Seismic performance of underwater RC bridge piers strengthened with self-compacting concrete-filled BFRP jacket

This paper presents an experimental study on underwater bridge columns strengthened with a combination of basalt fiber-reinforced polymer (BFRP) jacket and enlarging sectional area by filling self-compacting concrete. Due to the strengthening demand of underwater bridge column without cofferdam, the newly method was developed through using BFRP to make formwork jacket (namely BFRP jacket), and filling non-dispersible underwater concrete between the pier and BFRP jacket. Three circle bridge column specimens were manufactured and tested under lateral reserved cyclic loads along with a constant axial load. The seismic behavior of a specimen with ordinary agent and the other one with micro-expansion agent was compared, and the remaining one was used as the reference specimen. A finite element model was developed to study the effect of BFRP height, concrete strength grade and BFRP layer numbers on seismic performance of the columns strengthened with BFRP jacket. The retrofitting procedure of the BFRP jacket method was proved to be feasible and efficient through the experiments. The experimental results indicate that the ultimate load capacity and energy-dissipation capacity can be significantly enhanced, whereas the deformation capacity and displacement ductility exhibit little improvement of the columns strengthened with the BFRP jacket, and the seismic performance of the reinforced piers e.g. energy-dissipation capacity and ductility can also be improved in a certain extend by adding microexpansion agent. The finite element parameters analysis indicate that the seismic performance of piers can be effectively improved by strengthening in the plastic hinge zone, the increase of filler concrete strength has little effect on the seismic performance, and it is viable to use the 6-layer BFRP clothes to make BFRP jacket for the testing bridge column specimen.