预应力混凝土桥梁实体单元与杆单元组合模型收缩徐变效应分析研究

发布时间：2018-01-14 06:12

本文关键词：预应力混凝土桥梁实体单元与杆单元组合模型收缩徐变效应分析研究　出处：《交通运输部公路科学研究院》2016年硕士论文　论文类型：学位论文

【摘要】：混凝土结构在持续荷载作用下变形随时间不断增长的情况,称之为混凝土徐变。根据工程实际,混凝土的收缩徐变会占到混凝土变形的很大一部分比例,徐变变形逐步累计值可以达到同样的应力状态下弹性变形的1.5~3倍甚至更多,对混凝土结构的长期变形影响很大,而且会改变结构的应力状态。在预应力钢筋混凝土结构中,混凝土收缩徐变与配筋有关,混凝土要收缩徐变,钢筋不产生收缩徐变,而且对混凝土收缩徐变有一定的约束作用,从而引起预应力混凝土结构内部的应力重分布和预应力损失。对于施工过程中体系转换和超静定的预应力钢筋混凝土桥梁结构,收缩徐变变形受到约束会产生结构内力的重分布。所以收缩徐变变形是混凝土桥梁结构设计中必须要考虑的结构行为。现在主流的混凝土收缩徐变计算均建立在梁单元的基础上,钢筋是采用换算截面的方法加到混凝土截面上的,计算收缩徐变时钢筋和混凝土一同收缩徐变。从物理概念上钢筋和混凝土一同收缩徐变是不合理的。本文研究采用三维实体单元和杆单元组合的精细有限元计算模型分析预应力混凝土桥梁结构的收缩徐变,其中实体单元用来模拟混凝土结构,正面积杆单元用来模拟钢筋,负面积杆单元模拟孔道,并用位移约束方程关联实体和杆单元节点。钢筋的预应力通过杆单元初内力的形式施加。在精细化有限元模型的基础上通过逐步叠加单元应变的方法计算预应力混凝土桥梁的收缩徐变及施工过程体系转换问题并编制相应的程序模块。本文给出了编制模块的关键技术及思路,并通过算例对比分析验证编制的模块的正确性。
[Abstract]:It is called concrete creep when the deformation of concrete structure increases with time under the action of continuous load. According to the engineering practice, the shrinkage and creep of concrete will account for a large proportion of the deformation of concrete. The accumulative value of creep deformation can reach 1.53 times or more than that of elastic deformation under the same stress state, which has great influence on the long-term deformation of concrete structure. And it will change the stress state of the structure. In the prestressed reinforced concrete structure, the shrinkage and creep of concrete is related to the reinforcement, the concrete must shrink and creep, and the reinforcement does not produce shrinkage and creep. Moreover, it can restrain concrete shrinkage and creep to some extent. Thus, the stress redistribution and loss of prestress in prestressed concrete structure are caused. For the prestressed reinforced concrete bridge structure with system transformation and statically indeterminate during the construction process. The redistribution of internal force will occur when the shrinkage and creep deformation is restricted. Therefore, shrinkage and creep deformation is the structural behavior that must be considered in the design of concrete bridge structure. Nowadays, the mainstream calculation of shrinkage and creep of concrete is based on. On the basis of the beam element. The steel bar is added to the concrete section by the method of conversion section. It is not reasonable to calculate the shrinkage and creep of steel bar and concrete when they are shrinkage and creep. In this paper, the fine finite element method of 3D solid element and bar element combination is studied to calculate the shrinkage and creep of steel bar and concrete. The model is used to analyze the shrinkage and creep of prestressed concrete bridge structure. The solid element is used to simulate the concrete structure, the positive area bar element is used to simulate the reinforcement, and the negative area bar element is used to simulate the pore channel. The prestress of steel bar is applied through the form of initial internal force of the bar element. On the basis of the fine finite element model, the prestress is calculated by the method of superposing the strain of the element step by step. The shrinkage and creep of concrete bridge and the conversion of construction process system are discussed and the corresponding program modules are worked out. The key technology and train of thought of compiling the module are given in this paper. The correctness of the module is verified by comparison and analysis of an example.
【学位授予单位】：交通运输部公路科学研究院
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U441

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