主管受拉的K形圆管节点抗冲击性能试验研究

Experimental study of a tubular K-joint with preloaded axial tension on its chord under lateral impact loading

管节点是钢管结构的传力构件,在撞击、爆炸等突发事故中,节点可能因受到冲击荷载而被破坏,严重时甚至会引起结构坍塌。为研究不同主管径厚比以及初始受力状态对节点抗冲击性能的影响,本文采用落锤试验机对两组主管径厚比不同的K形圆管节点进行了抗冲击性能试验研究。每组3个试件,其初始受力状态分别为:主管及支管未施加初始轴力、主管施加轴拉力两支管同时施加轴压力、主管施加轴拉力两支管分别施加轴拉力和压力。基于试验结果,比较了国内外相关规范的冲击承载力确定方法。研究结果表明:所有节点的破坏模态均主要表现为主管顶部受冲击区域的凹陷破坏;冲击过程中,初始受力状态相同时,主管径厚比较大的试件的主管局部凹陷变形与横向变形分别增大了19%和3%,冲击力峰值降低8%,冲击持时增加11%;主管径厚比相同的试件中,主管及支管未施加初始轴力的试件的主管局部凹陷变形最小,冲击力最大,冲击持时最短;将冲击力时程曲线平台值作为抗冲击承载力较为合适。

As the support member of steel tubular structures,the tubular joint may be damaged under impact or explosion,and even cause the collapse of the entire structure.To study the effects of the initial stress and the ratio of diameter to thickness,on the anti-shock performance of the joint,6 tubular K-joints,devided into two groups,were tested by drop hammer testing machine.For each group of 3 specimens,the initial force states were set respectively as that:no initial axial force loaded on the chord and braces,axial tension loaded on the chord and axial pressure loaded on the two braces,axial tension loaded on the chord and tension and pressure forces loaded on the braces.Based on the results obtained from the test,the calculating methods for the impact bearing capacity in the relevant codes at home and abroad were compared.The results show that the failure mode of all joints is the dent failure of the top surface of chord at the impact zone.Under the same initial stress state,the local dent deformation and transverse deformation of the joint with larger diameter-thickness ratio increase by 19%and 3%respectively,the peak value of impact force decreases by 8%,and the impact duration increases by 11%.Under the same diameter-thickness ratio,and with no initial axial force applied on the chord and braces,the local dent deformation of the joint is the smallest,the impact force is the largest and the impact duration is the shortest.The platform value of the impact force time history curve is suitable to be taken as an index for the impact bearing capacity.