Steel arches are widely used to support large span membrane roofs. In order to obtain a lightweight solution, these arches might be formed as a truss. Both the strength of the material and the critical load can limit the load-bearing capacity of the steel arch. Due to the out-of-plane slenderness of a large span arch, it is with utmost importance to utilize the membrane as a restraint against the buckling of the arch. Hence, the investigated structure is supported along a curve in an elastic way, but this support has a highly nonlinear response.

The presented analysis of the roof is based on the Dynamic Relaxation Method (DRM). To model the membrane, an 8-node quadrilateral membrane element is used. The truss is modeled by straight bars. To obtain an appropriate model for the out-of-plane behavior of the truss, the flanges of the truss are modeled as sub-trusses: four flange 3D trusses are used to represent the proper stiffness of the real bending resistance of a flange. The truss model fits nicely into the highly nonlinear DRM algorithm of membrane structures.

In the equilibrium state of the structure, the classical eigenvalue problem is solved to obtain the critical parameter of the actual load. The elastic and the geometric stiffness of the membrane and respectively the truss elements must be selected to withstand the destabilizing effects safely.

钢拱被广泛用于支撑大跨度膜屋顶。为了获得轻巧的解决方案，这些拱门可以形成为桁架。材料的强度和临界载荷都会限制钢拱的承载能力。由于大跨度拱的面外细长，利用膜作为约束拱的屈曲至关重要。因此，所研究的结构沿曲线以弹性方式被支撑，但是该支撑具有高度非线性的响应。

提出的屋顶分析基于动态松弛法（DRM）。要对膜建模，请使用8节点四边形膜单元。桁架由直杆建模。为了获得桁架的平面外行为的合适模型，将桁架的法兰建模为子桁架：四个法兰3D桁架用于表示法兰的实际抗弯强度的适当刚度。桁架模型非常适合膜结构的高度非线性DRM算法。

在结构的平衡状态下，求解经典特征值问题以获得实际载荷的关键参数。必须选择膜以及桁架元件的弹性和几何刚度，以安全地承受不稳定作用。