Numerous situations occur in engineering practice where I-section members must be designed for a combination of flexure, shear, torsion, and/or axial loadings. Particularly in metal buildings and horizontally curved I-girder bridges, these member types may have variable web depth and stepped cross-section transitions along their length. Design guidance for handling combined loadings on these member types has been limited. Modern software systems that can accurately calculate combined second-order elastic demands and elastic buckling loads for general I-section members in general framing systems are increasingly available. This paper discusses new AISC 360 Chapter F provisions under consideration in the 2027 Specification development cycle. These provisions provide an improved, streamlined calculation of the flexural resistance of general I-section members. The calculations address recent research findings regarding the influence of moment gradient and corresponding web shear. The discussion of the new AISC 360 procedures is followed by a brief presentation of recommended ways to verify a design where the member is also subjected to axial compression and/or torsion based on experiences from European and American practice. The focus of the paper is on the essential concepts.

This paper discusses a combination of best practices and procedures from recent work in Europe and the US, providing rational and economical calculations addressing the complexities associated with frame design using nonprismatic members. Recommendations are provided in the context of US design practice. A primary objective is to achieve maximum simplicity, transparency, and design speed while facilitating rigor of the underlying calculations. The paper provides several focused examples illustrating the recommended design verification procedures.