Seismic Analysis of Geosynthetic-reinforced Soil (GRS) Bridge Abutments with Modular Block Facing

Abstract

The response of Geosynthetic Reinforced Soil (GRS) bridge abutments to earthquake loading remains a concern despite their great success under static loads. In order to advance and implement this new technology, especially in seismically active regions, this study was undertaken to examine the performance of GRS bridge abutments under seismic loads in a rational and critical manner. This research is focused on single span, simply supported bridges. The current seismic design methods, including pseudo-static and displacement methods, are not specifically developed for GRS bridge abutments where the foundation of the bridge superstructure is placed on the top surface of the GRS abutment and generally is subjected to large, sustained and often eccentric loads. This study is aimed to predict the seismic behavior of GRS bridge abutments with modular block facing. The full scale seismic GRS bridge abutment experiment was simulated using finite element program LS-DYNA. A series of laboratory testing of the materials were carried out to obtain results which assisted in determining the material model parameters used to represent the behavior of the components of the GRS bridge abutment system in the finite element model. The lab experiments and the process of determining material parameters are presented in detail. The results of the shake table test and finite element model were compared and a good agreement was found between experimental and finite element results. The validated finite element model was used to perform rigorous parametric analyses on the GRS abutments subjected to various earthquake loadings. In the parametric analysis the influence of soil friction angle, geotextile stiffness, geotextile spacing and bridge height as design variables were investigated. The response of the model abutment including the maximum and permanent lateral displacement of the wall, sill and bridge, displacement of the sill relative to facing and also maximum acceleration of the wall and bridge were investigated. Also a three dimensional finite element model of a GRS abutment bridge system was created to study the seismic behavior of the full scale structure subjected to earthquake loading in both longitudinal and transverse directions. The parametric analysis performed in the present study indicated that GRS abutments can withstand large earthquakes without exerting excessive stresses on the bridge superstructure.