同跨受火时两层两跨组合钢框架抗火性能的试验研究

利用自行研制的火灾试验炉,对两榀两层两跨组合钢框架在同跨火灾作用下的性能进行了试验研究,火灾工况包括:梁、板、柱同时受火、节点不受火,梁、板受火而柱、节点不受火两种。试验中量测了各种工况的炉温,框架梁、柱及混凝土楼板中的温度分布及框架水平和竖向位移。结果表明:钢柱四面受火时,钢柱翼缘、腹板的温度相差很小;对于钢梁,除了与混凝土接触的上翼缘外,其余H型钢梁的裸露部分温度分布基本均匀;混凝土内部的温升一般滞后于钢梁,钢筋混凝土板对钢梁有约束作用,升温时混凝土限制钢梁的膨胀、降温时则限制钢梁的收缩,致使钢筋混凝土板中出现很多裂缝;组合梁的抗火性能明显优于钢柱,工程中应对钢柱和节点实施保护;钢框架未受火部分对受火部分约束很大,导致受火跨边柱与中柱的变形不对称,同样也产生了内力重分布。

Experimental study on performance of 2-story,2-span composite steel frame subjected to fire in same span

The special fire furnace and experimental set-up designed for 2-span and 2-story composite steel frame were used,and performance of 2 full scale 2-span and 2-story composite steel frames subject to fire in same span were studied.There are two type of fire condition.During one fire condition,only the beam-column connections were protected,during the other,both the columns and beam-column connections were protected.The temperature distributions along steel beam,column profile and across reinforced concrete slab were measured;meanwhile the displacements at middle and top of columns were recorded as well during the experiments.It is found that the temperature at flange is almost the same as that at web of steel column when it exposed to fire from four faces.The temperature of steel beam outside reinforced concrete slab is equal,but the temperature of steel beam in concrete is different.The temperature rise of concrete is slower than that of steel,so there is different restraint action on steel beam incurred by concrete and much more cracks occurred in concrete slab after fire.It can be concluded that the fire resistance of composite beam is better than that of steel column,and the unheated part of structure have strong restraint action on heated part thus inducing internal force redistribution of the whole structure.