Mechanical Capability Study Of Steel Moment Connection With Welded Haunch

The widespread occurrence of connection failures in Northridge earthquake demonstrated the fundamental deficiencies of steel SMRF design and construction practice prior to the earthquake. Reducing stress of beam's flange and necessitating plastic hinging occurring at the designated location became an important idea to improve connection's performance in research after this earthquake. Welded haunch connection originated by SAC is an example of this idea.Welding a triangular haunch to the beam bottom flange significantly improved the cyclic performance in experimental research program. But the research in this field is still less, and previous research concentrate on contrastive experiment. Stress distribution has not been analyzed. The knowledge about function of welded haunch is still general and there was no analysis in theory. The mechanism of force-transfer is still unknown. These projects can not be slide over in this field.In this paper, the method of designing seismic connection model is discussed. The representational 3D FEA-model was setup. Stress distribution was got through nonlinear analyzing the model. The characteristic of stress distribution in connection was analyzed. The function of welded haunch and the way of welded-haunch connection transferring force are both ascertained. A new simplified model of welded haunch connection is presented。The mechanism of plastic hinging move out from welds after welding haunch is reasoned. The necessary condition of plastic hinging move out from welds after welding haunch is reasoned at stress point of view. The mechanism that welded haunch connection satisfy weak beam-strong column requirement is reasoned too.