Second-generation trapezoidal sheeting, characterised by longitudinal stiffeners in webs and flanges, is loaded near a support by a concentrated force and a bending moment. Currently, design codes predict related failure by: (a) determining the ultimate bending moment via the effective width approach or the Direct Strength Method (DSM); (b) finding the web crippling load via a curve-fitted formula; and (c) using an interaction rule to take into account the load combination. However, the effective width approach is quite complex to use for many longitudinal stiffeners, and the accuracy of the design codes is subject to improvement. Moreover, nowadays the DSM provides a consistent and well-established method to predict ultimate loads for cold-formed steel structures. Therefore, in this paper the application of the DSM for combined bending and web crippling of second-generation sheeting is investigated. First, to create a set of numerical experiments, an internationally representative set of second-generation trapezoidal sheeting types is found, and these types are used to design numerical three-point bending experiments with relevant span lengths and load bearing plate widths. Then, finite element models are developed and verified, and used to predict the buckling, yield, and ultimate loads for the set of numerical experiments. Additionally, all simulations are also carried out for pure bending, and (Interior One Flange) IOF and (Interior Two Flange) ITF web crippling cases. With the resulting data, an explicit DSM approach is developed, fitted to the data of the three-point bending simulations, which predicts the ultimate load for combined actions directly. Hereafter, also an interaction DSM approach is studied, which first predicts the ultimate bending moment by the DSM (by fitting the pure bending simulations), then the web crippling load by the DSM (by fitting either the IOF or ITF simulations), and then uses a classic interaction rule for the load combination. The explicit and implicit DSM approaches perform equally well, with a Coefficient of Variation (CoV) equal to 0.13. As most commercially available sheeting has been incorporated, and the DSM approaches allow for sections with an arbitrarily number of stiffeners in the web (different from the current design codes), it is recommended to include the DSM in future code revisions. The interaction DSM approach resembles the current design rules most and may therefore be preferred; however, the explicit approach is more direct and certainly deserves consideration too.

第二代梯形板，其特点是在腹板和翼缘中设有纵向加劲肋，在支撑附近通过集中力和弯矩加载。目前，设计规范通过以下方式预测相关失效： (a) 通过有效宽度法或直接强度法 (DSM) 确定极限弯矩；(b) 通过曲线拟合的公式找到网络瘫痪载荷；(c) 使用交互规则来考虑荷载组合。然而，有效宽度方法对于许多纵向加强筋来说使用起来相当复杂，并且设计规范的准确性有待提高。此外，如今 DSM 提供了一种一致且行之有效的方法来预测冷弯型钢结构的极限载荷。所以，在本文中，研究了 DSM 在第二代板材的组合弯曲和腹板断裂中的应用。首先，创建一组数值实验，找到一组具有国际代表性的第二代梯形薄板类型，并利用这些类型设计具有相关跨度长度和承重板宽度的数值三点弯曲实验。然后，开发和验证有限元模型，并用于预测一组数值实验的屈曲、屈服和极限载荷。此外，还针对纯弯曲和（内部一个法兰）IOF 和（内部两个法兰）ITF 腹板损坏情况进行了所有模拟。根据所得数据，开发了一种显式 DSM 方法，适用于三点弯曲模拟的数据，直接预测组合动作的极限载荷。此后，还研究了一种交互 DSM 方法，该方法首先通过 DSM（通过拟合纯弯曲模拟）预测极限弯矩，然后通过 DSM（通过拟合 IOF 或 ITF 模拟）预测腹板破坏载荷，然后对荷载组合使用经典的交互规则。显式和隐式 DSM 方法表现同样出色，变异系数 (CoV) 等于 0.13。由于大多数市售板材已被纳入，并且 DSM 方法允许在腹板中具有任意数量的加强筋（不同于当前的设计规范），因此建议在未来的规范修订中包含 DSM。交互 DSM 方法最类似于当前的设计规则，因此可能是首选；