梁上部钢筋跨中布置方式对结构连续倒塌影响分析

Study on influence of upper steel arrangement of beams on progressive collapse mechanism of structure

为研究梁上部钢筋跨中布置方式对钢筋混凝土框架结构连续倒塌机制的影响,设计了2个一层四跨梁柱子结构模型,梁上部钢筋分别按跨中截断与通长进行布置,并对结构连续倒塌过程进行有限元分析。通过比较竖向荷载、梁内部轴力、梁关键截面钢筋应力随结构竖向变形所产生的变化,得到梁上部钢筋跨中布置方式对结构连续倒塌机制的影响规律。结果表明,布置方式对梁机制作用前期抗倒塌能力影响较小,对后期压拱效应及悬链线机制影响较大,通长布置结构提前进入悬链线作用阶段;按经典塑性理论计算的塑性峰值荷载较实际的偏小;通长布置结构的最终承载力比截断布置的提高了18.2%,通长布置可增强结构抗连续倒塌性能。

In order to study the effect of arrangement of steel bars in the upper mid-span of beams on the progressive collapse mechanism of reinforced concrete frame structures,two one-layer and fourspan beam-column substructures whose steel bars in the upper mid-span of beams were untouched or truncated were designed,and the progressive collapse process of the substructures was analyzed. By comparing the changes of vertical load,axial force in the beam and stress in the critical beamsection,the influence of the steel bar arrangement on the progressive collapse mechanism was obtained. The results show that the arrangement has a slight effect on the early anti-collapse mechanism of beams,but it has a great effect on the later compressive arch action and catenary action. The load carrying capacity calculated based on the conventional plastic theory is smaller than the actual one. The ultimate bearing capacity of structure with untouched steel bars is improved by18. 2% comparing with the structure arranged by truncated steel bars,and untouched steel bars can enhance anti-collapse resistance of structures.