分期浇筑混凝土结合面上初始温度的取值方法

Determination of the Initial Temperature at the Joint Faces when Pouring Concrete By Stages

从热传导的偏微分方程和有限元法入手,分析了结合面上节点初始温度取值不同时,造成温度场计算结果偏差的数学原因.根据能量守恒原理,推导出确定混凝土浇筑结合面上节点初始温度的计算公式,揭示了结合面上节点温度初值与新老混凝土的密度、比热容、单元划分大小、温度之间的数量关系.为取平均值的经验做法提供了理论上的依据,并能准确的计算出因初始温度取值不同导致的误差值.最后结合一个数值算例,与理论解相比较,采用该取值方法所得计算结果的最大误差不超过理论解的6%.

Different initial temperatures at the joint faces during concrete construction result in errors during calculation of the temperature fields.The mathematical cause of this was determined by analyzing the partial differential equations describing heat exchange and by the finite element method.The principle of energy conservation was used to derive a formula for the initial temperature at the interface between old and newly poured concrete.A quantitative relationship between the main parameters,such as density,specific heat capacity,element size and temperature,was obtained.This provides a theoretical basis to explain the empirical values and allows accurate calculation of the errors from the variation in initial temperature.Results from a numerical example computed by the present method were compared with the theoretical solution.The maximum error was found to be less than 6%.