Experimental investigation on seismic retrofit of gravity railway bridge pier with CFRP and steel materials

•Seismic retrofit of gravity bridge pier with low reinforcement ratio is investigated.•Retrofitting techniques by the use of CFRP wrapping and bonded-steel are provided.•Bottom-anchoring system with planted steel bars and new concrete jacket are presented.•Seismic response of retrofitted piers is studied by quasi-static test of scaled model. Seismic retrofit is a cost-effective sustainable approach to strengthen older deficient bridges or repair damaged bridges, in seismic zones. The steel and CFRP materials could be used to retrofit gravity railway bridge pier with low longitudinal steel ratio, in China. Quasi-static tests for 1/8-scale model piers of a widely-used type of gravity railway bridge pier applied in quake-prone region of China were performed to evaluate the seismic performance before and after retrofitting. It was found that the gravity bridge pier with low longitudinal steel ratio was vulnerable at the pier-footing region and exhibited inadequate ductility under lateral cyclic loading. After retrofitting by the CFRP wrapping and bonded-steel, the load-carrying capacity of the bridge pier was enhanced by more than 100%. Moreover, the anchorage system with the planted steel bar and new concrete jacket on the column, above the footing, can relocate the fracture region of the retrofitted pier. The hysteretic behaviors indicated that the energy dissipation of retrofitted piers can be improved due to the deformation or failure of the wrapped-CFRP and bonded-steel during earthquake. Therefore, it can be concluded that seismic retrofitting techniques by the use of CFRP and steel materials are effective for the gravity railway bridge pier with low longitudinal steel ratio in China.