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4 ibc-1608-wind

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4 ibc-1608-wind

  1. 1. 162162 Section 1608Section 1608 -- Wind LoadsWind Loads nn Wind SpeedWind Speed nn ExposureExposure nn TopographyTopography nn Return PeriodReturn Period nn Methods & ProceduresMethods & Procedures nn ExamplesExamples
  2. 2. 163163 Basic Wind SpeedsBasic Wind Speeds 50 Year Return Period50 Year Return Period
  3. 3. 164164 33--Second Gust VelocitiesSecond Gust Velocities 50 Year Return Period50 Year Return Period
  4. 4. 165165 Wind VelocityWind Velocity nn Basic Wind Speed (70 mph)Basic Wind Speed (70 mph) •• Fixed distance/Variable timeFixed distance/Variable time •• Average Wind SpeedAverage Wind Speed nn 33--Second Gust Wind Speed (90 mph)Second Gust Wind Speed (90 mph) •• Variable distance/Fixed timeVariable distance/Fixed time •• Gust Portion of Wind ProfileGust Portion of Wind Profile •• National Weather Service MeasurementsNational Weather Service Measurements •• News Media ReportNews Media Report •• Includes Hurricane I FactorIncludes Hurricane I Factor
  5. 5. 166166 Exposure DefinitionsExposure Definitions nn Exposure AExposure A--Deleted due to variabilityDeleted due to variability nn Exposure BExposure B--Urban & Dense SuburbanUrban & Dense Suburban •• 2630 Ft or 10H Continuous Roughness2630 Ft or 10H Continuous Roughness •• 60% to 80% of all buildings60% to 80% of all buildings nn Exposure CExposure C--Open TerrainOpen Terrain nn Exposure DExposure D--Shorelines, flats, lakesShorelines, flats, lakes •• Open Water >1 MileOpen Water >1 Mile
  6. 6. 167167 Wind Load ExposureWind Load Exposure Exposure A Exposure B Exposure C & D
  7. 7. 168168 ExposureExposure--RoughnessRoughness Exposure B
  8. 8. 169169 Topographic EffectsTopographic Effects Kzt=(1+K1*K2*K3)2 K1=Feature Shape K2=Location from Crest K3=Building Height
  9. 9. 170170 Wind LoadWind Load--Return PeriodReturn Period
  10. 10. 171171 IBC 2003 MethodsIBC 2003 Methods nn Section 6 ASCE 7Section 6 ASCE 7 •• Exceptions:Exceptions: nn Simplified MethodSimplified Method nn SBCCI (R2 & R3 Buildings)SBCCI (R2 & R3 Buildings) nn AF & PA (1 & 2 Family Residences)AF & PA (1 & 2 Family Residences) nn NAAMM (Flagpoles)NAAMM (Flagpoles) nn TIA/EIA (Antenna)TIA/EIA (Antenna)
  11. 11. 172172 MethodsMethods nn Method 1Method 1--Simplified ProcedureSimplified Procedure nn Method 2Method 2--AnalyticalAnalytical •• RigidRigid nn Less than 60 FeetLess than 60 Feet nn All buildingsAll buildings •• FlexibleFlexible nn Gust FactorGust Factor nn Method 3Method 3--Wind TunnelWind Tunnel
  12. 12. 173173 IBC 2003/ASCE 7IBC 2003/ASCE 7 nn Method 1Method 1--Simplified ProcedureSimplified Procedure •• ConditionsConditions •• ProcedureProcedure •• DeterminationDetermination nn MWRS TableMWRS Table nn Components & Cladding TableComponents & Cladding Table
  13. 13. 174174 Method 1Method 1--ConditionsConditions nn Simple DiaphragmSimple Diaphragm nn Flat RoofFlat Roof nn <60 ft Height<60 ft Height nn EnclosedEnclosed BuldingBulding nn Regular ShapeRegular Shape nn Rigid (<1 Sec Period)Rigid (<1 Sec Period) nn No Topographic EffectsNo Topographic Effects nn Approximately SymmetricalApproximately Symmetrical
  14. 14. 175175 Method 1Method 1--ProcedureProcedure nn GG--Adjustment FactorAdjustment Factor nn IwIw--Importance FactorImportance Factor nn PsPs--Wind PressureWind Pressure P=P=GG**IIww*P*Pss
  15. 15. 176176 Method 1Method 1--DeterminationDetermination
  16. 16. 177177 ASCE 7ASCE 7--0202 nn Method 2Method 2--Analytical ProcedureAnalytical Procedure •• ConditionsConditions •• ProcedureProcedure •• DeterminationDetermination nn Rigid FormulaRigid Formula •• Less than 60 FtLess than 60 Ft •• All BuildingsAll Buildings nn Flexible FormulaFlexible Formula
  17. 17. 178178 Method 2Method 2--ConditionsConditions nn Regular ShapeRegular Shape nn No Dynamic Wind EffectsNo Dynamic Wind Effects
  18. 18. 179179 Method 2Method 2--ProceduresProcedures Step 1Step 1 nn KzKz--Exposure/HeightExposure/Height nn KztKzt--TopographyTopography nn KdKd--Building Configuration & Wind DirBuilding Configuration & Wind Dir nn VelocityVelocity--MapsMaps nn II--UseUse q=0.00256Kq=0.00256Kzz**KKztzt**KKdd*V*V22 *I*I
  19. 19. 180180 Method 2Method 2--MWRS ProcedureMWRS Procedure RigidRigid--Buildings Less than 60 FtBuildings Less than 60 Ft nn GCpfGCpf--External Pressure CoefficientExternal Pressure Coefficient nn GCpiGCpi--Internal Pressure CoefficientInternal Pressure Coefficient p=p=qqhh*(*(GCGCpfpf--GCpGCpii))
  20. 20. 181181 Method 2Method 2--MWRS DeterminationMWRS Determination RigidRigid--Buildings Less than 60 FtBuildings Less than 60 Ft
  21. 21. 182182 Method 2Method 2--MWRS ProcedureMWRS Procedure RigidRigid--All Building HeightsAll Building Heights nn GG--Gust Effect (0.85 Rigid Buildings)Gust Effect (0.85 Rigid Buildings) nn CpCp--External Pressure CoefficientExternal Pressure Coefficient nn GCpiGCpi--Internal Pressure CoefficientInternal Pressure Coefficient p=q*G*Cp=q*G*Cpp--qqii**GCGCpipi
  22. 22. 183183 Method 2Method 2--MWRS DeterminationMWRS Determination RigidRigid--All Building HeightsAll Building Heights
  23. 23. 184184 Method 2Method 2--MWRS ProcedureMWRS Procedure Flexible BuildingsFlexible Buildings nn GfGf--Gust Effect (Flexible)Gust Effect (Flexible) nn CpCp--External Pressure CoefficientExternal Pressure Coefficient nn GCpiGCpi--Internal Pressure CoefficientInternal Pressure Coefficient p=q*p=q*GGff*C*Cpp--qqii**GCGCpipi
  24. 24. 185185 Method 2Method 2--Flexible FormulaFlexible Formula Gust FactorGust Factor GfGf=0.925=0.925((1+1.7I1+1.7IzzKK(g(g22 QQQQ22+g+g22 RRRR22)))) 1+1.7g1+1.7gvvIIzz wherewhere ggRR==KK(2ln(3600n(2ln(3600n11))+))+ 0.5770.577 KK(2ln(3600n(2ln(3600n11)))) where R=where R=KK((1/((1/MM)R)RnnRRhhRRBB(0.53+0.47R(0.53+0.47RLL)))) wherewhere RRnn==7.47N7.47N11 (1+10.3N(1+10.3N11)^5/3)^5/3 etcetc…………..
  25. 25. 186186 Method 2Method 2--Load CasesLoad Cases MWRSMWRS •Case 1-100% Ea Dir •Case 2-75% Ea Dir •Case 3-Case 1 w/15%e •Case 4-Case 2 w/15%e
  26. 26. 187187 Method 2Method 2--C & C ProcedureC & C Procedure nn GCGCpp--External Pressure CoefficientExternal Pressure Coefficient nn GCGCpipi--Internal Pressure CoefficientInternal Pressure Coefficient p=p=qqhh*(*(GCGCpp--GCGCpipi) (h<60) (h<60’’)) p=q*p=q*GCGCpp--qqii**GCGCpipi (h>60(h>60’’))
  27. 27. 188188 Method 2Method 2--C & C DeterminationC & C Determination nn LocationLocation nn Tributary AreaTributary Area nn Walls/RoofsWalls/Roofs
  28. 28. 189189 ASCE 7ASCE 7--0202 nn Method 3Method 3--Wind Tunnel ProcedureWind Tunnel Procedure •• Irregular ShapeIrregular Shape •• Flexible (>1 sec)Flexible (>1 sec) •• WakeWake •• ChannelingChanneling •• Dynamic EffectsDynamic Effects
  29. 29. 190190 Dynamic Wind EffectsDynamic Wind Effects nn Vortex SheddingVortex Shedding
  30. 30. 191191 Dynamic Wind EffectsDynamic Wind Effects nn GallopingGalloping
  31. 31. 192192 Dynamic Wind EffectsDynamic Wind Effects nn FlutterFlutter--Flutter occurs when aFlutter occurs when a torsionaltorsional disturbance in the structuredisturbance in the structure increases theincreases the angle of attackangle of attack of theof the bridge (that is, the angle betweenbridge (that is, the angle between the wind and the bridge)the wind and the bridge)
  32. 32. 193193 Example 1Example 1--Simplified ProcedureSimplified Procedure nn CriteriaCriteria •• 130 mph130 mph •• Exposure CExposure C •• Flat TerrainFlat Terrain •• EnclosedEnclosed •• I=1.0I=1.0
  33. 33. 194194 Example 1Example 1-- Simplified ProcedureSimplified Procedure MWRSMWRS--Figure 6Figure 6--22 •Roof Pressure=-32 psf •Wall Pressure=27 psf •G=1.21 Roof=-39 psf MWRS=33 psf (Includes Internal Pressure)
  34. 34. 195195 Example 1Example 1--Simplified ProcedureSimplified Procedure C & C Wall PressuresC & C Wall Pressures--Figure 6Figure 6--33 nn TribTrib Area=15(15/3)=75Area=15(15/3)=75 sfsf Zone 4 p=27.2*1.21=33Zone 4 p=27.2*1.21=33 psfpsf Zone 4 p=Zone 4 p=--29.8*1.21=29.8*1.21=--3636 Zone 5 p=27.2*1.21=33Zone 5 p=27.2*1.21=33 Zone 5 p=Zone 5 p=--34.3*1.21=34.3*1.21=--4242
  35. 35. 196196 Example 1Example 1--Simplified ProcedureSimplified Procedure C & C Roof JoistsC & C Roof Joists--Figure 6Figure 6--33 nn TribTrib Area=30*5=150Area=30*5=150 sfsf or 30*30/3=300or 30*30/3=300 sfsf Zone 1 p=9.8*1.21=12Zone 1 p=9.8*1.21=12 psfpsf Zone 1 p=Zone 1 p=--27.8*1.21=27.8*1.21=--3434 Zone 2&3 p=9.8*1.21=12Zone 2&3 p=9.8*1.21=12 Zone 2&3 p=Zone 2&3 p=--33*1.21=33*1.21=--4040
  36. 36. 197197 Example 1Example 1--Simplified ProcedureSimplified Procedure C & C Roof PanelsC & C Roof Panels--Figure 6Figure 6--33 nn TribTrib Area=10Area=10 sfsf Zone 1 p=12.4*1.21=15Zone 1 p=12.4*1.21=15 psfpsf Zone 1 p=Zone 1 p=--30.4*1.21=30.4*1.21=--3737 Zone 2 p=12.4*1.21=15Zone 2 p=12.4*1.21=15 Zone 2 p=Zone 2 p=--51*1.21=51*1.21=--6262 Zone 3 p=12.4*1.21=15Zone 3 p=12.4*1.21=15 Zone 3 p=Zone 3 p=--77*1.21=77*1.21=--9393
  37. 37. 198198 Example 1Example 1--Simplified ProcedureSimplified Procedure Tributary Area EffectTributary Area Effect
  38. 38. 199199 Example 2Example 2--Analytical MethodAnalytical Method nn CriteriaCriteria •• 90 mph90 mph •• Exposure BExposure B •• Flat TerrainFlat Terrain •• EnclosedEnclosed •• I=1.0I=1.0 •• 33--DD AxisymmetricalAxisymmetrical HillHill
  39. 39. 200200 Example 2Example 2--Analytical MethodAnalytical Method MWRS, C & CMWRS, C & C nn qqzz=0.00256*=0.00256*KKzz**KKztzt**KKdd*V*V22 II •• KKdd=0.85=0.85 •• KKzz=0.57 Case II MWRS=0.57 Case II MWRS =0.7 Case I C & C=0.7 Case I C & C MWRSMWRS qqzz=0.00256*0.57*=0.00256*0.57*KKztzt*0.85*90*0.85*9022 1.01.0 =10.04*=10.04*KKztzt C & CC & C qqzz=0.00256*=0.00256*KKzz**KKztzt**KKdd*V*V22 II =12.3*=12.3*KKztzt
  40. 40. 201201 Example 2Example 2--Analytical MethodAnalytical Method MWRS, C & CMWRS, C & C H/L=0.4H/L=0.4 KK11=0.95*0.4=0.38=0.95*0.4=0.38 KK22=(1=(1--250/(1.5*600))=0.72250/(1.5*600))=0.72 KK33=e=e--4(15)/6004(15)/600 =0.9=0.9 KKztzt=(1+0.38*0.72*0.9)=(1+0.38*0.72*0.9)22 =1.56=1.56 nn q(MWRS)=15.7q(MWRS)=15.7 psfpsf nn q(C&C)=19.2q(C&C)=19.2 psfpsf
  41. 41. 202202 Wind LoadsWind Loads--SummarySummary nn Variable ConditionsVariable Conditions nn Lots of Different ParametersLots of Different Parameters nn Number of ProceduresNumber of Procedures nn More complex than you thinkMore complex than you think

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