On the influence of semirigid joints on the seismic response of one storey steel buildings

The paper investigates the influence of the actual behavior of beam-to-column and column base joints on the seismic vulnerability of one storey steel structures. A numerical study was conducted on as-built real steel buildings whose column bases and beam-to-column joints have a semirigid and partial-strength behavior, although they were originally designed as rigid and full strength. Finite element models of the selected buildings were developed, assuming both the theoretical and the actual joint behavior and their seismic performance was investigated through nonlinear time history analyses. Kinematic hysteresis models were assigned to semirigid joints to account for their actual stiffness, nonlinear behavior, and energy dissipation capacity. Then, fragility curves were derived, on both the theoretical and the as-built buildings, for various damage levels, with the aim of comparing the probabilities of ex-ceedance of the selected limit states.