Behavior of strengthened concrete beams damaged by thermal shock

In the last two decades, using of Carbon Fiber Reinforced Polymers (CFRP) in strengthening of deficient reinforced concrete structural elements has been increased due to their ease of installation, low invasiveness, high corrosion resistance, and high strength to weight ratio. Strengthening damage structures is a relatively new technique. The aims of this study is to investigate the effectiveness of using CFRP to regain shear capacity of shear-deficient reinforced concrete (RC) beams after being damaged by thermal shock. Firstly, a novel Nonlinear Finite Element Analysis (NLFEA) model is created and validated. Then, Ten RC beams (100×150×1400 mm) have been constructed and divided into two groups to scrutinize the effect of CFRP strip number and thermal shock impact. The performance of each beam was evaluated in terms of failure mode, CFRP strain, load-deflection behavior, ultimate deflection, ultimate load capacity, elastic stiffness, toughness, performance factor, and profitability Index of the CFRP Strips. Load carrying capacity and stiffness of RC beams decreased about 68 % and 71 %, respectively, as compared with reference un-damaged beam. Strengthening the thermal damaged RC beams allowed recovering the original load carrying without achieving the original stiffness. Strengthened beams with fully CFRP plates regained the original load capacity with a corresponding stiffness from 79 % to 105 %, respectively. Finally, the enhancement percentage increased with the increase of bonded area or number of CFRP strips and these percentages sharply dropped for damaged beams.