Semi-rigid joints for moment-resisting steel framed seismic-resisting systems

Abstract

This thesis describes the development of new semi-rigid joints for moment-resisting steel framed (MRSF) seismic-resisting systems. Intended as the weak link in the seismic-resisting system, in accordance with a strong column, weak joint philosophy, the joints and systems were designed and detailed to withstand the design level ultimate limit state (500 year return period) earthquake with minimum damage. To meet economic criteria, the joints and systems were also required to be cost-effective to design, fabricate and construct when compared with conventional MRSFS. Four joint systems between the beams and columns of a MRSF were considered. These were the: Ring Spring Joint (RSJ), where the beams are clamped to the columns with flush endplates and compressible ring spring elements Post-tensioned Tendon Joint (PTJ), where the beams are post-tensioned onto the columns with post-tensioning technology Flange Bolted Joint (FBJ), where the beams are bolted to the columns through flange and web plates that are designed and detailed to undergo dependable cyclic extension and compression under inelastic rotation demand Sliding Hinge Joint (SHJ), where the beam is pinned to the column at the top flange level and is connected at the bottom flange and the bottom of the web by a unique asymmetrical sliding shear detail The RSJ, FBJ and SHJ were developed through to the experimental stage, with large-scale tests on representative joints undertaken. The FBJ and SHJ were further developed, through small-scale static and dynamic testing, finite element and numerical integration time-history analyses into fully designed and detailed systems. Design procedures and detailing requirements for the two fully developed systems are presented, together with details of experimental testing, finite element analyses of joint components and numerical integration time-history analyses of complete structural systems. Design and detailing requirements for the joints and the frames are covered and fully worked design examples for the Flange Bolted and Sliding Hinge Joints are presented. The results demonstrate that the semi-rigid, strength-limited joints developed, when used in properly designed moment-resisting steel frames, have considerable advantages over conventional rigidly jointed frames for meeting strength, stiffness, ductility, damage-resistance and economic criteria.