306 JOURNAL OF STRUCTURAL ENGINEERING Vol. 49, No. 4, OCTOBER - NOVEMBER 2022 Journal of Structural Engineering Vol. 49, No. 4, October - November 2022 pp. 306-317 No. 49-24 Characterization of connections in the seismic assessment of steel moment resisting frames P. Jayarajan* ,  Email: puttatt1@gmail.com *Formerly Department of Civil Engineering, National Institute of Technology Calicut, Calicut - 673 601, INDIA. Received: 10 November 2022; Accepted: 29 April 2023 KEYWORDS: Beam-to-column connection; component method; moment-rotation curve; initial stifness; capacity design, hysteresis. The response of steel Moment Resisting Frames (MRF) under seismic excitations is largely governed by the characteristics of beam-to-column connections. The seismic design of steel structures require that the “dissipative zones” intended to dissipate the input seismic energy are correctly identifed based on the type of connections envisaged during engineering phase. Though extensive studies are reported in literature regarding response of beam-to-column connections under various types of loadings, it is strongly felt that a systematic joint characterization procedure required for seismic assessment of steel structures is still missing. Such a procedure will be eventually benefcial to the design engineers and researchers to ensure that the global seismic analysis is compatible with the assumed connection characteristics. The paper presents a detailed procedure for the characterization of beam-to-column joints necessary for seismic assessment of steel MRF structures. Extended end plate beam-to-column connections namely haunched, unstifened and stifened each of them representing full-strength, partial-strength and equal-strength design objectives are considered in the study. The characterization proceeds with development of moment-rotation curves using both the component method of Eurocode-3 and the Component Based Finite Element Method (CBFEM). The capacity design verifcations of the connections for the assumed overstrength are then performed using CBFEM. Finally, the hysteresis behaviour of the connections under cyclic loads, where required, is predicted using the modifed Richard - Abbott model. The seismic design of steel Moment Resisting Frames (MRF) as prescribed in modern seismic codes 1,2 permits the dissipative zones to be located either in the connected beams or in beam-to-column connections. The dissipative zones, where located in the connected beams result in “strong column-weak beam” philosophy with the columns being designed for amplifed seismic moments based on the material overstrength and beam capacity utilization. The beam-to-column connections in such cases shall be designed for an overstrength to ensure that they remain essentially elastic during seismic energy dissipation in critical regions. The above philosophy generally results in fully-restrained connections which are designed for a moment much higher than the plastic moment of resistance of connected beams. AISC 358 3 provide various connection types that are essentially Fully-Restrained (FR) prequalifed for use in column beam joints of Intermediate Moment Frames (IMF) and Special Moment Frames (SMF). Further to rigid-full strength connections, the European code EN 1998-1 2 also permit dissipative semi-rigid and/or partial-strength connections in steel MRF structures. However, in such cases connections shall have a rotation capacity consistent with the global deformations and the efect of connection fexibility on the structural response shall be taken into account using nonlinear static analysis (pushover) or nonlinear time history analysis. The column capacity design in the case of partial-strength connections shall be