【作者】 于婧；

【导师】 李英民；

【作者基本信息】 重庆大学 ， 结构工程， 2011， 博士

【摘要】 现浇钢筋混凝土(RC)结构在施工过程中无法实现混凝土的连续浇筑,当浇筑时间间隔超过混凝土的初凝时间,就会在先后浇筑的混凝土界面形成施工缝。已有试验研究表明施工缝处接缝混凝土存在抗拉和抗剪强度低于整浇混凝土的特点。在汶川地震中也发现一些典型的沿施工缝部位出现整齐的贯通裂缝、钢筋剪断、上下混凝土沿界面明显水平错动等震害现象。但是目前有关施工缝的研究仅限于少量静力试验,而关于施工缝对RC构件抗震性能的影响方面的试验研究极少。由于对施工缝在地震中对结构造成的影响缺乏较深的认识,存在施工缝是否会对结构构件的抗震性能造成不容忽视的影响、产生影响的条件如何界定、是否需要对结构抗震设计进行考虑等问题。为此,本文首先通过试验对施工缝的力学特性及其对RC构件抗震性能的影响进行了研究,在此基础上通过分析施工缝处的传力机制,基于试验数据和理论分析建立了施工缝数值模型,然后将其应用在RC框架结构的非线性分析中,研究施工缝对框架结构抗震性能的影响规律,界定需要考虑施工缝影响的范围,最后给出相应的设计建议。论文的主要研究工作如下:①通过单轴抗压强度试验、单轴抗拉强度试验及矩形短梁直接剪切试验研究了施工缝处接缝混凝土的抗拉、抗压、抗剪等基本力学性能。通过理论分析研究穿过缝面钢筋对施工缝各项力学性能指标的贡献。综合分析施工缝的两个组成成分在切向力和法向力中各自承担的作用,明确施工缝的传力机制。②对端部带施工缝的RC构件进行拟静力试验。通过与整浇构件的试验结果进行对比,从试件的破坏形态、顶点力-位移滞回曲线、承载力、变形、耗能能力、强度衰减、刚度退化、钢筋应变、柱底纵筋滑移、塑性铰区剪切变形与弯曲变形的变化规律等各个方面说明施工缝对RC构件抗震性能的影响。并结合试验数据与理论分析,给出带施工缝RC柱基于截面的剪切恢复力模型。③总结试验结果并结合理论分析,进一步明确施工缝的受力特点及传力机制,推导建立了施工缝模型。并在此基础上进一步推导建立了可以用来模拟带缝柱的纤维杆元模型。最后通过OpenSees非线性分析软件平台验证了新建模型的正确性和有效性。该模型可以用来在钢筋混凝土结构非线性分析中模拟施工缝。④对不同烈度区的规则RC框架结构建立“整浇框架”与“带缝框架”两种数值模型进行非线性分析,通过对比,研究施工缝对其各项抗震性能指标的影响。在对影响因素进行筛选分析的基础上,进一步考虑变化轴力对其抗震性能进行研究。然后,对同一烈度区不同高宽比的框架进行非线性数值分析,研究施工缝对其抗震性能的影响。总结施工缝对不同状态下的RC规则框架结构抗震性能的影响规律。⑤界定需要考虑施工缝影响的RC规则框架的范围,对于应考虑施工缝不利影响的框架结构,从概念设计、计算分析方法及控制措施等方面提出简化的抗震设计建议。解决了在RC规则框架结构中考虑施工缝作用的问题。更多还原

【Abstract】 Construction joint is inevitable in the cast-in-situ RC structure. Much tests have been done and found that the tensile strength of concrete across construction joint are much weaker than integral concrete, and it could barely resist shear stress if there were not special managements. Seismic damages around construction joints appeared in some RC components, especially columns of frame structure, which illuminates that construction joint may be a potential vulnerable point where a sliding failure developed. But the insufficiency is that most of the research is aimed at joints between existing and newly placed concrete, irrespective of dowelling action of the main reinforcement passing through the joint. And there are few of publication on mechanics or numerical model describing the seismic behavior of construction joint, which is necessary for a new nonlinear analysis method of RC structure taking joints into account. There is no criterion about how to consider the impact of construction joint in RC frame structure. The paper focuses on force transferring mechanics between joint through experimental research, the mechanical properties of construction joints and its affects on the seismic properties of RC component were studied, based on the experimental data and theoretical analysis,the numerical model of construction joint is established. Then apply the numerical model to the RC frame structure nonlinear analysis, the influence laws of construction joints on seismic performance of RC frame structures were studied,and the range of considering the effect of construction joints were defined, finally the corresponding design suggestions were given.The main contents of this paper as following:①Through the uniaxial compressive strength test,uniaxial tensile strength test and direct shear test of short rectangular beam,the basic mechanical properties of construction joint were studied. The contribution of lengthways reinforcements passing through the joint to mechanical properties of construction joint is researched by theoretical analysis. Through comprehensive analysis of construction joint of two component and their commitment to the role of the tangential force and the normal force, the force transfer mechanism of construction joint is cleared.②In order to study the influence of construction joint on seismic behavior of RC member, a serious of cantilever columns were tested under cyclic loading. The destruction of test specimen configuration, vertex load-displacement hysteretic curve, bearing capacity, deformation, energy dissipation capacity, strength reduction, stiffness degradation, reinforcement strain, a column bottom longitudinal slip, plastic hinge zone, shear deformation and bending deformation were analyzed based on the experimental study. Combined with the experimental data and theoretical analysis, the hysteretic shear model of RC member with construction joint were proposed.③By test results and theoretical analysis, the stress characteristics and transmission mechanism of construction joint are further clarified, then the model of construction joints is established. On this basis, a fiber line element model is derived which can be used to simulate the columns with construction joint. Finally, the new model is verified correctness through the OpenSees software. The model can be used in nonlinear analysis of reinforced concrete structure simulation of construction joint.④The influence of construction joint to seismic behavior of RC frame structures in different earthquake intensity regions was analyzed. Furthermore, analysis was continued in-depth considering the varying axial force. Then nonlinear numerical analyses of RC frame structures are done on the same intensity in different aspect ratio. The influencing factors were screened,and the influence laws of construction joints on seismic performance of regular RC frame structures were concluded.⑤Defining the scope of considering the effects of construction joints in the seismic design of regular RC frame structure. Then the simplified seismic design suggestions are putted forward from aspects of concept design, analysis method and control measures.更多还原