时变温度及剪切徐变对大跨径预应力混凝土梁桥长期变形的影响研究

Long-span prestressed concrete (PC) girder bridges (including continuous bridges and continuous rigid frame bridges) are used widely in China for their easy construction and low cost. However, in recent years the excessive long-term deformation and cracks becomes the main problem which limits the development of such bridges. There is exist research about the reason of excessive deformation, but the time-varying temperature distribution and shear creep effect to the three dimensional (3D) stress and long-term cycle deformation is rarely involved because of limitation of computation method and lack of representational experiment. According to the mechanical characteristics of long-span bridges, first the finite element (FE) method for 3D Temperature-Creep-Shinkage of PC girder bridges is studied; and based on this, by temperature distribution experiment of box girder segments through multi-directional angle, the time-varying feature and models of box girders' temperature are researched and established. As while, shear creep experiments in high stress PC are carried out and provide the shear creep parameters. Both of the experiments support the anlysis FE method considering concrete material nonlinear and time-effect nonlinear which used next to investigate the mechanism and solution method of long-term excessive cyclic deflection of long-span PC girder bridges. Last but not the least, the analysis method is certificated and modified according to the observing data of real background bridges and desmonstrate the problem of excessive deformation relatively completely and convincingly. The achivement of the research can be appied in the analysis and maintenace of similar bridges and other complex structures with a widely potential application prospect in the near future.

大跨径预应力混凝土梁桥(连续梁桥、连续刚构桥)在我国广泛应用，但近年来不断出现的长期变形过量及开裂问题严重制约了此类桥型的发展。目前有关长期变形过量的成因已有一定研究，但由于计算手段限制以及缺少表征性实验，对于时变温度场和剪切徐变作用下，混凝土梁桥的三维时变受力状态和长期往复变形特性研究缺乏。本课题针对大跨径桥梁空间受力特点，首先研究建立预应力混凝土梁桥"三维温度-徐变-收缩"的有限元计算方法；在此基础上通过多方位角混凝土箱梁温度场分布长期试验，探索箱梁空间温度场分布的时变规律并建立相关模型；同时引入高应力状态下预应力混凝土的剪切徐变试验得到相应材料参数；进而采用混凝土材料非线性和时变非线性耦合计算方法，探讨大跨径混凝土梁桥长期变形往复、下挠过量特性；最终结合桥梁实测数据，较为系统完整地解决大跨径混凝土梁桥长期变形问题。成果适用于同类桥梁及复杂结构的长期性能分析和维护，具有广泛的应用前景。

大跨径预应力混凝土梁桥(连续梁桥、连续刚构桥)在我国广泛应用，但近年来不断出现的长期变形过量及开裂问题严重制约了此类桥型的发展。目前有关长期变形过量的成因已有一定研究，但由于计算手段限制以及缺少表征性实验，对于时变温度场和剪切徐变作用下，混凝土梁桥的三维时变受力状态和长期往复变形特性研究缺乏。本课题进行了大跨径预应力混凝土梁桥长期变形的剪切影响及时变温度场的相关试验和理论研究，主要包括四个方面：①提出了剪切状态连续加载的试验方法，针对混凝土剪切徐变性能进行了为期3年、共3批次10组混凝土构件加载试验，研究了混凝土在剪切状态下的徐变规律和特点。②在西安、宜昌两地进行了模型试验和现场试验，采用智能传感器和自动巡检系统，连续采集并获取了不同纬度的空间温度场变化特性，提出了时变温度场的计算方法。③利用MATLAB和ANSYS混合编程，开发了混凝土结构三维徐变分析系统，可独立计入剪切徐变的影响。研究了大跨径混凝土梁桥在时变温度场和徐变耦合影响下结构的变形特性，并提出了相关建议。④研究了下挠桥梁工作状态的静力识别方法并进行了实桥验证。成果适用于同类桥梁及复杂结构的长期性能分析和维护，具有广泛的应用前景。