Influence of Size and Load-Bearing Mechanism of Piles on Seismic Performance of Buildings Considering Soil–Pile–Structure Interaction

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 (frictiona...

Influence of Foundation Type on Seismic Performance of Buildings Considering Soil–Structure Interaction

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 shallow foundation influences the dynamic characteristics and the seismic response of the building due to interaction between the soil, foundation, and structure, and therefore design engineer should carefully consider these parameters in order to ensure a safe and cost effective seismic design.

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The effects of foundation size on the seismic performance of buildings considering the soil-foundation-structure interaction

Parametric study for optimal design of large piled raft foundations on sand

Generalized Nonlinear Softening Load-Transfer Model for Axially Loaded Piles

Design method of piled-raft foundations under vertical load considering interaction effects

In the design of piled raft foundations, the control of total and differential settlements is crucial. On the basis of centrifuge tests, this study presents the feasibility of a fairly optimal pile arrangement scheme for reducing total and differential settlements. Two models of piled raft foundations having the same flexible raft and number of piles, the uniform pile arrangement model and the concentrated pile arrangement model, and one model having a rigid raft with a concentrated pile arrangement were designed for centrifuge tests. The settlements of three rafts of the piled raft models and the induced bending moments of two flexible rafts were measured during the load application process. The measured results were compared between the tests to illustrate the ability of the concentrated pile arrangement scheme in reducing total and differential settlements, as well as induced bending moment. Moreover, three piled rafts were simulated by the Plaxis 3D Foundation software package to calculate the...

Settlement of Piled Rafts with Different Pile Arrangement Schemes via Centrifuge Tests

Mononobe-Okabe (M-O) theory is widely used for evaluating seismic earth pressure of retaining wall. It was originally developed for gravity walls, which have rigid behavior, retaining cohesionless backfill materials. However, it is used for cantilever retaining wall on the various foundation conditions. Considering only inertial force of the soil wedge as a dynamic force in the M-O method, inertial force of the wall does not take into account the effect on the dynamic earth pressure. This paper presents the theoretical background for the calculation of the dynamic earth pressure of retaining wall during earthquakes, and the current research trends are organized. Besides, the discrepancies between real seismic behavior and M-O method for inverted T-shape retaining wall with 5.4m height subjected to earthquake motions were evaluated using dynamic centrifuge test. From previous studies, it was found that application point, distribution of dynamic earth pressure and M-O method are needed to be re-examined. Test results show that real behavior of retaining wall during an earthquake has a different phase between dynamic earth pressure and inertial force of retaining wall. Moreover, when bending moments of retaining wall reach maximum values, the measured earth pressures are lower than static earth pressures and it is considered due to inertial effects of retaining wall.

Seong-Bae Jo

Papers

Design method of piled-raft foundations under vertical load considering interaction effects

Parametric study for optimal design of large piled raft foundations on sand

Settlement of Piled Rafts with Different Pile Arrangement Schemes via Centrifuge Tests

A Case Study of Evaluating Inertial Effects for Inverted T-shape Retaining Wall via Dynamic Centrifuge Test

Effect of wall flexibility on the dynamic earth pressure for cantilevered retaining wall