Numerical investigation of the cyclic behavior of UHPC piers with Titanium alloy reinforcement bars based on distributed plasticity model

Traditional reinforced concrete (RC) structures are commonly susceptible to corrosion from diverse environmental factors such as salts, chlorides, carbonation, humidity, etc., leading to a continuous degradation which may comprise their designed service life (reduced durability). Moreover, the monitoring and maintaining corroded RC bridges is laborious and expensive. Recently, the use of titanium alloy bars (TiABs) in ultra- high-performance concrete (UHPC), namely TARUHPC, has been proposed as an alternative to increase the durability of RC structures in seismic regions, aiming for a service life exceeding 100 years. Some material and large-scale experimental tests have been conducted on TARUHPC bridge elements; however, their seismic performance and failure modes are not yet fully characterized, limiting the practical utilization of TARUHPC. This paper investigates numerically the cyclic behavior and seismic performance of TARUHPC bridge piers. To this end, detailed nonlinear Finite element (FE) models with distributed plasticity were used to assess the seismic performance of large-scale bridge specimens considering three combinations: (1) normal concrete with TiABs (NC-TI), (2) UHPC with conventional steel (U-TI), and (3) UHPC with TiABs(U-TI). These specimens were investigated by displacement-based, fiber-element models whose parameters were calibrated by model-updating between the models and experimental cyclic test results. The FE models were validated against experimental cyclic tests, previously reported by the authors. The numerical models were accurate in representing the hysteretic behavior, lateral strength, displacement capacity, strength degradation, and energy dissipation of the test specimens; nonetheless, these models showed some discrepancies in capturing bond-slip effects in some specimens. A parametric analysis was also conducted to explore the influence of some design parameters (e.g. reinforcement ratio, axial load level, etc.) on the deformation capacity and energy dissipation of TARUHPC.