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对在正对称Pratt桁架中出现的直腹杆受压大偏心N型圆钢管节点的静力性能进行了单调加载的实验研究。实施了4个负向大偏心、4个正向大偏心和1个无偏心直腹杆受压N型圆钢管节点实验。该文介绍了节点实验方案,考察了直腹杆受压大偏心圆钢管节点破坏现象,给出了竖向荷载-端位移曲线以及应变强度分布曲线,并将偏心率对节点极限承载力、刚度和延性的影响进行了讨论。实验研究结果表明:节点实验值基本接近刚接理论值,节点可以按照刚接节点处理;节点由负向大偏心过渡到正向大偏心率为0.25过程中,随着偏心率的增大极限承载力逐渐增大,在偏心率为0.25时节点的极限承载力达到最大,随着节点偏心率从0.25增加到1.00,节点极限承载力又逐渐减小;不论中国还是欧洲规范在负向大偏心时计算值均为一固定值与实验结果完全不符,且其计算结果偏于不安全;节点变为正向大偏心后由于两腹杆之间间隙较大,N型节点就逐步过渡到单独的两个Y型节点,节点形式的彻底变化导致两规范值小于实验值。
Experimental study on the monotonic loading of the static behavior of large eccentric N-joints with straight web compression in the symmetric Pratt truss was carried out. Four negative eccentricities, four positive eccentricities and one non-eccentric straight web compression N-type tubular joint were implemented. In this paper, the node experimental scheme is introduced, the failure phenomenon of large eccentric circular steel tube joints under direct compression is investigated, the vertical load-end displacement curve and the strain intensity distribution curve are given, and the influence of eccentricity on the ultimate bearing capacity, And the effects of ductility are discussed. The experimental results show that the experimental value of node is almost close to the theoretical value of the node immediately, and the node can be treated as just connected node. During the transition from negative eccentricity to large eccentricity, the ultimate bearing capacity increases with eccentricity When the eccentricity is 0.25, the ultimate bearing capacity of the joint reaches the maximum. As the eccentricity of the joint increases from 0.25 to 1.00, the ultimate bearing capacity of the joint decreases gradually. When the eccentricity is 0.25, the ultimate bearing capacity of the joint reaches the maximum. The calculated value is a fixed value completely inconsistent with the experimental results, and its calculation results partial unsafe; nodes become large positive eccentricity due to the larger gap between the two webs, N-type node gradually transition to a separate two A Y-node, the node changes in the form of two normative value is less than the experimental value.