新型冷弯薄壁型钢混凝土组合楼盖耐火性能数值模拟研究

Numerical analysis of fire resistance of a new type cold-formed thin-walled steel concrete composite floor

冷弯薄壁型钢混凝土组合楼盖主要由上部压型钢板混凝土组合楼板和下部冷弯薄壁型钢拼合梁组成,当楼盖下侧发生火灾时,冷弯薄壁型钢梁和压型钢板会直接受火。为提升组合楼盖的耐火性能,在型钢梁的下翼缘固定防火板材,形成防火保护层,从而提出一种新型冷弯薄壁型钢混凝土组合楼盖。然而,加入防火保护层后,楼盖的温度分布、变形和耐火极限均发生改变,新型楼盖的耐火性能有待研究。建立简化的三维楼盖有限元模型,分析了混凝土板厚、梁高、荷载比和防火保护类型对新型楼盖耐火性能的影响,发现压型钢板板肋方向与钢梁垂直的楼盖钢梁同一高度处的温度沿跨度方向基本一致,仅沿高度方向不均匀;适当增加混凝土板厚对耐火极限提升较小。得到了不同截面尺寸的楼盖在0.2~0.5荷载比下的受火侧翼缘临界温度以及不同防火保护类型楼盖的受火侧翼缘时间温度曲线,用于估算该类楼盖的耐火极限。

Cold-formed thin-walled steel concrete composite floor is fabricated with profiled steel sheet-concrete composite slab at the top and cold formed steel built-up beam at the bottom.When fire occurs on the lower side of the floor,the cold-formed thin-walled steel beams and profiled steel sheets will be directly exposed to fire.In order to improve the fire resistance of the floor,a new type cold-formed thin-walled steel concrete composite floor is proposed by fixing fireproof board on the lower flange of cold-formed steel beams to form a fire protection layer.However,the temperature distribution,deflection and fire resistance time of the new floor will change after adding fire protection,so fire resistance performance of the new floor needs to be studied.A simplified three-dimensional finite element model is established to analyze the influence of concrete slab thickness,beam height,load ratio,fire protection on the fire resistance of the new floor.It is found that the temperature at the same height of the steel beam is basically similar along the span direction but not uniform along the height direction when the direction of the profiled steel sheet is vertical to the steel beam.Increasing the thickness of concrete slab appropriately has little effect on fire resistance.In addition,the critical temperature of the hot flange with different cross-section sizes under the load ratio of 0.2~0.5 and the time-temperature curves of the hot flange with different fire protection are obtained,which can be used to estimate the fire-resistance time of the new floor.