Flexural performance of cold-formed ∩-shaped steel–lightweight aggregate concrete prefabricated composite beams

To improve construction efficiency and maintenance access in steel–concrete composite bridges, in this study, a prefabricated system is proposed using cold-formed ∩-shaped steel girders and lightweight aggregate concrete (LWCC) slabs. Four-point bending tests were conducted to compare the flexural performance of the proposed beam against a conventional composite beam. Key parameters, including failure modes, load capacity, stiffness and the performance of ultra-high-performance concrete (UHPC) wet joints with an anchorage length of 10d (where d is the bar diameter) were investigated. Experimental results show that the ∩-shaped steel–LWCC system achieves competitive structural performance. Specifically, the cracking load increased significantly by 31.7%, while ultimate load and flexural stiffness showed modest improvements (approximately 4%) compared to the conventional beam. Minimal interfacial slip confirmed reliable composite action, and the ∩-shaped configuration effectively reduced shear lag. The UHPC joints remained intact, ensuring monolithic behaviour. The system’s practical feasibility was validated through successful implementation in a bridge project. This study demonstrates that the novel system offers enhanced constructability, reduced self-weight and improved inspectability for prefabricated bridge applications.