火灾下钢筋混凝土板的热弹塑性有限元分析——基于S-R分解原理(Ⅰ:理论)

Thermal-elastic-plastic finite element analysis of reinforced slabs under fire-based on S-R decomposition theorem(Ⅰ:Theories)

火灾试验研究表明,火灾下钢筋混凝土受弯构件的变形非常大,转动也很大,尤其是单面受火的板。基于S-R分解原理的更新拖带坐标有限元法分析这类构件,有利于跟踪变形物体中各点的变化,保证单元的质量守恒。用有限元增量法求解,还可以避免对坐标的修正,而且将转动作为一个独立的自由度,提高了求解效率,特别适合于几何非线性、材料非线性问题的求解。本文采用此方法对火灾下钢筋混凝土板进行编程分析。同时,为克服在时间步内温度路径难于确定的问题,本文给出了平面应力状态下的混凝土热弹塑性积分方案的初值表达式。通过实际编程发现,该方法求解效率高,精度也比较好。

Experiment revealed that reinforced flexural concrete members in fire underwent large deformations with large rotations,especially in slabs exposed to fire on one face.Updated co-moving coordinate finite element based S-R decomposition theorem is convenient to track deformations of points in the deformed configures,to assure the mass equilibrium of element.It could avoid to modify the coordinates of points in the incremental solver of finite element.Regarding rotations as an independent freedom,efficiency is improved.So it is very suitable to geometrical non-linearity and material non-linearity problem.The finite element program with the method is developed for reinforced concrete slabs.The temperature path is difficult to determine in an incremental time,thus,initial value equations of concrete thermal-elastic-plastic integration under plane stress state is presented.Analytical and experimental results for the fire tests are basically in good agreement,indicating that reliable results can be achieved with high efficiency.