Plastic hinge location effects on the design of welded flange plate connections

Seismic design criteria have been heavily improved by the Federal Emergency Management Agency (FEMA) after the Northridge CA earthquake in 1994. Most of the damage observed was caused by brittle failure of moment frame connections. This failure was induced by the formation of the plastic hinge at undesirable locations in the beam and the column near the connection. Using welded flange plate (WFP) connections will force the formation of the plastic hinge away from the face of the column while preventing the brittle failure of the moment connection. FEMA-350 design criteria recommendations for WFP connections suggest that the plastic hinge will form away from the face of the column directly under the cover plate. The purpose of this research is to prove that the plastic hinge will form away from the face of the column, at a distance of approximately half the depth of the beam away from the cover plate. The further away the plastic hinge is from the face of the column the higher the connection demands. Therefore, underestimating the location of the plastic hinge could lead to under designed connections.;The modeling and analysis of WFP connections was performed using finite element analysis software. A total of eight models with half beam half column configuration were considered in this study. Each selected section of beam and column was first designed, modeled and analyzed using WFP connections design recommendations from FEMA-350, with calculations modifications to account for the proposed plastic hinge location. Results were computed and comparisons were made in terms of plastic hinge location from the cover plates. Strength obtained for each model using finite element analysis software was also compared with hand calculations. This research also proves that increasing the thickness of the cover plates will generate an increase in the connection capacity and strength.