Near-fault directivity pulse-like ground motion effect on high-speed railway bridge

CHEN Ling-kun(陈令坤)^{1, 2, 3, 4}, ZHANG Nan(张楠)¹, JIANG Li-zhong(蒋丽忠)^{3, 4}, ZENG Zhi-ping(曾志平)^{3, 4}, CHEN Ge-wei(陈格威)⁵, GUO Wei(国巍)^{3, 4}

(1. School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China;
2. College of Civil Science and Engineering, Yangzhou University, Yangzhou 225127, China;
3. School of Civil Engineering, Central South University, Changsha 410075, China;
4. National Engineering Laboratory for High-Speed Railway Construction (Central South University),
Changsha 410075, China;
5. Department of Civil and Environment Engineering, University of Auckland, Auckland 1142, New Zealand)

Abstract:The vehicle-track-bridge (VTB) element was used to investigate how a high-speed railway bridge reacted when it was subjected to near-fault directivity pulse-like ground motions. Based on the PEER NAG Strong Ground Motion Database, the spatial analysis model of a vehicle-bridge system was developed, the VTB element was derived to simulate the interaction of train and bridge, and the elasto-plastic seismic responses of the bridge were calculated. The calculation results show that girder and pier top displacement, and bending moment of the pier base increase subjected to near-fault directivity pulse-like ground motion compared to far-field earthquakes, and the greater deformation responses in near-fault shaking are associated with fewer reversed cycles of loading. The hysteretic characteristics of the pier subjected to a near-fault directivity pulse-like earthquake should be explicitly expressed as the bending moment-rotation relationship of the pier base, which is characterized by the centrally strengthened hysteretic cycles at some point of the loading time-history curve. The results show that there is an amplification of the vertical deflection in the girder’s mid-span owing to the high vertical ground motion. In light of these findings, the effect of the vertical ground motion should be used to adjust the unconservative amplification constant 2/3 of the vertical-to-horizontal peak ground motion ratio in the seismic design of bridge.

Key words:element; near-fault ground motion; directivity pulse; high-speed railway bridge; earthquake response