【作者】 庄江波；

【导师】 叶列平；

【作者基本信息】 清华大学 ， 土木工程， 2005， 硕士

【摘要】 将CFRP布(碳纤维布)直接粘贴在混凝土梁受拉面以增强构件的抗弯承载力,已经广泛地运用于建筑、桥梁等工程结构,但是这种加固方法不能有效的减小梁的挠度变形和裂缝宽度,也不能承受原结构的初始荷载,抵消初始变形,并且易发生CFRP布从混凝土表面的剥离破坏,CFRP布的高强度不能得到充分发挥。对CFRP布施加预应力可以有效的解决上述问题。本文首先针对工程的实际应用,改进了CFRP布张拉设备,并已形成定型产品和实用的施工技术。随后通过7根足尺预应力CFRP布加固T形混凝土梁的受弯性能进行了试验研究,研究参数包括CFRP布的加固量、预应力度、配筋率、加载历史、U形箍种类等。试验研究结果表明,采用预应力CFRP布加固混凝土梁,CFRP布的高强度性能能够得到充分发挥和利用,改变构件的破坏模式,显著提高构件的极限承载力。与普通CFRP布加固相比,预应力CFRP布加固混凝土梁可以延缓开裂,减小试件挠度和裂缝宽度,提高屈服荷载,可以满足正常使用极限状态的要求。在试验研究的基础上,本文按照四种不同的方法计算分析了预应力CFRP布加固钢筋混凝土梁的极限受弯承载力,通过与本文和国内试验数据的比较,建议了适合工程设计的设计计算公式。为研究U箍锚固对混凝土梁底粘贴FRP布的影响,本文以方团卿的文献资料为基础,寻求比较合适的界面粘结-滑移本构模型,包括本构模型形式、模型参数取值,运用有限元数值模型,初步分析了U形箍对于FRP布加固混凝土受弯梁剥离性能的影响和对承载力贡献。在分析研究基础上,提出了考虑U形箍影响的界面粘结-滑移本构模型,并利用该模型对本文试验梁进行了分析验证。研究表明,在锚固充足的情况下,对CFRP布施加预应力,可以使CFRP布的强度得到充分发挥。更多还原

【Abstract】 Strengthening RC (Reinforced Concrete) beams with CFRP (Carbon FiberReinforced Polymer) pasted on the tensile faces of the beams to improve theflexural capacities has been used widely in recent years. However, severaldrawbacks have been found for this strengthening method, including: thedefection and the width of flexural crack can not be effectively reduced withthis method, the CFRP sheets can not bearing the initial load in the beam torecover the initial deflection, and debonding always happens in theFRP-to-concrete interface, so that the strength of CFRP can not be fully used.On the contrary, if pre-stress is applied to the CFRP sheets, above problemscan be overcome.In this study, firstly, based on the real practices of strengthening, specialequipment for applying pre-stress to the CFRP sheets has been improved,which comes to be a mature product. And construction techniques forinstalling pre-stress on CFRP sheets with proposed equipment have beendeveloped. Then, 7 full size T shape RC beams have been tested thatstrengthened with pre-stressed CFRP sheets to study their flexural behaviors.The parameters studied in these specimens include: the quality of CFRPsheets, the pre-stress in CFRP sheets, the reinforcement ratio, the loadinghistory and the shapes of FRP U-jacketing. The test results show that the highstrength of CFRP can be fully used in pre-stressed CFRP strengthened beams.The failure modes of the specimens are changed, and the flexural strengths ofthe specimens are increased obviously. Furthermore, compared to thespecimens strengthened with normal (i.e. no pre-stress) CFRP sheets, thepre-stressed CFRP sheets can retard the cracking, reduce the deflection andthe crack width, and increase the yield strength, which results in thesatisfaction of service limit state.Based on the experimental research, 4 different methods are adopted tocompute the ultimate flexural capacity of RC beams strengthened withpre-stressed CFRP sheets. And by comparison with domestic test data, designformulas are proposed which can be used for engineering application.In order to study the contribution of FRP U-jacketing to the bond strength ofinterface between concrete and flexural strengthening CFRP sheets, RCbeams flexural strengthened with normal CFRP sheets in existing literaturesare simulated with finite element (FE) method. Different interfaceconstitutive models and model parameters are discussed to find a proper onefor the FRP-to-concrete interfaces with U-jacketing. The FE models illustratethe influence of U-jacketing to FRP-to-concrete the interfacial behavior andthe contribution of U-jacketing to the flexural strength. Then, anFRP-to-concrete interfacial constitutive model with U-jacketing has beenproposed and the specimens tested in this study have been simulated with thismodel. The numerical results show that with sufficient U-jacketing bond, thedebonding failure can be avoided for pre-stressed CFRP sheets. And thestrength of CFRP sheets can be fully used.更多还原