摘要
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。
Based on the characteristics of combustible fuel of actual civil building and a simplified combustion model of solid fuel, through numerical simulation of a single room in fire by use of the CFD simulation software FLUENT, this paper analyses the transient temperature distribution of the flue gas in the room. Then based on the thermal characteristics of reinforced concrete columns, the temperature-strain-stress constitutive characteristics, the paper analyses the evolutionary processes of the reinforced concrete columns temperature distribution and deformation regulations under four different elevated temperature conditions. The results indicate： because high calorific value and volatile fuel composition exist massively in the civil building, such as rubber and plastics, it makes fires with early rapid heating rate early, and the overall combustion temperature of the room is higher than ISO834 standards. Pre-fire, the axial deformation of reinforced concrete columns is mainly from thermal expansion in the meantime, compressive strain under constant load is relatively small; Post-fire, with the reduction of concrete strength, the compressive strain under constant load is enhanced. Overall, the axial expansion and back-compressive stress, coupled radial deformation result in the internal destruction and instability of RC column. With higher temperature rise rate, the column has a large temperature gradient; a smaller deflection before buckling damage is corresponding to shorter fire-resistant duration.
出处
《建筑科学》
北大核心
2012年第7期1-7,共7页
Building Science
基金
亚热带建筑科学国家重点实验室开放基金(No.2008KB34)
能源高效清洁利用广东普通高校重点实验室(KLB10003)
关键词
火灾
钢筋混凝土柱
升温速率
耐火极限
fire
reinforced concrete columns
temperature rise rate
fire resistance
