Local bearing capacity calculation model for UHPC-CA considering reinforcement and steel fiber confinements

The incorporation of coarse aggregates reduces the cost and shrinkage in UHPC, while introducing more interfaces in the matrix, resulting in the more complicated local bearing behavior. This work investigated the local bearing capacity (LBC) of coarse aggregate blended UHPC (UHPC-CA) and developed a unified LBC prediction model considering multiple key parameters. A database containing 208 sets of data was established, covering strength, local area aspect ratio, steel fiber volume fraction, reinforcement volumetric ratio, etc as the variables. The proposed calculation method primarily included the following aspects: (1) the weakening effects of reduced transverse expansion capacity caused by increased concrete strength on LBC; (2) the synergistic effects of steel fibers and reinforcements on the LBC of UHPC-CA; (3) the estimation method for the actual tensile stress of reinforcement under ultimate load; (4) the reasonable anchorage method for orthogonal reinforcements. The proposed LBC calculation method was validated against existing standard formulas, demonstrating superior prediction performance, and providing new insights into the theoretical and practical application of UHPC-CA in engineering.