Experimental Evaluation of the Influence of Titanium Alloy Bars on the Seismic Performance of Cast-in-Place Normal Concrete and Ultrahigh-Performance Concrete Bridge Piers

Traditional reinforced concrete (RC) bridges are known to be susceptible to corrosion from diverse environmental factors such as salts, chlorides, carbonation, and humidity. This deterioration, if not adequately corrected, can compromise the intended service life and/or safety of existing bridges. For this reason, recent research has focused on applying advanced composite materials to RC bridges to improve their durability. This paper experimentally evaluates the cyclic behavior and seismic performance of titanium alloy bar–reinforced ultrahigh-performance concrete (TARUHPC) bridge piers. This construction technology, which uses titanium alloy bars (TiABs) in place of traditional steel bars for reinforcing ultrahigh-performance concrete (UHPC), aims to increase the durability of RC bridges in seismic regions. Different large-scale bridge piers were tested under cyclic loads to evaluate their failure modes and deformation capacity. A total of four specimens with different material combinations were tested: (1) normal concrete with normal steel, (2) normal concrete with TiABs (NC-TI), (3) UHPC with conventional steel, and (4) UHPC with TiABs (U-TI). All specimens were subjected to a constant axial load, and quasi-static, displacement-controlled loads were applied until failure or significant strength degradation was noted. It was noted that the addition of TiABs significantly reduced the residual deformation in bridge piers with both normal concrete and UHPC. Nevertheless, the use of normal concrete limited the yielding of TiABs for the pier NC-TI, owing to the limited concrete compression capacity. Moreover, the addition of UHPC reduced the cracking and overall damage at the bottom section of piers, thus increasing the deformation capacity. However, it was noted that the foundation should also be cast with UHPC to avoid local damage at the pier–foundation interface. From all the specimens, U-TI (TARUHPC) showed the largest strength and deformation capacity (ductility at failure of above 15.0) with low residual deformations; however, it showed lower damping than Specimen U-NS, which was attributed to the fact that TiABs incurred in less limited deformations.