Date of Award
Master of Science
The earthquake of Northridge, CA in 1994 caused damages in steel moment frame buildings due to the brittle fractures in beam to column connections. This led to the modifications and improvements in the connection detailing used prior to the Northbridge earthquake. These improvements included use of better welding material and process, use of cover plates (such as Welded Flange Plate connections (WFP)), Reduced Beam Section (RBS) etc. RBS and WFP connections are the two most widely used connection configuration today. Both RBS and WFP connections allow the steel moment frame systems to extensively yield and deform plastically thus avoiding brittle fracturing occurring at the connections. Steel moment frames are comprised of beams and column, in which beams are rigidly connected with columns by welding or bolting. Members and joints resist flexural and shear forces and lateral stability is achieved through bending of the frame elements. WFP connection uses the cover plates of certain thickness and length. This addition of cover plate increases the depth of the beam at the face of the column and thus forces the plastic hinge to form away from face of the column at a certain distance. The RBS connection also protects the beam column connection by forcing the plastic hinge in a beam to form away from the face of the column at a certain distance within the reduced section. This research aims to compare the two types of steel moment connections, WFP and RBS connections, in terms of ductility, strength and stiffness. The connections were designed using the guidelines provided by Federal Emergency Management Agency FEMA-350 (2000) and AISC Seismic Design Manual. The modeling and analysis of the WFP and RBS connection was performed using finite element analysis software. A two story and two bay special moment resisting frame was considered for this study and the first story exterior beam column connection was designed using two different sections of beam and column. Total of four models were used in a half beam and half column configuration. Each selected section of beam and columns was first designed, modeled and analyzed using WFP criteria and then by RBS design guidelines. The span, height, boundary conditions and loads are kept typical for all four models. Results were computed and comparison is made in terms of ductility, strength and stiffness. Strength obtained for each model using finite element analysis software is also compared with hand calculations.
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