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类型 综合研究 预答辩日期 2018-03-07
开始(开题)日期 2014-10-13 论文结束日期 2017-12-29
地点 逸夫建筑馆1501会议室 论文选题来源 其他项目    论文字数 7.6 (万字)
题目 中高强钢筋混凝土梁的截面转动能力研究
主题词 钢筋混凝土,粘结行为,拉杆模型,受压软化线性模型,转动变形计算模型
摘要 塑性铰转动能力对于钢筋混凝土构件或结构的安全使用非常重要,一方面它保证了构件或结构有一定的变形能力来承受温度、徐变和支座位移等因素带来的影响。另一方面对于基于弯矩重分布设计的超静定结构而言,充足的塑性铰转动能力则是保证结构达到承载能力设计要求的必要条件。然而影响塑性铰转动能力的因素众多,准确地计算塑性铰转动能力并非易事,因此这一问题一直是结构工程界研究的热点与难点之一。 本文在分析与总结一部分塑性铰转动能力计算模型的基础上,对钢筋在屈服前后与混凝土的粘结行为、受拉刚化作用以及混凝土的受压行为进行了分析,并据此提出了通用的钢筋混凝土梁转动变形计算模型用以计算塑性铰转动能力。随后本文进行了8根不同配筋率与钢筋延性的钢筋混凝土三点弯曲梁试验,并根据试验的结果对提出的钢筋混凝土梁转动变形计算模型进行了验证。最后利用这一计算模型对弯矩调幅法中的一些参数进行了分析讨论。 本文主要的研究内容为: (1)对钢筋在屈服前后与混凝土的粘结行为进行了分析。引入界面断裂能的定义推出了均匀粘结应力模型,即用两个常量的粘结应力来表示钢筋屈服前后与混凝土的粘结行为。利用均匀粘结应力求解钢筋在混凝土中的应力、应变分布和滑移分布的解析解。推出了钢筋在屈服时滑移的公式,使得Engstrom粘结-滑移模型更加完备。提出了以钢筋应变为单一变量描述钢筋屈服前后与混凝土粘结行为的粘结应力-钢筋应变模型。利用级数的概念解释了钢筋屈服后在粘结应力-滑移关系曲线中出现的陡降现象。最后利用一些拉拔试验的结果推出了两个混凝土构件特征时期的均匀粘结应力代表值。 (2)将提出的均匀粘结应力模型与拉杆模型组合对钢筋混凝土间的受拉刚化作用做了解析性分析,求得了钢筋混凝土从开始受拉至钢筋断裂这一完整加载过程中钢筋与混凝土的应力、应变分布,并同其他受拉强化作用模型对钢筋混凝土的受拉试验进行了模拟与对比。 (3)对混凝土的受压行为进行了分析。参考对受拉混凝土的断裂分析,将Bazant断裂带理论拓展到了受压混凝土的变形计算,推出了混凝土受压线性软化模型。随后将Hognestad混凝土本构模型与线性软化模型分别用于受压混凝土峰值应力之前与峰值应力之后的应力-应变关系的描述,最后对混凝土受压试验结果进行了模拟与对比。 (4)根据钢筋混凝土梁受压软化行为的出现与否分情况讨论了钢筋混凝土梁转动变形的计算,但基本思路仍然是通过力的平衡与变形协调的要求,将混凝土的受压行为与钢筋混凝土受拉行为进行有效组合,得到弯矩-曲率关系曲线用于钢筋混凝土梁转动变形计算。在加载过程中,当梁顶部受压混凝土进入软化阶段前,受压混凝土可以视为均匀状态,梁的转动变形直接通过截面弯矩-曲率关系曲线进行评估;当部分受压混凝土进入软化阶段后,将钢筋混凝土梁划分为铰区与非铰区,非铰区的混凝土可以视为均匀状态,但对于铰区的压碎混凝土则采取了理想化的处理办法,将其视为由混凝土破坏面组成的特殊区域,求出可以考虑混凝土受压软化的弯矩-曲率关系曲线来进行梁的转动变形计算。 (5)分析了钢筋混凝土梁在斜裂缝出现后剪力对转动变形的影响。考虑了混凝土裂缝处的多种作用,对钢筋混凝土断裂膜模型进行了修正。讨论了定角膜单元中斜裂缝间距的计算。最后提出使用修正断裂膜模型计算剪力影响下无腹筋混凝土梁转动变形的方法。 (6)开展了钢筋混凝土三点弯曲梁试验,研究不同配筋率与钢筋延性对钢筋混凝土梁转动能力的影响。利用本文提出的转动变形计算模型与考虑剪力影响的转动变形计算模型对这一系列的试验进行了模拟与对比,并证实了这一计算模型的有效性。同时对模拟计算中使用的粘结应力进行了分析与讨论。 (7)利用提出的梁转动变形计算模型对钢筋的延性、跨高比等参数进行了一系列的分析。介绍了通过比较转动能力与转动需求确定弯矩调幅程度的方法,并对弯矩调幅系数与钢筋混凝土构件截面最大相对受压区高度的关系进行了讨论。最后结合参数分析的结果对弯矩调幅法提出了一些建议。 本文为研究钢筋与混凝土的粘结作用、混凝土受压、钢筋混凝土构件转动变形这些钢筋混凝土基本行为提供了新的思路。提出的钢筋混凝土梁转动变形计算模型可以对混凝土结构设计规范、规程中有关规定进行验证与评估,是进行钢筋混凝土结构安全与经济设计的一个很好的工具。
英文题目 Research on rotation capacity of reinforced concrete beams with medium-high strength reinforcement
英文主题词 reinforced concrete,bond behavior,tension chord model,linear compression softening model,analytical model for rotation
英文摘要 The difference between rotations of a RC member at the peak moment and at the yielding moment is the so-called rotation capacity, which is a particularly critical property for its relationships with redistribution of internal force, energy absorbability, resistance against imposed deformation, and so on. Owing to the nonlinear stress-strain response of materials and their complicated mutual interaction, the precise prediction about rotation response, especially in plastic range, of a RC member, which is the primary basis of quantifying the rotation capacity, is no easy matter; therefore this issue has still been one of the classic and intractable problems in structural engineering over the past decades. By investigating the deformation components constituting the rotation capacity and referring to the proposed analytical model to predict the rotation capacity, the improved Tension Chord Model, applied in tension zone and representing the tension stiffening effect in pre-and post-yield stages, and the linear softening model, employed in compression zone and predicting the compressive softening behavior of concrete, are subsequently derived. After that the stress-smeared strain curves of concrete and RC tension chord based on the two models are assembled to predict the advanced moment-curvature response with the standard plane-section analysis. And the evaluation procedures about rotation response of RC flexural members are divided into two cases in terms of the nonexistence and existence of damage zones in compressed concrete at failure. In order to validate the presented model, three-point bending tests with the variables regarding to the reinforcement ratios and ductility parameters of steel have been carried out. The main contents of this dissertation can be summarized as follows: (1) This paper derives the mean bond stresses in pre-and post-yield phases by resorting to the definition of interfacial fracture energy. Afterwards, the mean bond stresses, associating with the strain (stress) levels of reinforcement at cracks, are employed to simplify the evaluations towards the distributions of reinforcement strain and slip. Moreover, a bond stress-strain model is suggested to estimate the bond behavior of reinforcement in terms of the steel strain instead of the slip. Additionally, the phenomena of a cliff-like drop in bond stress after yielding is illuminated by series. Then the proposed models are utilized to simulate some well-known tests, and a good agreement with the experimental results validates the proposed models. Finally, the mean bond stresses implying several typical strain (stress) levels of reinforced concrete members are presented. (2) The presented mean bond model are implemented into the Tension Chord Method to investigate the stress and strain distributions of concrete and reinforcement, and tension stiffening effect with analytical method. Furthermore, the simulation results acquired this method agree with the test results. (3) The essential strategies of the crack band model, devoting to representing the concrete softening response in tensile damage zone, are extended to the concrete in compressive damage zone. As a consequence, the linear softening model for compressed concrete, inferred from the stress-strain response of unaxially compressed concrete, is employed to describe the compressive behavior of concrete in hinge region. Moreover, the Hognestad’s law is used to predict the pre-peak response of compressive concrete. As a result, the combination of two models have got good validation by the comparisons with experimental results. (4) The proposed models, applied to describe the mechanical behavior in tension zone and in compression zone of RC beams, are assembled to predict the advanced moment-curvature response with the standard plane-section analysis. And the evaluation procedures about rotation response of RC flexural members are divided into two cases in terms of the nonexistence and existence of damage zones in compressed concrete at failure. For the RC flexural member without strain localization at failure, the compressed concrete can be ideally treated as homogeneous. On the other side, as far as the distribution of steel strain is concerned, the smeared steel strain can be deemed constant along the member. So it can be further inferred that the smeared deformation of any plane-section remains plane in view of the distribution characteristics of concrete strain and smeared steel strain; as a result, the moment-curvature relationship, based on the common plane-section analysis, can be evaluated with the stress-strain curve of concrete material and the stress-smeared strain curve of RC tension chord. While for the RC flexural member with strain localization at failure, the compressive behavior of concrete cannot be thought of as homogeneous any more due to the existence of strain localization. Under this status, the frequently employed plane-section assumption is not valid any more due to the heterogeneity of compressed concrete caused by strain localization. Hence, the moment-curvature relationship, feasible to the overall RC flexural member, cannot be directly evaluated from the stress-strain response of materials. Whereas the assumption regarding plane-section remains plane is still individually applicable in hinge region and in non-hinge region in terms of smeared strain. Therefore, the advanced moment-curvature relationship considering strain localization, can be separately applied in hinge region and in non-hinge region. (5) The influence of shear on rotation deformation of RC beams has been analytically investigated. Then the Cracked Membrane Model was modified to consider the effect of stresses at the cracks. Moreover, the spacing of Modified Cracked Membrane Model was suggested. Finally, the modified model was proposed to implement the analysis toward the rotation of RC beams without transverse reinforcement. (6) A series of three-point bending tests with the variables as to reinforcement ratio and ductility parameter have been implemented, and the presented analytical models have achieved a good validation by the comparisons between the simulations and tests. (7) The influence of ductility of reinforcement and slenderness on the available rotation capacity and on the required rotation capacity of RC beams is investigated. Moreover, a method whereby the available rotation capacity is compared to the required rotation capacity to determine the available degree of moment redistribution is introduced herein. With the described method, the relation between the available degree of moment redistribution and the maximum relative compressive depth of RC beam section is studied to check the adequacy of the structural design method of linear elastic analysis with moment redistribution. This paper gives new approaches to analyze the bond behavior, concrete compressive response, and rotation capacity of RC flexural members, which are beneficial to the study towards the basic mechanical response of reinforced concrete. Besides, the presented rotation capacity model can be employed to assess the adequacy of the structural design method of linear elastic analysis with moment redistribution suggested by the codes, and is a good tool to design the safe and economical RC structures.
学术讨论
主办单位时间地点报告人报告主题
东南大学土木工程学院 2012.03.30 东南大学土木馆 蔡建国 可展结构研究
东南大学土木工程学院 2012.04.27 东南大学榴园宾馆 Zdenek P. Bazant 混凝土徐变研究
课题组研讨会 2012.12.20 东南大学榴园宾馆 周彬彬 高强钢筋混凝土梁受弯试验
课题组研讨会 2013.12.02 东南大学土木馆 周彬彬 高强钢筋混凝土梁受弯变形数值模拟
东南大学土木工程学院 2014.04.01 东南大学土木馆 陈耀 对称结构与群集理论
课题组研讨会 2014.09.26 东南大学土木馆 周彬彬 钢筋屈服后的受拉刚化效应
课题组研讨会 2015.11.01 东南大学土木馆 周彬彬 钢筋混凝土屈服前后的粘结行为研究
课题组研讨会 2015.11.07 东南大学土木馆 周彬彬 钢筋混凝土受弯转动变形计算
     
学术会议
会议名称时间地点本人报告本人报告题目
PhD Symposium at ibeton 2014.11.01 瑞士洛桑 Deformation of RC members
中山大学国际青年学者论坛 2017.06.21 中国广州 研究综述
     
代表作
论文名称
基于ARMA模型和时空Kriging插值联合模拟大跨结构的脉动风速时程
Displacement-based finite layer element analysis on rotational behavior of reinforced concrete beam
Two models for evaluating the bond behavior in pre- and post-yield phases of reinforced concrete
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
邱洪兴 正高 教授 博导 东南大学
汪基伟 正高 教授 博导 河海大学
孟少平 正高 教授 博导 东南大学
吴瑾 正高 教授 博导 南京航空航天大学
蔡建国 正高 教授 博导 东南大学
      
答辩秘书信息
姓名职称工作单位备注
陈耀 副高 副教授 东南大学