Seismic Performance of Underwater Bridge Columns Strengthened with Prestressed-Concrete Panels and FRP Reinforcement

Abstract

This paper presents an experimental study on the seismic performance of underwater bridge columns retrofitted with the combination of prestressed precast concrete panels (PPCP) and embedded fiber-reinforced polymer (FRP) reinforcements (PPCP-FRP). A newly developed retrofitting method with PPCP-FRP and the corresponding retrofitting processes were conceived based on the specific demands for underwater bridge columns. Traditional steel strands were placed outside the PPCP to connect the panels in a ring configuration and offset premature failure of the panels during an earthquake. Due to the potentially corrosive environment, the steel strands were designed to be easily replaced underwater, and the FRP reinforcement was set inside the PPCP to ensure a long-term service. A total of six 1/4-scale circular bridge column specimens were fabricated. Five specimens were strengthened either with different strengthened lengths of PPCP-FRP or with different types and reinforcement ratios of longitudinal FRP bars, and the remaining specimen was used as the control specimen. The retrofitting procedure of the PPCP-FRP method was verified as viable and efficient through experimentation. All column specimens were tested under reversed cyclic lateral loading along with a constant axial load. The load capacity, stiffness, ductility, and energy-dissipation capacity of the columns were significantly improved through strengthening. In addition, a more uniformly distributed column curvature and a reduced residual displacement were obtained for the strengthened columns, indicating enhanced repairability. A sufficient strengthening length and FRP reinforcements with a lower elastic modulus and higher ultimate strain are recommended during the retrofitting design with PPCP-FRP.