四角锥钢网架结构倒塌试验模型的数值模型分析

摘要

竖向荷载下四角锥网架结构的整体倒塌通常是拉杆屈服和压杆屈曲综合作用的结果.针对其倒塌破坏特征,以一个倒置四点支承四角锥网架结构为例,基于非线性有限单元法建立了考虑单杆初始弯曲的网架结构倒塌数值分析模型,并通过一个网架结构模型的倒塌试验对其可靠性进行了验证,进而考察了压杆屈曲对网架倒塌过程的影响程度.分析结果表明:考虑单杆初始弯曲的钢网架结构倒塌数值模型计算结果与试验结果吻合度较高,验证了数值分析方法的可靠性;考虑杆件初始弯曲的模型可完整揭示竖向荷载作用下网架结构的倒塌全过程;不考虑单杆初始弯曲将会过高的估计网架结构的极限承载力而偏不安全;在网架倒塌前削弱杆件均存在屈曲现象,削弱最靠近角支座位置的上弦压杆,对网架的抗倒塌性能最为敏感;压杆屈曲后性能对网架抗倒塌能力仍有贡献,直接杀死屈曲压杆的分析结果偏于保守.%Abstract:The overall collapse of quadrangular pyramid truss structure under vertical load is usually caused by both of compression members’ yielding and tension members’ buckling.For the collapse feature of one inverted quadrangular pyramid truss structure supported by four points,the numerical model of truss structure collapse is established by introducing initial bending of compression members based on the nonlinear finite element method,and the reliability of numerical model is verified through the collapse experiment of a truss structure.Furthermore,the effects of compression members buckling on the collapse process of truss structures are investigated.The results indicate that:the results of collapsed numerical model of steel truss structure which considers initial bending are consistent with the results of experiment,so the high reliability of numerical analysis method is validated;considering the initial bending of members,the whole collapse process of truss is presented under vertical loads;without considering the initial bending of members,the bearing capacity of truss will be overestimated.Weakening members have buckling phenomenon before the collapse of trusses,and the anti-collapse performance of truss is the most sensitive when the member closest to the corner is weakened.Post-buckling performance of compression members will still benefit for anti-collapse ability of truss,and the analysis results of deleting compression members directly are conservative.