Seismic Assessment and Strengthening Effectiveness of RC Frame Structures with Concrete Cover and Detailing Deficiencies: Field Evidence and Parametric Numerical Analyses

Abstract

While concrete cover is conventionally evaluated for durability and corrosion protection in reinforced concrete (RC) elements, its critical role in concrete-reinforcement bond efficiency, mechanical core confinement, and overall structural ductility during seismic action is often overlooked. Insufficient cover thickness, often stemming from poor site practices, significantly impairs force transfer and increases susceptibility to premature, brittle shear failure under intense lateral loading. The study presents the damage evaluation results of RC columns with insufficient concrete cover thickness following the 6 February 2023 Kahramanmaraş earthquakes. Pushover analyses were performed for ten different numerical models created for this purpose. The effects of insufficient concrete cover thickness, especially on shear force, were examined, and structural models with insufficient shear-force capacity were reinforced with fibrous polymer and RC jacketing. In Model III, where insufficient concrete cover thickness was considered in all ground-floor columns, the performance ratio (defined as the demand-to-capacity ratio, D/C) increased to 1.47, exceeding the shear capacity of these columns. The shear force was exceeded in columns with insufficient concrete cover thickness, and the capacity exceedance was eliminated with the applied reinforcement method. This study is especially important to reveal the reinforcement requirements of columns with insufficient concrete cover thickness in existing RC structures.