Modeling the panel zone in steel MR frames composed of built-up columns

This paper proposes an analytical model for the panel zone of connections of steel moment-resisting frames (SMRFs) composed of built-up columns with double sections and a vertical continuity plate. Panel zone in these connections consists of a middle panel, which is the vertical continuity plate, and two side panels, which are the webs of double sections of the column. Since the general behavior of these frames is governed by deformation of the middle panel, this panel is assumed as the primary one and the two side panels are assumed to be secondary. The column cover plates connecting the double sections and vertical continuity plate play an important role in providing compatibility of deformations. The new model proposed in this study is based on the previously developed models for the panel zones of connections in which the webs of beam and column are in the same plane, however, a number of refinements are introduced to capture the behavior of this type of connections. This quadri-linear model can be used for monotonic loading and accounts for both shear and bending deformations of panel zone. The results of this model are compared to those of finite element (FE) models verified by full scale experiments. The proposed model shows a good agreement, especially in elastic range, with the FE results. The results of FE analysis for important parameters affecting the panel zone behavior have also been compared to those obtained from the model in order to confirm the proposed model.