基于节点行为的空间索杆结构连续性倒塌机制与设计对策

The merits of light-weight and elegant-shape of large-span spatial cable-strut structures are usually accompanied by the expense of less redundancy, which in turn, makes structures more vulnerable to domino-like progressive collapse when local member failure occurs under unexpected loading conditions. Therefore, this project aims at ascertaining the collapse mechanism of large-span spatial beam-string structures and suspend-dome by conducting numerical, experimental and analytical research. The highlight of this project is that, by taking the behavior of typical joints under collapse scenario into consideration, the true responses of the large-span spatial cable-strut structures following initial local failure can be obtained. Highly efficient numerical computational procedure considering nonlinear mechanical behaviors including material plastic fracture that is caused by tension and/or shear force, and the sliding properties of the cable-strut joints will be established based on multi-scale computational simulation method. Novel experiments and testing method involving failure initiating at highly pre-stressed areas and complex spatial motion tracking system on detailed spatial cable-strut structure models will be conducted. Based on the numerical and experimental studies, the complete process of progressive collapse of spatial cable-strut structures including sequential failure of members, overall buckling, and final collapse and its reliability will be determined. Combined with the analytical analysis on the internal force redistribution, the collapse mechanism of large-span cable-strut structures triggered by local failure is uncovered. Anti-collapse design methods and guidelines, including easy-operating simplified method, precise complex method and conceptual method, will be proposed for the use of designer with different design conditions and different anti-collapse demands, so as to provide practical and reliable methods and necessary technical supports for collapse control design of large-span spatial cable-strut structures.

大跨度空间索杆结构在追求视觉冲击和质量轻盈的同时亦在一定程度上降低了结构的冗余度，因此一旦在非预期荷载作用下局部失效，极易引发多米诺骨牌似的连续性倒塌。基于此，本项目以大跨度张弦梁和弦支穹顶结构为具体研究对象，以节点在连续性倒塌工况导致的超常规受力状态下的力学行为为切入点，完善基于多尺度思想的包含有钢材拉-剪断裂模型和节点滑移失效等行为特征的高效数值算法，结合具有索破断触发装置和高速摄影测量系统的精细模型的倒塌试验，掌握空间索杆结构局部失效后渐进破坏、直至倒塌的行为响应，从而揭示大跨度张弦梁和弦支穹顶结构的连续性破坏机理与倒塌机制，构建面向不同抗倒塌水准和设计者条件的空间索杆结构抗连续性倒塌的简化设计方法、精细设计方法和概念设计方法，为结构冗余度低而又人群密集的大跨度空间索杆结构的安全提供技术支撑与保障。

本项目以大跨度张弦结构和弦支穹顶结构为具体研究对象，研究节点在连续性倒塌工况导致的超常规受力状态下的力学响应及其对整体结构连续性倒塌行为的影响。材料尺度上，进行了代表多种应力状态的材性试验，确定结构钢Q345的材料断裂特性；提出了基于剪切修正的GTN模型，用以模拟大跨度结构倒塌过程中可能出现的损伤与断裂，并提出了模型参数校核方法。节点尺度上，进行了索杆节点、钢管节点和檩条节点的全程加载试验，研究张弦结构和弦支穹顶结构体系中重要节点类型在倒塌工况下的行为，探究节点变形模式与失效机理；将断裂模型通过用户子程序引入通用有限元软件Abaqus的主程序，进而提出了节点断裂的数值模拟方法；基于组件法思想，建立了描述节点全程行为的理论模型。体系尺度上，开发了索破断触发装置和弦支穹顶精细化缩尺模型建造与施工技术，结合高速摄影测量方法，构建了刚-柔杂交体系连续性倒塌试验系统；进行弦支穹顶结构模型的连续性倒塌试验，掌握了空间索杆结构局部失效后渐进破坏、直至倒塌的行为响应；开发了表达节点滑移失效等行为特征的高效数值算法，对试验内容进行反演及延拓分析，揭示了大跨度网架结构、张弦结构和弦支穹顶结构的连续性破坏机理与倒塌机制；提出了空间索杆结构抗连续性倒塌的设计方法与设计建议。