The Effect of Different Slab Types on Seismic Performance in Reinforced Concrete Structures: A Comparison of Beam-Slab and Ribbed Slab Systems

Due to Türkiye’s location in an active seismic zone, the safe design of load-bearing systems in reinforced concrete buildings is essential. Under seismic effects, factors such as plan aspect ratio, slab type, and soil class directly influence the structural behavior, including building stiffness, diaphragm action, and lateral load transfer. In this study, a total of 12 reinforced concrete building models were analyzed using the STA4CAD software in accordance with the Turkish Building Earthquake Code (TBEC-2018), considering three key parameters: slab system (beam-slab and two-way ribbed slab), plan aspect ratio (1 and 4), and soil class (ZB, ZC, ZD). The models were evaluated in terms of natural periods, modal mass participation ratios, base shear forces, inter-story drifts, and second-order effects. Additionally, concrete, formwork, and reinforcement quantities were compared. The results indicated that as the soil class deteriorates, the demand for shear walls increases, which in turn shortens the natural periods by increasing stiffness. It was found that ribbed slab systems exhibit lower lateral stiffness and result in greater displacements and longer periods compared to beam-slab systems. Moreover, buildings with ribbed slabs required approximately 18–22% more reinforcement. Increasing the plan aspect ratio to 4 significantly increased the displacement in the weak direction and the need for shear walls. The findings highlight that slab type, soil class, and plan geometry collectively play a decisive role in seismic performance.