足尺L形方钢管混凝土组合异形柱受火后轴压承载力试验研究

对蒸压轻质加气混凝土板(ALC板)处理过的L形方钢管混凝土组合异形柱(SCFST柱)进行了3h耐火试验,结果表明该柱满足一级耐火等级柱构件的耐火极限要求。为了研究其受火后力学性能,对柱进行了轴压试验,得到其荷载-位移曲线、荷载-挠度曲线和荷载-应变曲线。通过分析试验曲线和现象发现,加载初期L形SCFST柱表现出良好的线弹性,达到极限承载力之后,柱表现出较好的延性,三肢单柱间协同作用良好。L形SCFST柱绕弱轴XX发生整体弯曲,最终由于固定端的混凝土被压碎和钢管鼓曲开裂导致承载力丧失。通过有限元模拟得到SCFST柱的极限承载力和破坏模态,以及采用叠加理论得到SCFST柱的极限承载力,均与试验结果基本吻合,证明了这两种方法的可行性。对比结果表明受火后SCFST柱的材料性能和结构构造并未受到明显的影响,仍具有较高的承载力,进而验证了SCFST柱采用ALC板作为防火处理措施的可行性。

Experimental study of axial compression bearing capacity for full-size L special-shaped column composed of concrete-filled square steel tubes after fire

The fire resistance test for L special-shaped column composed of concrete-filled square steel tubes ( SCFST column) covered by autoclaved lightweight concrete ( ALC board) was carried out. The results show that the column meets the requirements of the specification for the first grade refractory component. In order to analyze its mechanical properties after fire, axial compression test of the column was carried out, obtaining the load-displacement curve, load-deflection curve and load-strain curve. By analyzing the curves and experimental phenomena, L shaped SCFST column showed good linear elasticity in the loading initial stage. After reaching the ultimate bearing capacity, the column performed fine ductility and the three mono-columns showed good synergy work. The overall bending of L shaped SCFST column around the weak axial XX column was found. Finally, the crush of concrete and buckle-creak of steel tubes at the fixed end leaded to the loss of bearing capacity. The ultimate bearing capacity and failure mode of SCFST columns getting form finite element analysis and the ultimate bearing capacity obtained by superposition theory were basically identical to the results of test, showing that those two methods are feasible. The comparison results show that the material property and detail structure of SCFST column were not obviously affected by the fire and the SCFST column still has high bearing capacity, proving that it is feasible to use ALC board as fire precaution measure for SCFST column.