Quasi-static test of the gravity railway bridge pier with a novel preventative seismic strengthening technique

Abstract

A superior seismic strengthening technology should be not only secure and reliable, but also economical and feasible for the widespread structures. In China, the gravity pier with low longitudinal steel ratio has been widely used in railway bridges, and most of them have insufficient seismic performance due to limited technological level in the early days. In this study, a novel preventive seismic strengthening technology with steel grid by planting and welding measures was presented for gravity railway bridge pier with flexural failure modes. Five 1/8-scale piers, including two different reference piers and three strengthening piers, were fabricated and tested through quasi-static test. It was shown that the piers exhibit uplifting and swaying behaviors due to highly-centralized crack at pier-footing region under lateral loading. The strengthening using steel gird led to a reduction up to 50% in residual displacement approximately, which was effective to prevent collapse of piers. The strengthening piers exhibited an enhanced the load-carrying capacity and cumulative dissipated energy by 120% to 150%, compared to the pier without strengthening. Moreover, the initial stiffness and cracking load of strengthening piers also were improved where the maximum increment was 1.5 times. The effect of strengthening thickness on strengthening efficiency was more significant than that of strengthening height. Therefore, it could be concluded that the seismic strengthening technology, by steel grid with reasonable arrangement at the pier bottom region, are suitable for gravity railway bridge pier with low longitudinal steel ratio in seismic zones.