蜂窝双撑杆型索穹顶的构形和预应力态简捷计算法以及参数灵敏度分析

Configuration, simplified calculation method and parameter sensitivity analysis on prestress distribution of honeycomb-type cable dome with two struts

蜂窝双撑杆型索穹顶结构具有以下特点:一是上弦脊索选用了任意等腰六边形的蜂窝网格;二是抛弃了在上下弦节点只有一根垂直水平面撑杆的"拉索海洋和压杆孤岛"传统张拉整体Fuller构想,而是在上下弦节点设有倾斜形的双撑杆,这使上弦网格扩大,撑杆和整体结构的稳定性得到提高,可改善施工张拉成形的方便性,结构构形的建筑美和结构美协调融合。依据节点平衡方程,提出了结构预应力态的简捷计算法,推导了预应力态索杆内力一般性计算公式。对90个结构模型进行了分析计算,反映了该种索穹顶预应力态的索杆内力大小和分布规律,同时参数灵敏度分析结果表明,内力分布对矢跨比和是否开孔不敏感,下弦节点位置则影响较大。本文的研讨为索穹顶结构选型、设计和施工提供了一种新思路。

A honeycomb-type cable dome with two struts has the following characteristics: 1) honeycomb-shaped grids of random isosceles hexagon are adopted on upper chord ridge cables; 2) Fuller’s idea that tensegrity is an ocean of tensile cables and islands of compressed struts is discarded, so that two oblique struts are converged at both upper and lower chord nodes, instead of one vertical strut, which enlarge the upper chord grids and stabilize struts and the whole structure. Easy construction and combination of architectural and structural beauty are also achieved. A simplified calculation method of pretress distribution was proposed through nodal equilibrium equations. General calculation formulas of member forces at the prestress mode were given. Ninety examples of structural models were analyzed in order to show the magnitude and distribution features of member forces at the prestress mode. Parameter analysis showes that member forces are not sensitive to the rise-to-span ratio or whether an inner hoop is set, while the position of lower chord nodes is quite crucial. This study provided new ideas for structural selection, design and construction of cable domes.