Cyclic Behavior of FRP Concrete Bridge Pier Frames

Abstract

Concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs) were initially developed without any internal steel reinforcement as viable alternatives to conventional RC columns in nonseismic regions. Studies have shown that extending CFFT application to seismic regions requires a moderate amount of internal steel reinforcement. To date, cyclic performance of CFFTs as part of a structural frame has not been assessed. This paper describes testing of four one-sixth-scale two-column bents: a control RC, a glass FRP-concrete frame (GFF), a carbon FRP-concrete frame (CFF), and a hybrid glass/carbon FRP-concrete frame (HFF). Each frame was tested under reverse cyclic lateral loading with a constant axial load. Specimen HFF with hybrid FRP tubes demonstrated the highest moment capacity and initial stiffness, with an increase of 200 and 70%, respectively, over the control specimen. Specimen GFF showed no sign of cracking up to a drift ratio of 15% with considerable residual strength, whereas specimen CFF had the least ductility. Glass FRP tubes extended the plastic hinge length of the pier columns to twice that of the control RC frame.