Simplified Modeling of Unstiffened End-plate Connections in Nonlinear Analysis of Steel Frames at Elevated Temperatures

This work presents a simplified procedure for modeling the moment-rotation relationship of extended end-plate (EEP) and flush end-plate (FEP) connections at both ambient and elevated temperatures, to be incorporated in global frame analysis. The main interest of this paper is to offer a swift numerical routine providing direct application, reasonable accuracy, and analysis time saving. The procedure is divided into three main stages: estimating the initial joint characteristics at ambient temperature, updating those characteristics at elevated temperatures, and choosing a suitable mathematical representation of the moment-rotation curve. Regression analysis of experimental test database was applied to generate empirical formulae for estimation of the initial stiffness and moment strength of end-plate connections. Additionally, a parametric analysis routine, based on the Eurocode component method (CM) for a practical range of end-plate connection configurations, is utilized to enrich the database and to estimate the behavior of connections that are not existing in the database. The proposed formulae involve the geometrical and material parameters that have major influence on connection characteristics. The explicit presence of the material parameters in the proposed formulae enables the procedure to be extended to consider the effect of elevated temperatures. Two power models were discussed and suggested and compared to generate full moment-rotation curve of connections at both ambient and elevated temperatures. Moreover, the proposed procedure was applied and validated against previous work and showed good accuracy and low analysis time.