Experimental study on mechanical behavior of precast large-cantilevered UHPC bent caps with π-shaped cross-sections

To reduce the self-weight of the precast bent caps with large cantilevers commonly used in municipal bridge construction, an innovative thin-walled bent cap scheme made of ultra-high-performance concrete (UHPC) was proposed in this paper. Six scaled bent cap specimens, characterized by a scale ratio of 1:2.5, were subjected to static loading tests, encompassing both bending-shear and bending-shear-torsion combinations. Throughout the loading process, careful observations were made regarding the progressive development of crack patterns, stress distribution within various materials, and the identification of ultimate failure modes. It was observed that for the UHPC cap beams with small shear span-to-depth ratios, both the web shear cracks and flexural cracks were fully developed, leading to a combined shear and bending failure mode. With shear span-to-depth ratio increased, the effect of bending behavior became more and more dominate, resulting in an increased ductility. When subjected to a combined bending-shear-torsion loading, the UHPC bent caps exhibited conspicuous diagonal shear failure attributes, indicating that the torsion presented in the bent caps should be limited. In summary, the adoption of a pi-shaped section for the UHPC bent caps with large cantilevers results in an impressive weight reduction of 40%similar to 50% compared to the conventional solid cap beam design. Moreover, the proposed design not only aligns with specifications in terms of cracking strength and ultimate bearing capacity but also facilitates monolithic precast, making it exceptionally well-suited for practical engineering applications.