为揭示正放四角锥网架的连续倒塌破坏机理, 采用备用荷载路径法并结合基于构件承载能力的敏感性评价指标, 对正放四角锥平板网架进行动力非线性分析, 模拟了结构的连续倒塌破坏过程, 分析了厚跨比、跨度和支承形式对网架结构抗连续倒塌性能的影响．分析结果表明, 周边点支承正放四角锥网架结构中部下弦杆、中间支座处腹杆为敏感构件, 结构中部上弦杆、中间支座周围腹杆和上弦杆为关键构件; 周边支承网架冗余度指标分布规律与周边点支承网架相似, 冗余度指标小于周边点支承网架; 点支承网架角支座腹杆和上弦杆为敏感构件, 敏感构件相邻腹杆及中间支座腹杆为关键构件．通过加强关键构件的截面尺寸, 可以显著提高结构的抗连续倒塌性能．正放四角锥网架冗余度指标分布规律不随厚跨比、跨度的变化而改变, 冗余度指标大小与网架厚跨比、设计应力比成正比, 而与模型跨度关系不大． In order to reveal the progressive collapse mechanism of square pyramid space girds，a dynamic nonlinear analysis using alternate path method and sensitive indices based on bearing capacity of members was conducted. The progressive collapse process of structure was simulated，and the influence of span-thickness ratio，structural span and supporting form on the progressive collapse performance was analyzed. The results indicate that the sensitive components of square pyramid space grids with perimeter-point supports are the bottom chords in the center and the web members at intermediate supports，while the key components are the upper chords in the center and the upper chords and web members at intermediate supports. The distribution regularities of redundancy indices in grids with perimeter supports are similar to those of grids with perimeter-point supports，and the redundancy indices are much smaller. The sensitive components of grids with point supports are the upper chords and web members at corner supports，while the web members adjacent to the sensitive components and at the intermediate supports are the key members. By reinforcing the sectional dimensions of key components，the anti-progressive collapse performance of the structure can be significantly enhanced. The distribution regularities of redundancy indices do not change with the span-thickness ratio or structural span，and the value is proportional to span-thickness ratio and designed stress ratio but less related to structural span
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