Dynamic behavior of bridge columns reinforced with shape memory alloy rebar and UHPFRC under lateral impact loads

Abstract

This paper numerically evaluates the combined effect of ultra-high-performance fiber-reinforced concrete (UHPFRC) jacket and shape memory alloy (SMA) rebar on the dynamic response of a reduced-scale bridge pier under lateral impact loads of different velocities. The performance of the columns is assessed considering the variations of different parameters including the type of SMA rebars, thickness of UHPFRC jacket (tU), impact velocity (Vimp), and axial load ratio (ALR). From the FE simulations, it is found that the SMA rebars have a more positive influence on the lateral strength of the conventional columns with normal concrete (NC) compared to UHPFRC-strengthened columns when subjected to impact loadings at 5 m/s and 15 m/s velocities that represent relatively low- and medium-rate impacts, respectively. However, the positive effect of the SMA rebar is more pronounced on the resistance of UHPFRC-strengthened columns under a high-rate impact loading with Vimp = 25 m/s. In addition, a 60 mm-thick UHPFRC jacket is recognized as the optimal level based on the behavioral trend of the UHPFRC-strengthened columns when they are subjected to impact loads with velocities higher than 10 m/s (representing a medium-rate impact). From the evaluation of the effectiveness of ALR, an absolute positive influence of ALR on the impact resistance of the steel-reinforced columns is found when it ranges between 0.1 and 0.15. However, the increase of ALR beyond a critical value of 0.125 demonstrates a negative influence on the lateral strength of SMA-reinforced UHPFRC columns.