斜向U型箍控制复材加固混凝土梁板端破坏的试验研究

EXPERIMENTAL RESEARCH ON SUPPRESSION OF DEBONDING IN FRRMC-PLATED RC BEAM AND SLAB ENDS BY USING OBLIQUE U-JACKET

将树脂基纤维增强复合材料外贴或者表层嵌贴于钢筋混凝土梁受拉部位提升其抗弯承载能力,是钢筋混凝土结构受弯加固的主流技术之一。复材加固钢筋混凝土梁通常破坏于中部剥离或者混凝土保护层剥离,破坏发生时加固复材的最大应变通常仅为20%~40%的极限抗拉应变,导致复材抗拉强度高的特点没有得到很好的发挥。合理的锚固措施能够有效控制或延缓剥离破坏,从而很好地提升加固效率和复材利用率。国内外学者提出了不同形式的锚固措施,其效果、耐久性能、施工复杂程度存在差异,为此,提出采用斜向复材U型箍,控制或延缓板端剥离破坏(也称为混凝土保护层破坏)。通过4根足尺寸的复材加固钢筋混凝土梁的四点受弯试验,验证端部斜向复材U型箍对复材加固钢筋混凝土梁保护层剥离破坏的控制效果。试验结果表明:配置端部斜向U型箍能够对外贴和表层嵌贴复材加固钢筋混凝土梁的极限承载能力和延性分别提升62.03%和117.85%,61.08%和155.44%。

Fiber-reinforced polymer(FRP)composites are widely externally bonded on or near surface mounted into the tension side of reinforced concrete(RC)beams to enhance the flexural capacity.Such a technique becomes one of the mainstream techniques for the flexural strengthening of RC beams.FRP plated RC beams usually fail due to debonding failure in either intermediate crack induced debonding(IC debonding)or concrete cover debonding.The debonding failure usually occurs with the maximum strain of the FRP being only 20%~40%of its rupture strain,thus limiting the utilization of the high tensile strength of the materials.Appropriate anchorages can effectively suppress or delay the occurrence of the debonding failure,thus improving the strengthening efficiency and the utilization of the materials.The scholars at home and abroad have proposed different forms of anchoring measures,and their effects,durability,and construction complexity are different.The oblique U-jacket was proposed to suppress or mitigate the concrete cover debonding of RC beams.Four full-scale RC beams strengthened by FRP with or without end oblique U-jacket to identify the effect of the U-jacket on the suppression or mitigation of concrete cover debonding.The test results showed that the ultimate bearing capacity and ductility of the tested beams with externally bonded and near surface mounted reinforced concrete beams could be increased by 62.03%and 117.85%,61.08%and 155.44%,respectively.