火灾下组合构件内温度场分析的二维热阻单元

Two-Dimensional Thermal Resistance Elements for Analysis of Temperature Fields in Composite Structural Members in Fires

目的开发模拟钢与混凝土之间界面热传导的二维热阻单元,研究界面热阻对火灾下组合构件内温度分布的影响.方法把通过界面的热流当作混凝土单元和钢单元的对流边界条件,分别推导出热流边界对有限元方程的贡献,然后把这些贡献组合到一起,形成热阻单元的导热单刚.结果推导出了二维热阻单元导热单刚的通用积分表达式,并给出了六节点和四节点两种特殊矩形热阻单元导热单刚的显式表达式,这些单元已经装配到作者开发的温度场分析软件TFIELD中.结论数值算例表明,笔者开发的热阻单元能够模拟界面热阻对组合构件内温度分布的影响.

Two-dimensional thermal resistance elements simulating heat transfer at the interface between steel and concrete are simulated to study the influence of interface on temperature distribution in composite structural elements in fires. The interfaces were regarded as convective boundaries of concrete elements and steel elements,and the contributions from boundary flux were calculated separately. Instead of forming the stiffness matrices contribution from boundaries, contributions were grouped to give the conductivity matrix of the thermal resistance element. The general conductivity matrix defined by integrals for thermal resistance elements was derived, and conductivity matrices＇ explicit formulas for 6-node and 4-node rectangular thermal resistance elements were presented too. All these thermal resistance elements have been involved in TFIELD written by the authors for the analysis of temperature field in structural members exposed to fires. Numerical examples demonstrate that the effect of steel-concrete interface on the temperature distributions in composite structural members can be analyzed by the method suggested.