三面受火的矩形钢管混凝土柱受力机理与耐火极限

Mechanism and Fire Resistance of Concrete-Filled RHS Columns in Three-Surface Fire

受火边界作为研究结构构件抗火性能的基本前提条件之一,对结构构件抗火性能有着显著影响。已有钢管混凝土柱相关研究多假设其四面均匀受火,则针对实际结构中可能出现的三面受火这一情况,对矩形钢管混凝土柱进行抗火性能理论研究。分析了三面受火的矩形钢管混凝土柱温度场和耐火极限,以及高温全过程的构件受力机理,且与四面受火的矩形钢管混凝土柱进行了对比分析。研究表明:三面受火时构件截面的整体温度比四面受火时有显著降低,且三面受火时耐火极限高于四面受火;三面受火构件在高温全过程中轴向变形趋势与四面受火类似,而侧向变形可能会发生反转。

Fire boundary condition is a fundamental factor determining the fire performance of structural members. Previous research on concrete filled steel tubular （CFST） columns generally assumes that columns are in four-surface fire,but because of the thermal barrier effect, CFST columns may be exposed to three-surface fire. For this situation, the theoretical analysis of fire performance of concrete-filled rectangular hollow section （RHS） columns in three-surface fire was conducted in this paper. The thermal field, fire resistance and stress mechanism in the whole process of the three-surface fire were investigated and compared with that in four-surface fire. The results reveal that in three-surface fire,the cross sectional temperatures are generally lower than those in four-surface fire. It consequently brings higher fire resistance with lighter material damage. The development of axial deformation is similar to that in four-surface fire,but the lateral deflection may reverse from bending to exposed surface to unexposed surface, which is different from that in four-surface fire.