Proposed Panel Zone Model for Beam-To-Column Joints in Steel Moment Resisting Frames

In capacity designed steel moment resisting frames (MRFs), beam-to-column joints (i.e., panel zones) are designed to remain elastic. To potentially exploit the beneficial aspects of the stable panel zone hysteretic response in shear, a robust panel zone model is required. To assess the available panel zone models in the literature, a database of more than 100 experiments was systematically assembled. Experimental evidence suggests that available models may overestimate the panel zone shear strength by 40%. Regarding the model utilised in Europe, the column flange contribution to panel zone shear strength is disregarded, if continuity plates are not present, thereby underestimating the panel zone shear strength by 20%, on average. Moreover, only one doubler plate (if two are needed) is considered in the panel zone strength calculation. This paper examines realistic shear stresses in various panel zone geometries based on continuum finite element (CFE) simulations validated with available experimental data. The parametric analysis results are then leveraged to develop a new panel zone shear strength model for the seismic design of steel MRFs. Comparisons of the proposed panel zone shear stiffness and strength reveal a noteworthy accuracy of less than 10% error and decreased variation compared to existing models. Complementary CFE analyses on panel zones with doubler plates revealed that these are effective withstanding the shear strains developed in the column web. Thus, the panel zone thickness to be used in the proposed panel zone strength model should include the column web and the doubler plate(s).