框架高阶屈曲波形的应用价值分析

Application value analysis of high order buckling wave of frame

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 a four-layer and three-span steel frame without some columns in top layer was carried outby using the traditional calculation length coefficient method to calculate the lateral resistance stiffness of the layer. Thecomparison of the lateral resistance stiffness by traditional method and by the SAP2000 software was carried out. Resultsshow that two results are close when the ratio of the shear force of each layer by the horizontal load is equal to that the ratioof the lateral resistance stiffness of the layer by critical load method. The overall buckling analysis of the steel frame wascarried out, and the first buckling mode is pointed out to be the buckling of weak layer, and the second and higher bucklingmodes can not be used because they can not reflect the constraint of frame beam to frame column correctly. Lacking of somecolumns in top layer leads to increase of axial force in roof beam, decrease of critical load, and the decrease ordisappearance of the rotation constraint action of roof beam to frame column, which needs to be considered in calculation ofcalculation length coefficient of column in top layer.