Inelastic behavior and design of steel panel zones

The effect of panel zone yielding on the potential for fracture of welded-b olted steel connections is investigated, with the objective of gaining a be tter understanding of the inelastic behavior of the panel zone region and o f critically assessing current seismic provisions for steel panel zone desi gn. The research objectives are addressed through detailed, three-dimension al, nonlinear, finite-element analyses of connection subassemblies. The cha racteristics of the analysis configurations used in this research are deriv ed from the geometry of a typical pre-Northridge fully restrained beam-colu m steel connection. Important geometric parameters are varied over the prac tical range of interest in order to evaluate their effect on connection beh avior. To assess the influence of the parameters of interest, a number of d ifferent stress, strain, and combined stress/strain indices are employed. T hese quantities are sampled at connection plastic rotations ranging from 0. 0025 to 0.03 rad. Results from the finite-element analyses show that, altho ugh beam plastic rotation demands are smaller in connections with weak pane l zones, the stress conditions at the beam-column interface are more critic al at higher connection plastic rotations. Therefore, although the panel zo ne can effectively contribute to overall connection ductility, a weak panel zone can also lead to a greater potential for brittle and/or ductile fract ure at higher connection plastic rotations. The finite-element analyses als o suggest that current design provisions may not be appropriate when applie d to panel zones in exterior joints.