Effects of Internal Force Redistribution on the Limit States of Continuous Beams with GFRP Reinforcement

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.

Fatigue Experiment Study on Internal Force Redistribution in the Negative Moment Zone of Steel–Concrete Continuous Composite Box Beams

“…In addition, in continuous composite beams, the negative moment at the middle support leads to an unfavorable situation where the concrete slab is under tension and the steel beam is under compression [ 17 ]. When there are sufficient concrete cracks and stiffness degradation, a plastic hinge forms at the middle support, leading to an internal force redistribution in the continuous beams [ 18 , 19 ]. To date, many researchers have investigated the internal force redistribution of steel–concrete composite continuous beams under static tests.…”

Prediction of Structural Behavior of Continuous Reinforced Concrete Beams with Hybrid CFRP-Steel Bars

“…However, FRP is linearly elastic until rupture without yielding, thereby raising concerns about the flexural ductility of RC elements with FRP bars [ 9 , 10 ]. In continuous RC beams, the use of FRP bars may also negatively influence the ability to redistribute moments as the redistribution is closely related to flexural ductility [ 11 , 12 , 13 , 14 ]. Moreover, FRP commonly has a low elastic modulus, which may lead to excessive deflections [ 15 , 16 , 17 ] and crack width [ 18 , 19 ] of RC beams with FRP bars at the serviceability limit state.…”

Flexural Behavior of Two-Span Continuous CFRP RC Beams

“…In addition, moment redistribution in the beams was considerably improved by increasing the sagging-to-hogging bar ratio or decreasing the stirrup spacing, while the influence of bar ratio was more effective than the influence of stirrup spacing. Basa et al [26] presented the test results of six GFRP RC continuous beams with the investigated parameters including the sagging-to-hogging bar ratio and the type of GFRP bars. They concluded that in spite of the brittleness of GFRP bars, continuous beams reinforced with GFRP bars exhibited a certain level of ductility, offering sufficient warning prior to collapse.…”