Seismic rehabilitation design of steel moment connection with welded haunch

This paper describes a design procedure for the seismic rehabilitation of pre-Northridge steel moment connections using a welded haunch. Experimental results from cyclic testing of full-scale specimens demonstrated that welding a triangular haunch beneath the beam's bottom flange significantly improved the seismic performance of steel moment connections. The welded haunch drastically changed the beam shear force transfer mechanism, which assisted in reducing the demands at the beam flange groove welds. Analytical studies further showed that the tensile stress in the existing beam flange groove weld can be reduced to a reasonable level if the flange of the haunch is designed to provide sufficient stiffness and strength. However, traditional beam theory cannot provide a reliable prediction of the beam's flexural stress distribution near the column face. A simplified model that allows the designer to predict the stress level in the beam flange groove welds is presented.