钢-混组合结构桥梁混凝土的收缩徐变效应

Shrinkage and Creep Effect of Concrete of Steel⁃Concrete Composite Bridge

首先讨论混凝土收缩作用的等效降温取值问题,分析了构件理论厚度、环境平均相对湿度、预制板存梁期等因素对混凝土收缩的影响。然后探讨收缩徐变应力计算方法,并结合工程实例分析了混凝土徐变、抗剪连接键滑移和次内力对收缩应力的影响。最后提出了补偿收缩混凝土应用于钢-混组合梁桥时的注意事项。结果表明:对于我国大多数地区按等效降温15℃计算的收缩效应值较实际值偏小;抗剪连接键滑移主要影响距梁端1/10跨径范围内的应力分布;连续梁的混凝土板由收缩二次内力引起的结构应力远大于收缩一次内力引起的结构应力;补偿收缩混凝土的限制膨胀率宜根据收缩应变预测值和微膨胀对结构的不利影响综合确定。

First of all,the problem of equivalent cooling value of concrete shrinkage was discussed,and the influence of the theoretical thickness of the component,the average relative humidity of the environment,the storage period of the precast slab and other factors on concrete shrinkage was analyzed.Then the calculation method of shrinkage and creep stress was discussed,and the influence of creep,slip of shear connector and secondary internal force on shrinkage stress was analyzed with engineering examples.Finally,the points for attention in the application of shrinkage-compensating concrete to steel-concrete composite girder bridges were proposed.The results show that the shrinkage effect calculated by equivalent cooling of 15℃in most areas of China is smaller than the actual value.The slip of shear connector mainly affects the stress distribution within 1/10 span from the girder end.The stress of continuous girder concrete slab caused by secondary internal force of contraction is much greater than that caused by primary internal force of contraction.The limited expansion rate of shrinkage-compensating concrete should be determined comprehensively according to the predicted value of shrinkage strain and the adverse effect of micro-expansion on the structure.