Seismic design rules for ductile eurocode compliant two storey X concentrically braced frames

Two storey X bracings are currently very popular in European practice, as respect to chevron and simple X bracings, owing to the advantages of reducing the bending demand in the brace intercepted beams in V and inverted V configurations and optimizing the design of gusset plate connections. However, rules for two storey X braced frames are not clearly specified within current version of EN1998 1, thus leading to different interpretations of the code by designers. The research presented in this paper is addressed at investigating the seismic behaviour of two storey X concentrically braced frames in order to revise the design rules within EN1998 1. Therefore, five different design criteria are discussed, and their effectiveness is investigated. With this aim, a comprehensive numerical parametric study is carried out considering a set of planar frames extracted from a set of structural archetypes that are representative of regular low, medium and high rise buildings. The obtained results show that the proposed design criteria ensure satisfactory seismic performance.