Longitudinal shear performance of continuous steel-coarse and fine recycled aggregate concrete composite slabs

Steel-concrete composite slabs are the preferred members for structural applications involving recycled aggregate concrete (RAC). However, the impacts of coarse/fine recycled aggregate (CRA/FRA) and sustained loading history on the longitudinal shear behavior of continuous-span slabs have not been investigated. To address this, three continuous steel–recycled aggregate concrete composite slab (SRACCS) specimens (3 m × 2 span) were tested. The failure modes, load-deflection responses, load-slip curves, and sectional strain distribution were analyzed. A finite element model (FEM) accounting for the bond-slip performance was developed and subsequently validated using experimental results and literature databases. Finally, the applicability of the calculation methods for the simply supported SRACCS to continuous SRACCS was verified using FEM results. The results demonstrate that: (1) using CRA and FRA leads to an 11.2% lower ultimate load and a 9.9% lower initial stiffness in continuous composite slabs compared to natural aggregate concrete (NAC) specimens; (2) sustained loading history can increase the initial stiffness of continuous composite slabs by 20.1% while reducing their ultimate load by 10.0%; (3) the established FEM can effectively predict the load–deflection response of SRACCS, and (4) the calculation methods for simply supported SRACCS exhibit sufficient conservatism when applied to continuous SRACCS. These outcomes serve as a theoretical reference for applying RAC to continuous composite slab engineering.