【作者】 谭军；

【导师】 郑文忠；

【作者基本信息】 哈尔滨工业大学 ， 结构工程， 2008， 博士

【摘要】 预应力混凝土梁经历极限荷载之后,仍具有良好的裂缝闭合和变形恢复能力,若对局部被压碎的混凝土进行置换并粘贴CFRP布予以加固修复,加固后的预应力混凝土梁仍然具有良好的受力性能并继续服役。国内外学者对粘贴CFRP布加固预应力混凝土梁的研究非常有限,对粘贴CFRP布加固经历过极限荷载的预应力混凝土梁抗弯承载力的研究未见报道。针对上述问题,我们完成了16根粘贴CFRP布加固经历过极限荷载的两跨无粘结预应力混凝土连续梁的试验,考察了破坏形态、裂缝开展与变形发展、无粘结筋应力变化及控制截面平截面假定的符合程度等,获得了第一手试验资料。基于试验结果,我们认为粘贴CFRP布加固无粘结预应力混凝土梁的正截面破坏可分为继受拉非预应力钢筋屈服后CFRP布被拉断、继受拉非预应力钢筋屈服后受压边缘混凝土被压碎和CFRP布与混凝土剥离三种破坏形式。CFRP布与混凝土的剥离破坏可通过保障粘贴长度和粘贴质量及设置必要的CFRP布U型箍来避免。基于平截面假定和考虑初始损伤影响的本构关系,提出了判别继受拉非预应力钢筋屈服后CFRP布被拉断和继受拉非预应力钢筋屈服后受压边缘混凝土被压碎两种破坏的判别方法,分别建立了与两种破坏模式相对应的粘贴CFRP布加固经历过极限荷载的无粘结预应力混凝土连续梁正截面承载力计算方法。以往粘贴CFRP布加固梁的试验与研究是针对简支粱开展的,粘贴CFRP布加固连续梁试验与研究很少,粘贴CFRP布加固经历过极限荷载的两跨无粘结预应力混凝土连续梁的试验与研究尚属空白。粘贴CFRP布加固经历过极限荷载的无粘结预应力混凝土两跨连续梁从加荷到破坏会经历中支座控制截面两侧出现塑性铰、中支座控制截面受压边缘混凝土达到极限压应变、跨中控制截面出现塑性铰、跨中控制截面受压边缘混凝土达到极限压应变等受力过程。就是说,粘贴CFRP布加固经历过极限荷载的无粘结预应力混凝土两跨连续梁在达到承载能力极限状态之前有塑性内力重分布的过程。基于试验成果,建立了粘贴CFRP布加固经历过极限荷载的无粘结预应力混凝土两跨连续梁弯矩调幅系数计算公式。针对国家行业标准《碳纤维片材加固混凝土结构技术规程》(CECS 146:2003)未给出粘贴CFRP布加固混凝土梁的裂缝宽度和刚度计算方法相关条款的问题,在总结国内外相关试验结果的基础上,提出了粘贴CFRP布加固预应力混凝土梁裂缝宽度及刚度计算方法。为促进粘贴CFRP布加固预应力混凝土梁技术的发展,提出了包括“总则”、“材料”、“设计规定”及“其他”等内容的设计及施工建议。更多还原

【Abstract】 For the prestressed concrete beam, the crack can close and the deformation can restore after it undergos the ultimate loads. If the local crashed concrete is replaced by the new concrete and the CFRP sheet is used to reinforce the beam, the beam after being reinforced will have good mechanical performance and can be in service.The research on the prestressed concrete beam reinforced with CFRP sheet is limit at home and abroad, and there is no research on the flexural carrying capacity of prestressed concrete beam after ultimate loads reinforced with CFRP sheet. In consideration of this problem, 16 two-span unbonded prestressed concrete beams after ultimate loads reinforced with CFRP sheets are tested. Some status are investigated such as the failure mode, crack and deformation, varitey of stress of unbonded tendons and the plane section assumption at cractical section and so on. The first-hand data are got.Based on the test results, there are three failure modes for the flexural failure of this kind of beam: CFRP sheet breaking after the tensile non-prestressed steel bar yielding, concrete crushing after the tensile non-prestressed steel bar yielding and CFRP sheet separating from concrete. The last kind of failure mode can be avoided with the enough length of CFRP sheet for plastering, the good construction qualitity and setting some U-shaped hoop. Based on the plane section assumption and the constitution relation considering the original damage, the methods are presented to destinguish the two failure mode of CFRP sheet breaking after the tensile non-prestressed steel bar yielding and concrete crushing after the tensile non-prestressed steel bar yielding. The calculation methods for flexural carrying capacity of this kind of beam corresponding to the two failure modes are estabilshed.In the past, all test centres around the simple beam reinforced with CFRP sheets, and there few researches on the continuous beam reinforced with CFRP sheets. Moreover, there are no reserch on two-span unbonded prestressed concrete beam reinforced with CFRP sheets. For this kind of beam from loading to failure, the plastic hinge will occur in the intermediate support region, and concrete at the ultimate fibre in this region will reach the ultimate compressive strain, after that, the plastic hinge will occur in the midespan region, and concrete at the ultimate fibre in this region will reach the ultimate compressive strain. That is to say, there is redistribution of palstic internal force before the two-span unbonded prestressed concrete beam reinforced with CFRP sheets reachs the ultimate state. Basted on the test result, the calculation formulas for the coefficient of moment modification of this beam are set up.In consideration that the calculation formula for crack width and the stiffness of concrete beam reinforced with CFRP sheets are not given in the national industry standard Technical specification for strengthening concrete structures with carbon fiber reinforced polymer laminate (CECS 146:2003), on basis of the summation of test result abroad, the calculation formula for crack width and the stiffness for this kind of beam are put forward.In order to promote the development of prestressed concrete beam reinforced with CFRP sheets, the design and construction propositions are presented including“general principles”,“materials”,“design regulations”,“others”and so on.更多还原