四边形截面圆弧空间钢管桁架拱平面内稳定性及试验研究

Theoretical and experimental investigation on in-plane stability of spatial circular tube truss-arches with quadrangular section

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 buckling modes and failure mechanism of circular truss-arches with quadrangular sections under different load cases including horizontal uniform load, axially uniformly distributed load and concentrated load were investigated, and the influence of different geometric parameters of the truss-arches such as sectional height-to-width ratio, rise-to-span ratio, web-member included angle and sectional dimension on the failure mode and bearing capacities were also discussed, which shows that local buckling of chord members, local buckling of web members, global buckling and interactive buckling may occur under different conditions, and compared with global buckling and chord -member local buckling, the buckling of web members largely decreases bearing capacity of the whole truss-arch, which should be prevented in design. The tests of four truss-arch models with rectangular and trapezoidal sections were carried out, which indicates truss arches with the two types of sections mentioned above have almost the same stiffness and bearing capacity, and they can share the same design formula. Finally, the design formula for predicting the bearing capacity of circular truss-arches with quadrangular sections under combined compression and moments was proposed, based on both the quantities of numerical analytical results as well as the stability curve of the truss-arches only subjected to hydrostatic pressure.