混凝土人字形密肋网壳与下部结构共同工作动力特性分析

Dynamic Characteristics Analysis of Coincident Work between Concrete Herringbone Ribbed Reticulated Shell and the Lower Structure

对混凝土人字形密肋折板网壳与下部结构共同工作的动力特性,采用有限元方法计算24个算例,对比点支承网壳和屋盖与下部结构共同工作的自振频率与振型,有限元参数分析考虑屋盖矢跨比、肋刚度、脊线刚度和顶层抗侧刚度的影响。计算结果表明:屋盖点支承和与下部结构共同工作的自振频率分布均较为密集,点支承屋盖的振型主要为竖向振动,共同工作时,第1、2阶振型为平动振型,第3阶为扭动振型,高阶平动振型中伴随屋盖的竖向振动,屋盖不宜简化为理想点支承作抗震设计;屋盖矢跨比对整体结构前三阶频率的影响较小;提高顶层抗侧刚度有利于增大结构整体刚度;增大屋盖肋刚度时,结构整体刚度仍主要受下部结构刚度控制,屋盖肋截面在满足承载力需求前提下可按较小的高跨比确定;屋脊类似于屋盖拱向肋的系杆,不会影响结构整体刚度。

In order to analyze the dynamic characteristics of coincident work between concrete herringbone ribbed reticulated shell and the lower structure, 24 examples were calculated by finite element method with comparing the natural frequencies and mode shapes both point supporting reticulated shell and the roof with the lower structure working together. At the same time the finite element analysis considered the influence of the height-to-span, ribstiffness, rigidity of ridge and the top lateral stiffness. The results show that the natural frequency distribution of both point supporting reticulated shell and the roof with the lower structure working together is more intensive. The mode shapes of point supporting reticulated shell are mainly vertical vibration. When the roof and the lower structure work together, the mode shapes both the first and the second are translational vibration, the third mode shape is torsional vibration; the high order modes are translational vibration with the vertical vibration of roof. At the same time the roof should not be simplified as the ideal point supporting for the seismic design ; The influence of the height-to-span on the first to third orders of the whole structure is small ; Increasing the top lateral stiffness is beneficial to increase the whole structure stiffness; When increasing the rib stiffness, the stiffness of the whole structure is still mainly controlled by the stiffness of the lower structure. At the same time the section can be determined according to the low height-to-span under the load bearing capacity requirement; The rigidity of ridge is similar to the arch rib of roof that will not affect the overall stiffness of the structure.