大跨度Kiewitt型弦支穹顶结构的自振特性分析

ANALYSIS ON NATURAL VIBRATION CHARACTERISTICS OF KIEWITT SUSPENDOME WITH LARGE-SPAN

弦支穹顶结构是由单层球面网壳和下部张拉体系组合而成的一种新型的空间结构体系,以120m跨度K8型弦支穹顶结构为例,采用分块兰索斯(Lanczos)法对其自振特性进行了分析,分析时考虑拉索预应力、撑杆高度、结构跨度和荷载等4个因素对结构自振频率的影响。结果表明:当拉索预应力增大到一定程度,再增加预应力对结构的自振频率影响有限;结构自振频率随着撑杆高度的增加而增大;小跨度弦支穹顶与单层网壳自振模态相当接近,但大跨度弦支穹顶与同等跨度下的单层网壳自振模态明显不同。

Suspendome is a new type space structure system,which is consisted of single-layer spherical latticed shell and lower suspended structure.The finite element analysis models of K8 suspendome with span of 120m are established by the software ANSYS.Based on the cable prestress,bar length,span and load,the natural vibration characteristics of suspendome are analyzed by the block Lanczos method.Several conclusions can be made as follows：Improving cable tensions has little impact on the natural frequencies when the tension reaches a limit,and the natural frequencies of the structure increase with the bar length increasing.The modes of suspendome and single-layer spherical latticed shell are similar when the span is small,but the modes of them are different when the span is large.