Effect of concrete strength and detailing properties on seismic damage for RC structures

This study investigates the effects of concrete strength, lateral reinforcement detailing and design code on the seismic performance of reinforced concrete (RC) buildings representative of existing residential structures. A total of 48 nonlinear inelastic models of 2, 4, and 7 storey buildings, designed per the 1975 and 1998 Turkish seismic codes, were analyzed using nonlinear static and dynamic methods. Capacity curves were obtained through inelastic static analysis, while displacement demands were calculated for 264 ground motion records using nonlinear dynamic analysis. The exceedance ratios of performance levels—Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP)—were determined based on these demands. The findings reveal that the IO performance level is minimally affected by variations in material properties and detailing, as it primarily depends on structural strength. Paradoxically, in low-rise buildings, increased concrete strength and reinforcement can lead to higher IO exceedance ratios due to increased longitudinal reinforcement elongation at lower curvature values. The damage rate was found to be high in 4-storey buildings designed under the 1975 code showing higher exceedance ratios than 7-storey buildings due to relatively weaker structural systems and construction practices. In contrast, buildings designed per the 1998 code exhibited significantly lower exceedance ratios, highlighting the effectiveness of modern seismic design standards. The results underscore the importance of seismic detailing and retrofitting older buildings to improve resilience. This study may provide insights into the seismic behavior of RC buildings, offering guidance for structural engineers and policymakers in enhancing building safety.