Effect of steel grid on enhancing seismic performance of bridge pier with low reinforcement ratio: Shaking table test and numerical simulation

Abstract

The railway bridge piers with large cross section and low reinforcement ratio are easy to damage under earthquakes in China. The steel grid has been proved to be an effective strengthening method to improve the cyclic behavior using quasi-static test. In this study, shaking table tests were conducted to investigate the seismic response of three pier specimens. Experimental results indicated that the steel grid delayed the crack development and occurrence of uplifting-rocking phenomenon for the railway pier. For strengthened piers, about 7.5%-51.4% reduction, 9.1%-21.9% and 7.6%-27.4% enhancement is measured for displacement of pier top, acceleration of pier top and energy dissipation. To obtain the effect of design parameter variation of steel grid on seismic damage (i.e., the horizontal distance between steel grid and the surface of pier specimen, steel grid area and vertical spacing of steel grid), the numerical analysis mode of strengthened pier was established. The mechanical model of steel grid obtained by deriving the equivalent spring calculation method is used in the numerical simulation model. The results show that the horizontal distance variety between steel grid and surface of pier specimen has the most obvious impact to strengthening effect, while the vertical spacing of steel grid is the least. The smaller horizontal distance between steel grid and the surface of pier specimen, the higher steel grid area and shorter vertical spacing of steel grid are the most significant to reduce the different damage probability of the bridge pier.