大跨预应力混凝土箱梁桥收缩徐变效应测试与分析

预应力混凝土箱梁桥以其良好的结构整体受力性能在现代大跨桥梁结构中得到广泛应用，但迄今所修建的混凝土箱梁桥中，运营阶段箱梁开裂及下挠过大的现象较为普遍，实际混凝土箱梁桥中混凝土收缩徐变作用及其效应认识的不足是其可能产生的原因之一。现行有关混凝土收缩徐变的计算公式多以试验室模型试验结果为依据确定，由于实际混凝土箱梁结构的尺寸较大同时又处于复杂的自然环境中，因此对实际结构进行长期测试以获得能够验证现行规范混凝土收缩徐蛮计算公式的实测数据显得尤为重要。结合某高速公路上两座大跨预应力混凝土箱梁桥的修建及运营，对处于自然环境中的箱梁桥在混凝土收缩徐变作用下的真实反应进行测试，并详细地分析各测试数据，在此基础上提出同时考虑混凝土温度、环境相对湿度、箱梁局部理论厚度等因素及其变化的混凝土收缩应变和徐变系数计算方法．并烙其应用于实际桥梁的收缩徐变效应分析中，得出一些具有实用价值的结论，为实际箱梁桥的收缩徐变计算提供参考。

Test and Analysis of Shrinkage and Creep Effect of Long Span Prestressed Concrete Box girder bridge

Prestressed concrete Box girder bridge has been widely used in modern long-span bridge structures because of its good overall structural mechanical performance. However, in the concrete Box girder bridge built so far, the phenomenon of box girder cracking and excessive downward deflection during the operation stage is common. The lack of understanding of concrete shrinkage and creep effect and its effect in actual concrete Box girder bridge is one of the possible reasons. The current calculation formulas for concrete shrinkage and creep are mostly based on the results of laboratory model tests. Due to the large size of actual concrete box girder structures and their complex natural environment, it is particularly important to conduct long-term testing on the actual structure to obtain measured data that can verify the current specifications for concrete shrinkage and creep calculation formulas. Combined with the construction and operation of two large-span prestressed concrete Box girder bridge on an expressway, the real response of Box girder bridge in natural environment under the action of concrete shrinkage and creep is tested, and the test data are analyzed in detail. On this basis, a calculation method of concrete shrinkage strain and creep coefficient is proposed, taking into account the factors such as concrete temperature, environmental relative humidity, local theoretical thickness of box girder and their changes, And it is applied to the analysis of shrinkage and creep effect of actual bridges, and some conclusions with practical value are obtained, which provide reference for the calculation of shrinkage and creep of actual Box girder bridge