大跨度四边支承单层柱面网壳的稳定性能

Stability of large-span single-layer cylindrical reticulated shells supported along four edges

摘要:

为拓宽单层柱面网壳的应用跨度,以参数分析作为研究手段,利用通用有限元程序ANSYS以及自编的前后处理程序,针对波宽为20m四边支承柱面网壳开展400余例非线性全过程分析,考察屈曲模态、临界荷载、塑性发展分布等特征响应,总结长宽比、矢宽比、初始几何缺陷、荷载不对称分布等因素对网壳临界荷载的影响规律.研究结果显示:四边支承柱面网壳的直杆以受弯作用为主,壳面中部是结构的薄弱区域;当长宽比过大时,应通过增设加劲肋提高壳面刚度,加劲肋的间距应使得网壳长宽比保持在1.0为宜;柱面网壳对于初始几何缺陷较为敏感,当缺陷值达到波宽的1/300时,网壳的弹塑性临界荷载将降低30%以上;当荷载呈不对称分布且p/g=1.0时,网壳的临界荷载将降低到均布荷载作用情况下的86%～94%.

Abstract:

To widen the span range available for single-layer cylindrical reticulated shells,parameter analyses based upon nonlinear complete-process analysis were carried out.More than 400 examples of single-layer cylindrical reticular shells with width of 20 meters and supported along the four edges were calculated by finite element method software ANSYS and self-developed pre-and post-processing programs.The buckling modes,critical loads,plastic development levels were collected to investigate the effect of length-width ratio,rise-span ratio,initial geometric imperfection,and unsymmetrical distribution of loads.The results show that single-layer cylindrical reticular shells supported along the edges are still characterized by bending action,and the central regions of shell structure are the most sensitive areas.When the length-width ratio becomes larger,it is necessary to add the stiffening ribs to enhance the rigidity of shells,and the spacing of which should be set to make the length-width ratio be 1.0.The cylindrical reticulated shells are concluded to be sensitive to initial geometric imperfection,when the initial imperfection value reaches 1 /300 of the width,the critical loads of reticulated shell will be reduced by 30%.And when the loads are unsymmetrical distributed with p/g=1.0,the critical loads will be 86%-94% of those under symmetrical loading distribution.