| Fiber-reinforced polymers(FRP) are the composite materials that typically consist of strong fibers embedded in a resin matrix, which is high strength-weight ratio, superior corrosion resistance and ease of applying in strengthening applications. A major development of FRP for civil engineering has been the application of externally bonded FRP(EB-FRP) for retrofitting and strengthening of reinforced concrete(RC) structures. The research of FRP shear strengthened reinforced concrete beam(RC beam) is more and more, many investigations have made certain contribution for this purpose. However, it is still remains some problem to be resolved through analyzed and summarized predecessors’ research. It is still lack of systematic investigations for the FRP shear-strengthened beams. For example, the shear span-to-effective depth ratio(also as ―shear span/depth ratio‖) and stirrup ratio clearly affects the shear behavior but there is insufficient testing data to evaluate its effect. Those two factors have not been appropriately addressed in existing shear strengthening models and design guidelines of RC structures strengthened with FRP composites.This article research FRP shear effect of shear span-to-effective depth ratio and stirrup through the design experiment on the above-mentioned insufficient. The experiment includes three different shear span/depth ratios and three different stirrup ratios respectively, for investigating the effect of the shear span-to-effective depth ratio and stirrups on the shear behaviors of strengthening RC beams. The conclusions mainly include: to analysis loaddisplacement curve, strain mutual development of stirrups and FRP strips, discuss whether the stirrups affect the position of main crack of RC beams. Secondly, we analysis the rationality of the existing specifications through the database, and it is concluded that the existing specifications have some deviation on the predictions of FRP shear contribution. By analyzing the existing research, we can conclude that the way put the stirrup into FRP shear formula is inappropriate.It only considers the two kinds of these three materials(concrete-FRP-stirrup) when calculating the effective strain of FRP in the existing research, which may lead to the calculation model be not precise enough. So this paper proposes a new correction coefficient which considers the interactive relationship of these three materials(concrete-FRP-stirrup). And the thesis suggests an advanced FRP shear calculation equation. The predictive value for the FRP shear contribution by the proposed equation is closer to the experiment value than the existing calculation models. |
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