考虑二次受力的内嵌BFRP筋加固混凝土T形梁受剪性能试验研究

为了研究二次受力对内嵌BFRP筋加固混凝土梁受剪性能的影响，对6根内嵌BFRP筋混凝土T形截面加固梁和2根对比梁进行了受剪性能试验。对试件梁的受力过程、破坏模式、荷载-挠度曲线、荷载-应变曲线、斜截面应力重分布现象以及初始荷载大小、卸载程度和BFRP筋端部锚固长度等因素对加固梁的影响进行研究。研究结果表明：虽然加固梁发生了剪切破坏，但是破坏特征复杂且伴随着次生破坏；试件梁的斜截面在斜裂缝出现时和箍筋屈服时出现了重分布，对于二次受力试件梁，BFRP筋应变滞后现象明显，且BFRP筋应变分布不均匀，在进行加固梁承载力计算时应考虑此因素带来的承载力降低的影响；初始荷载、卸载程度及BFRP筋端部锚固有利于加固梁极限荷载的提高和延缓斜裂缝的开展，应在加固梁受剪承载力计算公式中引入相关系数或满足构造要求来体现这些因素的影响。

Experimental study on shear behavior of RC T-beams strengthened with near-surface mounted BFRP bars considering effect of secondary loading

A total of six RC T-beams strengthened with near-surface mounted (NSM) BFRP bars and two control beams in shear were conducted to investigate the effect of secondary loading on the shear behavior of the strengthened beam. The loading process, failure mode of the strengthened beams，load-deformation relationship, load-strain relationship, stress redistribution in inclined section, and the influence factors including initial load, the degree of unloading and embedded length at the end of BFRP bars were studied.The experimental results show that the shear failure of the strengthened beams is complicated and accompanied by secondary failure. When the diagonal crack appears and the stirrup yields, the stress redistribution in inclined section occurs.For the specimen subjected to secondary loading, the strain lag of BFRP bars is obvious, and the strain distribution of BFRP bars is uneven. The effect of the strain lag on the decrease of bearing capacity of the strengthened beam should be considered. The initial load, the magnitude of unloading and the appropriate embedded length at the end of BFRP bars in the flange are beneficial to improve the ultimate load and to delay the crack development. The correlation coefficient should be introduced in the calculation of the shear bearing capacity of the strengthened beam and the requirements of construction details should be satisfied, which reflect the influence of these factors.