不同跨受火混凝土连续双向板火灾试验及数值分析

为研究受火跨位置和数量对三跨混凝土连续板火灾行为的影响,对三块混凝土连续板进行边跨、边中两跨和三跨火灾试验,获得了各跨炉温、混凝土和钢筋温度、变形、板角约束力和破坏模式等变化规律。基于ABAQUS软件平台,采用塑性损伤模型,对试验板温度、变形和力学机理进行了数值模拟,并与试验结果进行对比分析。结果表明:受火跨位置和数量对连续板裂缝分布、变形和破坏模式有重要影响;受火跨板底边缘出现垂直板边裂缝,受火跨板顶及其附近内支座出现平行短跨方向裂缝;受火边跨跨中竖向变形随温度升高逐渐增加,而中跨变形趋势取决于自身和边跨火灾工况。此外,数值结果表明受火跨升降温阶段弯矩机制不同;相比跨中,内支座位置弯矩绝对值较大;升降温阶段,试验板内轴力以受压为主;等效塑性拉应变最大值主要位于板顶支座和板底外边缘位置。

EXPERIMENTAL STUDY AND NUMERICAL ANALYSIS ON THE BEHAVIOR OF REINFORCED CONCRETE CONTINUOUS TWO-WAY SLABS SUBJECTED TO DIFFERENT SPAN FIRES

To investigate the effect of the amount and position of the heated compartments on fire behaviour of continuous slabs, this paper conducted fire tests on three continuous slabs. One has fire exerted at the side span only, one has fire exerted at both the side and the mid spans, and the other has fire exerted at all the three spans. The furnace temperatures of each span, the temperature of concrete and steel, the slab deflection, the restraint forces at slab corners and failure modes were obtained. Adopting the plastic damage model on the ABAQUS platform, the numerical analyses were conducted to predict the temperature, the deflection and the mechanical mechanism of tested slabs. The comparison between the test results and numerical results were also conducted, showing that the amount and position of the heated spans have significant effects on the cracking pattern, the deflection and the failure mode of continuous slabs. The short vertical slab cracks appear on the bottom surface of the heated spans, the cracks paralleled to the short-span appear on the top surface of the heated spans and the cracks are adjacent to interior supports. The mid-span vertical deflection of the side span gradually increases with the increase of temperature, and the increase of the deflection of mid span mainly depends on the heated effect of its adjacent spans. In addition, numerical results show that the moment mechanisms of the heated span during the heating stage is different with that during cooling stage. The moments near the internal supports are larger than those at other places. The axial forces in the continuous slab are compressive, and the maximum equivalent plastic tensile strains mainly concentrate near the internal supports (top surface) and the outer sides (bottom surface).