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通过大挠度弹塑性有限元分析研究桁架拱在集中荷载、水平均布荷载、轴线均布荷载等不同荷载形式下的失稳与破坏机理,考察截面高宽比、矢跨比、腹杆夹角、腹杆尺寸等几何参数对桁架拱稳定承载力的影响,结果表明在不同参数条件下,桁架拱可能发生弦杆局部失稳、腹杆局部失稳、整体失稳以及局部与整体相关失稳等破坏形式;与拱的整体失稳和弦杆局部失稳相比,腹杆失稳会导致承载力的大幅下降,设计中应保证腹杆不先发生破坏。在理论分析的基础上,设计4榀矩形及梯形截面空间桁架拱模型进行了平面内稳定性能试验研究,分析表明两种截面形式的桁架拱在平面内具有基本相同的刚度和承载能力,其承载力设计可以采用相同公式。最后,基于静水压力作用下桁架拱的面内稳定设计曲线,通过大量的算例分析,提出轴力和弯矩共同作用下四边形截面圆弧形空间钢管桁架拱的整体面内稳定承载力设计方法。
The large-span elasto-plastic finite element analysis is used to study the instability and failure mechanism of truss arch under different loads, such as concentrated load, horizontal uniform load and uniform axial load. The effects of cross-section aspect ratio, The results show that under different parameters, the local instability of the chord, the partial instability of the web, the global instability and the local and overall destabilization of the truss arch may occur. And other forms of failure; compared with the overall instability chords partial instability of the arch, the instability of the web will lead to a substantial decline in bearing capacity, the design should ensure that the web without the occurrence of damage. Based on the theoretical analysis, the 4 榀 rectangular and trapezoidal cross-section space truss arch model is designed to study the in-plane stability of the truss arch. The analysis shows that the truss arch with the two cross-sections has the same stiffness and load carrying capacity in the plane. Force design can use the same formula. Finally, based on a large number of examples, the design method of the overall in-plane stability of the steel pipe truss arch with quadrangular cross-section and circular arc space under axial force and bending moment is proposed based on the in-plane stability design curve of the truss arch under hydrostatic pressure. .