大跨度预应力混凝土箱梁桥开裂的形变机理研究

发布时间：2018-04-05 00:27

本文选题：形变　切入点：破坏准则　出处：《西南交通大学》2014年博士论文

【摘要】：大跨度预应力混凝土箱梁桥在运营中过量下挠和普遍开裂一直困扰着桥梁工程师,是一个亟待研究解决的问题。过去,人们习惯从受力角度去分析和研究这一问题,虽然取得了一些成果,但没有解决根本问题。本文紧紧抓住材料破坏的形变本质,从研究混凝土材料形变与破坏的关系出发,建立混凝土的形变破坏准则,探讨大跨度预应力混凝土箱梁桥开裂的形变机理。1、对国内部分大跨度预应力混凝土箱梁桥的典型裂缝进行了调查研究,分析了导致这些裂缝的荷载因素和变形因素,总结了国内外的既有研究成果,指出从受力分析不能很好地解释部分裂缝的成因,提出从形变角度来研究大跨度预应力混凝土箱梁桥的开裂问题。2、将固体材料在应力作用下的形状和体积变化定义为形变,在直角坐标系下以应变张量表示,推导了在八面体上和在Haigh-Westergaard坐标系下的形变量。指出混凝十的形变包括瞬时形变和徐变形变,建议使用非线弹性正交异性本构模型计算瞬时形变,按依时本构模型计算徐变形变。本文在总结混凝土在单轴、双轴和三轴等不同应力状态下空间徐变规律的基础上提出了基于徐变泊松比的单徐变度依时本构模型；在分析混凝土徐变机理的基础上,提出了球徐变度和偏徐变度的概念,建立了混凝土的双徐变度依时本构模型。3、指出固体材料破坏的本质是形变超过自身的承受能力而发生形体失稳,在此基础上探讨了混凝土材料的形变破坏理论。研究了混凝土材料形变与破坏的关系,分别以应力空间破坏准则推导了混凝土形变破坏准则,根据以试验数据直接建立的应变空间破坏准则建立了考虑徐变形变的混凝土形变破坏准则。4、为了验证混凝土形变破坏准则,提出并建立了一套基于单轴加载设备实现混凝土立方体试件双轴加载和基于普通应变计实现混凝土立方体试件空间应变测试的方法,试验结果与计算结果随应力发展的趋势吻合较好,但应变值在高应力水平时存在一定偏差。根据试验和计算得到的形变结果,分别计算形变破坏判断指标r/r*,在应强比σ3/σ3f较小时,二者吻合较好,应强比σ3/σ3f较大时有一定偏差,这是由于试验测试应变存在偏差造成的。整体上,形变破坏判断指标r/r*随应强比σ3/σ3f变化的趋势吻合较好,在σ3/σ3f0.90～0.95时,r/r*1,可以判定混凝土未破坏,在σ3/σ30.90时,r/r*随σ3/σ3f迅速增大,在接近极限强度点时r/r*超过临界值,可以判定混凝土破坏,较好地验证了本文提出的混凝土形变破坏准则。5、比较研究了几种常用的收缩徐变模型,根据考虑因素、适用范围及预测结果优劣,选择GL2000模型用于分析大跨度预应力混凝土箱梁桥的收缩徐变效应。提出了考虑箱梁截面非均匀收缩的结构收缩效应计算方法,考虑混凝土空间徐变的结构徐变效应计算方法。在研究混凝土箱梁的口照辐射温度场和比较研究国内外几种梯度温度模式的基础上,分析了大跨度预应力混凝土箱梁桥的结构温度效应。6、以一座大跨度预应力混凝土箱梁桥为例,应用本文提出的结构效应计算方法采用实体单元有限元对结构进行了分析,根据计算结果利用形变破坏准则从形变角度很好地解释了腹板斜裂缝的形成机理。
[Abstract]:Large span prestressed concrete box girder bridge in the operation of excessive deflection and crack generally has been plagued by bridge engineers, is an urgent need to study and solve the problem. In the past, people used to force from the point of view to analyze and study this issue, although achieved some results, but did not solve the fundamental problem. The paper grasps the essence of deformation the failure of materials, from the perspective of the relationship between deformation and damage of concrete materials, the deformation failure criterion of concrete is established, the.1 deformation mechanism of cracking of large span prestressed concrete box girder bridge, the typical crack of large span prestressed concrete box girder bridges are part of the domestic research, analyzes the causes of the cracks and deformation of the load factor factors, summarizes the existing research results, points out that well explain the cause of part of the crack from stress analysis cannot be put forward from the angle of deformation. .2 cracking problems of long span prestressed concrete box girder bridge, the solid material under stress shape and volume change is defined as the deformation, with the strain tensor in the Cartesian coordinate system, is derived in eight sides and in the Haigh-Westergaard coordinates of the shape variables. It is pointed out that the mixed coagulation including instantaneous deformation ten deformation and Xu recommends using non deformation, elastic orthotropic constitutive model to calculate the instantaneous deformation, according to constitutive model calculation. This paper summarizes Xu deformation of concrete under uniaxial stress state under different foundation, Xu Biangui space law and three axis of biaxial creep Poisson's ratio of the single degree of creep according to the constitutive model based on; based on the analysis of concrete creep mechanism, put forward the concept of ball creep rate and creep deflection, creep of concrete is established according to constitutive model of.3, pointed out that the destruction of solid materials Quality is the deformation exceed the capacity of its own body and the occurrence of instability, on the basis of the deformation of the concrete material damage theory. To study the relationship between the material deformation and fracture of concrete, respectively in the stress space failure criterion is deduced according to the deformation of concrete failure criterion, strain test data space to directly establish the failure criterion of concrete is established creep deformation deformation failure criterion of.4, in order to verify the deformation of concrete failure criterion, and proposes a method based on the concrete specimens under biaxial loading and based on the common strain gauge implementation of concrete specimens under uniaxial loading space strain test equipment, test results and calculation results with the stress development trend are in good agreement but there is a certain deviation, the strain value at high stress level. According to the test results and the calculated deformation, calculated form The destructive evaluation index of r/r*, should be stronger than 3/ in sigma sigma 3F is small, two good agreement, should be stronger than the 3/ sigma sigma 3F is larger when there are some errors, this is because the test strain deviation caused. On the whole, the deformation failure judgment index r/r* with 3/ is stronger than the trend of sigma sigma 3F anastomosis well, the sigma 3/ Sigma 3f0.90 ~ 0.95, r/r*1 can determine the concrete is not destroyed in the sigma 3/ Sigma 30.90, sigma Sigma r/r* increases quickly with 3/ 3F, r/r* exceeds the critical value close to the ultimate strength point, can determine the failure of concrete, verified the variable shape concrete failure criterion.5 a comparative study of shrinkage and creep, several common models, according to the consideration, the applicable scope and the performance of the prediction results, select the GL2000 model for the analysis of shrinkage and creep effect of long-span prestressed concrete box girder bridge. Considering the box girder non uniform shrinkage of the folding structure The calculation method of effect, structure calculation method considering the creep effect of concrete creep space. In the research of concrete box girder in radiation temperature field and study several temperature gradient model, analyzed the.6 structure of the temperature effect of long span prestressed concrete box girder bridge, a long-span prestressed concrete box girder bridge for example, the structure effect is presented in this paper by using the calculation method of solid finite element of structure was analyzed according to the calculation results using the deformation failure criterion from deformation angle can better explain the formation mechanism of Web diagonal cracks.

【学位授予单位】：西南交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U448.213

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