高层主次结构受力特点及刚度计算方法

近年来，主次结构广泛应用在超高层建筑中，但对其受力特点和刚度形成机制的系统研究却很少。为明确主次结构刚度形成机制、指导主次结构结构设计，通过有限元分析对主次结构受力特点进行研究，给出主次结构抗侧刚度形成机制，并推导主次结构刚度计算方法。以巨型框架结构、主次框架结构、主次框架-单斜撑结构、主次框架-X斜撑结构为研究对象，以构件内力分布特点、变形特性、刚度贡献为重点关注指标。研究结果表明，主次结构在竖向及水平荷载作用下均表现出显著的二级受力特性。水平荷载作用下，主柱沿模块高度呈现弯剪型变形，主次框架-单斜撑、主次框架-X型支撑结构表现出显著的桁架受力特点。次柱轴力沿高度呈周期性分布，次结构传递荷载对主结构变形和内力影响不大，但是其对结构整体刚度贡献不可忽略。分析结果表明，主次结构抗侧刚度关键参数为支撑轴向刚度、主柱轴向刚度、主框架抗剪刚度、次框架抗剪刚度。基于刚度形成机制，给出主次结构刚度简化计算方法，并与有限元方法结果进行对比，验证了刚度形成机制及刚度简化计算方法的有效性。

Mechanical properties and stiffness calculation method of primary-secondary structure for high-rise building

The primary-secondary structures have been widely applied in super high-rise buildings in recent years, but there are few systematic studies on the mechanical properties and stiffness formation mechanism of the structures. In order to clarify the stiffness formation mechanism and guide the design of primary-secondary structures effectively, the mechanical properties of primary-secondary structures were systematically studied by finite element analysis, the lateral stiffness formation mechanism of primary-secondary structures was proposed, and a stiffness calculation method for primary-secondary structures was derived. In this study, mega frames, primary-secondary frames, primary-secondary frames with diagonal braces, primary-secondary frames with X-braces were taken as the research objects, and the distribution characteristics of internal force, deformation characteristics and stiffness contribution of members were taken as the key indexes. The study reveals that primary-secondary structures exhibit the characteristic of two-level distribution of internal forces obviously under vertical or lateral loads. Under the action of lateral loads, the primary columns present bend-shear deformation along the height of the module, the primary-secondary frames with diagonal braces and the primary-secondary frames with X-braces show mechanical characteristics of truss structures. The axial force of the secondary columns distributes periodically along the height. The load transferred by the secondary structure has little effect on the deformation and internal force of the primary structure, but its contribution to the structural stiffness cannot be ignored. The results show that the key parameters of lateral stiffness of primary-secondary structures are the axial stiffness of braces, axial stiffness of primary columns, shear stiffness of primary frame and shear stiffness of secondary frame. Based on the stiffness formation mechanism, the simplified calculation method of the stiffness ofprimary-secondary structures was derived. The comparison with the results of the finite element method verifies the effectiveness of the stiffness formation mechanism and the simplified calculation method.