An expression for cross-sectional bending capacity prediction curve is proposed in this study based on the Direct-Strength-Method (DSM) approach using a comprehensive data from the literature on structural carbon steel Circular-Hollow-Sections (CHSs). Later, according to the Equivalent-Resistance-Capacity-Method (ERCM), improved empirical expressions for the equivalent CHS diameter of Elliptical-Hollow-Section (EHS) are derived using the proposed CHS bending capacity prediction curve and the data of EHSs from the literature. A unified set of cross-section slenderness limits for assessing the CHS and EHS members under bending is proposed. Also, the proposed expression for the bending resistance curve based on DSM is transformed into the generalized form of the traditional cylindrical shell buckling capacity curve as a practical solution in harmony with the newly introduced Reference-Resistance-Design (RRD) guidelines. Finally, the behaviour of EHS cantilever members under cyclic bending is assessed in terms of cyclic moment resistance and rotation capacities based on the authors' previous study.

在这项研究中，基于直接强度法（DSM）方法，使用来自结构碳钢圆空心截面（CHS）文献的综合数据，提出了截面弯曲容量预测曲线的表达式。后来，根据等效电阻容量法（ERCM），使用拟议的CHS弯曲容量预测曲线和EHS的数据，得出了椭圆空心截面（EHS）等效CHS直径的改进的经验表达式。文学。提出了一套统一的横截面细长极限值，用于评估弯曲状态下的CHS和EHS构件。也，基于DSM的抗弯曲线的拟议表达式被转化为传统圆柱壳屈曲能力曲线的广义形式，作为与新引入的参考-抗性设计（RRD）准则相协调的实用解决方案。最后，根据作者先前的研究，根据循环抗弯矩和旋转能力评估了EHS悬臂成员在循环弯曲下的行为。