COLUMN REINFORCEMENT DESIGN FORSEISMIC AND NON-SEISMICMOMENT-RESISTING CONNECTIONS INSTEEL FRAME STRUCTURES

摘要

In the years following the unexpected fractures thatrnoccurred in moment-resisting connections in steelrnframe structures after the 1994 Northridge, Californiarnearthquake, structural engineers have often beenrnmore conservative than may be necessary in therndesign and detailing of these connections in bothrnseismic and non-seismic zones within the UnitedrnStates. In particular, continuity plates and webrndoubler plates have sometimes been specified whenrnthey may not be needed, and, when columnsrnstiffeners are necessary, thicker plates and weldsrnhave often been specified than may have beenrnneeded. There has also been initiative to developrnnew column reinforcement details that avoid weldingrnin the column ‘k-area', as prior studies have reportedrnthat the base metal in the k-area may exhibit lowerrnnotch toughness than the remainder of the wideflangerncross section. In this paper, economicalrnalternatives are presented for detailing columnrnstiffeners in steel moment-resisting connections thatrnavoid welding in the k-area and that exhibit ductilernperformance both for non-seismic and seismicrnloading. These details were evaluated usingrnmonotonically-loaded pull-plate experiments,rncyclically-loaded cruciform experiments of weldedrnunreinforced flange-welded web (WUF-W)rnconnections, and corroborating three-dimensionalrnnonlinear finite element analyses. Results arernpresented documenting the performance of thernalternative fillet-welded column reinforcementrndetails. The results also document the performancernof unstiffened columns both for monotonic and cyclicrnloading conditions, and the response of connectionsrnthat permit more extensive panel zone shear asrncompared to current U.S. design provisions. ExistingrnU.S. design equations are reassessed for limit statesrnappropriate for column reinforcement detailing, andrnnew design equations are presented that correlaternbetter with test data from the current work as well asrnfrom past research.