高温下混凝土中热—湿—气—力学耦合过程数值模拟

NUMERICAL MODELING OF COUPLED THERMO-HYGRO-MECHANICAL PROCESSES IN CONCRETE AT HIGH TEMPERATURE

对高温下混凝土中热-湿-气-力学耦合过程分析提出了一个多孔多相介质的非混溶-混溶两级数学模型。数学模型基于控制干空气、湿份及基质溶解物的质量守恒、混凝土介质混合体的动量守恒和焓(能量)守恒的耦合偏微分方程组。给出了模型的控制方程、状态方程与所采用的本构定律。发展了相应的非线性耦合问题的有限元数值分析过程,以数值模拟火灾和热辐射等热荷载作用下的热-湿-气-力学耦合行为,并进而分析所发生的破坏现象。数值结果例题显示所发展的数学模型和数值方法在重现高温下混凝土中热-湿-气-力学耦合行为的有效性。

A hierarchical mathematical model for analysis of coupled thermo-hygro-mechanical processes in concrete at high temperature is presented. The concrete is modeled as deforming porous media filled with two immiscible pore fluids： gas mixture and liquid mixture, at immiscible-miscible levels. The mathematical model consists of a set of coupled, partial differential equations governing the mass balance of the dry air, the mass balance of the water species, the mass balance of the matrix components dissolved in the liquid phases, the enthalpy （energy） balance and momentum balance of the whole medium mixture. The governing equations, the state equations for the model and the constitutive laws used in the model are given. The finite element procedures are developed for corresponding non-linear coupled problems to numerically simulate thermo-hygro-mechanical behavior causing material failures in concrete subjected to fire and thermal radiation. Numerical results demonstrate the performance and the effectiveress of the proposed model and its numerical procedures in reproducing coupled thermo-hygro-mechanical behavior in concrete.