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结合实际民用建筑可燃物特点,基于简化的固体可燃物燃烧模型,利用CFD场模拟软件FLUENT对单室房间进行了火灾模拟,得到了烟气温度场分布情况。在此基础上,结合钢筋混凝土热工特性、温度—应变—应力本构特性,分析对比了钢筋混凝土柱在四种不同火灾条件下的温度场分布及变形规律。结果表明:由于现代建筑物中橡胶、塑料等高热值、易挥发性燃料成分的大量存在,使火灾初期具有快速的升温速率,而且火场整体燃烧温度高过ISO834标准。火灾发生前期,钢筋混凝土柱的轴向形变主要来源于热膨胀,恒载荷下的压应变相对作用较小;火灾发生后期,随着混凝土强度的降低,恒载荷下的压应变作用增强。整体而言,轴向膨胀和回压,耦合径向弯曲变形,导致构件内部破坏失稳。升温速率越大,截面温度梯度越大,破坏前能承受的挠度越小,耐火时间越短。
Combining with the characteristics of real combustibles of civil buildings, the fire simulation of single room was carried out by using CFD simulation software FLUENT based on simplified solid combustibles combustion model, and the distribution of temperature field of flue gas was obtained. On this basis, combined with the thermal characteristics, temperature-strain-stress constitutive characteristics of reinforced concrete, the temperature field distribution and deformation of reinforced concrete columns under different fire conditions were analyzed and compared. The results show that due to the high calorific value of rubber and plastics and the presence of volatile fuels in modern buildings, the rapid heating rate in the early stage of fire is higher than that of the ISO834 standard. In the early stage of fire, the axial deformation of the reinforced concrete column mainly comes from thermal expansion, and the relative compressive strain under constant load is relatively small. In the late stage of fire, the compressive strain under constant load increases with the decrease of concrete strength. Overall, the axial expansion and back pressure, coupled with the radial bending deformation, resulting in instability within the component failure. Larger heating rate, the greater the cross-section temperature gradient, the smaller the deflection before failure, the shorter the refractory time.