Seismic analysis and design assisted by numerical simulation of slender steel portal frame structures

Lightweight (thin-walled or cold-formed) steel portal frame structure could be a popular and effective alternative to the traditional hot rolled structure and, with care to avoid buckling, could be used in earthquake areas owing to its economy and ease of fabrication and transportation, but no recommendations for seismic design of these structures is provided in the design codes. Accordingly, there is need for a lightweight design that is suitable for earthquake areas, which could be transported using lighter vehicles and erected quickly using smaller plant than is required for conventional hot rolled sections following an earthquake. The present paper shows some stages in the development of an earthquake-resistant frame, designed for by combining numerical finite element investigations with analytical check calculations based on EN 1993-1-3 for cold-formed steel members and EN 1993-1-1 for design of steel structures to estimate the loads on the frame structure within the use of EN 1998-1seismic design requirements. Although the initial buckling modes have been avoided, the frame still needs further modification to improve its ductility. It is planned to use this work to assist with the development of performance-based design recommendations for future structures that cover both thin-walled steel and cold-formed steel portal frame structures.