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对顶层抽柱的四层三跨钢框架进行屈曲分析,采用传统计算长度系数法计算层抗侧刚度,并与SAP2000软件计算的层抗侧刚度比较发现,施加水平荷载求得的各层剪力之比与采用临界荷载方法计算的层抗侧刚度之比相等时,两者结果接近。对钢框架进行整体屈曲分析,指出第1屈曲模态对应的是薄弱层的屈曲,第2及以上屈曲模态因不能正确反映框架梁对框架柱的约束,不能直接加以应用。顶层抽柱导致屋面梁轴力加大,自身临界荷载降低,使得屋面梁对顶层柱的转动约束作用减小或消失,需要在顶层柱计算长度系数计算中予以考虑。
The buckling analysis of the four-storey three-span steel frame with top-drawn columns was carried out. The traditional calculation of length coefficient method was used to calculate the lateral stiffness of the layer. Comparing with the calculated lateral stiffness of the layer by SAP2000 software, The results of the two methods are close to each other when the ratios of the ratios of the lateral stiffness of layers calculated by the critical load method are equal. The overall buckling analysis of the steel frame shows that the first buckling mode corresponds to the buckling of the weak layer. The second and the above buckling modes can not be directly applied because they can not correctly reflect the constraint of the frame beam to the frame column. The top draw-column causes the axial force of the roof beam to increase and the critical load of the roof beam to decrease. As a result, the restraining action of the roof beam on the top pillars decreases or disappears, which needs to be considered in calculating the length coefficient of the top pillars.