New Mathematical Modeling of Steel Panel Zone with Thin to Thick Column Flanges

The response of a steel moment resisting frame (MRF) depends on the specifications of its main components, namely the columns, beams and connections. One important connection element which can significantly affect frame behavior is the panel zone (PZ). The PZ is described to be an element mainly subjected to shear stresses and its failure mode is often governed by shear yielding. Several analytical models for PZ behavior exist, in terms of shear force-shear distortion relationships. Among these models, the Krawinkler PZ model is the most popular one which is used in codes. Some studies have pointed out that Krawinkler’s model gives good results for the range of thin to medium column flanges thickness. The model presented here is applicable to both thin and thick column flange. More than four-hundred beam-column connections are included in the parametric study, with varied parameters being: beam depth, column flange thickness, column web thickness, and beam flange thickness. The elastic stiffness, shear yield strength and ultimate shear strength of the PZ obtained from FE analysis, are compared with those obtained from available mathematical models to show differences, especially in the case of thick column flanges. In the paper a simple mathematical model for estimating the stiffness and shear strength in the PZ is introduced. In this model both shear and bending deformations are considered. A comparison between the results of proposed method herein with FE analyses shows the average error is significantly reduced which demonstrates the accuracy, efficiency, and simplicity of the proposed model.