Seismic Performance of RCS Frame with Slab: Numerical Simulation and Damage Analysis

While reinforced concrete column–steel beam (RCS) joints are well-studied, the seismic performance of RCS frames incorporating floor slabs remains inadequately explored. This study extends previous experimental findings, developing and validating an OpenSees finite element model of an RCS frame with slabs against test data. The model accurately replicated hysteretic responses, with peak load and ductility errors within 5%. A parametric study quantified the effects of the axial compression ratio, concrete strength, beam flange/web thickness, and shear span ratio. The results demonstrate that increasing the concrete strength from C40 to C70 boosted the lateral bearing capacity by 45.45%. In contrast, a higher axial compression ratio increased the initial stiffness but accelerated the subsequent stiffness degradation. Furthermore, recalibrating the energy dissipation coefficient ( β ) in the Park–Ang damage model yielded an excellent correlation ( R 2 = 0.994) between the simulated and experimental cumulative damage indices, providing a refined tool for seismic damage assessment.