中文摘要：

在合理确定混凝土和钢材热工参数的基础上，根据四面均匀受火下圆钢管混凝土离散体积单元的能量平衡建立有限差分平衡方程，采用放大混凝土比热的办法考虑混凝土中自由水、结合水的物理化学反应对混凝土温度场的影响．通过编制四面受火下圆钢管混凝土截面温度场非线性有限差分程序，并结合火灾下钢管混凝土柱温度场的试验结果，合理确定了钢管表面热传递系数和混凝土比热放大系数．结果表明，四面均匀受火下钢管混凝土柱温度场的计算结果与试验结果符合较好．本文的研究工作可为火灾下圆钢管混凝土柱非线性有限元分析创造条件．

英文摘要：

Based on the thermal properties of concrete and steel, using an elemental energy balance approach, the finite difference equations for concrete filled circular steel tubes （CFST） in fire was presented. The influence of the physical or chemical reaction of free or combined water in concrete on the temperature field of concrete core was considered by magnifying the specific heat of concrete. The program for the nonlinear finite difference analysis of the temperature field within CFST was developed, and the coefficient of heat transfer of steel and the magnifying coefficient of the specific heat of concrete were determined by matching the numerical results with experimental results from references. It is indicated that the calculated results fit with the experimental data satisfactorily. This work is a base for the further researches on the nonlinear finite element analysis of CFST in fire.