Peak load prediction and interface behavior analysis of steel–ECC composite slabs: Experiments, simulations and theoretical models

Steel–concrete composite structures are widely used in bridges, industrial facilities, and nuclear containments. Due to its excellent ductility and mechanical properties, engineered cementitious composites (ECC) have strong potential for application in steel–concrete composite systems. This study conducts push-out tests on steel–ECC specimens and static loading tests on steel–ECC composite slabs. The results show that ECC significantly enhances the interface shear resistance, improves the ductility of the slabs, and increases the second peak load. Specifically, the ECC slabs exhibit a second peak load approximately 54.7 % higher and a ductility improvement of about 53.8 % compared with the normal concrete slabs. Through experimental observations, the failure mechanism and failure modes of steel–ECC composite slabs were analyzed. A finite element model was developed to investigate the interface failure process and plastic energy of the slab, which served as the basis for establishing a theoretical interface model and slab model. Finally, based on theoretical analysis and simulation results, a calculation method was proposed for predicting the first and second peak loads of steel–ECC composite slabs, incorporating the effect of interface slip. This model enables a more accurate assessment of load-bearing capacity, offering theoretical support for the safe and efficient design of ECC-based steel–concrete composite structures.