Tăng cường độ ổn định trong dầm thép

Tăng cường độ ổn định trong dầm thép

Transverse Stiffener Requirementsin Straight and Horizontally CurvedSteel I-GirdersYoon Duk Kim, Se-Kwon Jung andDonald W. WhiteGeorgia Institute of TechnologySchool of Civil and Environmental EngineeringAtlanta, GA2005 AASHTO Bridge Committee Agenda Item 38June 27, 2005 Problem Statement Identify the demands on transversestiffeners in curved and straightI-girders designed within theAASHTO (2004) limits: Transversely-stiffened I-girders with do/D < 3 D/tw< 150 Longitudinally-stiffened I-girders with do/D < 1.5 D/tw< 300 FEA Parametric Studies,Test Configuration Parametric Studies (Transversely-Stiffened I-Girders) D = 96 in (8 ft) do/D = 0.5, 1, 2 & 3 Straight & Curved with R = max(10do, 100 ft) D/tw= 150 (other D/twvalues considered for flat webs) Fyw= Fys= 70 ksi (other Fyvalues considered for flat webs) Fyf= 100 ksi (other Fyvalues considered for flat webs) bf/2tf= 6.47 (compact limit),except bf/2tf= 5 for do/D = 3 bfdetermined such that Mu~ 0.75Mnbased on theone-third rule bt/tp= 10 in primary studies (other bt/tpconsidered insupplementary studies) Various one- and two-sided stiffener sizes Parametric Studies (Longitudinally-Stiffened I-Girders) D = 96 in (8 ft) do/D = 0.5, 1 & 1.5 Straight & Curved with R = max(10do, 100 ft) D/tw= 300 (other D/twvalues considered for flat webs) Fyw= Fys= 70 ksi (other Fyvalues considered for flat webs) Fyf= 100 ksi (other Fyvalues considered for flat webs) bf/tf= 6.47 (compact limit) bfdetermined such that Mu~ 0.75Mnbased on theone-third rule bt/tp= 10 in primary studies (other bt/tpconsidered insupplementary studies) Various one- and two-sided stiffener sizes Longitudinal stiffener not included in models TFA Strength vs It/Itcrdo/D = 1, D/tw= 150Itcr= Itreq’d to develop Vn= VcrIt= ntpbt3/3It= nbt4/3/(bt/tp)It= As2(bt/tp)/3n TFA Strength vs It/Itcrdo/D = 1, D/tw= 150AASHTO (2004)area requirement,two-sided stiffenersAASHTO (2004)area requirement,one-sided stiffenersRecommended Shell Model - Perspective View ofDeformed Geometry at Max LoadIt= Itcr, do/D = 1, D/tw= 150, 1-sided stiffenerStraight I-girder (note: 18.5Itcris req’d to satisfy the AASHTO (2004) area reqmt)Undeformed geometryDeformed geometry(Scale Factor = 5.0) Shell Model – Mid-thickness Von MisesStress Distribution at Max LoadIt= Itcr, do/D = 1, D/tw= 150, 1-sided stiffenerStraight I-girder (note: 18.5Itcris req’d to satisfy the AASHTO (2004) area reqmt)(Scale Factor = 5.0) Perspective View of DeformedGeometry at Max LoadIt= 6Itcr, do/D = 1, D/tw= 150, 1-sided stiffenerCurved I-girder(Scale Factor = 5.0)Undeformed geometryDeformed geometry 123doc.vn