Local Strain-Based Low-Cycle Fatigue Assessment of Joint Structure in Steel Truss Bridges During Earthquakes

Abstract

During the 2011 Tohoku Earthquake, a truss bridge joint structure was cracked due to large cyclic deformation, making us recognize the importance of assessing the seismic performance of joint structures in truss bridges from the viewpoint of low-cycle fatigue. In this study, seismic response analysis of an actual deck truss bridge was performed under different seismic waves, and local strain behavior generated at welded joints around a joint structure was clarified using a zooming analysis technique. The results revealed the possibility that welded joints for a lateral gusset-plate in a joint structure can be cracking sites during earthquakes. In addition, it was indicated that seismic isolation bearings can significantly reduce the local strain at the joint structure and improve its low-cycle fatigue performance. Moreover, as a simple countermeasure, weld toe treatment by grinding is also effective to decrease the possibility of low-cycle fatigue cracking at the joint structure.