Nonlinear Static Response of Low-Moderate Ductile Chevron Concentrically Braced Frames Designed According to Eurocode 8

Abstract

Steel frames equipped with chevron bracing (Λ-CBF) are usually less ductile than other steel systems. Therefore, in many cases, it can be convenient to design Λ-CBF to exploit their stiffness and resistance to enforce a pseudo-elastic seismic response of the building in low to moderate seismic zones. In current EC8, the rules for moderate Λ-CBF are the same as those for high ductile frames, thus potentially leading to massive, over-resistant and uneconomic systems. In the next version of EC8 new rules have been set to design moderate ductile Λ-CBF, aiming to enhance the ease of use of the code as well as to obtain less expensive structures. The new rules of the updated EC8 are based on local requirements and elastic calculation without any plastic analysis. This paper discusses these rules that are numerically investigated by means of nonlinear static analyses on a set of 8-storey steel frames designed for different seismic intensities. The performed analyses show that the frames designed according to the updated EC8 exhibit moderate ductility, preventing damage to brace-intercepted beams and reducing ductility demand on braces under compression.