Experimental study on longitudinal seismic damage progress and failure mode of a three-tower extradosed bridge

Abstract

To understand the longitudinal seismic damage progress and failure mode of extradosed bridges, an experimental investigation was conducted on a 1/20 scaled shake table test model. Detailed design of the test model is firstly introduced. During the experimental investigation, the test model was longitudinally subjected to the site-specific artificial ground motion with the peak ground acceleration (PGA) ranging from 0.1 g to 1.5 g. Test results show that the seismic damage progress of the extradosed bridge could be categorized into four stages: (1) No damage (PGA = 0.1 g − 0.3 g); (2) Mild damage (PGA = 0.4 g − 0.6 g); (3) Moderate damage (PGA = 0.7 g − 1.2 g); (4) Severe damage (PGA = 1.3 g − 1.5 g). The bottom and top regions of four-column piers are earthquake-vulnerable regions, while short towers are not. The failure mode of the test model could be characterized by buckling of the rebar and crushing of the core concrete at the bottom region of four-column piers. Moreover, unlike conventional cable-stayed bridges, the longitudinal deformation of the short tower is quite small in each loading case, and the residual longitudinal displacement of the test model is negligible after the whole tests.