开洞网架结构的稳定性分析

以弹性支座下的开有矩形洞口的双层正放四角锥网架结构为研究对象,利用SAP2000对开洞网架和不开洞网架分别进行了线性屈曲和非线性屈曲分析,获得了开洞网架结构的屈曲荷载、极限荷载及塑性铰发展过程,并分析了不同开洞大小和位置对网架结构整体稳定性的影响。分析结果表明：洞口大小与位置对网架的稳定性影响不可忽略,开洞网架结构较不开洞网架的稳定性承载力显著减小,必须限制洞口的长宽比以减小对稳定性的不利影响;开洞网架与不开洞网架结构屈服机制不同,未开洞网架的屈服一般从中央上弦杆开始而开洞网架结构塑性铰则首先出现在洞口四角处的腹杆上;在洞边增加拉压杆对提高网架结构的稳定性效果并不明显,需采取加大杆件截面尺寸等加强措施以避免洞口处杆件过早屈服。

Stability Analysis of Grid Structure with Open Hole

The double-layer pyramid grid structure with a rectangular opening was studied under the elastic support.The linear and nonlinear buckling analysis of space grid and space grid with openings was conducted by the FEM of SAP2000.The buckling load,the limit load and the process of plastic hinge development of space grid with openings were obtained.The influences of the parameters from different locations and sizes of openings on space grid static stability loads were analyzed.The results indicate that the influences of the size and the location of openings on the stability of the grid can not be ignored.With comparison to the un-open-hole grid,the stability bearing capacity of open-hole grid structure is obviously reduced,and the aspect radio of openings must be limited to reduce the adverse effects on the stability.The yield mechanism between the two structures is different,the yield of the un-open-hole grid generally started from central chord,however,the plastic hinges firstly appear in the web members located at the four corners of the hole.It is not dramatic to erect the tension and compression bar in the hole edge for improving the stability of grid structure,and it should be taken to increase the bar section dimensions for avoiding the premature yield of the bars at the hole.