基于纤维梁模型的火灾下多层混凝土框架非线性分析

为分析和模拟多层混凝土框架结构在火灾下的反应规律及其破坏过程,基于建筑结构分析中常用的纤维梁单元,建立了钢筋混凝土梁、柱构件的火灾破坏数值模型。模型将构件截面划分成多个纤维,可以考虑构件截面的不均匀温度场分布以及材料非线性和几何非线性问题。对单层单跨混凝土框架进行火灾反应分析,并与试验结果进行比较,验证了此数值模型的准确性。通过对多层框架进行火灾反应模拟,比较不同火灾场景的模拟结果,分析其反应规律以及破坏过程。结果表明,纤维梁单元模型可以较好地模拟钢筋混凝土结构的受火破坏过程,并且火灾发生的位置不同,结构的破坏机制也不同,一定条件下蔓延的火灾比不蔓延的火灾对多层混凝土框架结构的破坏性更大。分析结果可以为实际结构的防火设计提供参考。

Nonlinear analysis of multi-story concrete frame under fire with fiber beam model

In order to analyze and simulate the response and collapse of multi-story reinforced concrete frame structures under fire,a novel numerical model based on the fiber beam model was proposed in this paper.By dividing the cross section of beam element into many small concrete and steel fibers,this model could consider the non-uniform temperature distribution across the section and simulate the behavior of material nonlinearity and geometry nonlinearity.This fiber model was validated by comparing with experimental results from a one-story,one-bay frame fire test.Then,the response and collapse process of a multi-story reinforced concrete structure were analyzed and the influence of different fire scenarios were discussed.It can be concluded that the proposed fiber model can be used to simulate the collapse process of reinforced concrete frames under fire,and different fire scenarios lead to different collapse mechanisms.It is found that the spreading fire may cause more severely damage to multi-story reinforced concrete structures than the fire without spread.The results provide a useful reference for practical fire resist design for structures under fire.