Numerical Investigation of the Bond-Slip Behavior Between Ultra-High- Performance Concrete and Titanium Alloy Bars

Conventional reinforced concrete (RC) structures (composed of steel and concrete) are usually designed for a service life of around 50 years, but they are susceptible to corrosion from various environmental agents (salts, chlorides, carbonation, humidity, etc.) which overtime may compromise their expected service life. Recently, the use of titanium alloy bars (TiABs) in place of traditional steel rebars for reinforcing and Ultra-High Performance Concrete (UHPC) has been proposed as an attractive construction method (TARUHPC) to increase the durability of RC structures in seismic regions. Although some element and sub-assembly tests on TARUHPC have been conducted, its bond behavior is still not fully characterized. This paper extends previous experimental efforts by investigating numerically the bond behavior between TiABs and UHPC. Detailed nonlinear Finite element (FE) models were used to assess the pull-out strength of TARUHPC specimens. For comparison, the pull-out strength of specimens with normal concrete (NC) and TiABs was also evaluated. In order to consider realistic assumptions, the interaction and bond between concrete and rebar was simulated using the cohesive zone modeling method, whose parameters were obtained by model-updating between the FE models and the experimental pull-out test results. The FE models were validated against the experimental pull-out tests and the models were able to capture adequately the bond-slip behavior, bond strength, and failure modes of test specimens. A parametric analysis was conducted for some parameters such as bar diameter, and embedment length. Based on the results, some design recommendations for TARUHPC are provided.