火灾蔓延作用下混凝土连续板力学行为试验研究与模拟

为研究火灾蔓延作用对三跨混凝土连续板力学行为影响，对四块混凝土连续板进行仅边（中）跨和三跨依次受火试验，获得各跨温度、变形、裂缝、爆裂和破坏模式等变化规律。在此基础上，对一块混凝土试验板火灾行为进行数值分析，研究了几何（非）线性和混凝土热膨胀应变对火灾蔓延作用下连续板各跨弯矩分布和薄膜机理影响规律。结果表明:混凝土板裂缝和爆裂主要出现于受火跨，非受火跨裂缝较少；板底和板顶具有完全不同裂缝分布，即板底短裂缝多出现在板边区域，板顶多为平行短跨方向通长裂缝。同时，混凝土连续板各跨跨中变形趋势取决于自身位置和火灾蔓延方向，变形最大值取决于自身受火时长和炉温。此外，数值分析表明，火灾蔓延行为对连续板各跨最大弯矩分布和拉压薄膜效应发展有重要影响；相比Lie模型，EC2模型计算结果较为合理，且几何非线性影响不可忽略。

EXPERIMENTAL STUDY AND NUMERICAL ANALYSIS OF CONCRETE CONTINUOUS SLABS SUBJECT TO TRAVELING FIRE

To investigate the effect of the traveling fire on the mechanical behavior of three-span continuous slabs,this paper conducted mechanical tests on the edge,middle-span and three-span specimens subjected to different fire sequences.The temperature,deflection,cracking,spalling and the failure mode were investigated.In addition,the fire behavior of one tested slab was simulated based on the numerical model.The model was used to investigate the effect of the geometrical nonlinear(linear)property and the concrete thermal strains on the moment distribution and the membrane action of different spans in the concrete continuous slab subjected to traveling fire.The results indicate that the cracking and spalling mainly occurred on the heated spans,with less cracks on the unheated spans.There were different failure modes on the top and bottom surfaces of the concrete slabs.Edge short cracks and short-span cracks appeared on the bottom and top surfaces,respectively.The deflection distribution of each span was dependent on its positon and the fire traveling direction.The maximum deflection was dependent on the fire duration and furnace temperatures.The numerical results showed that the fire traveling behavior had important effect on the maximum moment and the tensile or compressive membrane action of each span in the continuous slab.Compared to the Lie model,the prediction based on the EC2 model was relatively reasonable,and the effect of the geometrical nonlinearity should be considered in the analysis.