Cyclic Behavior of Fiber Reinforced Polymer-Encased Engineered Cementitious Composite for Bridge Columns

Abstract

This study is based on merging two promising materials to develop a new hybrid system. Engineered cementitious composites (ECC) allow optimization of the microstructure of the material to achieve ultra-high strength, ductility and fracture toughness. Studies during past two decades have also shown that fiber reinforced polymer (FRP) tubes can help eliminate the need for lateral steel reinforcement for confinement and shear in reinforced concrete (RC) columns, while also improving the flexural strength, ductility and energy dissipation. Analytical models were developed for several 1/6-scale bridge columns based on three different combinations of ECC, FRP tube and steel reinforcement. The models were simulated under constant axial load and reverse cyclic lateral loads. The results show a promising hybrid system, in which the FRP tube is filled with ECC only within the plastic hinge length and with conventional concrete for the remainder of the column. The proposed column does not have any lateral or longitudinal steel reinforcement, while performing the same as a typical RC bridge column. Furthermore, an experimental work has been designed and is already being carried out by the authors to validate the analytical simulation results. The study also focused on a series of uniaxial compression tests on FRP-confined ECC stub specimens with different fiber types and wrap thicknesses. The results showed that FRP confinement causes a significant enhancement in strength and ductility of FRP-confined ECC. Moreover, the study shows that the available confinement models for conventional concrete cannot predict the behavior of FRP-confined ECC columns.