Seismic progressive collapse of MRF–EBF dual steel systems

Designing structures to resist progressive collapse during an earthquake is a key challenge for structural engineers working in seismic zones. This paper introduces a more appropriate brace configuration based on an upper-bound estimation of the probability of seismic progressive collapse in moment-resisting, eccentrically braced frames designed to the third edition of the Iranian seismic code. The code currently only has provisions for the capacity of moment frames, with no detail given for bracing elements. A numerical modelling study of low- to mid-rise residential and office buildings was undertaken. The results show that for five-storey buildings the optimum number of braced bays is 10–20% of the building's perimeter bays, whereas for eight-storey buildings the optimum proportion is 20–30%. Results also show that regular bracing in internal bays is more appropriate for resistance against progressive collapse.