DesignDESIGN OF STEEL PLATE GIRDER BRIDGE1.0DATAEffective span of girderL=30mPermanenet load as open floorFLL=7.50kN/mRail GaugeG=1.676mEquivalent total moving load per track for bending moment calculationWm=2727kNEquivalent total moving load per track for shear force calculationWs=2927kNTop of rail levelTRL=108mFoundation levelFL=100.50mEmbankment side slopeES=01:01.5Width of abutmentWa=4mPermissible bending stressbc=141N/sq.mmAverage shear stress for mild steel having yield stress of 236 N/sq.mmT_V=85N/sq.mmInterval of cross bearings as effective length of compression flangeLf=6mPermissible shear stress through fillet weldtt=102N/sq.mmConstant 'K' for angle between platesK=0.7Permissible bearing stressPBS=189N/sq.mmWind loadPw=1.5kN/sq.mCoefficient for wind load on Leeward GirderCw=0.25Lateral load by racking forcespl=6kN/mLength of cross frame for lateral brackingLlb=2mTensile strength of steelst=250N/sq.mmDepth of web plateDw=1500mmThickness of web platetw=12mm2.0PERMANENT LOADPermanent load of open floor track=7.50kN/mSelf weight=0.2 * L + 1=7.00kN/mTotal Permanent LoadWf=14.50kN/m

3.0MOVING LOADTotal moving load per girder for B.M.Wl1=1363.50kNTotal moving load per girder for S.F.Wl2=1463.50kN

4.0IMPACT FACTORThe impact factor for steel rail bridge is given by Coefficient of Dynamic AugmentI=0.3725.0BENDING MOMENTSB.M. by Permanent Load=Wf*L2/8=1631.25kN-mB.M. by Moving Load=Wl*L/8=5488.13kN-mB.M. by Impact on Moving Load=2041.58kN-mTotal Design Bending MomentM=9160.96kN-m6.0SHEAR FORCES.F. by Permanent Load=Wf*L/2=217.50kNS.F. by Moving Load=Wl2/2=731.75kNS.F. by Impact on Moving Load=272.21kNTotal Design Shear ForceV=1221.46kN7.0TRIAL SECTION OF WEB PLATETentative depth of girderD1=L*1000/10=3000.00mmEconomical depth of girderD2=5*((M/bc)*(2/3))=2165.71mmWeb depth of girder based on Shear Force consideration assuming 12 mm thick plate is calculated as:D3=V/(T_V*12)=1197.51mmLet us adopt a web plate Aw=Dw * twDw=1600mmtw=12mm8.0TRIAL SECTION OF FLANGE PLATETentative flange areaAf=[(M/bc*Dw)-(Aw/6)]=40114.22sq.mmFlange widthB1=L*1000/40=750mmB2=L*1000/45666.67mmLet us tryBf=700mmRequired thickness of Flange Plate=tf=Af/Bf=57.31mmLet us adopt the Flange PlatesAf=Bf*tfBf=700mmtf=53mm9.0CHECK FOR MAXIMUM STRESSESDistance from centre of flange plate to x-x axis located at mid sectionr=(Dw/2) + (tf/2)=827mmMoment of inertia about x-x axisIxx=(tw*Dw3/12)+(2*Af*r2)=54782186950mm4Moment of inertia about y-y axis, which vertical passing through the webIyy=(2*tf*Bf3/12)+(2*Aw/12)=3029836533.33333mm4A=2*tf*Bf + Dw*tw=93400sq.mmry=sqrt(Iyy/A)=180.11mmThe critical compressive stress for I-sections having equal Moment of Inertia about y-y axis is given by:Le=Lf*1000=6000mmD0=Dw + 2*tf=1706mmCs=1.1609194002=2473N/sq.mmThe permissible working stress bc for different values of critical stress Cs is given in Table 2From the Table 2 corresponding to Cs=2473N/sq.mmandsy=236N/sq.mmPermissible bending stressbc=158N/sq.mmDistance from top fibre to mid sectiony=(Dw/2) + tf=853mmActual maximum bending stressbc=M*y/Ixx=142.64N/sq.mmHence actual flexural stresses are within SAFE permissible limits.Permissible Average Shear Stress depends on=Dw/tw=133.33With stiffner spacingC=0.9 * Dw=1440mmAdopt stiffner spacing=1500mmFrom Table 3, the permissible average shear stress for steel for sy = 236 N/sq.mm is obtained as 87 N/sq.mm Average shear stress=V*103/(Dw*tw)=63.62N/sq.mmHence average shear stress is within permissible limits.10.0JOINT OF FLANGE AND WEBMaximum shear force at the joint of web and flange is given byT=V * Af * y/IxxV=1221.46kNAf=Bf * tf=37100sq.mmy=(Dw/2) + (tf/2)=826.50mmT=683.69N/mmProviding continuous fillet weld on either side,Strength of weld of sizeS=2 * K * S * tt =142.8S N/mmS=4.79mmAdopt, 6 mm fillet weld on either side continuously.11.0INTERMEDIATE STIFFENERSDw/tw=133> T_VVertical stiffeners are requiredSpacing=0.33*Dw=528mmto=1.5*Dw=2400mmAdopt SpacingC=1464mm~1500mmMaximum unsupported panel length of web=1500mmRequirement=270*tw=3240mm> 1500 mmIntermediate stiffeners are desired for minimum moment of inertiaI=1.5*Dw3*Tw3/C2=4718592mm4For 10mm thick stiffeners plate, outstand should not exceed h=12*t=120mmAdopt stiffeners plate of size=10mm=120mmI=5760000mm412.0CONNECTIONS OF VERTICAL STIFFENERS TO WEBShear on welds joining stiffeners to web=125*tw*tw/h=150N/mmFor size of weldS=150/(K*tt)=2.10mmEffective minimum length of weld=10 * tw=120mmAdopt Lc = 160 mm long, 5 mm minimum size intermittent fillet welds on either side.13.0END BEARING STIFFENERMaximum shear forceV=1221.46kNThe end bearing stiffener is designed as columnhe=300mmhe/tw=25 > 12Bearing area required=V / PBS=6463sq.mmUsing two plates of size 300mm x 25 mm provided.=2*300*25=15000sq.mm>6463sq.mmtb=25mmDb=300mmThe length of web plates which acts along with the stiffener plates to bear the end reactionWb=20*tw=240mmMoment of Inertia of end bearing two stiffeners platesI=((tb*((Db*2+tw)3)/12)+((2*Wb*tw3)/12)=477612720mm4AreaA=(Db*2+tw)*tb + 2*Wb*tw=21060sq.mmL=1120mmr=sqrt(I/A)=151mmSlenderness ratio=L/r=7.44From Table 4, Permissible stress in axial compressionac=138N/sq.mmArea required=V/ac=8851.17sq.mm14.0CONNECTIONS BETWEEN BEARING STIFFENERS AND WEBLength available for welding using alternate intermittent welds=2*(Dw-40)=3120mmRequired strength of weld=V/L=391.49N/mmSize of weld=5.48mmAdopt 6 mm fillet welds of length Lc = 160 mm intermittently on either side.15.0LATERAL BRACINGTo resist the structure against wind, racking and centrifugal forces, lateralbracing is provided End cross frames and intermediate cross frames areprovided for spans more than 20 m.Wind loadPw=1.5kN/sq.mmCoeffCw=0.25Depth of girderD=(Dw+2*tw)/1000=1.624mSpanL=30mWind load on windward girder=Pw*D*L=73.08kNWind load on leeward girder=Cw*73.08=18.27kNTotal wind load=91.35kNLateral load by racking forces=pl=6kN/mTotal racking force=6*L=180kNTotal lateral load=271.35kNLateral load at each end=135.68kNConsidering length of each cross frames=L/b=2mMaximum tension in the diagonal=211.24kNArea required=1408.24sq.mmAdopt angle section 100mm x 100mm with 10mm thicknessMaximum compressive force in horizontal member of each frame=135.68kNLength of MembersG=1.676mEffective Length=0.65 * G=1.089mFor angle section 100 mm x 75 mm with 10 mm thicknessAreaA=1650sq.mmr=21.6mmSlenderness ratio=50.4From Table 4, Permissible Stressac=124N/sq.mmSafe load on member=(Dw+tw/2)*ac/1000=199kN>271/2kN16.0DESIGN OF CROSS FRAMESLateral load to be resisted by one frame=135.68kNTension in the diagonal=136*sec=177kNArea required=1183sq.mmProvide angle section 90mm x 60mm with 10mm thickness Area provided=1401sq.mmAdopt interval of cross frames at 6m.

Sheet11PERMANENT LOAD2MOVING LOAD3IMPACT FACTOR4BENDING MOMENTS5SHEAR FORCE6TRIAL SECTION OF WEB PLATE7TRIAL SECTION OF FLANGE PLATE8CHECK FOR MAXIMUM STRESSES9JOINT OF FLANGE AND WEB10INTERMEDIATE STIFFENERS11CONNECTIONS OF VERTICAL STIFFENERS TO WEB12END BEARING STIFFENER13CONNECTIONS BETWEEN BEARING STIFFENERS AND WEB14LATERAL BRACING15DESIGN OF CROSS FRAMES