Abstract
Fiber-reinforced polymers (FRP) are commonly used as internal reinforcement in RC structures in aggressive environments. The design of concrete elements reinforced with FRP bars is usually ruled by serviceability criteria rather than the ultimate limit state. Six continuous concrete beams over two spans with longitudinal and transverse glass FRP (GFRP) reinforcement were investigated until failure to estimate the effects of different reinforcement arrangements on the limit states of continuous beams. The ratio of longitudinal reinforcement between the midspan and middle support sections (i.e., the design moment redistribution) and the type of GFRP reinforcement were the main parameters. The experimental results were compared to prediction models and other code formulations under serviceability and ultimate limit states. The bond-dependent coefficient kb was investigated to assess adhesion conditions for GFRP reinforcement and concrete. The results showed that moment redistribution in continuous beams with GFRP reinforcement happens with slippage between the reinforcement and concrete in the middle support without the load capacity being reduced. A modified model was suggested for better deflection prediction of continuous beams reinforced with GFRP bars. Based on deformability factors, the tested continuous beams, although containing GFRP reinforcement that has brittle behavior, showed a certain kind of ductile behavior.
Highlights
Continuous concrete beams are often used within RC structures that are exposed to aggressive environmental conditions, such as garages, bridges, overpasses, reservoirs, marine structures, and retaining walls
New cracks in the midspan can occur until failure, while new cracks in the middle support area stop appearing at a load corresponding to 50% of the failure load
For beams with ribbed glass FRP (GFRP) bars with epoxy, the values of the maximal crack widths were less than those predicted by actual codes, while for beams with wrapped GFRP reinforcement with polyester they were higher than predicted
Summary
Continuous concrete beams are often used within RC structures that are exposed to aggressive environmental conditions, such as garages, bridges, overpasses, reservoirs, marine structures, and retaining walls. In these environments, a reduction of concrete alkalinity occurs, which often results in steel reinforcement corrosion, endangering the serviceability and functionality of the RC structures. In order to overcome this problem, fiber-reinforced polymer (FRP) bars and stirrups have lately been used as alternative solutions in RC structures, especially in aggressive conditions. The use of FRP reinforcement can provide significant savings related to the maintenance, strengthening and recovery of structures, in particular when they are exposed to various destructive influences during their service life, certainly leading to economic benefits. Several authors have proposed modification of Branson’s equation for calculation of the effective moment of inertia (Toutanji and Saafi [4], Yost et al [5], Rafi and Nadjai [6], Mousavi and Esfahani [7], Adam et al [8], Ju et al [9]), while Bischoff [10,11]
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