双重弯剪型抗侧力结构的屈曲及其二阶效应

BUCKLING AND THEIR SECOND-ORDER EFFECT OF DUAL SYSTEMS CONSISTING OF TWO SHEAR-FLEXURAL STRUCTURES

该文采用连续模型对刚度和轴力均匀的双重弯剪型抗侧力结构的屈曲进行分析,得到了计算临界荷载的精确公式。公式表明:双重抗侧力结构总的临界荷载是两个结构作为独立结构时各自临界荷载的简单相加,与竖向荷载在两个结构上的分布无关。对在均布水平荷载和顶端竖向集中荷载共同作用下的双重弯剪型结构进行了二阶分析,得到了弯曲侧移、剪切侧移、总侧移及其两个结构中的弯矩的二阶效应放大系数,并提出了简化计算公式。该公式用于顶部侧移计算非常精确,用于下部侧移计算精度良好且偏于安全;该公式也可以用于子结构整体弯矩的计算,子结构是框架的情况下也可以用于框架柱柱端弯矩的放大计算,在下部2/3高度范围内偏于安全。整个解析解的推导过程表明,这些放大系数也与竖向荷载在两个结构上的分布没有关系。

A closed form of solution for the buckling of dual systems consisting of two shear-flexural structures is provided, and a simple formula for the total buckling load is obtained. It is found that the total buckling load is simply a summation of the buckling loads of two component structures when they work independently, and it is independent of the distribution of vertical loads among the two structures. Linear and second-order analyses are carried out for dual systems loaded by uniform horizontal forces along height and vertical loads at the top. Amplification factors for the lateral displacements and bending moments are analyzed, a simple formula is suggested. The proposed formula is very accurate in predicting the total lateral displacement at the top of the system and slightly greater if used for displacements below the top. It has also acceptable accuracy for either bending moments of component structures as a whole or bending moments of columns when the component structure is a frame： it is slightly greater for bending moments below 2/3 of the total height, and slightly smaller for the top 1/3 height. From the derivation it is also found that the various amplification factors are also independent of the distribution of vertical loads among the two structures.