【作者】 魏巍巍；

【导师】 贡金鑫；

【作者基本信息】 大连理工大学 ， 结构工程， 2011， 博士

【摘要】 钢筋混凝土构件的抗剪机理是一个非常复杂的问题,至今已经有100多年的研究历史。迄今为止,国内外提出的钢筋混凝土结构剪切破坏分析方法主要有：桁架理论、极限平衡理论、统计分析法(经验方法)、断裂力学方法和非线性有限元方法等。桁架理论包括经典45桁架模型、改进的桁架模型、压力场理论、修正压力场理论、扰动应力场理论、软化桁架理论、桁架—拱理论等,其中20世纪80年代加拿大多伦多大学从力学模型角度提出的修正压力场理论开辟了一条解决钢筋混凝土构件受剪问题的新途径,已经得到国际上的广泛认可,并成为加拿大规范和美国桥梁设计规范抗剪设计方法的基础。近几十年来,除了对钢筋混凝土构件受剪承载力不断进行研究外,钢筋混凝土偏心受压构件(如柱或剪力墙)在地震作用下的荷载-变形性能也一直是不断研究的课题。水平荷载下柱端产生的水平变形包括弯曲变形、柱端钢筋滑移引起的变形和剪切变形。国内外已经提出了很多研究模型,其中修正压力场理论是描述钢筋混凝土板或梁柱节点荷载-剪切变形性能的经典理论模型,很多研究者用该理论的分析结果研究柱或剪力墙等构件的荷载-剪切变形关系。本文在修正压力场理论的基础上,对钢筋混凝土构件受剪承载力和变形进行了研究,主要包括以下内容：1.在修正压力场理论基础上做了进一步研究,提出沿受弯构件斜裂缝表面平均剪应力的计算公式,并考虑混凝土构件的尺寸效应提出抗剪强度的简化计算公式。与所收集的国内外无腹筋梁的512个试验结果的比较表明,采用本文提出的斜裂缝表面平均剪应力公式按修正压力场理论及按本文简化公式计算的受剪承载力与试验结果的变异性很小,可用于无腹筋混凝土梁的抗剪分析和设计。2.由于修正压力场理论忽略了受压区承担的剪力,所计算的构件受剪承载力偏小。本文在修正压力场理论的基础上,根据钢筋混凝土受弯构件的剪切破坏机理,考虑上部受压区混凝土和下部受拉区骨料咬合力及箍筋共同提供受剪承载力,提出截面的受剪承载力计算方法以及简化的设计方法。与所收集的国内外有腹筋梁的275个试验结果的比较表明,采用本文方法计算的受剪承载力与试验结果的符合较好,可用于钢筋混凝土梁的抗剪分析。3.为得到轴向荷载及水平荷载作用下钢筋混凝土柱的荷载-变形曲线,本文利用简化的修正压力场理论描述剪切特性以及符合平截面假定的弯曲理论描述弯曲特性,并认为柱端产生的总水平变形由弯曲变形、剪切变形和钢筋滑移产生的变形组成,提出了一种分析轴向荷载及水平荷载作用下钢筋混凝土柱荷载-变形的新方法,可模拟钢筋混凝土柱弯曲破坏、弯剪破坏和剪切破坏的过程。最后将荷载-变形计算结果与15根矩形柱低周反复荷载试验结果进行了对比分析。研究表明,按本文方法计算的荷载-变形计算结果与滞回曲线的外包线基本一致,可用于轴向荷载和水平荷载作用下钢筋混凝土柱的荷载-变形性能的分析。4.采用修正压力场单元和本文推导的沿裂缝面骨料咬合力平均剪应力公式,研究了钢筋混凝土剪力墙荷载-变形性能的分析方法。分析中单元刚度采用割线刚度,结合平面矩形单元的增量方法编制了计算程序,得到了钢筋混凝土矩形截面剪力墙的荷载-变形曲线,与搜集的10片剪力墙试验结果相比较吻合较好。该方法可用于预测钢筋混凝土剪力墙、深梁等构件从开始加载至最大承载力的非线性性能。更多还原

【Abstract】 For reinforced concrete members, shear failure mechanism is a complex issue. It is not yet fully understood. To this day, many shear analysis methods for reinforced concrete have been developed, including truss theory, limit equilibrium theory, statistical method, fracture mechanics method and nonlinear finite element method. Truss theory includes classical 45-degree truss model, improved truss model, compression field theory, modified compression field theory, disturbed stress field theory, softened truss theory, truss-arch theory and so on. In these theories, modified compression field theory, MCFT, developed in 1980s based on the research of Michael P Collins and his co-workers at the University of Toronro has opened up a new way of resolving the shear of reinforced concrete structures, and have been widely recognized by the international community so far. This theory has been used in the Canadian codes and the American codes.The past research has been primarily focused on estimation of the maximum lateral load capacity of reinforced concrete columns or shear wall rather than the load-deformation relation, which includes flexure, bond-slip and shear deformation components. Nevertheless, the effect of transverse loading, e.g., as in an earthquake, on reinforced concrete column or shear wall behavior has been an attractive topic of research for the last few decades. In recent decades, a few of theoretical models presented continuous monotonic lateral load-shear displacement response for RC panels or beam-columns on basis of mechanical fundamentals were developed, e.g. MCFT. Many researchers used analysis results of this theory to develop simplified lateral load-shear deformation response envelops of reinforced concrete compressive members.In this paper, a further research was made based on the modified compression field theory. The detailed works listed as follows:1. A further research on reinforced concrete beams without stirrups was made based on the MCFT. An expression of the average shear stress across the crack was derived and a simplified equation of shear strength considering the size effect in shear was developed. The obtained equations were verified with extensive sets of experimental data from different source (512data in total). It was found that the variation coefficients of ratio of shear strength calculated using the derived average shear stress across the crack based on modified compression field theory and simplified expressions to test data is small. Thus, it is suitable for shear analysis and design of reinforced concrete beams without stirrups.2. The shear capacity of RC members calculated by MCFT was underestimated due to ignortion of the shear carried by concrete in compression zone. According to shear failure mechanism of reinforced concrete members, a further research on reinforced concrete beams with stirrups was made based on the MCFT. A general method and its simplified method of the shear capacity considering the shear contribution of concrete in compression, shear stress transmitted across crack interface, and stirrups based on shear failure mechanism of reinforced concrete member were developed and verified with extensive sets of experimental data from different source (275 data in total). It was found that consistency between shear strength calculated using the derived expressions and test data were well. So it is suitable for shear analysis of reinforced concrete beams.3. To model lateral load-deformation relationship for reinforced concrete columns subjected to combined action of axial load and lateral load, a new method is developed using MCFT to model shear behavior and conventional section analysis to model flexure behavior, and considering the total lateral deformation of a column at its ends is comprised of deformations due to flexure and shear. The lateral load-deformation courses of reinforced concrete column failing in flexure, flexure-shear and shear can be presented in this method. Finally, the proposed model is compared with 15 rectangular columns from various low-cycle reverse loading tests. In general, the model predicted the lateral load-deformation response envelop reasonably well, so it can be used in lateral load-deformation analysis for reinforced concrete columns subjected to combined action of axial load and lateral load.4. The finite element procedure herein is made to reflect the nonlinear behavior of reinforced concrete shear wall by adopting the stress-strain formulations of the MCFT. In this method, aggregate interlock force along crack is calculated by proposed average shear stress formula. Such analysis is based on a secant stiffness formulation and utilizes only the lowest order finite elements (rectangular elements). The obtained lateral load-deformation response by this procedure has yielded excellent agreement with experimental results. This method can be used to predict the nonlinear behavior of shear wall, deep beams and other components up to the maximum shear strength.更多还原