复合受力下钢筋混凝土构件承载力的统一表达

发布时间：2018-03-17 20:07

本文选题：钢筋混凝土构件　切入点：统一破坏方程　出处：《上海交通大学》2014年博士论文　论文类型：学位论文

【摘要】：在各种灾害作用下，钢筋混凝土构件的复杂受力实际是由轴力、弯矩、剪力、扭矩的不同组合形成，其破坏机理十分复杂。目前，除轴力、弯矩单一受力情况国内外有比较统一的计算方法外，对剪、扭加入引起的破坏理论并不统一。长期以来，国内外研究学者对钢筋混凝土构件在复合受力作用下的研究已取得许多成果。一些靠试验数据回归得到的承载力计算公式，如我国现行的钢筋混凝土结构设计规范，缺少统一的理论基础，各回归公式之间也不存在内在联系。多年来，众学者一直致力于钢筋混凝土构件组合受力统一破坏理论的研究,利用协调，平衡和本构关系对构件受复合力作用进行全过程分析，取得了一些领先的成果。目前仅有这种理论可以分析钢筋混凝土构件受拉-压弯剪扭作用的破坏机理，但由于在计算中引入协调条件使计算变得复杂，让工程界难以接受。一个成熟的理论，它应该在理论上是统一的，在表达上是简明的。总之，与相对完善和成熟的钢结构计算理论相比，钢筋混凝土构件在复合力作用下的破坏理论还不够成熟。为方便工程应用，尤其是分析构件在灾难荷载作用下的破坏，本文针对量大面广的矩形断面的钢筋混凝土构件在轴力、弯矩、剪力、扭矩共同作用下的破坏提出了一个形式简单并且能展示构件破坏机理的统一理论。本文的理论利用了钢筋和混凝土的破坏准则，寻找到承载力极限状态下不违反边界条件且满足平衡条件的应力分布，从而得到构件承受复合力破坏时各个外力的相互关系。依据极限分析中下限解定理可知，本文得到的结果是一个偏于安全的极限下限解，本文寻找的极限应力状态越接近实际情况，这个下限解应该越接近真实解。根据大量试验现象可知，构件在承受的轴压力相对较小时，构件的混凝土随着荷载的增大，首先出现裂缝，之后部分混凝土退出工作，剩余的混凝土和钢筋继续承担的荷载越来越大，直到构件破坏，此类破坏为延性破坏；而在构件承受轴压力相对较大时，在混凝土先被压碎的同时构件也随之完全破坏，几乎没有像延性破坏那样的破坏发展阶段，此类破坏为脆性破坏。本文在利用极限下限解定理建立统一破坏方程时，根据两类破坏模式的不同机理，分别建立了破坏方程。在研究延性破坏时本文建立了如下的分析思路：首先需要寻找到构件在极限状态下的三维翘曲破坏面，其次描述出破坏面上的应力分布，最后根据平衡条件可以得到各个外力之间的相互关系。在研究极限状态下的破坏面时，本文提出了一种全新的组成破坏面各边角的计算方法，根据这个方法找到的破坏面不仅能够描述构件在受复合力作用时的三维翘曲破坏面，还可以在构件承受单一荷载时较为准确地退化成简单的破坏面。在寻找破坏面上的应力状态时，本文对钢筋和混凝土的贡献分别进行了详细的分析。通过对理论和试验研究的分析，本文总结出破坏面上的钢筋的贡献，由于不需借助协调条件进行计算，表达简单便于应用。破坏面上的混凝土分为受拉区和受压区。受拉区的混凝土由于骨料咬合的作用在开裂后可继续承担部分外力，本文提出了一种简便的计算方法，仅需一个可以简单计算的折减系数kT，便可量化受拉开裂区混凝土的贡献。对处于复杂应力状态且受压破坏的混凝土，可以用主应力空间混凝土三维破坏准则计算应力状态。这样，破坏面上的混凝土的应力分布得到了简单并较为准确的量化。由于构件承受复合力的不同，受压区不同，破坏面形态也不同，在分析不同破坏形态下的极限平衡条件后，构件受拉-压弯剪扭作用下的破坏方程可以用非常简明的方式表达出来，同时破坏方程还清晰的表现了各个外力间的相互关系。脆性破坏的最明显的特征是，随着混凝土先被压坏构件也破坏，此时混凝土的应力状态直接决定着构件的状态。根据破坏机理，本文寻找到了构件受复合力作用时的正应力和剪应力的分布，当混凝土的应力状态满足主应力空间内三维破坏准则时，认为构件破坏。得到的分析方法计算简单，便于应用，并反映了构件破坏的最主要特征。经和试验结果对比后发现，本文得到的破坏理论与实际破坏情况吻合较好。本文用相同的分析方法对更复杂的受力情况，即矩形截面钢筋混凝土构件受双向拉-压弯剪扭作用时的破坏情况，进行了初步探索。和试验对比发现，本文理论取得了比较理想的结果。与现行混凝土结构设计规范相比，统一破坏理论不仅计算出的极限承载力更为准确，，还能展示出破坏时各个外力之间的相互作用关系。与其他分析方法相比，能够分析拉-压弯剪扭共同作用的理论与数值方法都比十分繁琐，不适于工程中推广，而本文得到的统一破坏理论恰好弥补了这个工程应用中的空缺。总之，本论文提出的矩形截面钢筋混凝土构件受复合力作用下的统一破坏理论不仅能够清晰合理的阐释构件的破坏机理，并能快速便捷的分析出构件的极限承载力和破坏模式，对于推广到工程实际应用中有重要的参考意义。
[Abstract]:In a variety of disasters under complicated stress of reinforced concrete members is actually by the axial force, bending moment, shear force, different combinations of torque formation, the failure mechanism is very complicated. At present, in addition to the axial force, bending force calculation method of single unified situation at home and abroad, to join the shear failure theory caused by torsion are not uniform. For a long time, domestic and foreign research scholars have made many achievements on the study of the reinforced concrete member in the composite under the action of stress. Some test data obtained by regression calculation formula for the bearing capacity, such as the current design specification for concrete reinforced concrete structure, the lack of a unified theoretical basis, the regression formulas there is no inherent relationship. Over the years, many scholars have been committed to the combination of reinforced concrete member stress theory, damage by using the unified coordination, balance and constitutive relation of components by the combined forces of the whole History analysis, has made some achievements. At present only the leading theory can analysis of reinforced concrete member subjected to tension bending shear failure mechanism of torsion effect, but due to the introduction of coordination conditions in the calculation of the calculation is complex, so that the engineering is difficult to accept. A mature theory, it should in theory be unified. The expression is simple. In short, compared with the steel structure is relatively perfect and mature calculation theory, the damage theory of reinforced concrete member in the composite force is not mature enough.
For the convenience of engineering application, especially in the role of disaster analysis of component loading damage of reinforced concrete members with rectangular section in view of the large volume of the axial force, bending moment, shear force and torque under the interaction of failure presents a simple form and can show the failure mechanism of the component theory unified the theory. Using the failure criterion of concrete and steel, find the bearing stress distribution of stress under the limit state does not violate the boundary conditions and satisfy the equilibrium conditions, resulting in failure of each component under combined force force relationship. According to the limit analysis in lower bound theorem, the results of this paper is a safe limit the lower bound solution, this paper tries to find the ultimate stress state is closer to the actual situation, the lower bound solution should be closer to the real solution.
According to the experimental results, the component in the axial pressure is relatively small, the concrete as the load increases, the first part of the concrete cracks, then quit working load of steel and concrete and the remaining continue to bear the larger component until broken, such as failure and ductile failure; in the structure under axial pressure relatively large, in the first concrete crushed the component also completely destroyed, almost no ductility failure like stage of development. So, this kind of damage is brittle failure. In this paper using limit limit solution to establish the unified equation theorem, according to the different mechanism of two kinds of failure modes, failure equations were established.
In the study of ductility damage analysis method is established in this paper are as follows: first of all need to find the component in the limit state of 3D warping failure surface, then describe the failure stress distribution on the surface, according to the balance conditions can get the relationship between the various forces. In the study of failure surface under the ultimate limit state, is proposed in this paper. A new composition of the failure surface of each corner of the calculation method, according to the failure surface this method can not only find the description of component in 3D by composite force warping failure surface, but also in the structure under single loads accurately to degenerate into a simple failure surface. The failure surface should be looking for the stress state, the contribution of steel and concrete are analyzed. Based on the theoretical analysis and experimental research, this paper summed up the failure surface of the reinforced contribution, not because of Need to be calculated by means of coordination condition, simple expression and easy to apply. The failure surface of the concrete is divided into tension and compression zone. The tension zone of concrete due to the effect of aggregate interlock can continue to take part in force after cracking, this paper presents a simple calculation method, only a simple calculation can fold the reduction coefficient of kT, can be quantified by concrete tensile cracking zone contribution. In the complex stress state and compressive failure of concrete, we can use the principal stress space dimensional concrete failure criterion to calculate the stress state. In this way, the failure surface of the concrete stress distribution have been quantified and more accurate. Because of simple components under complex stress of different compression zone, failure surface is different, in the analysis of the limit equilibrium condition of different failure modes under tension, Bending Shear Torsion equation under the action of a non member Jane often It is expressed in the way of the Ming, and the destruction of the equation clearly shows the relationship between various external forces.
The most obvious characteristic of brittle failure, with the first being crushed concrete components are also destroyed, at this time the concrete stress state directly determines the member state. According to the failure mechanism, this paper find the component stress of composite force and shear stress distribution, when the concrete stress state to meet the principal stress space three-dimensional failure criterion, that component analysis methods have been destroyed. The calculation is simple and convenient for application, and reflects the main features of the damage of components.
After comparison with the test results, it is found that the damage theory obtained in this paper is in good agreement with the actual failure conditions.
In this paper, the same analysis method is used to make a preliminary exploration of the more complex loading condition, that is, the failure condition of reinforced concrete members with rectangular section subjected to biaxial tension compression bending, shear and torsion. Compared with the experiment, it is found that the theory has achieved satisfactory results.
Compared with the existing code for design of concrete structures, the unified failure theory is more accurate than the calculated failure capacity. It can also show the interaction between external forces during failure.
Compared with other analytical methods, the theoretical and numerical methods for analyzing the combined action of tension, compression, bending, shear and torsion are more complicated than those of other methods, and are not suitable for engineering promotion. The unified failure theory obtained in this paper just fills up the vacancies in this engineering application.
In short, the failure mechanism of reinforced concrete members with rectangular section to explain the failure under the unified theory of composite force can not only clear and reasonable, and can fast and convenient analysis of bearing capacity and failure modes of structure limit, for promotion to have important reference for practical engineering application.

【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU375;TU312.1

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