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为了研究地震作用下钢框架结构的落层倒塌效应,根据相关文献提供的9层钢框架模型,利用非线性显式动力有限元程序LS-DYNA分析其在地震作用下的结构响应,同时模拟相关文献中的振动台结构倒塌试验,分析结果同文献对比较为吻合,验证了模型的合理性。对该钢框架在强震作用下的倒塌效应进行仿真,分析表明强震作用下首先由于结构中部薄弱层层间位移角发展达到1/10并持续增大,发生落层倒塌,上部楼层碰撞作用于下部楼层,使下部相邻楼层柱轴力突增,加剧该层P-?效应,导致下层倒塌;此外第1层层间位移角亦发展达到1/10并持续增大,继而导致钢框架整体发生连续倒塌破坏。分析了落层倒塌碰撞作用下,薄弱层相邻下层柱总轴力变化规律,其动力放大系数可能大于规范取值。加强薄弱层抗侧刚度可有效防止钢框架发生倒塌破坏;合理设计的钢框架结构当薄弱层层间位移角超过规范限值但未出现持续增大现象时,不出现倒塌破坏。
In order to study the falling effect of the steel frame under earthquake, according to the 9-story steel frame model provided by the relevant literature, the structural response of the steel frame under earthquake action is analyzed by the nonlinear explicit dynamic finite element program LS-DYNA, In the literature, the shaking table structure collapse test, the analysis results are in good agreement with the literature, which verifies the rationality of the model. The collapse effect of the steel frame under the action of strong earthquake is simulated. The analysis shows that under the action of strong earthquake, the displacement angle between the weak layers in the middle of the structure first reaches 1/10 and continues to increase, and the falling of the falling layer and the collision of the upper floor occur On the lower floor, sudden increase of column axial force on the adjacent lower floors exacerbated the P-γ effect in this layer, leading to the collapse of the lower floor. In addition, the displacement angle of the first floor also developed to 1/10 and continued to increase, The overall collapse occurred in a row. The variation law of the total axial force of the lower column adjacent to the weak layer under the action of falling collapse collision is analyzed. The dynamic amplification factor may be larger than the standard value. Strengthening the stiffness of the weak layer can effectively prevent the collapse of the collapse of the steel frame; a properly designed steel frame structure does not collapse when the displacement angle between the thin layers exceeds the specification limit but does not increase continuously.