基于环索内力相等的椭球形弦支穹顶结构的预应力分析

PRESTRESSING ANALYSIS OF ELLIPSOIDAL SUSPEN-DOME STRUCTURES BASED ON EQUIVALENT INTERNAL FORCES OF HOOP CABLES

当椭球形弦支穹顶结构的同圈环索内力相等时,张拉环索是一种高效的预应力施加方式。该文利用平衡矩阵理论分析了3种常见椭球形弦支穹顶索撑体系的可行预应力模态,发现了当索撑体系的超静定次数不小于环索单元数时同圈环索内力可相等的规律。然而相比联方型和凯威特型椭球索撑体系,肋环型索撑体系的超静定次数低,同圈环索内力不能相等,导致不能直接采用张拉环索方式施加预应力。为使肋环型椭球弦支穹顶的同圈环索内力相等,采用扩展力密度法对其索撑体系重新找形分析,得到了同圈环索内力相等的改进肋环型椭球索撑体系。最后对一肋环型椭球弦支穹顶算例进行了找形分析验证,并利用ANSYS有限元软件对传统型和改进型肋环椭球弦支穹顶进行了力学性能的对比分析,提出了张拉环索施工时将张拉点布置在长轴方向下方的建议,这为以后类似工程的施工设计提供了参考依据。

Tension hoop cable is a high efficiency construction method for the prestressing system of suspen-domes, when equivalent internal forces of hoop cables in the same circle are ensured. Feasible prestressing distribution of three common ellipsoidal cable-strut systems are analyzed based on the equilibrium matrix theory, and the conclusion is obtained that the equivalent internal forces of hoop cables could be ensured when the degree of the indeterminacy of the cable-strut system is not less than the number of hoop cables. However the degree of the indeterminacy of rib-patterned cable-strut system is low compared with that of Lamella system and Kiewitt system, which results in unequal internal forces of hoop cables and inadaptability of tensioning hoop cables. Thus, extended force density method is adopted in the form-finding to build a modified structure. Finally, a numerical example for a modified rib-patterned suspen-dome is presented, and a comparative analysis of the modified structure and the original one using the Ansys software is performed. Suggestion is given that tensioning points should be arranged beneath the long axis of the structure, which provides a reference for both design and construction of the ellipsoidal suspen-dome in the future.