碳纤维片材抗弯加固高配筋混凝土大梁性能试验及分析

Experimental research on heavily reinforced concrete girders flexure-strengthened with externally bonded CFRP laminates

鉴于大比例、高配筋混凝土梁粘纤维增强片材加固试验数据相对不足,完成了9根外贴碳纤维布或板加固实尺模型梁的受弯性能试验,以考察梁表面处理方式、加固前预载历史和加固片材类型对加固梁抗弯能力和破坏形态的影响.研究结果表明,梁面打磨不如凿毛处理时粘结牢靠,破坏形态为剥离;若能避免剥离,碳纤维布和板均有良好的加固效果;当碳纤维片材的轴向抗拉刚度相等时,贴布的加固效果优于贴板;加固时梁上既有荷载越小,则加固效果越好;大梁比小梁更易出现界面应力超限,更易剥离.基于《碳纤维片材加固混凝土结构技术规程》的基本假定,考虑既有荷载的影响,对试验梁的开裂弯矩、屈服弯矩和极限弯矩进行了计算,其结果与实测值吻合较好.

In view of the scarity of test data on large scale and quite heavily reinforced concrete girders strengthened with externally bonded laminate of fiber reinforced polymer, real-size experiments have been carried out by the authors on the behavior of RC beams strengthened in flexure by bonding CFRP sheet or plate. The influence of the way of treating concrete substrate, the level of pre-loading before strengthening and the type of CFRP laminate on flexural capacity and failure mode was investigated in this study. The tests show that reliable interfacial bond is achieved in beams with concrete surface roughened by picking. In contrast, delaminating happens in case of surface planning. If debonding failure is avoided, CFRP laminates have good strengthening effect with somewhat better results from CFRP sheet than the plate with same axial tensile stiffness. The flexural capacity declines as the pre-load increases. In comparison with small beams, large beams are subject to an excess of the maximum interracial stresses over the bond strength and thus debonding failure. With the assumptions in the specifi-cation crete are in and in consideration of the preloads, the characteristic bending moment at concracking, rational rebar yielding and ultimate crushing are calculated and the predictions agreement with the test results.