICTOR STEP OF THE ITERATIVE GLOBAL-LOCAL ANALYSIS OF BEAMS', INTERNATIONAL JOURNAL FOR MULTISCALE COMPUTATIONAL ENGINEERING, vol. 14, no. 5, pp. 455-477.
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The aim of the study is to develop a stiffness modification technique that considers the effects of local deformations/damages within the predictor step of iterative global-local analysis. The procedure is based on internal springs introduced in a beam element formulation whose constants are obtained according to the force vs. displacement results of the global-local analysis. Within the beam element formulation, strong discontinuities are introduced in the form of an internal enrichment considering additional local degrees of freedom associated with the deformations of local springs. Determination of the spring constants introduced in this study is an inverse problem, as given independent end-displacements and end-forces, corresponding spring stiffness terms are sought. Discussions on the heuristic nature of this problem are included and a regularization option is introduced to give rise to a unique solution for the problem. Nevertheless, it is shown that by using the proposed approach the number of iterations can be significantly reduced within the iterative global-local analysis algorithm. In the corrector step of the global-local analysis a local membrane finite element model is used to obtain the internal stress field.
Foster, SJ, Stewart, MG, Loo, M, Ahammed, M & Sirivivatnanon, V 2016, 'Calibration of Australian Standard AS3600 Concrete Structures: part I statistical analysis of material properties and model error', Australian Journal of Structural Engineering, vol. 17, no. 4, pp. 242-253.
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© 2016 Engineers Australia. Assessment of the reliability of design models developed for Australian Standards is of paramount importance for determination of public safety. Poorly calibrated models and safety factors can lead to overly safe and uneconomic construction or, worse, to an insufficient level of safety. This study investigates the reliability of the models used in the Australian Concrete Structures Standard AS3600–2009 for the design of beams and slabs in bending and shear and columns under combined bending and axial loading. The study is in two parts; in Part I, strength and variability of over 20,000 concrete cylinders cured under standard conditions and tested at 28 days are statistically analysed. The data were collected from all cities and regional areas in Australia and for all concrete strength grades; similarly, variability of reinforcement product is analysed. Next, reliable databases of laboratory tests for beams, slabs and columns were established for members failing in flexure, shear and compression and model errors, and their variability, determined for the code design models. It is concluded that improvements in the production of concrete and of bar products, over time, have led to reduced variability in their materials properties–with potential for increasing code strength reduction factors and, thus, reducing excessive conservatism in design. This is assessed in Part II of this study.
Gao, C, Huang, L, Yan, L, Kasal, B & Li, W 2016, 'Behavior of glass and carbon FRP tube encased recycled aggregate concrete with recycled clay brick aggregate', Composite Structures, vol. 155, pp. 245-254.
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© 2016 Elsevier Ltd In literature, there are few studies which investigated compressive behavior of fibre reinforced polymer (FRP) tube confined recycled aggregate concrete (RAC) where the recycled aggregates (RAs) mainly came from demolished old concrete components. Study which considered FRP tube confined RAC using recycled clay brick aggregates (RCBA) originating from demolished brick masonry components is rare. Thus, this paper reports a systematic study on axial compressive behavior of FRP tube encased RAC containing RCBA (termed as FRP-confined RAC-RCBA). The experimental variables considered are, i.e., replacement ratio of RCBA (r = 0, 50, 70 and 100%), FRP tube thickness (nf=2, 4 and 6 layers) and type of fibre material (GFRP and CFRP). This study shows that both GFRP and CFRP tubes enhanced strength and deformation of the confined RAC-RCBA specimens remarkably. The ultimate compressive stress of the confined specimens decreased with an increase of RCBA replacement ratio but their axial deformation kept approximately constant. Failure mode and the compressive stress-strain behavior of G/CFRP-confined RAC-RCBA were similar to these tube confined normal aggregate concrete (NAC) and the ultimate compressive strength of G/CFRP tube confined RAC-RCBA specimens enhanced with an increase in FRP tube thickness. The CFRP-confined specimens showed higher ultimate strength but lower ultimate axial strain than those of GFRP-confined specimens. The applicability of eight widely used confinement models, i.e., 5 design-oriented and 2 analysis-oriented models, for FRP-confined NAC to FRP-confined RAC-RCBA was also evaluated.
Ghosh, B, Fatahi, B & Khabbaz, H 2016, 'Mechanical Model to Analyse Multilayer Geosynthetic Reinforced Granular Layer in Column Supported Embankments', ADVANCES IN TRANSPORTATION GEOTECHNICS III, vol. 143, pp. 387-394.
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© 2016 The Authors. Published by Elsevier B.V. The objective of this paper is to develop a mechanical model to predict the behaviour of a multilayer geosynthetic reinforced granular fill soft soil system improved with controlled modulus columns beneath the embankment. Deformation of geosynthetics embedded granular layer due to bending and shear is considered in this study. Therefore, geosynthetic reinforced granular fill has been idealised as a reinforced Timoshenko beam while the columns and the soft soil have been idealised as a layer of linear springs with varied stiffness. Plane strain conditions are considered for the loading and reinforced foundation soil system. Tension developed in the geosynthetics, rotation and settlements of the improved soft ground are predicted using the proposed model. This study shows the effects of multilayer geosynthetics on the settlement response of the granular layer. A notable reduction of the settlement has been observed as a result of the using multilayer weaker geosynthetic reinforcement system when compare to one stronger geosynthetics layer. It is also observed that the top reinforcement layer is subjected to maximum mobilised tension at the column edge whereas bottom reinforcement layer is more effective in controlling the deflection in the middle of two columns.
Gu, X, Li, J, Li, Y & Askari, M 2016, 'Frequency control of smart base isolation system employing a novel adaptive magneto-rheological elastomer base isolator', Journal of Intelligent Material Systems and Structures, vol. 27, no. 7, pp. 849-858.
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In the past decades, base isolation techniques have become increasingly popular for seismic protection of civil structures owing to its capability of decoupling buildings from harmful ground motion. However, it has been recognised recently that the traditional passive base isolation technique could encounter a serious problem during earthquakes due its incapability in adjusting the isolation frequency to cope with the unpredictability and diversity of earthquakes. To address this challenge, a great deal of research efforts have been conducted to improve traditional base isolation systems, most of which focused on hybrid supplementary devices (passive, active and semi-active types) for the isolators to control displacement or to dissipate seismic energy. On the other hand, the most effective approach to address the aforementioned challenge should lay on varying isolator stiffness in real-time to achieve real-time spontaneous decoupling. A recent advance of the development of an adaptive magneto-rheological elastomer base isolator has brought such idea to reality as the new magneto-rheological elastomer base isolator is capable to alter its stiffness significantly in real-time. In this article, an innovative smart base isolation system employing such magneto-rheological elastomer isolator is proposed and a novel frequency control algorithm is developed to shift the fundamental frequency of the structure away from the dominant frequency range of earthquakes. Such design enables the building to avoid resonant state in real-time according to the on-coming spectrum of the earthquakes. Extensive simulation has been conducted using a five-storey benchmark model with the isolation system, and testing results indicate that the proposed control system is able to significantly suppress both the floor accelerations and inter-storey drifts simultaneously under different earthquakes.
Gu, X, Li, Y & Li, J 2016, 'Investigations on response time of magnetorheological elastomer isolator for real-time control implementation', Smart Materials and Structures, vol. 25, no. 11, pp. 11LT04-11LT04.
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© 2016 IOP Publishing Ltd. Utilising the unique features of MRE materials for vibration isolators has been intensively studied over the last several years. Real-time control of the MRE isolators holds the key to unlock MRE materials' unique characteristics, i.e. instantly changeable shear modulus in continuous and reverse fashion. However, one of the critical issues for the applications of real-time control is the response time delay of MRE vibration isolators, which has not yet been fully addressed and studied. This paper identified the inherent response time of the MRE isolator and explored two feasible approaches to minimise the response time delay. Experiments were designed and conducted to evaluate the effectiveness of the proposed approaches on minimising time delay on: (i) the transient response of current of a large coil that generates magnetic field and (ii) the transient response of shear force from the MRE isolator. The results show that the proposed approaches are effective and promising. For example, the proposed approach is able to reduce the force response time from 421 ms to 52 ms at rising and from 400 ms to 48 ms falling edges respectively. Such level of short response time of the MRE isolators demonstrates the feasibility of application of real-time control and hence is the essential step on the realisation of real-time control of vibration suppression system based on MRE isolator.
Gu, X, Yu, Y, Li, J, Li, Y & Alamdari, MM 2016, 'Semi-active storey isolation system employing MRE isolator with parameter identification based on NSGA-II with DCD', Earthquakes and Structures, vol. 11, no. 6, pp. 1101-1121.
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© 2016 Techno-Press, Ltd. Base isolation, one of the popular seismic protection approaches proven to be effective in practical applications, has been widely applied worldwide during the past few decades. As the techniques mature, it has been recognised that, the biggest issue faced in base isolation technique is the challenge of great base displacement demand, which leads to the potential of overturning of the structure, instability and permanent damage of the isolators. Meanwhile, drain, ventilation and regular maintenance at the base isolation level are quite difficult and rather time- and fund- consuming, especially in the highly populated areas. To address these challenges, a number of efforts have been dedicated to propose new isolation systems, including segmental building, additional storey isolation (ASI) and mid-storey isolation system, etc. However, such techniques have their own flaws, among which whipping effect is the most obvious one. Moreover, due to their inherent passive nature, all these techniques, including traditional base isolation system, show incapability to cope with the unpredictable and diverse nature of earthquakes. The solution for the aforementioned challenge is to develop an innovative vibration isolation system to realise variable structural stiffness to maximise the adaptability and controllability of the system. Recently, advances on the development of an adaptive magneto-rheological elastomer (MRE) vibration isolator has enlightened the development of adaptive base isolation systems due to its ability to alter stiffness by changing applied electrical current. In this study, an innovative semi-active storey isolation system inserting such novel MRE isolators between each floor is proposed. The stiffness of each level in the proposed isolation system can thus be changed according to characteristics of the MRE isolators. Nondominated sorting genetic algorithm type II (NSGA-II) with dynamic crowding distance (DCD) is utili...
Hao, H, Hao, Y, Li, J & Chen, W 2016, 'Review of the current practices in blast-resistant analysis and design of concrete structures', Advances in Structural Engineering, vol. 19, no. 8, pp. 1193-1223.
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In contemporary society, industrialization and rising of terrorism threats highlight the necessity and importance of structural protection against accidental and intentionally malicious blast loads. Consequences of these extreme loading events are known to be catastrophic, involving personnel injuries and fatalities, economic loss and immeasurable social disruption. These impacts are generated not only from direct explosion effects, that is, blast overpressure and primary or secondary fragments, but also from the indirect effects such as structural collapse. The latter one is known to be more critical leading to massive losses. It is therefore imperative to enlighten our structural engineers and policy regulators when designing modern structures. Towards a better protection of concrete structures, efforts have been devoted to understanding properties of construction materials and responses of structures subjected to blast loads. Reliable blast resistance design requires a comprehensive knowledge of blast loading characteristics, dynamic material properties and dynamic response predictions of structures. This article presents a state-of-the-art review of the current blast-resistant design and analysis of concrete structures subjected to blast loads. The blast load estimation, design considerations and approaches, dynamic material properties at high strain rate, testing methods and numerical simulation tools and methods are considered and reviewed. Discussions on the accuracies and advantages of these current approaches and suggestions on possible improvements are also made.
Hasan, H, Dang, L, Khabbaz, H, Fatahi, B & Terzaghi, S 2016, 'Remediation of Expansive Soils Using Agricultural Waste Bagasse Ash', Procedia Engineering, vol. 143, pp. 1368-1375.
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© 2016 The Authors. Published by Elsevier B.V. Bagasse is a fibrous material remaining after crushing sugarcane to extract its juice; and bagasse ash is produced after burning bagasse. Improper disposal of this material can create environmental problems around sugar manufacturing plants. Bagasse ash, comprising a high percentage of silica (SiO2), is considered as a sensible pozzolanic material with non-reactive behaviour and has potential to be used in road subgrade stabilisation. One of the main challenges for transportation organisations in Australia is to treat subgrades including expansive soils. Expansive soils exhibit significant movements when the moisture content changes, and hence it causes substantial damage to road pavements constructed over these type of soils. Road engineers need to employ materials having acceptable strength, relatively low price and being eco-friendly. In order to demonstrate the potential ability of bagasse ash in curtailing the adverse effects of expansive soils on roads, an array of experimental tests using bagasse ash have been conducted. In this study to activate and improve the effectiveness of bagasse ash, hydrated lime was used and mixed with black soil samples, collected from Queensland Australia. Samples were prepared using different contents of bagasse ash and hydrated lime (0%, 6%, 10%, 18% and 25% by the dry mass of soil), at a ratio of 3:1, respectively. The results of free swell ratio (FSR) test, unconfined compression strength (UCS) and California bearing ratio (CBR) tests are presented for untreated and treated samples after various curing time periods of 3, 7 and 28 days. The outcomes of these tests clearly demonstrate that stabilisation of expansive soils using bagasse ash and hydrated lime not only improves the strength, but also facilitates to cope with environmental concerns through reduction of sugar industry waste material.
Ho, L & Fatahi, B 2016, 'One-Dimensional Consolidation Analysis of Unsaturated Soils Subjected to Time-Dependent Loading', International Journal of Geomechanics, vol. 16, no. 2, pp. 04015052-04015052.
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Ho, L, Fatahi, B & Khabbaz, H 2016, 'Analytical solution to axisymmetric consolidation in unsaturated soils with linearly depth-dependent initial conditions', Computers and Geotechnics, vol. 74, pp. 102-121.
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© 2016. This paper introduces an analytical solution for the axisymmetric consolidation of unsaturated soils subjected to constant external loading. The analytical procedure employs variables separation and Laplace transformation techniques while capturing the uniform and linear initial excess pore pressure distributions with depth. Excess pore-air and pore-water pressures as functions of time, radial and vertical flows are determined using Laplace transforms, Fourier Bessel and sine series, respectively. In this study, the consolidation behavior, in terms of changes in excess pore-air and pore-water pressures and the average degree of consolidation, are investigated against the air to water permeability ratio. The effects of radial distance from the drain well on the dissipation rate are likewise highlighted in worked examples. Excess pore pressure isochrones and the matric suction varying with time are also presented.
Hokmabadi, AS & Fatahi, B 2016, 'Influence of Foundation Type on Seismic Performance of Buildings Considering Soil-Structure Interaction', INTERNATIONAL JOURNAL OF STRUCTURAL STABILITY AND DYNAMICS, vol. 16, no. 8, pp. 1-29.
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© 2016 World Scientific Publishing Company. In selecting the type of foundation best suited for mid-rise buildings in high risk seismic zones, design engineers may consider that a shallow foundation, a pile foundation, or a pile-raft foundation can best carry the static and dynamic loads. However, different types of foundations behave differently during earthquakes, depending on the soil-structure interaction (SSI) where the properties of the in situ soil and type of foundation change the dynamic characteristics (natural frequency and damping) of the soil-foundation-structure system. In order to investigate the different characteristics of SSI and its influence on the seismic response of building frames, a 3D numerical model of a 15-storey full-scale (prototype) structure was simulated with four different types of foundations: (i) A fixed-based structure that excludes the SSI, (ii) a structure supported by a shallow foundation, (iii) a structure supported by a pile-raft foundation in soft soil and (iv) a structure supported by a floating (frictional) pile foundation in soft soil. Finite difference analyzes with FLAC3D were then conducted using real earthquake records that incorporated material (soil and superstructure) and geometric (uplifting, gapping and P-Δ effects) nonlinearities. The 3D numerical modeling procedure had previously been verified against experimental shaking table tests conducted by the authors. The results are then presented and compared in terms of soil amplification, shear force distribution and rocking of the superstructure, including its lateral deformation and drift. The results showed that the type of foundation is a major contributor to the seismic response of buildings with SSI and should therefore be given careful consideration in order to ensure a safe and cost effective design.
Hunt, A, Thomas, P, James, D, David, B, Geneste, J-M, Delannoy, J-J & Stuart, B 2016, 'The characterisation of pigments used in X-ray rock art at Dalakngalarr 1, central-western Arnhem Land', Microchemical Journal, vol. 126, pp. 524-529.
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© 2016 Elsevier B.V. The chemistry of pigments used to create rock art at a rock shelter in northern Australia has characterised so as to gain a better understanding of the origins of the colours used. The site, Dalakngalarr 1, located in Jawoyn Country in Arnhem Land contains hundreds of paintings in various colours and styles. Striking and well-preserved X-ray images were painted across the site using ochre pigments that contain an iron oxide colourant mixed with clay to produce yellow, red and a distinctive purple colour. Infrared and Raman microscopy were used to confirm that the yellow pigment colouration is due to the presence of goethite. Both the red and purple pigments were shown to contain haematite, but there are microstructural differences between the two that account for the differences in the observed colour. Optical microscopy and scanning electron microscopy also demonstrate differences in the morphologies of the red and purple pigments. The purple pigment was found to a have a pure haematite structure, which is proposed to result from heating of the pigment source.
Indraratna, B, Nimbalkar, S & Rujikiatkamjorn, C 2016, 'A critical review of rail track geotechnologies considering increased speeds and axle loads', Geotechnical Engineering, vol. 47, no. 4, pp. 50-60.
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Ballasted railroads are designed to provide high speed commuter and heavy haul transportation. Ballast is one of most important load bearing components of the track substructure. However, it often experiences excessive settlement, lateral deformation and particle breakage when subjected to large dynamic (cyclic and impact) stresses. In addition, tracks constructed along coastal areas often undergo large settlements over soft compressible estuarine deposits, leading to frequent and costly track maintenance. The use of artificial inclusions such as geogrids, geocomposites, shock-mats (rubber) and prefabricated vertical drains (PVDs) are attractive options to maintain the vertical and horizontal alignment of tracks and to curtail excessive maintenance costs. This critical review paper provides a deeper insight to the recent advancements in rail track geotechnology at increased train speeds and axle loads.
Indraratna, B, Nimbalkar, SS, Ngo, NT & Neville, T 2016, 'Performance improvement of rail track substructure using artificial inclusions – Experimental and numerical studies', Transportation Geotechnics, vol. 8, pp. 69-85.
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© 2016 Elsevier Ltd Large and frequent loads from heavy freight and passenger trains often lead to the progressive track deterioration. The excessive deformation and degradation of ballast and unacceptable differential settlement of track and/or pumping of underlying soft subgrade soils necessitates frequent and costly track maintenance. However, artificial inclusions such as geogrids and shockmats can mitigate ballast degradation and improve track performance. A quantitative assessment of the influence of breakage, fouling, and the effects of artificial inclusions on the shear behaviour of ballast can be performed either experimentally or numerically. Numerical modelling can simulate these aspects subject to various types of loading and boundary conditions for a range of material properties so in this study, the stress–strain and degradation response of ballast was analysed through discrete element (DEM) and finite element (FEM) methods. In DEM, irregularly shaped ballast aggregates were simulated by clumping together spheres in appropriate sizes and positions. In FEM, a composite multi-layer track system was simulated and an elasto-plastic model with a non-associative flow rule was used to capture ballast degradation. These DEM and FEM simulations showed a good agreement with large-scale laboratory tests. This paper outlines the advantages of the proposed DEM and FEM models in terms of capturing the correct stress–strain and degradation response of ballast with particular emphasis on particle breakage and fouling, as well as applications of geosynthetic grids and shockmats.
Indraratna, B, Sun, Y & Nimbalkar, S 2016, 'Laboratory Assessment of the Role of Particle Size Distribution on the Deformation and Degradation of Ballast under Cyclic Loading', Journal of Geotechnical and Geoenvironmental Engineering, vol. 142, no. 7, pp. 04016016-04016016.
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© 2016 American Society of Civil Engineers. The deformation and degradation of ballast is influenced by the size of the aggregates. In this study, a series of cyclic drained triaxial tests was conducted on ballast with different sizes using the large-scale cylindrical triaxial apparatus designed and built at the University of Wollongong, and two different frequencies of cyclic loading were used to simulate low-speed and high-speed trains. From the laboratory results, coarse particles experience less vertical and lateral strains, whereas the volumetric strains decrease and then increase as the coefficient of uniformity increases, regardless of the loading frequency. Resistance to deformation and degradation is found to be improved by increasing ballast density. Different trends between the extent of breakage and particle size are observed for different breakage indices, and accordingly the extent of breakage is characterized into two distinct zones, depending on the coefficient of uniformity (Cu), where the significantly reduced breakage corresponds to a value of Cu larger than 1.8. The variation of particle shape before and after test is also quantified. A new particle size distribution that incorporates the size characteristics is proposed, as a result of this study.
Jiang, J, Chen, Q & Nimbalkar, S 2016, 'Field Data Based Method for Predicting Long-Term Settlements', American Journal of Engineering and Applied Sciences, vol. 9, no. 3, pp. 466-476.
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© 2016 Jianping Jiang, Qingsheng Chen and Sanjay Nimbalkar. The estimation of the long-term foundation settlement in soft soil is very complex, which is attributed to a number of uncertainties associated with various factors, such as: (i) The compressibility parameters obtained in the laboratory from samples of relatively small size that are more homogeneous compared to heterogeneous field sediments in which various soil types may be interlayered at random and may occur without exhibiting any real stratification; (ii) limitations and unrealistic assumptions prevailing in the conventional consolidation analysis. These have often resulted in the large discrepancy between actual in-situ settlements and the predictions from the conventional consolidation models (e.g., Terzaghi’s model). In this study, a field data based method inspired from an observational approach is proposed and validated against a number of high quality long-term field settlement data. Moreover, the corresponding geological soil properties obtained from field and laboratory tests have been presented, with the aim of providing useful practical references for other projects with similar geological profile. Furthermore, the proposed model is compared with existing prediction models. The results show that the newly proposed model can provide more reliable and accurate prediction of foundation settlements compared with other methods established in practice.
Khabbaz, H & Fatahi, B 2016, 'Environmental geotechnics challenges in Australia', Environmental Geotechnics, vol. 3, no. 1, pp. 2-3.
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Khezri, N, Mohamad, H & Fatahi, B 2016, 'Stability assessment of tunnel face in a layered soil using upper bound theorem of limit analysis', Geomechanics and Engineering, vol. 11, no. 4, pp. 471-492.
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Underground tunnelling is one of the sustainable construction methods which can facilitate the increasing passenger transportation in the urban areas and benefit the community in the long term. Tunnelling in various ground conditions requires careful consideration of the stability factor. This paper investigates three dimensional stability of a shallow circular tunnel in a layered soil. Upper bound theorem of limit analysis was utilised to solve the tunnel face stability problem. A three dimensional kinematic admissible failure mechanism was improved to model a layered soil and limiting assumptions of the previous studies were resolved. The study includes calculation of the minimum support pressure acting on the face of the excavation in closed-face excavations. The effects of the characteristics of the layers on the minimum support pressure were examined. It was found that the ratio of the thickness of cover layers particularly when a weak layer is overlying a stronger layer, has the most significant influence on the minimum tunnel support pressure. Comparisons have been made with the results of the numerical modelling using FLAC3D software. Results of the current study were in a remarkable agreement with those of numerical modelling.
Khorsandnia, N, Valipour, H, Schänzlin, J & Crews, K 2016, 'Experimental Investigations of Deconstructable Timber–Concrete Composite Beams', Journal of Structural Engineering, vol. 142, no. 12, pp. 04016130-04016130.
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Le, TM & Fatahi, B 2016, 'Trust-region reflective optimisation to obtain soil visco-plastic properties', Engineering Computations, vol. 33, no. 2, pp. 410-442.
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Purpose A non-linear creep function embedded in an elastic visco-plastic (EVP) model can simulate the decrease of creep compression rate with time. It overcomes the limitation of a linear logarithmic creep function, by which creep continuously increases to infinite value as time approaches infinity. However, the determination of the creep model parameters is a challenging task to apply the EVP model. Therefore, this paper presents a new numerical solution to determine the EVP model parameters applying trust-region reflective least square optimisation algorithm and the finite difference scheme to simulate stress-strain behaviour of soft soil. Design/methodology/approach In this paper, the developed method is verified against the field case study of Väsby test fill. A set of EVP model parameters is obtained by applying the developed method to the available laboratory consolidation results of Väsby clay. Then, the predictions of settlement and the excess pore water pressure at different depths are compared to the available field measurement. Findings The analysis results show the developed method is a reliable tool to evaluate the long-term performance of soft soils under embankments. Practical implications Practicing engineers can use the proposed optimisation algorithm to increase the accuracy of the soil visco-plastic model parameters by utilising all laboratory results of several loading stages during and after the...
Li, J, Wu, C, Hao, H, Su, Y & Liu, Z 2016, 'Blast resistance of concrete slab reinforced with high performance fibre material', Journal of Structural Integrity and Maintenance, vol. 1, no. 2, pp. 51-59.
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Concrete is now the most abundantly used material in construction. Despite good compressive strength, concrete is marked with brittleness and low tensile strength. A widely adopted method to enhance the concrete material performance especially the tensile strength and ductility is fibrous material addition. In the present study, concrete mix designs with different fibre additions have been developed, and high-performance polyethylene fibre and micro steel fibre are considered with varying volume fractions in the concrete matrix. Material static properties are obtained from laboratory tests, and further study on the dynamic performance of theses fibre reinforced concrete materials is investigated through field blast tests. Concrete slabs with high-performance polyethylene fibre reinforcement and hybrid steel and polyethylene reinforcement are casted and tested under close-in blast scenarios. Discussion on the structural damage and material performance is briefed based on the test results.
Li, J, Wu, C, Hao, H, Wang, Z & Su, Y 2016, 'Experimental investigation of ultra-high performance concrete slabs under contact explosions', International Journal of Impact Engineering, vol. 93, pp. 62-75.
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© 2016 Elsevier Ltd. All rights reserved. Unlike ductile behaviour under static loads, a reinforced concrete structure can respond in a brittle manner with highly localised damage like concrete spalling, cratering and reinforcement rupturing under close-in or contact explosions. High speed fragmentation resulting from concrete spall may cause severe casualties and injuries. It is therefore important to have a better understanding of the concrete spall phenomena and fragments distribution. In the present study, contact explosion tests were carried out on concrete slabs to observe the concrete crater and spall damage. Seven slabs including two control specimens made of normal strength concrete (NRC) and five ultra-high performance concrete (UHPC) slabs are tested. The superior blast resistance capacity of UHPC slabs is verified through comparison against NRC slabs. The influence of longitudinal reinforcement spacing and slab depth on the spall resistance of UHPC slabs is investigated. Predictions through available empirical methods are made and compared with the test observations. The accuracy of these empirical methods is discussed. All fragments resulting from the contact blast tests are collected and analysed through sieve analysis. It is found that Weibull distribution can be used to model the fragments size distribution of NRC slabs while Log-normal distribution better models the fragments size distribution of UHPC slabs.
Li, W, Huang, Z, Zu, T, Shi, C, Duan, WH & Shah, SP 2016, 'Influence of Nanolimestone on the Hydration, Mechanical Strength, and Autogenous Shrinkage of Ultrahigh-Performance Concrete', Journal of Materials in Civil Engineering, vol. 28, no. 1, pp. 04015068-04015068.
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© 2015 American Society of Civil Engineers. The influence of nanolimestone/nanoCaCo3 (NC) on the properties of ultrahigh-performance concrete (UHPC) cured at standard and heat conditions was experimentally investigated. The NC was used at ratios of 1, 2, and 3% as partial mass replacement for cement. Incorporating NC accelerated the hydration reactions of UHPC because of the nucleation effect. On the mechanical properties aspect, a threshold value of the NC content was found so that the compressive, flexural strengths, and flexural to compressive strength ratio of the UHPC were found to increase as the NC content increased towards the threshold content, and then to decrease with the increase of NC contents when the threshold was surpassed. Conversely, replacing cement with NC decreased flowability and increased the amount of autogenous shrinkage of the UHPC. While the NC accelerated the cement hydration process, it also acted as an effective filling material, resulting in enhanced mechanical properties and denser microstructure compared with the control UHPC mixture. Thus, through the use of NC, more environmentally friendly UHPC can be produced by reducing its cement factor and achieving enhanced engineering properties.
Li, W, Kawashima, S, Xiao, J, Corr, DJ, Shi, C & Shah, SP 2016, 'Comparative investigation on nanomechanical properties of hardened cement paste', Materials and Structures, vol. 49, no. 5, pp. 1591-1604.
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© 2015, RILEM. Three types of nanomechanical methods including static nanoindentation, modulus mapping and peak-force quantitative nanomechanical mapping (QNM) were applied to investigate the quantitative nanomechanical properties of the same indent location in hardened cement paste. Compared to the nanoindentation, modulus mapping and peak-force QNM allow for evaluating local mechanical properties of a smaller area with higher resolution. Beside, the ranges of elastic modulus distribution measured by modulus mapping and peak-force QNM are relatively greater than that obtained from nanoindentation, which may be due to a result of the shaper probe and local confinement effect between multiple phases. Moreover, the average value of elastic modulus obtained using peak-force QNM were consistent with those obtained by modulus mapping, while the different in modulus probability distribution could be related to the different nanomechancial theories and contact forces. The probability distributions of elastic modulus measured using nanomechanical methods to provide a basis for the different types of phases existing in cement paste. Based on the observation with high spatial resolution, cement paste can be likely found as nanocalse granular material, in which different submicron scale or basic nanoscale grain units pack together. It indicates that the peak-force QNM can effectively provide an effective insight into the nanostructure characteristic and corresponding nanomechanical properties of cement paste.
Li, W, Luo, Z, Long, C, Wu, C, Duan, WH & Shah, SP 2016, 'Effects of nanoparticle on the dynamic behaviors of recycled aggregate concrete under impact loading', Materials & Design, vol. 112, pp. 58-66.
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A 100 mm-diameter split Hopkinson pressure bar (SHPB) was applied to investigate effects of nanoparticles on the dynamic mechanical properties of recycled aggregate concrete (RAC) under impact loading. The nano-SiO2 (NS) and nano-CaCO3 (NC) were incorporated to replace cement by mass of 1 and 2% in RACs. The impact velocities were set as 7.7, 9.8 and 11.6 m/s in the SHPB tests. The effects of nanoparticles on failure patterns, compressive strengths, elastic modulus, peak strain and dynamic increase factor (DIF) of RACs under different strain rates were analyzed and discussed. The results show that nanomodified RACs exhibit higher both quasi-static and dynamic compressive strengths compared to control RAC. Dynamic elastic modulus of RAC seems not be affected by nanoparticle dosages and impact velocities. Compared to NC, NS is more effective to improve dynamic compressive strengths of RAC. On the other hand, the nanoparticles modified RACs exhibit lower DIF values than that of the control RAC. Moreover, NC obviously more reduces the DIF values of nanomodified RAC than NS.
Liu, Z, Liang, J & Wu, C 2016, 'The diffraction of Rayleigh waves by a fluid-saturated alluvial valley in a poroelastic half-space modeled by MFS', Computers & Geosciences, vol. 91, pp. 33-48.
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Mahdavi, H, Fatahi, B, Khabbaz, H, Vincent, P & Kelly, R 2016, 'Comparison of Coupled Flow-deformation and Drained Analyses for Road Embankments on CMC Improved Ground', Procedia Engineering, vol. 143, pp. 462-469.
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© 2016 The Authors. Published by Elsevier B.V. The use of controlled modulus columns (CMC) is gaining increased popularity in the support of rail and road bridge approach embankments on soft soils. The further columns are driven into the competent firm soils, the further the design will rely on the inclusions to take the bulk of the vertical loads, as they become rigid inclusions. The advantage of this design approach is that it produces increased control over the settlement, but as a result the columns will attract greater loads, including bending moment and shear force in situations where non-uniform loading or ground conditions exist. The load on the composite soil-CMC is uniformly distributed by the upper layer of granular load transfer platform (LTP), which also includes a layer of reinforcement. Finite difference program FLAC3D has been used to numerically simulate an embankment on the improved ground with end-bearing CMC. A geosynthetic reinforcement layer has been simulated using the inbuilt FLAC3D geogrid element. In this paper, a comparison has been made between the drained and coupled flow-deformation analyses. The force in the reinforcement layer, in particular, has been compared for the two analysis approaches. It was found that according to the numerical simulation, the drained analysis provides lower estimates of the settlement, lateral displacement; and therefore, predicts less tension in the geosynthetic layer.
Makki Alamdari, M, Samali, B, Li, J, Kalhori, H & Mustapha, S 2016, 'Spectral-Based Damage Identification in Structures under Ambient Vibration', Journal of Computing in Civil Engineering, vol. 30, no. 4, pp. 04015062-04015062.
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Metia, S, Oduro, SD, Duc, HN & Ha, Q 2016, 'Inverse Air-Pollutant Emission and Prediction Using Extended Fractional Kalman Filtering', IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING, vol. 9, no. 5, pp. 2051-2063.
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© 2016 IEEE. It is essential to maintain air-quality standards and to take necessary measures when air-pollutant concentrations exceed permissible limits. Pollutants such as ground-level ozone (O3), nitrogen oxides (NOX), and volatile organic compounds (VOCs) emitted from various sources can be estimated at a particular location through integration of observation data obtained from measurement sites and effective air-quality models, using emission inventory data as input. However, there are always uncertainties associated with the emission inventory data as well as uncertainties generated by a meteorological model. This paper addresses the problem of improving the inverse air pollution emission and prediction over the urban and suburban areas using the air-pollution model with chemical transport model (TAPM-CTM) coupled with the extended fractional Kalman filter (EFKF) based on a Matérn covariance function. Here, nitrogen oxide (NO), nitrogen dioxide (NO2), and O3 concentrations are predicted by TAPM-CTM in the airshed of Sydney and surrounding areas. For improvement of the emission inventory, and hence the air-quality prediction, the fractional order of the EFKF is tuned using a genetic algorithm (GA). The proposed methodology is verified with measurements at monitoring stations and is then applied to obtain a better spatial distribution of O3 over the region.
Mirmomeni, M, Heidarpour, A, Zhao, X-L, Hutchinson, CR, Packer, JA & Wu, C 2016, 'Fracture behaviour and microstructural evolution of structural mild steel under the multi-hazard loading of high-strain-rate load followed by elevated temperature', Construction and Building Materials, vol. 122, pp. 760-771.
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Mohammadi, I, Khabbaz, H & Vessalas, K 2016, 'Enhancing mechanical performance of rubberised concrete pavements with sodium hydroxide treatment', MATERIALS AND STRUCTURES, vol. 49, no. 3, pp. 813-827.
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© 2015, RILEM. This research evaluates performance of rubberised concrete prepared with sodium hydroxide (NaOH) treated rubber. Numerous studies have investigated the method of treating rubber with NaOH. However, the level of improvement achieved by this method has not been consistent between different studies. Hence, it is worthwhile to study application of this treatment method. Ten series of concrete specimens with different water cement ratios and a variety of rubber content were prepared. The fresh and hardened mechanical tests were conducted on concrete samples. It was found that the duration of 24 h for treatment of crumb rubber was the most promised duration, which resulted in favourable fresh and hardened concrete characteristics. Compared to rubberised concrete prepared with untreated rubber, rubberised concrete prepared with the 24-h NaOH treated method had 25 and 5 % improvement in compressive and flexural strength, respectively. It is experimentally indicated that using this treatment method resulted in notable improvement for the compressive strength, and moderate enhancement in the flexural strength.
Navaratnarajah, SK, Indraratna, B & Nimbalkar, S 2016, 'Application of Shock Mats in Rail Track Foundation Subjected to Dynamic Loads', Procedia Engineering, vol. 143, pp. 1108-1119.
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© 2016 The Authors. Published by Elsevier B.V.Rail track substructure (ballast, subballast and subgrade) is the most essential component of the railway system in view of track stability. The ballast is the largest component of the track substructure and it is the key load-bearing stratum packed with rock aggregates underneath and around the sleepers, thereby providing structural support against dynamic stresses caused by moving trains. However under large dynamic stresses exerted by heavy haul and high speed trains, the degradation of track substructure including ballast becomes significant. This in turn affects the track stability and creates frequent maintenance, thus increasing the life cycle cost of the rail network. Therefore, mitigating degradation of the ballast layer is vital in view of track longevity. In recent years, the use of resilient soft pads (shock mats) above the ballast (i.e. Under Sleeper Pad, USP) and below the ballast (i.e. Under Ballast Mat, UBM) has become a common practice. Many countries, including Australia have adopted the use of resilient pads in the rail track foundation. Currently, the studies on resilient mats are mostly limited to the reduction of vibration and noise. There is a lack of proper assessment of the geotechnical behavior of ballast when used along with shock mats. This paper provides an assessment of the triaxial behavior of the track substructure with and without shock mats under dynamic loading condition. A numerical model was developed based on the modified stress-dilatancy approach to capture the stress-strain and volume change behavior of ballast during impact loading. Model predictions are compared with laboratory results. It was found that the shock mats provide significant advantages in terms of reduced particle breakage and enhanced track stability.
Neupane, K, Kidd, P, Chalmers, D, Baweja, D & Shrestha, R 2016, 'Investigation on compressive strength development and drying shrinkage of ambient cured powder-activated geopolymer concretes', Australian Journal of Civil Engineering, vol. 14, no. 1, pp. 72-83.
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© 2016 Engineers Australia. Geopolymer is an inorganic polymer binding material, generally formed by the reaction between aluminosilicate materials and alkali activator solution. Previous researches on geopolymer concrete around the world suggested that geopolymer concrete possess superior mechanical and durability properties over ordinary Portland cement (OPC) concrete, such as higher indirect tensile strength and resistance to sulphate attack. Generally, fly ash-based geopolymer concrete was cured in elevated temperature for higher early age strength because of their longer setting time in ambient temperature. Published engineering properties of geopolymer concrete cured at ambient temperature are not abundant. In this research, two types of powder-activated geopolymer binders were used as binding material. A detailed study of compressive strength and drying shrinkage of different grades (40, 50, 65 and 80 MPa) of geopolymer and OPC concrete with different workability levels (normal-workable and super-workable) were carried out. All the concrete specimens were cured at standard laboratory temperature. The compressive strength development of geopolymer concrete in early age was relatively lower than OPC concrete; however, the later age strength was significantly higher. The drying shrinkage of geopolymer concrete was similar to OPC concrete of same grade and complied with Australian Standard 1379; however, it was higher than estimated values from Australian Standard 3600. The drying shrinkage results of this study were higher than drying shrinkage of accelerated cured geopolymer concretes in previous investigations. Super workable concrete exhibited higher drying shrinkage than normal workable concrete of same grade.
Nguyen, HH, Khabbaz, H, Fatahi, B & Kelly, R 2016, 'Bridge Pile Response to Lateral Soil Movement Induced by Installation of Controlled Modulus Columns', Procedia Engineering, vol. 143, pp. 475-482.
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© 2016 The Authors. Published by Elsevier B.V. Controlled modulus columns (CMC) for ground improvement are installed using a hollow stem displacement auger to induce lateral soil displacement effect, followed by grout injection. While the method reduces spoils, the excessive lateral soil displacement may damage adjacent structures. Although there has been growing interest in quantifying such effects, only a handful of studies have been attempted. This paper presents the results of a numerical investigation on the CMC installation effect on an existing bridge pile using the three-dimensional finite difference software package FLAC3D. It has been found that when the CMC is long and the existing bridge pile is slender, the pile bending moment and pile lateral movement, induced by the CMC installation effect, can be significant.
Nguyen, L & Fatahi, B 2016, 'Behaviour of clay treated with cement & fibre while capturing cementation degradation and fibre failure – C3F Model', International Journal of Plasticity, vol. 81, pp. 168-195.
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Crown Copyright © 2016 Published by Elsevier Ltd. All rights reserved. Soil treated with cement becomes brittle because its shear strength decreases rapidly in a post-peak state, which is why in recent years the inclusion of fibre into soil treated with cement has become an increasingly popular research area. This paper presents a constitutive model to simulate the behaviour of the fibre reinforced cement treated soil, referred to as the improved soil composite. In this model, a non-linear failure envelope was formulated to merge with the Critical State Line (CSL) of the reconstituted soil mixture at high levels of stress in order to capture the broken cementation bonds and ruptured fibre. A non-associated plastic potential function and a general stress strain relationship that includes the softening of the composite soil were also proposed to simulate the pre-and-post peak state. Moreover, many researchers focus on the addition of fibre into sand, soft clay, and sand treated with cement, whereas the behaviour of soft clay treated with fibre and cement requires further investigation. Hence, in this study a series of undrained triaxial tests were carried out on natural Ballina clay treated with cement and 0.3%-0.5% of fibre to determine how the amount of fibre and cement affects the behaviour of soft clay. SEM images were also analysed to study the structure of the improved Ballina composite at the micro-structural level. The laboratory results indicated that the combined effects of cementation and fibre reinforcement increased the shear strength and ductility of treated soft clay. Under triaxial conditions the peak shear strength of soft clay treated with cement and fibre increases dramatically due to the formation of cementation bonds and the bridging effect provided by the fibres, and the brittleness caused by the cementation bonds breaking also improves significantly due to the inclusion of fibre. However, when shearing at a high mean effective stress the ceme...
Nguyen, L, Fatahi, B & Khabbaz, H 2016, 'Predicting the Behaviour of Fibre Reinforced Cement Treated Clay', ADVANCES IN TRANSPORTATION GEOTECHNICS III, vol. 143, pp. 153-160.
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© 2016 The Authors. Published by Elsevier B.V. Treating soft clay with cement and fibre has become an effective ground improvement technique for transport infrastructure. Application of recycled fibres in deep soil mixing columns in soft soil sections of road and rail projects is being considered by designers and clients as an efficient technique. However, the combined effect of cement and fibre at failure requires further investigation. As the effective stresses increase to a sufficiently high stress, the effect of cementation is diminished due to the degradation of cementation bonds and the fibre exhibits failure due to either complete pull-out or breakage from the soil matrix. Thus, the failure envelope of the reinforced soil gradually merges with that of un-reinforced soil at higher stresses. In this paper, a constitutive model is proposed to simulate the behaviour of the cement treated-fibre reinforced soil based on the Critical State Soil Mechanic and the Modified Cam Clay model. In particular, the proposed model captures the beneficial effects of cementation and fibre reinforcement such as the improvement in strength and ductility while the cementation degradation and the failure mechanism of the fibre are also considered. In addition, a series of un-drained triaxial tests were conducted to verify the performance of the proposed model. This paper concludes that adding fibre into the cement treated soil clearly improves its residual strength, thus, a significant increase in ductility is observed and well simulated. In this study, by modifying the mean effective stress to include the cementation degradation and the fibre failure mechanism, the proposed model results in realistic prediction for the behaviour of soil treated with cement and fibre.
Nguyen, QV, Fatahi, B & Hokmabadi, AS 2016, 'The effects of foundation size on the seismic performance of buildings considering the soil-foundation-structure interaction', Structural Engineering and Mechanics, vol. 58, no. 6, pp. 1045-1075.
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Copyright © 2016 Techno-Press, Ltd. Shallow footings are one of the most common types of foundations used to support mid-rise buildings in high risk seismic zones. Recent findings have revealed that the dynamic interaction between the soil, foundation, and the superstructure can influence the seismic response of the building during earthquakes. Accordingly, the properties of a foundation can alter the dynamic characteristics (natural frequency and damping) of the soil-foundation-structure system. In this paper the influence that shallow foundations have on the seismic response of a mid-rise moment resisting building is investigated. For this purpose, a fifteen storey moment resisting frame sitting on shallow footings with different sizes was simulated numerically using ABAQUS software. By adopting a direct calculation method, the numerical model can perform a fully nonlinear time history dynamic analysis to realistically simulate the dynamic behaviour of soil, foundation, and structure under seismic excitations. This three-dimensional numerical model accounts for the nonlinear behaviour of the soil medium and structural elements. Infinite boundary conditions were assigned to the numerical model to simulate free field boundaries, and appropriate contact elements capable of modelling sliding and separation between the foundation and soil elements are also considered. The influence of foundation size on the natural frequency of the system and structural response spectrum was also studied. The numerical results for cases of soil-foundation-structure systems with different sized foundations and fixed base conditions (excluding soil-foundation-structure interaction) in terms of lateral deformations, inter-storey drifts, rocking, and shear force distribution of the structure were then compared. Due to natural period lengthening, there was a significant reduction in the base shears when the size of the foundation was reduced. It was concluded that the size of a...
Nguyen, T, Ghabraie, K, Tran-Cong, T & Fatahi, B 2016, 'Improving Rockbolt Design in Tunnels Using Topology Optimization', International Journal of Geomechanics, vol. 16, no. 1, pp. 04015023-04015023.
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© 2015 American Society of Civil Engineers. Finding an optimum reinforcement layout for underground excavation can result in a safer and more economical design, and is therefore highly desirable. Some works in the literature have applied topology optimization in tunnel reinforcement design in which reinforced rock is modeled as homogenized isotropic material. Optimization results, therefore, do not clearly show reinforcement distributions, leading to difficulties in explaining the final outcomes. To overcome this deficiency, a more sophisticated modeling technique in which reinforcements are explicitly modeled as truss elements embedded in rock mass media is used. An optimization algorithm extending the solid isotropic material with penalization method is introduced to seek for an optimal bolt layout. To obtain the stiffest structure with a given amount of reinforced material, external work along the opening is selected as the objective function with a constraint on the volume of reinforcement. The presented technique does not depend on material models used for rock and reinforcements and can be applied to any material model. Nonlinear material behavior of rock and reinforcement is considered in this work. Through solving some typical examples, the proposed approach is proved to enhance the conventional reinforcement design and provide clear and practical reinforcement layouts.
Nimbalkar, S & Indraratna, B 2016, 'Field Assessment of Ballasted Railroads Using Geosynthetics and Shock Mats', Procedia Engineering, vol. 143, pp. 1485-1494.
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© 2016 The Authors. Published by Elsevier B.V.The ballasted railroads form an integral part of the modern transportation infrastructure in Australia. However, they are subjected to large stresses especially on mixed traffic lines, where heavy freight trains are operated. Under such adverse operational conditions, ballast progressively degrades contributing to overall track deformations and frequent maintenance. Maintaining geometry of ballast embankments is necessary to improve safety and efficiency of railway operations. The use of artificial inclusions (geosynthetics and shock mats) as well as recycled (discarded) ballast in track can be economically viable options. In order to gain more insight, the CGRE has conducted extensive field trials on two rail lines in Bulli and Singleton in New South Wales supported by Sydney Trains and Australian Rail Track Corporation, respectively. In these studies, different types of geosynthetics (geogrid, geotextile and geocomposite) and shock mats were installed beneath the ballast layer constructed on varying subgrade conditions. Relative advantages of different geogrids were studied. Traffic induced stresses, ballast breakage, transient and permanent deformations were routinely monitored using precise instrumentation schemes. This paper discusses the details of track construction, instrumentation, monitoring processes and results of these field studies.
Nimbalkar, S & Indraratna, B 2016, 'Improved Performance of Ballasted Rail Track Using Geosynthetics and Rubber Shockmat', Journal of Geotechnical and Geoenvironmental Engineering, vol. 142, no. 8, pp. 04016031-04016031.
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Oduro, SD, Ha, QP & Duc, H 2016, 'Vehicular emissions prediction with CART-BMARS hybrid models', TRANSPORTATION RESEARCH PART D-TRANSPORT AND ENVIRONMENT, vol. 49, pp. 188-202.
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Vehicular emission models play a key role in the development of reliable air quality modeling
systems. To minimize uncertainties associated with these models, it is essential to
match the high-resolution requirements of emission models with up-to-date information.
However, these models are usually based on average trip speed, not on environmental
parameters like ambient temperature, and vehicle’s motion characteristics, such as speed,
acceleration, load and power. This contributes to the degradation of its predictive performance.
In this paper, we propose to use the non-parametric Classification and
Regression Trees (CART), the Boosting Multivariate Adaptive Regression Splines (BMARS)
algorithm and a combination of them in hybrid models to improve the accuracy of vehicular
emission prediction using on-board measurements and the chassis dynamometer testing.
The experimental comparison between the proposed CART-BMARS hybrid model with
the BMARS and artificial neural networks (ANNs) algorithms demonstrates its effectiveness
and efficiency in estimating vehicular emissions.
Ouyang, J, Han, B, Cao, Y, Zhou, W, Li, W & Shah, SP 2016, 'The role and interaction of superplasticizer and emulsifier in fresh cement asphalt emulsion paste through rheology study', Construction and Building Materials, vol. 125, pp. 643-653.
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© 2016 Elsevier Ltd The workability and mechanical properties of cement asphalt emulsion (CA) mortar are unstable due to the complex interaction between cement and asphalt emulsion. To reveal the interaction between cement and asphalt emulsion, the effect of emulsifier and superplasticizer on the rheology of cement paste and asphalt emulsion is investigated, respectively, and the effect of the interaction between emulsifier and superplasticizer on the rheology of cement paste is studied in this paper as well. Results show that the apparent viscosity and yield stress of asphalt emulsion increase with superplasticizer and emulsifier dosage. Emulsifier can change the yield stress and apparent viscosity of cement paste, and its effect on cement paste differs greatly with the type and dosage of emulsifier. Some emulsifiers can increase the yield stress of cement paste, but some emulsifiers can decrease the yield stress of cement paste. Emulsifier has interaction with superplasticizer, thus affecting the reducing water effect of superplasticizer on cement paste. There is a competition relationship between emulsifier and superplasticizer when they are adsorbed by cement particles. The mixing method, in which superplasticizer is mixed with cement before emulsifier added, is beneficial to obtain a lower apparent viscosity of cement paste for all tested emulsifiers.
Parsa-Pajouh, A, Fatahi, B & Khabbaz, H 2016, 'Experimental and Numerical Investigations to Evaluate Two-Dimensional Modeling of Vertical Drain–Assisted Preloading', International Journal of Geomechanics, vol. 16, no. 1.
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© 2015 American Society of Civil Engineers. In this study, the efficiency of proposed formulations for plane-strain modeling of vertical drain-assisted consolidation was evaluated. For this aim, the vertical drain-assisted preloading process was experimentally simulated using a fully instrumented large-scale Rowe cell. Nine pore-water-pressure transducers were installed in various locations to measure the changes in pore-water pressure during the test. Two pressure/volume controllers were connected to an infinite-volume controller to provide continuous water flow. Soft clays with predefined properties were used to form the intact and smear zones. A numerical code was developed by using the finite-difference program FLAC 2D to simulate the consolidation test. A numerical study was conducted to evaluate the efficiency of the proposed solutions for converting the axisymmetric state to a plane-strain condition and was subsequently compared with corresponding numerical analysis. From the results, it is observed that some of the proposed methods resulted in more accurate predictions of settlement and changes of pore-water pressure in the early stages of the consolidation process, whereas other proposed methods performed more accurately in the later stages of consolidation. Thus, three-dimensional modeling with actual soil-permeability properties to simulate the time-dependent behavior of soft soil improved with vertical drains is recommended.
Pokhrel, A, Li, JC, Li, YC, Maksis, N & Yu, Y 2016, 'Comparative Studies of Base Isolation Systems Featured with Lead Rubber Bearings and Friction Pendulum Bearings', Applied Mechanics and Materials, vol. 846, pp. 114-119.
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Due to the fact that safety is the major concern for civil structures in a seismic active zone, it has always been a challenge for structural engineers to protect structures from earthquake. During past several decades base isolation technique has become more and more popular in the field of seismic protection which can be adopted for new structures as well as the retrofit of existing structures. The objective of this study is to evaluate the behaviours of the building with different seismic isolation systems in terms of roof acceleration, elastic base shear and inter-storey drift under four benchmark earthquakes, namely, El Centro, Northridge, Hachinohe and Kobe earthquakes. Firstly, the design of base isolation systems, i.e. lead rubber bearing (LRB) and friction pendulum bearing (FPB) for five storey RC building was introduced in detail. The non-linear time history analysis was performed in order to determine the structural responses whereas Bouc-Wen Model of hysteresis was adopted for modelling the bilinear behaviour of the bearings. Both isolation systems increase the fundamental period of structures and reduces the spectral acceleration, and hence reduces the lateral force cause by earthquake in the structures, resulting in significant improvement in building performance; however the Lead Rubber Bearing provided the best reduction in elastic base shear and inter-storey drift (at first floor) for most of the benchmark earthquakes. For the adopted bearing characteristics, FPB provided the low isolator displacement.
Rao, P, Chen, Q, Zhou, Y, Nimbalkar, S & Chiaro, G 2016, 'Determination of Active Earth Pressure on Rigid Retaining Wall Considering Arching Effect in Cohesive Backfill Soil', International Journal of Geomechanics, vol. 16, no. 3, pp. 04015082-04015082.
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Rijal, R, Samali, B, Shrestha, R & Crews, K 2016, 'Experimental and analytical study on dynamic performance of timber floor modules (timber beams)', Construction and Building Materials, vol. 122, pp. 391-399.
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Shi, C, Li, Y, Zhang, J, Li, W, Chong, L & Xie, Z 2016, 'Performance enhancement of recycled concrete aggregate – A review', Journal of Cleaner Production, vol. 112, pp. 466-472.
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© 2015 Elsevier Ltd. All rights reserved. Recycled concrete aggregate differ from natural aggregate as the former contains hardened cement mortar. The adhered cement mortar on recycled concrete aggregate has higher porosity and water absorption and lower strength than natural aggregate do. It has negative effects on the mechanical properties and durability of fresh and hardened concrete made with recycled concrete aggregate. Therefore, it will facilitate the applications of recycled concrete aggregate if the adhered cement mortar can be enhanced. Removing and strengthening the adhered mortar are the two main methods for enhancing the properties of recycled concrete aggregate. This paper reviews the published enhancement methods for recycled concrete aggregate, and points out their advantages and disadvantages so as to facilitate the selection and further development of suitable enhancement methods for recycled concrete aggregate. It suggests that carbonation treatment is an efficient and feasible method for improving the mechanical properties and durability of recycled concrete aggregate. Carbonation treatment of recycled concrete aggregate is not only an efficient way for enhancing the properties of recycled concrete aggregate, but also an environmental friendly approach.
Sirivivatnanon, V, Mohammadi, J & South, W 2016, 'Reliability of new Australian test methods in predicting alkali silica reaction of field concrete', CONSTRUCTION AND BUILDING MATERIALS, vol. 126, pp. 868-874.
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© 2016 Elsevier Ltd Two new Australian Standard methods to test alkali-silica reactivity (ASR) of aggregates – AS 1141.60.1 accelerated mortar bar test (AMBT) and AS 1141.60.2 concrete prism test (CPT) were published in September 2014. The methods adopted test procedures correspondingly from ASTM C1260 and ASTM C1293 with improved performance limits leading to a new class of slowly reactive aggregates. This paper examines the accuracy of these new testing methods in predicting the ASR of aggregates in field conditions based on international research data. AS 1141.60.1 was found to be a relatively good accelerated test which correctly classified ‘slowly reactive’ and ‘reactive’ aggregates consistent with field performance with few exceptions. It is however a poorer screening test for non-reactive aggregates than ASTM C1260. Both AS 1141.60.2 and ASTM C1293 concrete prism tests were found to be more reliable than AMBT as both correctly classified almost all 64 aggregates against known field performance.
Stewart, MG, Foster, S, Ahammed, M & Sirivivatnanon, V 2016, 'Calibration of Australian Standard AS3600 concrete structures part II: reliability indices and changes to capacity reduction factors', Australian Journal of Structural Engineering, vol. 17, no. 4, pp. 254-266.
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© 2016 Engineers Australia. Capacity reduction factors (ϕ) for flexure, shear and axial loadings are derived for reinforced concrete (RC) structures based on a reliability-based calibration of the Australian Concrete Structures Standard AS3600. The structural reliability analysis considers the bias and variability of material properties, dimensions, loads and model error. The target reliabilities (βT) are selected based on consideration of past practice and Australian and international standards. The capacity reduction factors (ϕ) for the new code AS3600-2009 are selected using the most recent statistical parameters for material strengths for 20–100 MPa strength concrete using Class N (ductile) 500N reinforcement. The reliability-based calibration found that the ϕ-factor can be increased from 0.80 to 0.85 for members in bending, and increased from 0.60 to 0.65 for axial loading of short (stocky) columns where the ratio of the live load to the dead load is at least 0.25. No changes are recommended for shear or torsion, at this time, or for slender columns; further research is needed to better refine the design models for these cases and reduce the variation in their model error. The proposed increases in capacity reduction factors will result in up to an 8.3% increase in design strength that, in turn, provides efficiency in the use of materials. The proposed changes provide for modest savings in greenhouse gas emissions.
Su, Y, Li, J, Wu, C, Wu, P & Li, Z-X 2016, 'Effects of steel fibres on dynamic strength of UHPC', Construction and Building Materials, vol. 114, pp. 708-718.
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In modern civil engineering, steel fibres are widely used as reinforcement in the design of high performance concrete material. The addition of steel fibres in the concrete matrix can greatly improve the material ductility and durability as well as the impact and abrasion resistance. The performance of steel fibre reinforced concrete changes with varying concretes, fibre geometries, distribution, orientation and densities. In the recent study, an innovative ultra-high performance concrete (UHPC) material with nano-material addition is developed. In the mix design of this UHPC material, steel fibre is taken as an important composite. Great improvement of static compressive strength and split tensile strength had been obtained. In the current research, Split-Hopkinson-Pressure-Bar (SHPB) tests are conducted on this UHPC material to investigate its dynamic properties. Different types of steel fibres including two kinds of micro fibres and two kinds of twisted fibres are mixed in the UHPC. In total, 80 UHPC samples were tested in Swinburne University of Technology in 2011 and 190 specimens were tested in the Central South University of China in 2013. The influence of steel fibre addition on the dynamic strength of UHPC is experimentally investigated. It is found that steel fibre additions have prominent influence on the concrete dynamic strength, however, Dynamic Increase Factors (DIF) of steel fibre reinforced UHPC are constantly lower than that of conventional concrete material.
Su, Y, Li, J, Wu, C, Wu, P & Li, Z-X 2016, 'Influences of nano-particles on dynamic strength of ultra-high performance concrete', Composites Part B: Engineering, vol. 91, pp. 595-609.
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Known for its high strength, ductility and durability, ultra-high performance concrete (UHPC) is a topic of interest in recent years for scientists and civil engineers. Great potential application of UHPC has driven increasingly more investments and research into this industry. In recent studies, taken advantage of the nanotechnology, novel UHPC material with nano material addition was developed. Great static performance improvement was observed when compared with normal strength concrete. To obtain full understanding of material properties, especially dynamic performance, Split-Hopkinson Pressure Bar (SHPB) tests were conducted on this new concrete material. For comparison purpose, static properties from uniaxial compression and split tensile tests are obtained and discussed. In this paper, effects of nanomaterials on behaviour of UHPC are assessed through group comparison. Dynamic increase factor (DIF) values for both the dynamic compressive strength and tensile strength are generated. It is found that the strength of UHPC increases with the rising of strain rates and dosage of nano material influences UHPC dynamic properties. However, UHPC is noted to be less rate sensitive comparing with normal strength concrete. Microscopy analysis including Scanning Electron Microscope (SEM) Analysis, X-Ray Diffraction (XRD) Analysis and X-Ray Fluorescence (XRF) Analysis are conducted to understand the macroscopic failure phenomenon, element composition and concrete hydration process.
Subhani, M, Li, J, Samali, B & Crews, K 2016, 'Reducing the effect of wave dispersion in a timber pole based on transversely isotropic material modelling', Construction and Building Materials, vol. 102, pp. 985-998.
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© 2015 Elsevier Ltd. Round timbers are used for telecommunication and power distribution networks, jetties, piles, short span bridges etc. To assess the condition of these cylindrical shape timber structures, bulk and elementary wave theory are usually used. Even though guided wave can represents the actual wave behaviour, a great deal complexity exists to model stress wave propagation within an orthotropic media, such as timber. In this paper, timber is modelled as transversely isotropic material without compromising the accuracy to a great extent. Dispersion curves and mode shapes are used to propose an experimental set up in terms of the input frequency and bandwidth of the signal, the orientation of the sensor and the distance between the sensors in order to reduce the effect of the dispersion in the output signal. Some example based on the simulated signal is also discussed to evaluate the proposed experimental set up.
Sun, Q, Indraratna, B & Nimbalkar, S 2016, 'An Elasto-plastic Method for Analysing the Deformation of the Railway Ballast', Procedia Engineering, vol. 143, pp. 954-960.
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© 2016 The Authors. Published by Elsevier B.V.In this study, a series of monotonically drained triaxial tests were conducted using the large-scale cylindrical triaxial apparatus. The effect of particle breakage and confining pressure on the mechanical behaviour of ballast were investigated. Based on the experimental findings, mathematical expressions for critical state stress ratio and specific volume are proposed to incorporate the evolution of particle breakage during monotonic shearing. An elasto-plastic constitutive model is formulated within the critical state soil mechanics framework in order to capture the stress-strain behaviour and degradation of ballast. The non-linear variation of shear strength envelope at a given range of confining pressures is taken into account. Mathematical expressions for shear hardening and stress-dilatancy relations are proposed. The constitutive model is calibrated against the results of large-scale laboratory tests and further validated using experimental results available from past independent studies. It is proved that the proposed method can promisingly predict the deformation of the ballast layer in a typical railway environment.
Sun, QD, Indraratna, B & Nimbalkar, S 2016, 'Deformation and Degradation Mechanisms of Railway Ballast under High Frequency Cyclic Loading', Journal of Geotechnical and Geoenvironmental Engineering, vol. 142, no. 1, pp. 04015056-04015056.
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Ubaidillah, Imaduddin, F, Li, Y, Mazlan, SA, Sutrisno, J, Koga, T, Yahya, I & Choi, S-B 2016, 'A new class of magnetorheological elastomers based on waste tire rubber and the characterization of their properties', Smart Materials and Structures, vol. 25, no. 11, pp. 115002-115002.
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© 2016 IOP Publishing Ltd. This paper proposes a new type of magnetorheological elastomer (MRE) using rubber from waste tires and describes its performance characteristics. In this work, scrap tires were utilized as a primary matrix for the MRE without incorporation of virgin elastomers. The synthesis of the scrap tire based MRE adopted a high-temperature high-pressure sintering technique to achieve the reclaiming of vulcanized rubber. The material properties of the MRE samples were investigated through physical and viscoelastic examinations. The physical tests confirmed several material characteristics - microstructure, magnetic, and thermal properties-while the viscoelastic examination was conducted with a laboratory-made dynamic compression apparatus. It was observed from the viscoelastic examination that the proposed MRE has magnetic-field-dependent properties of the storage modulus, loss modulus, and loss tangent at different excitation frequencies and strain amplitudes. Specifically, the synthesized MRE showed a high zero field modulus, a reasonable MR effect under maximum applied current, and remarkable damping properties.
Vakhshouri, B & Nejadi, S 2016, 'Mix design of light-weight self-compacting concrete', Case Studies in Construction Materials, vol. 4, pp. 1-14.
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© 2015 Published by Elsevier Ltd. In recent decades, the utilization of mineral and chemical admixtures in concrete technology has led to changes in the formulation and mix design which has, in turn, made the concrete stronger and more durable. Light weight concrete (LWC) is an excellent solution in terms of decreasing the dead load of the structure, while self-compacting concrete (SCC) eases the pouring and removes construction problems. Combining the advantages of LWC and SCC is a new field of research. Considering its light weight of structure and ease of placement, Light-weight self-compacting concrete (LWSCC) may be the answer to the increasing construction requirements of slender and more heavily reinforced structural elements. Twenty one laboratory experimental investigations on the mix proportion, density and mechanical properties of LWSCC have been published in the last 12 years and these are analyzed in this study. The collected information is used to investigate the mix proportions including the chemical and mineral admixtures, light weight and normal weight aggregates, fillers, cement and water. Analyzed results are presented in terms of statistical expressions. It is very helpful for future research to choose the proper components with different ratios and curing conditions to attain the desired concrete grade according to the planned application.
Vakhshouri, B & Nejadi, S 2016, 'Self-compacting light-weight concrete; mix design and proportions', STRUCTURAL ENGINEERING AND MECHANICS, vol. 58, no. 1, pp. 143-161.
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© 2016 Techno-Press, Ltd. Utilization of mineral and chemical admixtures in concrete technology has led to changes in the formulation and mix design in recent decades, which has, in turn, made the concrete stronger and more durable. Lightweight concrete is an excellent solution in terms of decreasing the dead load of the structure, while self-compacting concrete eases the pouring and removes the construction problems. Combining the advantages of lightweight concrete and self-compacting concrete is a new and interesting research topic. Considering its light weight of structure and ease of placement, self-compacting lightweight concrete may be the answer to the increasing construction requirements of slender and more heavily reinforced structural elements. Twenty one laboratory experimental investigations published on the mix proportion, density and mechanical properties of lightweight self-compacting concrete from the last 12 years are analyzed in this study. The collected information is used to investigate the mix proportions including the chemical and mineral admixtures, light weight and normal weight aggregates, fillers, cement and water. Analyzed results are presented in terms of statistical expressions. It is very helpful for future research to choose the proper components with different ratios and curing conditions to attain the desired concrete grade according to the planned application.
Valipour, H, Khorsandnia, N, Crews, K & Palermo, A 2016, 'Numerical modelling of timber/timber–concrete composite frames with ductile jointed connection', Advances in Structural Engineering, vol. 19, no. 2, pp. 299-313.
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Due to the scarcity of experimental data, this article focuses on the application of detailed finite element models for evaluating structural behaviour of timber–concrete composite frames with post-tensioned beam-to-column joints. In the developed finite element models, nonlinear behaviour and failure mode of timber and concrete under biaxial stress state are captured by hypo-elastic constitutive laws based on the equivalent uniaxial strain concept. In addition to material nonlinearities, the effect of geometrical nonlinearities and nonlinearity of contacts at the concrete slab-to-beam, beam-to-column and slab-to-column interfaces are considered in the finite element models. The accuracy of developed finite element models is verified against available experimental data on post-tensioned timber frames, and the validated analytical tool is used to undertake a parametric study. It is shown that elastic modulus of timber and the details of concrete slab-to-column connection can significantly affect the drift response and failure mode, whereas the compressive strength of timber and stiffness of timber–concrete composite connection have only a minor influence on the drift and failure mode of the timber/timber–concrete composite frames with ductile jointed connections.
Xia, Y, Wu, C, Liu, Z-X & Yuan, Y 2016, 'Protective effect of graded density aluminium foam on RC slab under blast loading – An experimental study', Construction and Building Materials, vol. 111, pp. 209-222.
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© 2016 Elsevier Ltd. All rights reserved. In recent decades, bomb incidents have significantly increased due to various blast accidents and growing terrorist threats. Therefore, the protection of important infrastructures against blast loading has never been more important. Aluminium foam, which is often used as a protective layer to absorb impact energy, has demonstrated its ability to mitigate blast effect in several studies. The outstanding energy absorption capacity of aluminium foam is mainly resulted from its long-lasting plateau-stress region which allows it to only transmit a small stress (which is equal to the plateau stress) to the protected structure while absorbing the rest by self-compaction. For aluminium foam that is manufactured by the same method, the overall energy absorbing capacity per unit volume increases proportionally with mass density; however, the plateau stress also increases with mass density which means a larger stress would be transmitted to the protected structure. Therefore, there is a trade-off between the mass density and the transmitted stress. In order to increase the overall energy absorbing capacity of aluminium foam while keeping the transmitted stress at a reasonably low magnitude, the idea of density-graded foam has been proposed which is simply a foam structure with various densities along its thickness. In this paper, the effectiveness of density-graded foams has been investigated. A number of static compressive tests are conducted on different types of aluminium foams including aluminium foams with uniform density, density-graded aluminium foams with linear gradient as well as density-graded aluminium foams with unordered gradient. In addition, a blast test program is also carried out to investigate the blast mitigation effect of graded density foams on reinforced concrete (RC) slabs.
Xiao, J, Qu, W, Li, W & Zhu, P 2016, 'Investigation on effect of aggregate on three non-destructive testing properties of concrete subjected to sulfuric acid attack', Construction and Building Materials, vol. 115, pp. 486-495.
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© 2016 Elsevier Ltd. All rights reserved. In order to investigate the effect of aggregates on the concrete sulfuric acid resistance, accelerated corrosion experiments were conducted with four types of concretes composed of coarse and fine aggregates with two different chemical compositions. All the concretes with the same water/cement ratio of 0.45, and the pH value was kept in the range of 0.93-0.97. With continuous monitoring of each concrete specimen, corrosion depth, mass loss, and dynamic modulus elasticity loss were calculated. The results showed that the dynamic modulus of elasticity loss can be regard as an acceptable indicator for evaluating the resistance of concrete to sulfuric acid attack as well as corrosion depth and mass loss. A regression model proposed in this paper could provide good predictions. Concrete with marble aggregates rich in calcium carbonate have better performances in sulfuric acid solution than that with inert aggregates. Effect of fine aggregate on concrete sulfuric acid corrosion rate is more significant than coarse aggregate in the term of corrosion depth, mass loss, and dynamic modulus of elasticity loss.
Xu, J, Wu, C, Xiang, H, Su, Y, Li, Z-X, Fang, Q, Hao, H, Liu, Z, Zhang, Y & Li, J 2016, 'Behaviour of ultra high performance fibre reinforced concrete columns subjected to blast loading', Engineering Structures, vol. 118, pp. 97-107.
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Ultra high performance fibre reinforced concrete (UHPFRC) is a cement-based composite material mixing with reactive powder and steel fibres. It is characterized by its high strength, high ductility and high toughness and such characteristics enable its great potential in protective engineering against extreme loads such as impact or explosion. In the present study, a series of field tests were conducted to investigate the behaviour of UHPFRC columns subjected to blast loading. In total four 0.2 m × 0.2 m × 2.5 m UHPFRC columns were tested under different designed explosions but all at a standoff distance of 1.5 m. Blast tests were also performed on four high strength reinforced concrete (HSRC) columns with the same size and reinforcement as UHPFRC columns to evaluate their behaviour under the same loading conditions. The data collected from each specimen included reflected overpressures, column deflections at centre and near the supports. Three major damage modes, including flexural, shear and concrete spalling failure modes, were observed. The post blast crack patterns, permanent deflections and different levels of damage observations showed that UHPFRC columns performed superior in blast loading resistance as compared with HSRC columns.
Ying, X-Y, Ding, G, Hu, X-J & Zhang, Y-Q 2016, 'Developing planning indicators for outdoor wind environments of high-rise residential buildings', Journal of Zhejiang University-SCIENCE A, vol. 17, no. 5, pp. 378-388.
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© 2016, Zhejiang University and Springer-Verlag Berlin Heidelberg. The construction of a building may change the microclimate in the vicinity, and planning indicators in a master plan may directly affect the outdoor physical environmental quality in residential areas. An inappropriate plan for a site may accelerate wind and intensify vortexes over places on the pedestrian levels, which leads to an adverse outdoor environment. Therefore, the design of a cluster of buildings should not focus only on the buildings but also provide a good outdoor environment around the buildings. To tackle the problem of inadequate wind environment, the relationship between the building’s floor area ratio and height was identified in this study as the main planning indicator to be examined on its effects on the outdoor wind environment. A computational fluid dynamics (CFD) model was hence developed to simulate the wind conditions generated by some typical site layouts with different values for planning indicators under relevant weather conditions, which were typical of those in Hangzhou, China. The simulated wind conditions are assessed using the wind speed ratio over the whole area of the building cluster at the pedestrian level. The effects on the local wind condition due to the varying of the planning indicators are discussed whilst considering the potential construction costs. The indicators resulting in better external conditions are highlighted in the conclusion as the recommendation which could be used as a rule of thumb by architects and planners at the master planning stage. The study disproves the common belief in the practice that a lower floor area ratio means fewer buildings and therefore greater external comfort. In fact, the higher the building, the greater the outdoor comfort wind zone for pedestrians. However, the increment in comfort area is limited to buildings extending from 25 to 30 levels.
Yu, Y, Li, J, Yan, N, Dackermann, U & Samali, B 2016, 'Load capacity prediction of in-service timber utility poles considering wind load', Journal of Civil Structural Health Monitoring, vol. 6, no. 3, pp. 385-394.
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© 2016, Springer-Verlag Berlin Heidelberg. This paper presents a numerical investigation on the influence of different types of damage to the load capacity of in-service timber utility poles. Current design codes do not highlight a pole’s strength performance due to different types of damage. However, damages typically found in ageing timber poles, such as damage due to fungus or termite attack, have very different characteristics and result in various effects on the strength properties of timber poles. Hence, the presented study investigates the influence of typical common types of damage to the strength properties and load capacities of timber utility poles. The study considers the damage type, location and severity. Wind load is considered as critical load due to the practical issue. The research shows that external damages at ground level significantly affect the load capacity of a timber pole. While internal damage, such as termite nests, has less influence on the load capacity regardless of the damage location and severity.
Yu, Y, Li, Y, Li, J & Gu, X 2016, 'A hysteresis model for dynamic behaviour of magnetorheological elastomer base isolator', Smart Materials and Structures, vol. 25, no. 5, pp. 055029-055029.
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© 2016 IOP Publishing Ltd. In recent years, an adaptively tuned magnetorheological elastomer (MRE) isolator for a base isolation system has been designed and tested with the benefits of low power cost, fail safe manner and fast responses. To make full use of this striking device for design of smart structures, a highly precise model should be developed to effectively and accurately forecast the shear force of the device in real-time so as to adopt a proper control strategy to improve the responses of the protected structures. In this work, a novel mechanical model is presented to characterize this nonlinear hysteresis for its implementation in structural vibration control. This model employs the displacement and velocity of the device as well as the applied current as the inputs and just has the limited constant parameters to be identified compared with some classical hysteretic models such as Bouc-Wen, improved Dahl and LuGre models. Performance evaluation of this novel hysteresis model has been conducted based on the testing data from an MRE base isolator. The results show that the proposed model has high modelling accuracy and is able to perfectly portray the unique and complicated behaviours of the device with various excitations.
Yu, Y, Li, Y, Li, J & Gu, X 2016, 'Self-adaptive step fruit fly algorithm optimized support vector regression model for dynamic response prediction of magnetorheological elastomer base isolator', NEUROCOMPUTING, vol. 211, pp. 41-52.
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© 2016 Elsevier B.V. Parameter optimization of support vector regression (SVR) plays a challenging role in improving the generalization ability of machine learning. Fruit fly optimization algorithm (FFOA) is a recently developed swarm optimization algorithm for complicated multi-objective optimization problems and is also suitable for optimizing SVR parameters. In this work, parameter optimization in SVR using FFOA is investigated. In view of problems of premature and local optimum in FFOA, an improved FFOA algorithm based on self-adaptive step update strategy (SSFFOA) is presented to obtain the optimal SVR model. Moreover, the proposed method is utilized to characterize magnetorheological elastomer (MRE) base isolator, a typical hysteresis device. In this application, the obtained displacement, velocity and current level are used as SVR inputs while the output is the shear force response of the device. Experimental testing of the isolator with two types of excitations is applied for model performance evaluation. The results demonstrate that the proposed SSFFOA-optimized SVR (SSFFOA_SVR) has perfect generalization ability and more accurate prediction accuracy than other machine learning models, and it is a suitable and effective method to predict the dynamic behaviour of MRE isolator.
Yu, Y, Li, YC, Li, JC, Gu, XY, Royel, S & Pokhrel, A 2016, 'Nonlinear and Hysteretic Modelling of Magnetorheological Elastomer Base Isolator Using Adaptive Neuro-Fuzzy Inference System', Applied Mechanics and Materials, vol. 846, pp. 258-263.
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Magnetorheological elastomer (MRE) base isolator is a semi-active control device which has currently obtained increasing attention in the field of vibration control of civil structures. However, the inherent nonlinear and hysteretic response of the device is regarded as a challenge aspect for using the smart device to realize the high performance. Therefore, an accurate and robust model is essential to make full use of these unique features for its engineering applications. In this paper, to solve this issue, adaptive neuro-fuzzy inference system (ANFIS) is utilized to characterize the dynamic behavior of the device. In this proposed model, the inputs are historical displacements and applied current of the device while the output is the shear force generated. To validate its forecast performance, the ANFIS model is also compared with some conventional models. Finally, the result verifies that ANFIS has the best perfection ability among existing MRE-based device models.
Yu, Y, Royel, S, Li, J, Li, Y & Ha, Q 2016, 'Magnetorheological elastomer base isolator for earthquake response mitigation on building structures: modeling and second-order sliding mode control', Earthquakes and Structures, vol. 11, no. 6, pp. 943-966.
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© 2016 Techno-Press, Ltd. Recently, magnetorheological elastomer (MRE) material and its devices have been developed and attracted a good deal of attention for their potentials in vibration control. Among them, a highly adaptive base isolator based on MRE was designed, fabricated and tested for real-time adaptive control of base isolated structures against a suite of earthquakes. To perfectly take advantage of this new device, an accurate and robust model should be built to characterize its nonlinearity and hysteresis for its application in structural control. This paper first proposes a novel hysteresis model, in which a nonlinear hyperbolic sine function spring is used to portray the strain stiffening phenomenon and a Voigt component is incorporated in parallel to describe the solid-material behaviours. Then the fruit fly optimization algorithm (FFOA) is employed for model parameter identification using testing data of shear force, displacement and velocity obtained from different loading conditions. The relationships between model parameters and applied current are also explored to obtain a current-dependent generalized model for the control application. Based on the proposed model of MRE base isolator, a second-order sliding mode controller is designed and applied to the device to provide a real-time feedback control of smart structures. The performance of the proposed technique is evaluated in simulation through utilizing a three-storey benchmark building model under four benchmark earthquake excitations. The results verify the effectiveness of the proposed current-dependent model and corresponding controller for semi-active control of MRE base isolator incorporated smart structures.
Zhang, F, Wu, C, Zhao, X-L, Xiang, H, Li, Z-X, Fang, Q, Liu, Z, Zhang, Y, Heidarpour, A & Packer, JA 2016, 'Experimental study of CFDST columns infilled with UHPC under close-range blast loading', International Journal of Impact Engineering, vol. 93, pp. 184-195.
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© 2016 Elsevier Ltd. All rights reserved. Concrete-filled double-skin tubes (CFDST) have been increasingly popular in the field of engineering in recent years. A lot of research has been carried out to investigate the behaviour of CFDST members under a variety of loading conditions. This paper presents an experimental investigation on ultra-high performance concrete infilled double-skin tube columns subjected to close-in blast loading. Two types of CFDST columns were investigated in the experiments - one with both inner and outer tubes circular and the other one with both square. The main test parameters included the explosive charge weight and the magnitude of axial load. After the blast tests, there was no visible buckling nor ruptures found on the steel tubes and only minor cracks, of no more than 1mm width, were observed in the core concrete when the outer steel tube was removed. Based on the findings of the experiments, it is evident that CFDST column has excellent blast resistance. This feature has the potential to be used in high-value structures which may be the targets of terrorist attacks, such as embassies, government buildings and critical infrastructures.
Zhao, L-S, Zhou, W-H, Fatahi, B, Li, X-B & Yuen, K-V 2016, 'A dual beam model for geosynthetic-reinforced granular fill on an elastic foundation', Applied Mathematical Modelling, vol. 40, no. 21-22, pp. 9254-9268.
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In this study, a new dual beam model was proposed for a geosynthetic-reinforced granular fill with an upper pavement. This dual beam model was subjected to a uniform surcharge loading and resting on an elastic foundation which was simulated by a Pasternak model. The upper pavement was modeled by an Euler-Bernoulli beam while the geosynthetic reinforced granular fill was simulated by a reinforced Timoshenko beam. The explicit derivation process for the behavior of this dual beam-foundation system was presented and an exact solution was obtained. A two-dimensional finite element analysis and a Pasternak model for simulating the granular fill were carried out to validate the reliability of the proposed dual beam model. A parametric analysis was put forward to investigate the behavior of this dual beam-foundation system. It was found that the length of the pavement structure and vertical uniform loading, the stiffness and shear modulus of the foundation soil had significant influences on the behavior of the dual beam-foundation system.
Zheng, J, Ouyang, Q, Li, Z, Li, Y & Wang, J 2016, 'Experimental analysis of separately controlled multi-coils on the performance of magnetorheological absorber under impact loading', Journal of Intelligent Material Systems and Structures, vol. 27, no. 7, pp. 887-897.
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A magnetorheological absorber is capable of actively adapting any gun recoil condition by means of controlled Coulomb force. The objective of multi-coil magnetorheological absorber with individual input currents is to mitigate the peak force transferred to the buffer structure during bullet firing, and thus to increase the structural fatigue life. This article investigates various cases by applying random combinations of input currents to the magnetic coils. The impact tests were conducted by obtaining and analyzing the force, displacement, and velocity. As a reference, input currents with equivalent magnitude are considered statistically, in terms of average peak force and occurrence time. The experimental results show that separately controlled multi-coils contribute to the magnitude and occurrence time of peak force significantly. Furthermore, to reduce peak forces, a simple open-loop control strategy was proposed and validated effectively by the experimental results.
Alamdari, MM, Khoa, NLD, Runcie, P, Li, J & Mustapha, S 1970, 'Characterization of gradually evolving structural deterioration in jack arch bridges using support vector machine', Maintenance, Monitoring, Safety, Risk and Resilience of Bridges and Bridge Networks - Proceedings of the 8th International Conference on Bridge Maintenance, Safety and Management, IABMAS 2016, pp. 2322-2327.
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The main objective of structural health monitoring is to provide reliable information about the health state of the critical structures by implementing a damage characterization strategy to detect the presence of damage, location, severity as possibly failure prediction as soon as the damage occurs. This paper presents a robust approach to detect and characterize a gradually evolving damage based on time responses data captured from a steel reinforced concrete structure. The presented method is in the context of unsupervised and nonmodel-based approaches, hence, there is no need for any representative numerical/finite element model of the structure to be built. In this work, we propose one-class support vector machine as an anomaly detection method. One-class support vector machine fits well for damage diagnosis in structural health monitoring since there may exist many damaged patterns and one-class support vector machine can detect all of them as anomalies. To demonstrate the feasibility of the method in the detection and assessment of a gradually evolving deterioration, a test bed was established to replicate a concrete jack arch which is a main structural component on the Sydney Harbour Bridge – one of Australia’s iconic structures. The structure is a concrete cantilever beam with an arch section which is located on the eastern side of the bridge underneath the bus lane. It is assumed that the structure is subjected to Gaussian white noise excitation. A crack is introduced in the structure using a cutting saw and its length is progressively increased in four stages while the depth was constant; these four damage cases correspond to less than 0.5% reduction in the first three modes of the structure. The damage identification results using the presented approach demonstrated the feasibility of applying support vector machine as a learning technique for damage characterization in structural health monitoring. The method accurately separated two states ...
Banihashemi Namini, SS, Ding, GKC & Wang, J 1970, 'Identification of BIM-Compatible Variables for Energy Optimization of Residential Buildings: A Delphi Study', AUBEA 2016 The 40th Australasian Universities Building Education Association Conference, Australian Universities Building Education Association Annual Conference, Central Queensland University, Cairns, Australia, pp. 281-291.
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It is believed that drawing an applicable, relevant and coherent batch of variables is a fundamental tenet in the success of having an integrated BIM-based energy optimisation but in order to achieve a high level of usefulness, these variables need to be refined and prioritised. Thus, this paper is to investigate BIM compatible variables which are of top priorities for energy optimisation of residential buildings in the design stage. A sequential exploratory research was conducted to find out the most relevant and significant variables that have a high impact on the energy consumption of residential buildings. A pool including more than 30 variables was established and refined through running Delphi approach with energy and BIM experts to reach the final list of prioritized variables. Conducting a three-round Delphi enabled authors to obtain more meticulous results via a consensus agreement among the respondents on the top 13 variables through lenses of BIM compatibility, applicability to optimization and design stage.
Benn, BT, Baweja, D & Mills, JE 1970, 'The effect of limestone mineral addition and cement kiln dust on the chloride ingress into mortar specimens made with cement, fly ash and slag', fib Symposium, pp. 1-13.
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Following changes to the cement standard, AS 3972 General and blended cement, in 2010 the author commenced research into the effect of increased levels of limestone mineral addition plus cement kiln dust on the rate of chloride ingress though mortar and concrete. The research also incorporates the effect of replacing some of the cement with fly ash and ground granulated blastfurnace slag. This paper concentrates on the chloride ion ingress data that has been produced as part of the research. The mixes reported in this paper are based on mixes made with cement containing limestone mineral levels of 4%, 10% and 15% with and without 5% cement kiln dust additions and mixes where the cement was replaced with 20% fly ash or 30% slag again with and without 5% cement kiln dust. The chloride ingress of the mortar has been determined on specimens that have been subjected to standard water curing for up to one year and tested using a method based on Nord Test Build NT Build 492 (1999).
Booth, N, Imperia, P, Davidson, G, Lee, S, Stuart, B, Thomas, P, Komatsu, K, Yamane, R, Prescott, S, Maynard-Casely, H & Nelson, A 1970, 'Three impossible things before lunch or that sounds challenging, you want it when?', 9th International Workshop on Sample Environment at Scattering Facilities, Gettysburg.
Cao, D, Hong, G & Wang, J 1970, 'Preliminary investigation to the feasibility of chemical heat storage for saving the exhaust gas energy in a spark ignition engine', Website proceedings of the 20th Australasian Fluid Mechanics Conference, Australasian Fluid Mechanics Conference, The 20th Australasian Fluid Mechanics Conference, Perth, Australia, pp. 1-4.
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Heat storage has become more important because it utilizes the wasted energy to improve the overall efficiency of energy systems. This study was aimed to develop a chemical heat storage system using magnesium hydroxide (Mg(OH)2) and its endothermic and exothermic reactions to recover the thermal energy of the exhaust gas in internal combustion engines. It was proposed that the reactor receives the thermal energy of exhaust gas in the dehydration of Mg(OH)2 to become MgO and H2O, and releases the stored energy in the hydration of MgO. To increase the thermal conductivity of pure Mg(OH)2 for enhancing the reactor’s performance, the working material used, EM8 block, is the mixture of Mg(OH)2 and expanded graphite at a ratio of 8:1. Experiments were conducted on a 6-cylinder spark ignition engine (Toyota Aurion 2GR-FE 3.5L) at stoichiometric air/fuel ratios to estimate the amount of energy loss in the exhaust gas. Experimental data of exhaust gas temperature and volume ratios of exhaust gas constitutions were used to calculate the energy rates of each of the exhaust gas constituents and to estimate the reactor efficiency in the dehydration process. Results of the preliminary investigation show that the proposed chemical heat storage system may be feasible to recover approximately 5.8 % of the heat loss in the exhaust gas
Dang, LC, Dang, CC, Khabbaz, H & Fatahi, B 1970, 'Numerical Assessment of Fibre Inclusion in a Load Transfer Platform for Pile-Supported Embankments over Soft Soil', Geo-China 2016, Fourth Geo-China International Conference, American Society of Civil Engineers, Shandong, China, pp. 148-155.
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© 2016 ASCE. This study presents the results of a numerical investigation in the performance of natural fibre reinforced load transfer platform (NFRLTP) for pile supported embankment construction over soft soil. A numerical analysis based on finite element method (FEM) was carried out on an NFRLTP pile-supported embankment in a two-dimensional plane strain condition. The effects of natural fibre inclusion in the load transfer platform on the stress transfer mechanism, generation and dissipation of excess pore water pressure have been analyzed and discussed in detail. The findings indicate that natural fibre reinforced soil as a load transfer platform facilitated the load transfer process from the embankment to piles, while decreases the intensity of load transferred to soft soil, the excess pore water pressure and the overall settlement.
Dinh, TH, Ha, QP & La, HM 1970, 'Computer vision-based method for concrete crack detection', 2016 14th International Conference on Control, Automation, Robotics and Vision (ICARCV), 2016 14th International Conference on Control, Automation, Robotics and Vision (ICARCV), IEEE, Phuket, Thailand, pp. 1-6.
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© 2016 IEEE. This paper presents a computer vision-based method to automatically detect concrete cracks. We focus on images containing the concrete: background and crack, where the background is the major mode of the gray-scale histogram. Therefore, we address the detection problem of potential concrete cracks by dealing with histogram thresholding to extract regions of interests from the background. We first employ line emphasis and moving average filters to remove noise from concrete surface images obtained from an inspection robot. The developed algorithm is then applied for automatic detection of significant peaks from the gray-scale histogram of the smoothed image. The biggest peak and its corresponding valley(s) are consequently identified to calculate the threshold value for image binarization. The effectiveness of our proposed method was successfully evaluated on various test images, where cracks could be identified without the requirement of some heuristic reasoning.
Gardner, AP, Goldsmith, R & Vessalas, K 1970, 'Using practice architectures theory to compare consecutive offerings of the same subject', Proceedings of the 27th Annual Conference of the Australasian Association for Engineering Education (AAEE2016), Australasian Association of Engineering Education annual conference, Southern Cross University, Coffs Harbour.
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CONTEXTTwo consecutive offerings (2015 and 2016) of the same subject, Concrete Technology and Practice, prompted opposite reactions from students. The academics involved in 2015 and/or 2016 sought to explore the similarities and differences between these consecutive offerings in reflecting on the learning and teaching practices in their classroom. PURPOSEPractice architectures theory provides a framework for examining and understanding the differences between these consecutive offerings of ostensibly the same subject. This paper also provides an example of how a theoretical framework can be used to examine teaching practices – even our own by practitioners who are also acting as researchers in this context. APPROACHEvidence used in comparing the 2015 and 2016 offerings of this subject is drawn from focus group discussions with students and observations of each of the researcher/practitioners involved. Additional data includes the end of semester Student Feedback Survey results including written responses to open-ended questions. RESULTSDifferences in aspects of the cultural-discursive, material-economic and socio-political arrangements of the 2015 and 2016 offerings of Concrete Technology and Practice became apparent from the analysis. CONCLUSIONSUsing the theory of practice architectures gave us insights into the inter-relationships between the different arrangements inherent in teaching and learning practices. It also highlighted the resilience of ‘taken for granted’ practices.
Ghosh, B, Fatahi, B, Khabbaz, H & Hsi, J 1970, 'Reinforced Timoshenko Beam Theory to Simulate Load Transfer Mechanism in CMC Supported Embankments', Proceedings of 12th Australia New Zealand Conference on Geomechanics, Australia New Zealand Geomechanics conference, Australian Geomechanics Society, Wellington, New Zealand, pp. 1099-1106.
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Controlled modulus column (CMC) supported embankments are increasingly being used for construction of major highway embankments on soft ground particularly near waterways or coastal regions. CMCs are sustainable and cost-effective ground improvement technology that transmit the load from the traffic and the embankment to a lower bearing stratum through a composite CMC/soil matrix. The key influencing components of the load transfer mechanism include embankment fill, load transfer platform (LTP) with one or more layers of geosynthetics, CMC and the foundation soils. Rapid growth of the application of geosynthetics between two granular layers in the column supported embankment has been observed in the last two decades. The use of LTP enhances the load transfer mechanism in the CMC improved soft ground and minimises the post construction settlement of the ground. In this paper, reinforced Timoshenko beam theory is adopted to simulate the LTP with one layer of geosynthetics that is resting on elastic foundation with columns. A parametric study is conducted to investigate the importance of the LTP on the load transfer mechanism for the CMC supported embankment. Special attentions are given to the thickness of the LTP, the use of geosynthetics and its influence on deflection of the LTP, the shear force developed in the LTP and the tension developed in geosynthetics. The parametric study reveals that the thickness of the LTP has a significant effect on the behaviour of LTP up to a certain limit.
Ghosh, B, Fatahi, B, Khabbaz, H & Kamruzzaman, AHM 1970, 'Analysis of CMC-Supported Embankments Considering Soil Arching', IN SITU AND LABORATORY TEST METHODS FOR SITE CHARACTERIZATION, DESIGN, AND QUALITY CONTROL, GeoChina International Conference, American Society of Civil Engineers, Jinan, Shandong, China, pp. 286-293.
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© ASCE. In this paper, the behaviour of geosynthetic-reinforced controlled modulus column-supported embankments is studied for different distributions of loadings induced by arching on the load transfer platform (LTP). This study proposes a mechanical model for idealising the response of LTP-soft soil-column system, by representing each sub-system using commonly used mechanical elements such as rough-elastic membrane, beam, and spring. The soil arching effect is incorporated in the model to determine the deflection of the soft soil as well as mobilised tension in the geosynthetics more accurately. The effects of the column stiffness and consolidation of saturated soft soils are also incorporated in the model. Moment and shear force in the LTP, tension developed in the geosynthetics, and settlements of the improved soft ground are predicted using the proposed model. To evaluate the proposed model, a parametric study is conducted to investigate the influence of different pressure distribution due to different arching theories. It is observed that the pattern of distribution of the arching loads affect the performance of controlled modulus column-supported embankments significantly.
Hailu, M, Shrestha, R & Crews, K 1970, 'Long-Term Deflection of Timber-Concrete Composite Beams in Cyclic Humidity Conditions in Bending', Composite Construction in Steel and Concrete VII, International Conference on Composite Construction in Steel and Concrete 2013, American Society of Civil Engineers, North Queensland, Australia, pp. 146-157.
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© ASCE. A laboratory investigation to determine the long-term behaviour of timber-concrete composite (TCC) beams was started from August 2010 at the University of Technology, Sydney. The test was conducted on four six-meter-span TCC beams; this paper reports the results to-date for only two beams. The materials used are laminated veneer lumber (LVL) for the joists and 32 MPa concrete for the flanges. From the start of the test (August 2010), the specimens have been under sustained loads of (1.7kPa) whilst the environmental conditions have been cyclically alternated between normal and very humid conditions (typical cycle duration is six to eight weeks) and the temperature remains quasi constant (22 °C). During the test, the mid-span deflection, moisture content of the timber beams and relative humidity of the air are continuously monitored. The investigation is still continuing and this paper reports the results of the experimental investigation for the last two and half years.
Hasan, H, Khabbaz, H & Fatahi, B 1970, 'Impact of Quicklime and Fly Ash on the Geotechnical Properties of Expansive Clay', Geo-China 2016, Fourth Geo-China International Conference, American Society of Civil Engineers, Shandong, China, pp. 93-100.
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© ASCE. Severe damages can occur on civil engineering structures and infrastructure including roads, channels, houses, sidewalks, and driveways if built on expansive soils. In this study to limit the expansive soil impacts on roads, quicklime and class F fly ash were employed as potential stabilisers in enhancing the engineering properties of expansive soils. The samples were prepared by integrating artificial soils combined with a mixture of quicklime-fly ash at a ratio of 1:3. Various contents of quicklime-fly ash were applied on soil samples, composed of 40% bentonite (B) and 60% kaolin (K). Sample properties were measured at 3, 7, and 28 days of curing time. Moreover, another set of soil samples were prepared containing 20% B and 80% K to study the effect of bentonite content on the soil mechanical properties of the stabilised soil.
Lewis, K, Basaglia, B, Shrestha, R & Crews, K 1970, 'The use of cross laminated timber for Long span flooring in commercial buildings', WCTE 2016 - World Conference on Timber Engineering.
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Long span timber floor solutions have demonstrated their potential to compete with concrete and steel construction for multi-storey commercial buildings. Due to the high strength-to-weight ratio of timber, serviceable vibration performance is a critical structural design issue for long spans. This project investigates the vibration performance of cross laminated timber for long span floors in the Australian and New Zealand building sector. Laboratory experiments and computer analysis are used to study the effect of the increased transverse stiffness, inherent to a cross laminated timber, on the vibration performance of the floor. The effect of boundary conditions, connection and support type, are investigated and quantified where possible. A timber joist floor with a plywood sheath is analysed and tested to validate the methods used in this study.
Li, J, Wu, C & Hao, H 1970, 'Experimental and numerical study of a new composite slab under blast loads', 4th International Conference on Protective Structures, Tianjin Chengjian University & Tianjin University, China, Beijing.
Li, J, Wu, C & Hao, H 1970, 'Spallation of reinforced concrete slabs under contact explosion', 2016 Second Asian Conference on Defence Technology (ACDT), 2016 Second Asian Conference on Defence Technology (ACDT), IEEE, Changmai, Thailand, pp. 42-45.
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© 2016 IEEE. Structures and their occupants are imposed to great threat under blast loading environment. The current design and research practices mainly focus on structural responses and damages under far field or close-in detonations. The blast scenarios involving contact explosions are not extensively investigated. Under contact explosions, highly localized damage caused by severe stress wave propagation is commonly seen, and this damage mode is significantly different from other dynamic loading types in which structural members usually respond in flexural or shear mode. In recent decades, the necessity of gaining in-depth knowledge about this extreme loading event is highlighted as threat from terrorism activities is rising. In the present study, contact test results on reinforced concrete members are presented. Performances of slabs made of normal strength concrete and steel wire mesh reinforced concrete are compared and discussed.
Mahdavi, H, Fatahi, B, Khabbaz, H, Krzeminski, M, Santos, R & Marix-Evans, M 1970, 'Three-Dimensional Simulation of a Load Transfer Mechanism for Frictional and End Bearing CMC Supported Embankments on Soft Soil', Geo-China 2016, Fourth Geo-China International Conference, American Society of Civil Engineers, Shandong, China, pp. 60-67.
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© ASCE. Recently, the use of controlled modulus columns (CMC) has gained popularity in the support of rail and road bridge approach embankments on soft soils. If the columns are extended into a competent firm soil, and designed to take nearly all the vertical loads, they become rigid inclusions. The advantage of this design approach is that settlement will be controlled, but the drawback is that the columns will attract greater load, including bending moment and shear force in situations where non-uniform loading or ground conditions exist. The load on the composite soil-CMC is uniformly distributed by the upper layer of granular load transfer platform (LTP). In this paper, the effect of CMC length on the load transfer mechanism is numerically investigated. Coupled flow-deformation analysis has been performed for a long period to understand the system response in the long term, while interface elements capable of simulating gapping and sliding between CMC and the surrounding soil are considered. A geosynthetic reinforcement layer has been simulated using the inbuilt FLAC3D geogrid element. The force in the reinforcement layer has been evaluated, and in particular, a clear comparison is made between the stresses in CMC and the ground settlement with floating and end-bearing columns.
Makki Alamdari, M, Khoa, NLD, Runcie, P, Li, J & Mustapha, S 1970, 'Characterization of gradually evolving structural deterioration in jack arch bridges using support vector machine', MAINTENANCE, MONITORING, SAFETY, RISK AND RESILIENCE OF BRIDGES AND BRIDGE NETWORKS, 8th International Conference on Bridge Maintenance, Safety and Management (IABMAS), CRC Press, Foz do Iguacu, BRAZIL, pp. 555-555.
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Moshiri, F, Shrestha, R & Crews, K 1970, 'Predictive Models for the Stiffness of Vertical Screws as Shear Connection in Timber-Concrete Composite Floors', Composite Construction in Steel and Concrete VII, International Conference on Composite Construction in Steel and Concrete 2013, American Society of Civil Engineers, Palm Cove, Australia, pp. 661-675.
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© ASCE. The stiffness, strength, and arrangement of the shear connection play a crucial role in the design of timber-concrete composite (TCC). This paper reviews the available analytical models for prediction of the stiffness of TCC shear connections. The methodology of different analytical models for stiffness of the mechanical fastener TCC connection is discussed and the accuracy of these models is examined based on push out test results for shear connectors. The simplified stiffness models underestimated the experimental data of normal wood screw with an error ranging approximately 10-40%, whereas the models based on Winkler's theory were inaccurate and calculated a much lower stiffness compared to that of experimental test with an error of approximately 60%. The reasons attributed to inaccuracy of the stiffness models are described. This paper recommends further investigation on the prediction of foundation moduli of timber and concrete as the main input parameters of the models based on the Winkler's theory.
Nguyen, HH, Khabbaz, H, Fatahi, B, Santos, R, Marix-Evans, M & Vincent, P 1970, 'Installation Effect of Controlled Modulus Columns on Nearby Existing Structures', Geo-China 2016, Fourth Geo-China International Conference, American Society of Civil Engineers, Shandong, China, pp. 125-133.
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© 2016 ASCE. Controlled modulus columns (CMC) ground improvement technique is a novel approach to reduce ground settlement. To install CMC, a rotary displacement auger is used to form a vertical cylindrical cavity, by displacing the surrounding soils laterally, followed by grout injection. While the method reduces spoil generation, excessive lateral soil displacement may damage the adjacent structures and freshly-grouted CMCs. Although there has been growing interest in quantifying such effects, only a handful of studies have been attempted. This paper presents results of a numerical investigation on the CMC installation effect on an existing bridge pile using the three-dimensional finite difference software package FLAC3D. The bridge pile response to the lateral soil movement induced by the CMC installation are presented and discussed.
Nguyen, L, Fatahi, B & Khabbaz, H 1970, 'A Novel Model to Simulate the Behaviour of Cement-Treated Clay under Compression and Shear', Geo-China 2016, Fourth Geo-China International Conference, American Society of Civil Engineers, Shandong, China, pp. 152-158.
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© ASCE. Soft clay treated with cement shows an improvement on strength due to the chemical interaction between cement and clay particles. Laboratory results showed that the peak strength of the cement treated clay reduces as the mean effective stress increases due to the effect of cementation degradation. Therefore, in this paper, a constitutive model was developed to simulate the behaviour of cement treated clay. Based on the critical state soil mechanics, the model proposed the non-linear failure envelope for the cement treated clay to merge with the critical state line (CSL) of the un-reinforced clay when the reinforced samples reach a sufficiently high stress levels. Moreover, a modified mean effective stress was proposed to include the contribution of cementation and its cementation degradation. Furthermore, the proposed model was evaluated by comparing the proposed model predictions against the Singapore clay treated with 10% cement available from the literature. The validation suggested that the proposed model can be used to predict the behaviour of cement treated clay very well.
Nguyen, QV, Fatahi, B & Hokmabadi, AS 1970, 'Influence of Shallow Foundation Characteristics on the Seismic Response of Mid-Rise Buildings Subjected to Strong Earthquakes', Geotechnical Special Publication, GeoChina International Conference, American Society of Civil Engineers, Shandong, China, pp. 117-124.
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Performance based seismic design is a modern approach to earthquake-resistant design shifting emphasis from 'strength' to 'performance'. In this study, the influence of the shallow foundation (footing) size on the seismic performance of the buildings subjected to strong earthquakes is investigated considering soil-structure interaction (SSI). A fifteen storey moment resisting frame sitting on shallow foundation over soft soil with different foundation size is simulated numerically using ABAQUS software. The developed three dimensional numerical simulation accounts for nonlinear behaviour of the soil medium by considering the variation of soil stiffness and damping as a function of developed shear strain in the soil elements during earthquake. Elastic-perfectly plastic model is adopted to simulate foundations and structural elements. Four strong earthquake records, including El Centro 1940, Hachinohe 1968, Northridge 1994, and Kobe 1995 have been taken as input accelerations for time history analysis in time domain. Due to natural period lengthening, there was a significant reduction in the base shears when the size of the foundation was reduced. It can be concluded that the foundation size can influence the dynamic characteristics and seismic response of the building due to SSI and should therefore be given careful consideration in order to ensure a safe and cost effective seismic design.
Nimbalkar, S & Indraratna, B 1970, 'In-situ performance assessment of ballasted railway track stabilised using geosynthetics and shock mats', Proceedings of the 5th International Conference on Geotechnical and Geophysical Site Characterisation, ISC 2016, International Conference on Geotechnical and Geophysical Site Characterisation, Australian Geomachanics Society, Gold Coast, pp. 1411-1416.
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In Australia, ballasted railway tracks are one of major modes of transportation. The main objectives of Australian railways are to cater for the demands of the supply chain in the mining and agriculture sectors, as well as to provide quicker and cost effective commuter transport in urban areas. However several geotechnical problems in the populated coastal areas pose significant issues. Ballasted tracks are conventionally constructed on compacted granular embankments overlying the natural subsoil. The granular embankments comprises of ballast and capping layers which undergo substantial deformations and degradation under the heavy cyclic loading of passenger and freight trains. This in turn, may lead to a loss of track geometry, and require costly frequent maintenance. In order to rectify these issues, appropriate stabilization techniques for ballast and capping are necessary, the extent of which depends also on the type of subgrade. When appropriately designed and installed, synthetic inclusions such as geosynthetics and/or shock mats can provide a cost effective alternatives to traditional techniques of ground improvement. Comprehensive field trials were carried out on two railway networks in Bulli and Singleton in New South Wales, Australia. In these studies, several track sections were instrumented with precise sensors for real-time monitoring of stress-deformation response of granular embankments. Different types of geosynthetics were placed beneath the ballast embankment. Recoverable and irrecoverable components of vertical deformations of the track substructure were routinely monitored. The amount of ballast breakage was evaluated by collecting samples from the field and by performing sieve analysis in the laboratory. It was evident that geosynthetics in the form of geogrids can decrease the vertical strains of the ballast layer, resulting in reduced maintenance costs. This paper describes the comprehensive field instrumentation, site geology, co...
Nimbalkar, S, Indraratna, B & Mahdi Biabani, M 1970, 'Deformation and Degradation of Railroad Granular Layers under High Frequency Cyclic Loading and the Benefits of Using Geosynthetics', Geo-Chicago 2016, Geo-Chicago 2016, American Society of Civil Engineers, Chicago, Illinois, United States, pp. 222-232.
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The granular media (i.e., ballast and sub-ballast) used in ballasted rail tracks undergo large deformations along with particle breakage when subjected to cyclic loads exerted by heavy and fast trains. The deformation and degradation of such granular layers severely affects track geometry and results into increased maintenance costs. The use of artificial inclusions in planar (geogrid, geotextile, and geocomposite) as well as three-dimensional form (geocell) is essential to curtail such costs and improve track stability. A series of cyclic drained triaxial tests were conducted using large-scale prismoidal process simulation apparatus designed and built at the University of Wollongong. Effects of external confining pressure, frequency, and number of load cycles were investigated. The test results showed that large deformation and degradation of ballast was imminent under high frequency cyclic loading. It was also shown that settlement of the ballast and sub-ballast can be reduced significantly employing geocomposites and geocells, respectively. The results revealed the effectiveness of the geocell, when they are used at low confinement and higher frequencies. This paper provides an insight to cyclic behavior of railroad granular substructure and demonstrates the role of confinement induced through the use of artificial inclusions.
Panahian, M, Ding, G & Ghosh, S 1970, 'Measuring Sustainability Performance For A Multiunit Residential Development Case Study In Sydney', Conference Proceedings AUBEA 2016, Australian Universities Building Education Association Annual Conference, Central Queensland University, Cairns, Australia, pp. 647-659.
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Multiunit residential development numbers are on the rise close to SydneyCentral Business District (CBD) as more people are choosing to live inapartments. Energy efficiency and water savings in these developmentsare significantly important to develop sustainable communities of future.This paper selects and examines a large multi-dwelling residential estatecase study in an eastern suburb of Sydney, located approximately withineight kilometres radial distance from Sydney’s CBD. Based on theelectricity and water usage data, current electricity consumption forcommon areas and water usage for gardens are estimated. Three keysustainable options examined are: potential onsite renewable electricitygeneration from roof solar PV installation; techniques for reducingswimming pool heat loss and to maintain year wide adequate watertemperature and roof rainwater harvesting potential. Associated costs areexamined to comprehend useful energy and water efficient solutions.Recommendations suggest that solar PV installation, using an appropriateswimming pool cover and rain rainwater collection from the roof couldmeaningfully improve overall sustainability performance of the selectedcase study.
Pham, NH, La, HM, Ha, QP, Dang, SN, Vo, AH & Dinh, QH 1970, 'Visual and 3D Mapping for Steel Bridge Inspection Using a Climbing Robot', Proceedings of the International Symposium on Automation and Robotics in Construction (IAARC), 33th International Symposium on Automation and Robotics in Construction, International Association for Automation and Robotics in Construction (IAARC), Auburn University, Alabama, United States, pp. 141-149.
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There are over six hundred thousand bridges in the US which require great amount of human effort along with expensive and specialized equipment for maintenance. Current bridge inspections are manually performed by inspectors which are inefficient and unsafe. This article presents visual and three dimensional (3D) structure inspection for steel bridges and steel structures using the developed climbing robot. The robot can move freely on steel surface, carry several sensors, and collect data then send to the ground station for real-time monitoring as well as further processing. Steel surface image stitching and 3D map building are conducted to provide a current condition of the structure.
Phung, MD, Quach, CH, Chu, DT, Nguyen, NQ, Dinh, TH & Ha, QP 1970, 'Automatic interpretation of unordered point cloud data for UAV navigation in construction', 2016 14th International Conference on Control, Automation, Robotics and Vision (ICARCV), 2016 14th International Conference on Control, Automation, Robotics and Vision (ICARCV), IEEE, Phuket, Thailand, pp. 1-6.
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© 2016 IEEE. The objective of this work is to develop a data processing system that can automatically generate waypoints for navigation of an unmanned aerial vehicle (UAV) to inspect surfaces of structures like buildings and bridges. The input includes data recorded by two 2D laser scanners, orthogonally mounted on the UAV, and an inertial measurement unit (IMU). To achieve the goal, algorithms are developed to process the data collected. They are separated into three major groups: (i) the data registration and filtering to generate a 3D model of the structure and control the density of point clouds for data completeness enhancement; (ii) the surface and obstacle detection to assist the UAV in monitoring tasks; and (iii) the waypoint generation to set the flight path. Experiments on different data sets show that the developed system is able to reconstruct a 3D point cloud of the structure, extract its surfaces and objects, and generate waypoints for the UAV to accomplish inspection tasks.
Stuart, B, Thomas, P, Maynard-Casely, H, Booth, N & Leung, A 1970, 'A neutron diffraction investigation of shear forces on a model lipid for forensic application', ANZFSS 23rd International Symposium on the Forensic Sciences, Auckland.
Sun, QD, Indraratna, B & Nimbalkar, S 1970, 'The Deformation and Degradation of Granular Material under High-Frequency Cyclic Loading', Geotechnical and Structural Engineering Congress 2016, Geotechnical and Structural Engineering Congress 2016, American Society of Civil Engineers, Pheonix, Arizona, United States, pp. 1700-1707.
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© ASCE.In order to understand the permanent deformation and degradation of railway ballast under high speed train loading, a series of cyclic triaxial tests were conducted using large-scale cylindrical apparatus. The frequency was used from 5 Hz to 60 Hz corresponding to the train speeds from about 40 km/h to 400 km/h. Three types of permanent deformation mechanisms were observed in response to the applied cyclic loads, namely, plastic shakedown at relatively lower frequency, ratcheting at an increased frequency, and plastic collapse at higher frequencies. Correspondingly, four types of particle degradation were observed. The magnitudes of ballast deformation and degradation were found to increase with the frequency and number of load cycles. A critical train speed was identified. Moreover, a good correlation was obtained between particle breakage and volumetric strain under cyclic loading.
Sun, W-J, Chen, C, Liu, S-Q, Sun, D-A, Liang, X-H, Tan, Y-Z & Fatahi, B 1970, 'Study on GMZ bentonite-sand mixture by undrained triaxial tests', E3S Web of Conferences, European Conference on Unsaturated Soils, EDP Sciences, Paris, France, pp. 18006-18006.
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© 2016 The Authors.It is particularly necessary to study the deformation, strength and the changes of pore water pressure of bentonite-based buffer/backfill materials under the undrained condition. A series of isotropic compression tests and triaxial shear tests under undrained conditions were conducted on the compacted saturated/unsaturated GMZ bentonite-sand mixtures with dry mass ratio of bentonite/sand of 30:70. During the tests, the images of the sample were collected by photographic equipment and subsequently were cropped, binarized and centroids marked by image processing technique. Based on identification of the variation of the position of marked centroids, the deformation of the sample can be determined automatically in real-time. Finally, the hydro-mechanical behaviour of saturated and unsaturated bentonite-sand mixtures under the undrained condition can be obtained. From results of triaxial shear tests on unsaturated samples under constant water content, inflated volumetric deformation transforms to contractive volumetric deformation due to the increase of the confining pressure and lateral expansion deformation are observed due to the increase in the shearing stress. Moreover, the net mean stress affects the initial stiffness, undrained shear strength and deformation of the sample during the undrained shear tests.
Vahedian, A, Shrestha, R & Crews, K 1970, 'Modelling the bond slip behaviour of FRP externally bonded to timber', WCTE 2016 - World Conference on Timber Engineering.
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Recent studies and applications have demonstrated that Fibre Reinforced Polymer (FRP) has become a mainstream technology for the strengthening and/ or rehabilitation of ageing and deteriorated structures. However, one of the main problems which limit the full utilisation of the FRP material strength is the premature failure due to debonding. This research study presents 1) a review of available FRP-to-timber and FRP-to-concrete bonded interface models, and 2) investigates factors affecting bond strength. A stepwise regression method has then been employed to evaluate the influence of potential factors on the bond strength. The proposed stepwise regression model is based on 195 experimental results of FRP-to-timber bonded interfaces. Results of this stepwise regression analysis are then assessed with results of pull-out tests and satisfactory comparisons are achieved between measured failure loads (R2=0.59) and the predicted loads (R2=0.71, P<0.0001).
Vakhshouri, B & Nejadi, S 1970, 'ANFIS application to predict the compressive strength of lightweight self-compacting concrete', 2016 Future Technologies Conference (FTC), 2016 Future Technologies Conference (FTC), IEEE, San Francisco, CA, USA, pp. 28-35.
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© 2016 IEEE. Light-weight Self-Compacting Concrete (LWSCC) might be the answer to the increasing construction requirements of slenderer and more heavily reinforced structural elements. However there are limited studies to prove its ability in real construction projects. In conjunction with the traditional methods, artificial intelligent based modeling methods have been applied to simulate the non-linear and complex behavior of concrete in the recent years. Twenty one laboratory experimental investigations on the mechanical properties of LWSCC; published in recent 12 years have been analyzed in this study. The collected information is used to investigate the relationship between compressive strength, elasticity modulus and splitting tensile strength in LWSCC. Analytically proposed model in ANFIS is verified by multi factor linear regression analysis. Comparing the estimated results, ANFIS analysis gives more compatible results and is preferred to estimate the properties of LWSCC.
Vizcarra, GC, Nimbalkar, S & Casagrande, M 1970, 'Modeling Behaviour of Railway Ballast in Prismoidal Apparatus Using Discrete Element Method', Procedia Engineering, International Conference on Transportation Geotechnics (ITGC), Elsevier BV, Advances in Transportation Geotechnics 3, pp. 1177-1184.
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© 2016 The Authors. Published by Elsevier B.V.This article presents the results of numerical simulations of loading tests conducted on coarse particles that simulate railroad ballast. The objective of this study was to evaluate the deformation of ballast under vertical loading and to study the influence of the two different particle size distributions. One of them was according to particle size distribution recommended by Indraratna and co-workers in the past as an improvement to Australian Standard and the other was prepared in accordance with Brazilian standard. The discrete element method offers a new means of studying the response characteristics of railway ballast. The basic idea of discrete element method (DEM) is that arbitrary discontinuities are divided into a set of rigid elements, making each rigid element satisfy the equations of motion, use time step iteration method for solving the equations of motion of rigid elements, and then obtain the overall movement patterns of arbitrary discontinuities. In this study, the discrete element method of analysis has been used to simulate the geotechnical behaviour of railway ballast observed during the triaxial testing. Three-dimensional numerical simulations were performed using discrete element modeling approach.
Woods, AC, Lay, HM & Ha, QP 1970, 'A novel extended potential field controller for use on aerial robots', 2016 IEEE International Conference on Automation Science and Engineering (CASE), 2016 IEEE International Conference on Automation Science and Engineering (CASE), IEEE, Fort Worth, TX, USA.
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Unmanned Aerial Vehicles (UAV), commonly known as drones, have many potential uses in real world applications. Drones require advanced planning and navigation algorithms to enable them to safely move through and interact with the world around them. This paper presents an extended potential field controller (ePFC) which enables an aerial robot, or drone, to safely track a dynamic target location while simultaneously avoiding any obstacles in its path. The ePFC outperforms a traditional potential field controller (PFC) with smoother tracking paths and shorter settling times. The proposed ePFC's stability is evaluated by Lyapunov approach, and its performance is simulated in a Matlab environment. Finally, the controller is implemented on an experimental platform in a laboratory environment which demonstrates the effectiveness of the controller.
Wu, C, Hao, H & Li, J 1970, 'Post-Blast Residual Loading Capacity of Ultra-High Performance Concrete Columns', First International Interactive Symposium on UHPC, First International Interactive Symposium on UHPC, Iowa State University Digital Press.
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Xu, R, Fatahi, B & Hokmabadi, AS 1970, 'Influence of Soft Soil Shear Strength on the Seismic Response of Concrete Buildings Considering Soil-Structure Interaction', Geo-China 2016, Fourth Geo-China International Conference, American Society of Civil Engineers, Jinan, Shandong, China, pp. 17-24.
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© ASCE. Influences of undrained shear strength on seismic response of moment resisting concrete building considering soil-structure interaction (SSI) have been studied. A 15-storey building model resting on class Ee soil with different values of undrained shear strength has been simulated through FLAC3D. Fully nonlinear dynamic analysis under four different earthquakes including two far-field and two near-field recordings has been conducted by direct method and results in terms of base shear, maximum lateral displacement, inter-storey drift and spectral acceleration have been compared and discussed. Results indicate that by increasing the undrained shear strength of the subsoil, the superstructure experiences extra base shear under earthquake excitations due to SSI. Furthermore, the maximum lateral displacements and inter-storey drifts of the superstructure increase by adopting higher values for the undraied shear strength of the subsoil. It is concluded that practicing engineers should treat soil properties gained from field or laboratory tests with extreme care when dealing with numerical based seismic design of the soil-structure systems.