薄壁钢梁-陶粒混凝土装配式组合楼板受火后受力性能研究

由冷弯薄壁钢梁和陶粒混凝土预制板组成的装配式组合楼板具有轻质、高强和施工方便等优点。为研究该类组合楼板的抗火性能及高温后的受力性能,对6块遭受温度为700℃、持续90min烃类火灾升温作用的简支组合楼板试件进行受火后受力性能试验研究。结果表明：当施加的等效均布荷载达到2kN/m²时，受火作用后的组合楼板试件最大挠度小于跨度的1/400，且在加载过程中薄壁钢梁虽已明显扭曲、混凝土板多处开裂，但组合楼板试件未出现整体坍落现象；以普通栓钉为抗剪键的受火后组合楼板试件，其极限荷载比薄壁钢抗剪键组合楼板试件的提高14.2%；当用钢量相同时，主梁数量较多的组合楼板试件采用U形钢筋作为拉结件，其火灾后极限荷载比采用钢条拉结件的组合楼板试件的增加33%，且整体刚度也有所提高；该类组合楼板在受火后仍具有较高承载能力和整体刚度，且抗剪键类型、预制板之间设置的拉结件以及拉结件与抗剪键的连接方式均对其受火后的受力性能有较大的影响。引入组合效应系数可以较好地反映受火后组合楼板试件的组合效应及内部损伤程度。

Post-fire mechanical property of thin-walled steel beam-ceramsite concrete assembled composite floors

The new assembled composite slabs formed with thin-walled steel beam and ceramsite concretes have the advantages of lighter weight, higher strength and being convenient for construction.To study the fire-resistance performance and post-fire mechanical property of the slabs, experimental study of the post-fire mechanical performance of six simply-supported composite slabs after exposure to hydrocarbon fire heating with maximum temperature of 700℃ and duration time of 90min was conducted. The results show that the overall collapse of the composite slabs will not take place even when there are serious torsion of thin-walled steel beam and more than one serious crack in the concrete, and the maximum deflection of the slabs is less than L/400 for bearing uniform load of 2kN/m²; The ultimate load of the composite slab specimens after fire for which the commonly used nails are set is 14.2% greater than that with the shear keys made with thin-walled steel plate; As for the composite slab specimens in which there are more main beams for the constant steel quantity,the ultimate load of the composite slab specimens after fire for which the U-type steel ties are used as pull pieces is 33% higher than that of the specimen in which U-type tie bars are used, and the global stiffness of the composite slabs has the similar results. It is concluded that the composite slabs after exposure to fire still have higher bearing capacity and global stiffness, and type of the shearing keys, pull pieces between the precast concrete panels and the connection way of shearing keys to pull pieces have great effect on the post-fire mechanical property of the composite slabs. It can be seen that the combined effect coefficient presented here can be used to properly reflect the combined effect of the concrete panels and thin-walled steel beams and the damage degree of the slabs.