CFRP布混合粘贴加固RC梁斜截面抗剪性能研究

Study on Shear Performance of RC Beam Oblique Section Strengthened with Hybrid Bonding CFRP Sheets

为了研究CFRP布混合粘贴技术加固钢筋混凝土梁斜截面抗剪性能,设计了4组钢筋混凝土T梁抗剪加固试验。分别对比了未加固的试验T梁、CFRP布普通外贴方式加固的试验T梁和CFRP布混合粘贴方式加固的试验T梁,同时对于加固的试验T梁考虑了分阶段加载二次受力性能。研究表明CFRP布混合粘贴加固的钢筋混凝土梁斜截面抗剪承载力较未加固的试验T梁有显著提高,同时比CFRP布普通粘贴加固方式提高了9.34%。在挠度变形、混凝土裂缝的抑制、箍筋受力的改善以及碳纤维布材料强度利用率上均优于CFRP布普通外贴方式。二次受力的试验T梁因加固前腹板斜裂缝已经出现,因此整体刚度有所降低,导致挠度变形大于一次受力的试验T梁,二次受力的试验T梁其箍筋应力发展水平和一次受力梁差异不大,破坏时斜截面抗剪承载力降低了4.83%,降低程度较小。CFRP布混合粘贴加固形式中单根碳纤维布提供的抗剪贡献较大,钢板锚固件可以延缓CFRP布的剥离过程,阻止CFRP布向锚固件另一侧剥离发展。试验T梁最终破坏时,同一根CFRP布表面应变在两个钢板锚固件之间分布较为均匀且应变数值发展较大,CFRP混合粘贴加固形式充分利用了碳纤维布高强度和高弹性模量的特点,加固后CFRP布与箍筋受力协调关系较好。

To investigate the shear performance of RC beam oblique sections strengthened with hybrid bonding CFRP sheets, we designed shear strengthening test on 4 groups of PC T-shaped beams. We compared the test T-shaped beams without strengthening, the test T-shaped beams strengthened with ordinary CFRP sheets and the test T-shaped beams strengthened with hybrid bonding CFRP sheets respectively, and considered the strengthened test T-shaped beams under secondary load in different stages. The research shows that （1） the shear performance of the oblique sections of the RC beam strengthened with hybrid bonding CFRP sheets is improved remarkably comparing with the non-strengthened T-shaped beams, and the shear performance increased by 9. 34% compared with the T-shaped beams strengthened with CFRP sheets ; （2） its deflection deformation, the control of the concrete cracking, the improvement of stirrup behavior and the utilization rate of CFRP sheets strength are all superior to the strengthening method with the ordinary CFRP sheets ; （3） because of the appearance of the diagonal cracks on the web of the test under secondary loading before strengthening, the rigidity of the whole T-shaped beams decreased, and the deflection deformation is bigger than that under primary load, while the stress development of the stirrups of the beams under secondary load and that under primary load do not have much difference, the shear capacity of the oblique sections decreased by 4. 83% ; （4） the shearing contribution of the single CFRP sheet-fastening in the hybrid bonding CFRP sheets is bigger, the steel sheet-fastening can postpone the stripping process of CFRP sheets and stop the stripping of the CFRP sheets to the other side; （5） the distribution of the CFRP sheet＇s strain between 2 steel sheet-fastenings is relatively uniform and the strain changed more; （6） the hybrid bonding CFRP strengthening method takes full advantage of the high strength and the high elasticity modulus characteristics of the carbon fiber sheets, the coordinate relation between CFRP sheets and stirrup behavior after strengthening is good.