Nonlinear Behavior and Simulation of Concrete Columns Reinforced by Steel-FRP Composite Bars

Abstract

Steel-fiber-reinforced polymer (FRP) composite bars (SFCBs) have been proposed as a new form of reinforcement for concrete structural elements, such as bridge columns. SFCBs have high initial elastic stiffness provided by the inner steel bars before yielding, positive postyield stiffness owing to the outer FRP after the inner steel bars yield, and superior anticorrosion performance. Furthermore, the postyield stiffness of SFCBs can be fully tailored by changing the steel-to-FRP ratio. Consequently, concrete columns reinforced by SFCBs have exhibited good initial stiffness and stable postyield stiffness experimentally. One potential benefit of the stable and designable postyield stiffness exhibited by SFCB-reinforced columns is to reduce the residual displacement, which is a vital index for evaluating the postearthquake recoverability of bridges. In this paper, the mechanical properties of SFCBs and pushover behavior of concrete columns reinforced by SFCBs are first simulated numerically and validated with experimental results. The influence of FRP types is further evaluated in terms of column deformation capacity. Concrete columns reinforced by steel-basalt FRP composite bars (SBFCBs) demonstrate a better performance-to-cost ratio than that of steel-carbon FRP composite bars (SCFCBs). Nonlinear dynamic analyses of SFCB columns are subsequently conducted under a suite of near-fault ground motions with noticeable acceleration and velocity pulses. The numerical results show that the residual displacement is closely correlated with the peak ground velocity (PGV) and that it decreases with an increase in the postyield stiffness ratio