考虑焊缝几何缺陷影响时整体与局部轴向压力共同作用下薄壁圆柱壳稳定性分析

STABILITY OF THIN-WALLED CYLINDRICAL SHELLS UNDER COMBINED LOADING OF OVERALL AND LOCAL AXIAL COMPRESSION CONSIDERING WELD GEOMETRICAL IMPERFECTION

大型薄壁圆柱壳结构广泛应用于化工、电力等工程中,壳内通常需设置一些设备支承梁,常采用在壳壁上开矩形孔洞,将梁与壳壁焊接连接。壳壁因此承受由梁传递来的局部轴向压力,同时承受由上部壳体、顶盖等自重形成的沿环向均匀分布的整体轴向压力。该文考虑环向焊缝初始几何缺陷的影响,对开洞环向跨角小于10°的先作用整体轴压,后作用局部轴压的218个薄壁圆柱壳的稳定性进行了非线性数值分析。研究表明开洞上方环向焊缝缺陷对于柱壳局部轴压下的稳定承载力影响很小,但会显著削弱后屈曲承载能力。开洞下方最不利的焊缝缺陷位置受整体荷载水平和开洞尺寸的影响而改变。随着整体荷载水平提高,柱壳局部轴压下的稳定承载力降低。整体荷载水平较低时,柱壳局部轴压稳定承载力随着焊缝缺陷幅值的增大而减小;整体荷载水平较高时,柱壳局部轴压稳定承载力随着焊缝缺陷幅值的增大而增大。根据大量数值计算结果提出了整体与局部轴向压力共同作用时的圆柱壳稳定性设计建议。

Large-scale thin-walled cylindrical shells are widely used in chemical or electric power engineering. Within the shell, some beams are usually installed to support equipments. The rectangular cutouts in the shell wall are prepared to connect the beams by weld. Consequently, the shell wall is subjected to local axial compression from the beam and the circumferentially uniformly distributed overall axial compression resulting from the self-weight of the upper part and the roof. In consideration of circumferential weld initial geometrical imperfection, the nonlinear numerical analyses of 218 cylinders with the circumferential subtended angle of the cutout being less than 10° are conducted. The cylinders are firstly loaded under overall axial compression then under local compression. It is found that, the circumferential weld imperfections above the cutout influence the buckling bearing capacity of the cylinder subjected to local axial compression slightly, but significantly reduce the post-buckling bearing capacity. The location of the most unfavorable weld imperfection beneath the cutout is related to the magnitude of the overall load and the cutout size. As the magnitude of the overall compression increases, the buckling bearing capacity of the cylinder under local compression decreases. When the magnitude of overall load is low, the buckling bearing capacity of the cylinder under local compression decreases as the amplitude of the imperfection increases. When the magnitude of overall load is high, the buckling bearing capacity of the cylinder under local compression increases as the amplitude of the imperfection increases. Based on numerical computation results, the design recommendation of the cylinders subjected to the combined loading of overall and local axial compression is provided.