Quasi-static test on seismic ductility of round-end hollow-section railway piers
Shao Changjiang1 Qi Qiming1 Wei Wang1 Hu Chenxu1 Wang Meng1 Xiao Zhenghao1 Xiao Laichuan1
1. School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China;
2. National Engineering Laboratory of Disaster Prevention Technology in Land Transportation, Southwest Jiaotong University, Chengdu 610031, China
Abstract：To investigate the ductile performance of round-end hollow-section railway piers in intensive seismic zone, five 1:6 scaled models were tested under low-cyclic loading. The damage behavior and plastic hinge evolution mechanism were analyzed, as well as the hysteretic performance, displacement ductility, strength/stiffness and equivalent damping ratio of the specimens with different design parameters. The quantification for seismic performance object was implemented using displacement ductility combined with damage assessment. The relationship between seismic performance objectives and strength/stiffness degradation was also established through the regression analysis of test data. Due to the existing models being not appropriate to evaluate the equivalent damping ratio of round-end hollow piers, a proposed model was regressed based on the test results. The experimental and analytical results show that all specimens have a flexural failure due to concrete spalling, buckling or fracture of longitudinal rebar at the region of solid-to-hollow section, and the flexural crack distribution nearly covers 0.61 to 0.75 of the pier height. The plastic hinge region is extended and moves up wholly due to the existing of solid-section part, the transition part of solid-to-hollow section and variable hollow-section. With the increase of stirrup ratio, the displacement ductility capacity is obviously improved. The increased axial load ratio can improve the flexural capacity to some extent, but excessive axial load will lead to decreasing ductility for premature concrete crushing. The pier is at medium damage state under the ductility factor limitation of 4.8 in the current seismic code of railway engineering, which indicates seismic safety of piers designed using the code.
