NONLINEAR STATIC CALCULATION MODEL AND PSEUDO-STATIC TEST OF PILE GROUP BRIDGE FOUNDATIONS
ZHANG Yongliang1，2，CHEN Xingchong2，SUN Jianfei2
(1. Key Laboratory of Road and Bridge and Underground Engineering of Gansu Province，Lanzhou Jiaotong University，Lanzhou，Gansu 730070，China；2. School of Civil Engineering，Lanzhou Jiaotong University，Lanzhou，Gansu 730070，China)
Abstract：Horizontal bearing characteristics of bridge pile foundations can be analyzed by using linear elastic subgrade reaction method(m-method) when displacement of pile foundation is generally smaller. However，displacement of pile foundations is often larger under the effect of strong earthquakes. In order to understand the horizontal bearing capacity and deformation characteristics of pile foundations considering nonlinear behaviors of pile shaft and subsoil，a model of pile foundations is constructed. Failure mechanism，bearing capacity，deformation characteristics and hysteresis characteristics of pile foundations are studied by using pseudo-static test. A nonlinear static calculation model of pile group foundations is put forward under horizontal load. The elastoplasticity of pile shafts in variable axial loads is simulated by distributed PMM plastic hinge；and nonlinearity of subsoil is simulated by the curves of p-y，t-z and q-z，respectively，which have been given in the code of American API；where p is horizontal soil resistance at lateral of pile shaft；y is horizontal displacement；t is vertical frictional resistance around piles shaft；q is vertical bearing resistance at pile tip；z is vertical relative displacement of interface between pile and soil. The results show that：(1) The numerical results are in good agreement with those obtained from experiments. (2) Hysteretic characteristics of pile foundations can be simulated using Clough degradation bilinear model. (3) Weak positions of pile shaft are 0–4 times around the radius of pile below pile top. The results can provide references for evaluating seismic performance of bridge pile foundation using capacity spectrum method.
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2013, Vol. 32 
