主管内填混凝土钢管T形节点受火后剩余承载力研究

Post-fire residual strength of steel tubular T-joint with concrete-filled chord

在试验研究基础上,对主管填充混凝土的T形节点受火后的剩余承载力进行有限元分析,结果表明:经历400℃以下的高温作用后,T形节点的剩余承载力未出现明显下降。但随着受火温度的升高,T形节点的剩余承载力呈非线性下降;同时,内填混凝土后钢管T形节点的受火后平均剩余承载力是相同参数空钢管T形节点剩余承载力的3倍以上,这是因为内填混凝土后可有效防止主管与支管节点处发生凹陷,使得钢管T形节点的破坏模式由节点相贯区主管凹陷破坏变为主管弯曲破坏,从而使钢管和混凝土的材料强度能够得到充分发挥;但内填混凝土抗压强度对承载力影响有限;此外,当试件从高温下冷却到常温后,由于混凝土强度未能同钢材得到较大恢复,因此内填混凝土T形节点受火后剩余承载力相比空钢管T形节点减少的更为明显。

The post-fire behavior of steel tubular T-joints with a concrete-filled chord( CFC) was experimentally and numerically investigated. The results reveal that the residual strength has no obvious decrease after lower than or equal to 400 ℃ fire exposure,but as the fire temperature increases,it is significantly linear decreased. Meanwhile,the average residual strength of the T-joints is increased by at least three times after infilling concrete. This is mainly because the in-filled concrete can prevent the T-joints areas from indenting,and the T-joints' failure mode changes from buckling to bending failure of the chord. Thus the mechanical properties of these steel and concrete joints are fully developed. However,the influence of concrete strength on the residual strength is very limited. Moreover,the post-fire residual strength of T-joints with CFC decreases more than that of T-joints without CFC as the damage of concrete in fire is irreparable.