钢筋桁架装配式密肋楼盖火灾行为试验研究

Study on Fire Behavior of Steel Truss Assembled Waffle Slab

为适应当前装配式建筑发展需求,提出了一种新型装配式密肋楼盖体系,该楼盖由预制钢筋桁架现场拼装形成钢筋骨架,纵横向钢筋桁架节点处采用特制螺栓连接件形成整体,并利用预制物理发泡轻质混凝土块作为填充物,置于相邻桁架之间起到隔热保温效果,在钢筋桁架和泡沫混凝土块上方铺设预制钢筋网,现场浇筑高流动混凝土形成楼盖肋梁和面层结构。同时,研发了与该装配式楼盖匹配应用的条带式、可循环使用的铝合金模板,避免了满堂模板布设,该楼盖具有节省自重、轻质高强、装配便捷的特点。为掌握该楼盖在火灾(高温)下的性能,对两块该楼盖试件进行自然火灾试验,研究了不同区格条件下混凝土温度场分布、钢筋温度、裂缝模式等火灾行为,试验结果发现,两个试件在均布荷载下经历了2 h的火灾作用后,楼盖结构未发生任何严重损伤,泡沫混凝土块未脱落,具有良好的抗火性能,能够满足现行规范对楼盖耐火极限要求。在火灾作用下沿肋板厚存在非线性温度场和较大的温度梯度,且越靠近板底温度梯度越大;与炉温相比,混凝土和钢筋均存在明显的温度滞后效应。采用有限元软件ABAQUS建立了该楼盖的温度场模型,模拟分析结果与试验进行对比,二者吻合较好,验证了温度场模型的有效性,能够为预测火灾(高温)下该楼盖的性能提供技术支撑。

A new type of assembled waffle slab system consisted of steel truss,foamed concrete block,concrete rib and cast-in-situ concrete layer was proposed in order to meet the increasing requirement of prefabricated building.The orthogonal steel trusses which is connected at the cross joint by special bolts could be assembled to form reinforcing bar system.Precast foamed concrete blocks were arranged between adjacent trusses as filling materials with the function of heat insulation.There is steel bar mesh on the top of both trusses and foamed concrete block,and self-compact concrete would be cast for rib and top concrete layer.A specific formwork system composed of recycled aluminum alloy strips was also developed to adapt the construction of the slab system.Such waffle slab system is characterized by low self-weight,high strength and convenient assembly.In order to investigate the fire behavior of this type of slab,a test was carried out on two slabs with different compartment and different restraint type exposed to natural fire.The temperature field distribution of steel and concrete and crack pattern was studied.The experiment results showed that there was no obvious damage on slab surface after two-hour fire exposure and no spalling or bond failure of foamed concrete block occurred.The post-fire behavior of such slab system could meet the requirement of current fire code.The temperature field along the height of rib presented typically nonlinear distribution.The closer to slab bottom,the greater the temperature gradient was.There was temperature lag in the concrete and steel compared to the temperature development of furnace.The ABAQUS software was used to establish the temperature model of slab.The simulation result indicated a good agreement with the experimental data which verified its effectiveness in temperature prediction and the FE model could provide technical guidance for the fire performance analysis of this type of steel truss assembled waffle slab system.