Structural Performance of Old One-Way RC Slabs Reinforced with Smooth Bars Strengthened Using Galvanized Flat and Corrugated Steel Sheets and Near-Surface Mounted Steel Bars: Experimental, Numerical, and Analytical Investigation

A large number of existing reinforced concrete (RC) slabs reinforced with smooth steel bars suffer from weak bond characteristics, reduced stiffness, and inadequate flexural capacity, creating a need for effective and sustainable strengthening techniques. This study experimentally, numerically, and analytically investigates the flexural strengthening of one-way RC slabs reinforced with smooth bars using externally bonded reinforcement (EBR) galvanized flat/corrugated steel sheets and near-surface mounted (NSM) galvanized steel bars. Eleven slabs were tested under monotonic loading, including one control slab and ten strengthened slabs. The investigated parameters included the strengthening technique (EBR, NSM, and combined EBR/NSM), sheet profile (flat or corrugated), strengthening configuration, and sheet thickness. The results demonstrated significant improvements in cracking behavior, stiffness, ultimate flexural capacity, and energy absorption. The cracking load increased by more than twice, while the ultimate flexural moment increased by approximately 50% compared with the control slab. Finite element models were developed and validated against the experimental results, showing good agreement with deviations below 8%. In addition, a simplified analytical equation was proposed to estimate the ultimate moment capacity, and its reliability was verified through a parametric study.