BFRP加固钢筋混凝土梁受弯开裂荷载试验及计算分析

Experiment and Calculating Analysis on Flexural Crack Loads of RC Beams Reinforced with BFRP

为了研究玄武岩纤维增强复合材料(BFRP)加固单筋矩形截面钢筋混凝土(RC)梁的开裂荷载,设置5根加固RC梁和1根普通RC梁进行开裂荷载试验,对开裂荷载、跨中挠度、钢筋及纤维布的应变、跨中截面沿高度方向的应变分布等进行分析;考虑BFRP、受拉钢筋及混凝土的协同受力作用,通过建立力学模型,提出一种BFRP加固单筋矩形截面RC梁受弯开裂荷载的计算方法,并将计算值与试验结果进行对比。结果表明:采用不同BFRP布层数和不同加固方式对RC梁加固,可以使其抗裂性能得到一定程度的改善,开裂荷载平均增幅在10%以上;加固RC梁和基准梁在达到开裂荷载时,跨中挠度不超过净跨度的0.05%,荷载-挠度曲线的变化规律也基本相同;钢筋的应变在开裂后增大较快,而纤维布的荷载-应变曲线在开裂前、后的变化规律差异不明显;加固前、后和开裂前、后的RC梁跨中截面沿高度方向的应变分布近似满足平截面假定;根据提出的BFRP加固单筋矩形截面RC梁受弯开裂荷载的计算方法所得计算值与试验结果吻合良好。

To study crack loads of single rectangular section reinforced concrete(R C)beams strengthened with basalt fiber reinforced polymer(B FR P),the crack load experiment of five RC beams strengthened with BFRP and one ordinary RC beam was set up.The crack lo ad s,mid-span deflection,strain of steels and B F R P,and strain distribution along theheight direction of mid-span section were analyzed.Considering the synergistic effect of B F R P,tensile steels,and concrete,a calculation method on the crack loads of the single steel rectangle section RC beams reinforced with BFRP was proposed by establishing the mechanical model,and the calculated values were compared with the experimental results.The results show that the crack performance of RC beams strengthened with different BFRP layers and different reinforcement methods can be improved to a certain extent and the average increase of crack loads are more than10%.When the RC beams reinforced with BFRP and reference beam reaches the crack loads,the mid-span deflection does not exceed0.05%and the change law of the load-deflection curve is basically the same.The strain of the steels increases rapidly after cracking,however,the variation of the load-strain curves of the BFRP before and after cracking are not obvious.The strain distributions along the height direction of the cross section of the RG beams before and after reinforcement and cracking satisfy approximately the plane-section assumption.The calculated values by the proposed calculation method on the crack loads of the single steel rectangle section RG beams reinforced with BFRP are in good agreement with the experimental results.