Fatahi, B, Van Nguyen, Q, Xu, R & Sun, WJ 2018, 'Three-dimensional response of neighboring buildings sitting on pile foundations to seismic pounding', International Journal of Geomechanics, vol. 18, no. 4.View/Download from: UTS OPUS or Publisher's site
© 2018 American Society of Civil Engineers. Seismic pounding occurs when the separation gap between buildings and structures is not wide enough, particularly during major earthquake events; this can cause them to collide, causing local damage or, in extreme cases, collapse. This study investigated the impact that this separation gap has on the seismic response of midrise buildings supported on piles while considering seismic soil-pile-structure interaction (SSPSI). To achieve this aim, three 15-story reinforced concrete buildings sitting on pile foundations and with five different separation gaps under excitations from the 1994 Northridge and 1995 Kobe earthquakes were numerically simulated. This study used three-dimensional numerical modeling to simultaneously capture the effects of seismic pounding and SSPSI. Because the considered structure, pile foundation, and soil deposit are three-dimensional in nature, the adopted three-dimensional numerical modeling can provide a more realistic simulation to capture the seismic behavior of the system. The nonlinear behavior of structural elements was included, and the dynamic soil properties were obtained from field data and backbone curves. A contact pair interface with small-sliding surface-to-surface formulation between buildings was used to capture possible seismic pounding, and contact interfaces with a finite-sliding formulation were used to simulate the interaction between the piles and the soil. The results, including lateral building deflections, interstory drifts, structural shear forces, foundation rocking, lateral pile deflections, and the distributions of bending moments and shear forces of the piles, are presented and discussed. The findings of this study will give engineers a better insight into the possible effects of seismic pounding on the seismic performance of buildings, and the response of endbearing piles in soft soils.
Xu, R & Fatahi, B 2018, 'Influence of geotextile arrangement on seismic performance of mid-rise buildings subjected to MCE shaking', Geotextiles and Geomembranes, vol. 46, pp. 511-528.View/Download from: UTS OPUS or Publisher's site
Geotextile layers make it possible to construct mid-rise buildings sitting on shallow foundations in unfavourablesoil conditions; this study investigates how the arrangement of geotextiles affects the seismic performance ofmid-rise buildings under Maximum Considered Earthquake (MCE) shaking. The geotextile arrangement con-sidered here includes the stiffness (5000 kN/m–12000 kN/m), the length with respect to width of the foun-dation (B) (1B–4B), the number of geotextile layers (1–7 layers), and their spacing (250 mm–1000 mm).FLAC3D is used for the numerical simulation and to carry out nonlinear dynamic analysis in the time domain,and an inelastic constitutive model is used to simulate the behaviour of the structure and the geotextile layersunder seismic loads. Variations in the shear modulus of soil and the corresponding damping ratio with cyclicshear strain are considered using a hysteretic damping algorithm to model the reasonable dissipation of energyin the soil. The interface between the foundation and ground surface, including the material and geometricalnonlinearities, are used to capture any possible slide and uplift in the foundations. The results are presented withregard to the geotextile arrangement considered, and include the tensile force mobilised in the geotextile layers,the response spectra at the bedrock and ground surface, the shear force developed in the structure, the maximumrocking angle of the foundation, permanent foundation settlement, maximum lateral displacement and themaximum and residual inter-storey drifts. The results show that the geotextile layers close to the edges of thefoundation sustained most of the stress induced by foundation rocking, and the geotextile arrangement has asignificant influence on the seismic response of mid-rise buildings. Thus, to satisfy the seismic performance ofbuildings and to optimise the design of foundations reinforced with geotextiles, the stiffness, length, number andspacing of the geotextile layers sh...
Xu, R & Fatahi, B 2018, 'Geosynthetic-reinforced cushioned piles with controlled rocking for seismic safeguarding', Geosynthetics International, vol. 25, no. 6, pp. 561-581.View/Download from: UTS OPUS or Publisher's site
© 2018 2018 Thomas Telford Ltd. In this study, a cushioned pile foundation reinforced with geosynthetics is proposed to protect buildings and foundations from seismic energy. This composite foundation utilises piles to control foundation settlement while the geosynthetic-reinforced cushion modifies the dynamic structural characteristics and the load transfer mechanism. The seismic performance of this proposed foundation system is evaluated numerically using FLAC3D software. A fully coupled nonlinear dynamic analysis was conducted in the time domain. The variation of shear modulus corresponding to shear strains in the soil is used to simulate the dynamic behaviour of the soil, while the influence of the plasticity index is also captured. The soil-geosynthetic interface utilises the Mohr-Coulomb failure criterion to capture possible sliding and pull-out of the reinforcement layers. 3D numerical predictions of the tensile forces mobilised in the geosynthetic layers, the shear forces, the lateral deformations and maximum and residual inter-storey drifts in the building are presented and discussed in this paper, as well as how the shear forces and bending moments develop in the piles, and the lateral pile displacements. The results indicate that the proposed geosynthetic-reinforced cushioned pile foundation can provide design engineers with an alternative solution for safeguarding buildings constructed on soft soils in earthquake-prone regions. r2018 Thomas Telford Ltd.
Xu, R, Li, D & Fatahi, B 2017, 'Effects of Soil Stiffness on Seismic Response of Buildings Considering Soil-Pile- Structure Interaction', Proceedings of the 19th International Conference on Soil Mechanics and Geotechnical Engineering, 19th International Conference on Soil Mechanics and Geotechnical Engineering (19ICSMGE), Seoul, South Korea, pp. 1619-1622.View/Download from: UTS OPUS
In this study, a fifteen-storey moment resisting building sitting on an end-bearing pile foundation in soil socketed in rock is selected in conjunction with four values of shear wave velocity. Effects of corresponding shear strength are studied through numerical modelling using finite difference software FLAC3D. Fully nonlinear dynamic analysis under the influence of Northridge earthquake is performed. The results indicate that soil plasticity should be taken into account while conducting dynamic analysis considering soil-pile-structure interaction. However, the dynamic response of the structure regarding base shear, foundation slab rotation, pile lateral deflection and structure lateral deflection is sensitive to the effect of shear strength with the increase in shear wave velocity and corresponding shear modulus. Also, the results show that the dynamic response of structures sitting on end-bearing pile foundations depends not only on base shear attracted by the superstructure but also on the foundation slab rotation. Therefore, to perform realistic seismic analysis and to conduct reasonable seismic design of mid-rise building resting on end-bearing pile foundations, the consideration of foundation slab rotation is essential.
Xu, R, Fatahi, B & Li, D 2017, 'Effects of Soil Stiffness on Seismic Response of Buildings Considering Soil-Pile-Structure Interaction', The 19th International Conference on Soil Mechanics and Geotechnical Engineering, Seoul, Korea.View/Download from: UTS OPUS
Xu, R. & Fatahi, B. 2016, 'Influence of Soft Soil Shear Strength on the Seismic Response of Concrete Buildings Considering Soil-Structure Interaction', 4th GeoChina International Conference, Jinan, Shandong, China.View/Download from: UTS OPUS or Publisher's site
Xu, R, Fatahi, B & Hokmabadi, AS 2016, 'Influence of Soft Soil Shear Strength on the Seismic Response of Concrete Buildings Considering Soil-Structure Interaction', GeoChina International Conference 2016 Proceedings, GeoChina International Conference, AMER SOC CIVIL ENGINEERS, Jinan, Shandong, China.View/Download from: UTS OPUS or Publisher's site
Xu, R. & Fatahi, B. 2015, 'Three Dimensional Numerical Analysis of Seismic Soil-Structure Interaction Considering Soil Plasticity', 6TH INTERNATIONAL CONFERENCE ON EARTHQUAKE GEOTECHNICAL ENGINEERING, Christchurch, New Zealand.View/Download from: UTS OPUS
Xu, R & Fatahi, B 2015, 'Three Dimensional Numerical Analysis of Seismic Soil-Structure Interaction Considering Soil Plasticity', The New Zealand Geotechnical Society (NZGS), INTERNATIONAL CONFERENCE ON EARTHQUAKE GEOTECHNICAL ENGINEERING, The New Zealand Geotechnical Society (NZGS), Christchurch, New Zealand.View/Download from: UTS OPUS