Evaluation of PR steel frame connection with torsional plate and its optimal placement

Characteristics of connections in steel moment-resisting frames are of utmost importance in determining the seismic performance of these structural systems. The results of several previous experimental studies have indicated that Partially-restrained (PR) connections possess excellent properties, which makes this connection a reliable substitution for Fully-restrained (FR) connections. These properties include needing less base shear, being more economic and in many cases, being able to absorb more energy. In this study, the behavior of two proposed PR connections with torsional plate is studied through finite element simulations. The results of the numerical studies regarding initial stiffness and maximum strength capacity of the proposed connections are calibrated against the results of solid mechanics formulations. Over 50 parametric studies are performed to determine the importance of various design variables of the proposed PR connections. A relation based on spring model is proposed to estimate the maximum strength capacity of the proposed connection. Seismic performance of the proposed connection is studied in a typical portal frame with various connection characteristics using nonlinear time-history analysis. The results explicitly show that using PR connections can considerably reduce the moment-rotation demands in the columns and as a result, higher performance levels can be achieved according to ASCE41.