wind engineering in 2006 - huston
TRANSCRIPT
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ASCE STRUCTURAL
ENGINEERING CONFERENCE
Wind Engineering in the 2006
IBC and ASCE 7-05Monday, November 6, 2006
Presented by
Ed Huston, PE, SE for the
Structural Engineers Association of Washington
Wind Engineering Committee
Hosted byIOWA STATE UNIVERSITY
OF SCIENCE AND TECHNOLOGY, Ames, Iowa
November 2006 Edwin T. Huston
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November 2006 by Edwin T. Huston, PE, SE. All rights reserved.This book or any part thereof may not be reproduced in any formwithout the written permission of the author, 16307 Fremont Pl N.
Shoreline, WA 98133.
CREDITSThe materials used herein are used with permission and are based on:
ASCE 7-xx, Standard Minimum Design Loads for Buildings and Other Structures,Published by The American Society of Civil Engineers
International Building Code 200x Published by The International Code Council
DISCLAIMERWhile the information presented in this seminar and proceedings isbelieved to be correct, SEAW and the speaker assume no liabilityfor its accuracy or for the opinions expressed herein. The materialspresented in this seminar and proceedings should not be used orrelied upon for any specific application without express examinationand verification of its accuracy, suitability and applicability by
qualified professionals. Users of information from this seminar andproceedings assume all liability arising from such use.
Included documents prepared by others are subject to change bythe preparers. Users are cautioned to obtain the latest versions ofall such documents prior to use on a specific project.
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Wind Engineering in the 2006Wind Engineering in the 2006
IBC and ASCE 7IBC and ASCE 7--0505
Ed Huston, PE, SEEd Huston, PE, SE
Smith & Huston, Inc.Smith & Huston, Inc.
Seattle, WASeattle, WA
Copyright 2006 by Edwin T. Huston. AllCopyright 2006 by Edwin T. Huston. Allrights reserved, no reproduction or userights reserved, no reproduction or use
without written permissionwithout written permission
Why are we here?Why are we here?
The wind is like air, only pushier.The wind is like air, only pushier.--55thth Grade Science StudentGrade Science Student
Wind Engineering SeminarWind Engineering Seminar
WhatWhats new in Wind Designs new in Wind Design -- 2006 IBC2006 IBC
ProvisionsProvisions
Changes in ASCE 7Changes in ASCE 7--0505
SEAWSEAWss Rapid Solutions MethodologyRapid Solutions Methodology (RSM)(RSM)
ProvisionsProvisions
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IBC 2003 & ASCE 7IBC 2003 & ASCE 7--0202
Wind Load ProvisionsWind Load Provisions
Where are we today?Where are we today?
IBC Wind LoadsIBC Wind Loads -- HighlightsHighlights
ASCE 7ASCE 7--02 by Reference.02 by Reference.
Replaced Fastest Mile Maps withReplaced Fastest Mile Maps with
Three Second Gust Maps.Three Second Gust Maps.
Clarified Stability Requirements.Clarified Stability Requirements.
RequiredRequired all partsall parts of all buildings andof all buildings and
structures be designed for wind.structures be designed for wind.
Section 1609.1Section 1609.1
General RequirementsGeneral Requirements
Introduced the use of 1609.6Introduced the use of 1609.6 --
Simplified Low Rise Method for SimpleSimplified Low Rise Method for Simple
Diaphragm Buildings.Diaphragm Buildings. Minimum Wind Load of 10 psf forMinimum Wind Load of 10 psf for
MWFRS and C&C.MWFRS and C&C.
Must meet seismic detailing even ifMust meet seismic detailing even if
wind Loads are greater.wind Loads are greater.
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Section 1609.1Section 1609.1
General RequirementsGeneral Requirements
StabilityStability -- Overturning, Uplift, SlidingOverturning, Uplift, Sliding 1.5 safety factor when resistance is provided by1.5 safety factor when resistance is provided by
dead load.dead load.
Only dead loads likely to be in place during aOnly dead loads likely to be in place during a
design wind event should be used.design wind event should be used.
Only 2/3 of the dead loads likely to be in placeOnly 2/3 of the dead loads likely to be in place
during a design wind event is used with theduring a design wind event is used with the
alternate basic load combinations.alternate basic load combinations.
2003 IBC Section 1609.6 Simplified2003 IBC Section 1609.6 Simplified
Provisions for Low Rise BuildingsProvisions for Low Rise Buildings
Allows wide range of buildings up toAllows wide range of buildings up to
60 feet in height.60 feet in height.
Applies loads like SBC SimplifiedApplies loads like SBC Simplified --
on projected areas.on projected areas.
Restricted to Simple DiaphragmRestricted to Simple Diaphragm
Buildings.Buildings.
IBC 2006IBC 2006
Wind Load ProvisionsWind Load Provisions
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Major Changes in the 2006 IBCMajor Changes in the 2006 IBC
Removal of most of the provisionsRemoval of most of the provisions
The simplified wind provisions have beenThe simplified wind provisions have been
removed from the 2006 IBCremoved from the 2006 IBC
TheThe environmental triggersenvironmental triggers --wind speedswind speeds
and exposures are still in the IBC so they canand exposures are still in the IBC so they can
be locally modified.be locally modified.
The default exposure is nowThe default exposure is now CC notnot BB..
Wind Engineering SeminarWind Engineering Seminar
WhatWhats new in Wind Designs new in Wind Design -- 2006 IBC2006 IBC
ProvisionsProvisions
Changes in ASCE 7Changes in ASCE 7--0505
SEAWSEAWss Rapid Solutions MethodologyRapid Solutions Methodology (RSM)(RSM)
ProvisionsProvisions
Example ProblemsExample Problems
Changes from ASCE 7Changes from ASCE 7--02 to ASCE 702 to ASCE 7--0505
The document will be referenced with the 2006 IBC:The document will be referenced with the 2006 IBC:
The definition of simple diaphragm buildings isThe definition of simple diaphragm buildings isclearer and the charts are expanded (Figures 6clearer and the charts are expanded (Figures 6--22
and 6and 6--3)3) A definition is given for Eave Height (Section 6A definition is given for Eave Height (Section 6--2)2)
Definitions of solid signs & solid freestandingDefinitions of solid signs & solid freestandingwalls and the design method for these elementswalls and the design method for these elementsare significantly different (Sections 6.3 & 6.5.14)are significantly different (Sections 6.3 & 6.5.14)
The topographic effect can be used in theThe topographic effect can be used in thesimplified method (Section 6.4)simplified method (Section 6.4)
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Changes from ASCE 7Changes from ASCE 7--02 to ASCE 702 to ASCE 7--0505
The prohibition of using the simplified method in aThe prohibition of using the simplified method in abuilding with an expansion joint is dropped and thebuilding with an expansion joint is dropped and the
intent is moved to the definitions. (Section 6.2 andintent is moved to the definitions. (Section 6.2 and6.4.1.1)6.4.1.1)
Guidance is given for estimating basic wind speedsGuidance is given for estimating basic wind speedsfrom Regional Climatic Data in areas outside hurricanefrom Regional Climatic Data in areas outside hurricane--prone regions (6.5.4.2)prone regions (6.5.4.2)
Exposure categories B is based on the ground surfaceExposure categories B is based on the ground surfaceroughness condition in the upwind direction for aroughness condition in the upwind direction for adistance ofdistance of 26002600ft orft or 2020times the height of thetimes the height of thebuilding (6.5.6.3)building (6.5.6.3)
Changes from ASCE 7Changes from ASCE 7--02 to ASCE 702 to ASCE 7--0505
Exposure categories D is based on the groundExposure categories D is based on the ground
surface roughness condition in the upwindsurface roughness condition in the upwind
direction for a distance of 5000 ft ordirection for a distance of 5000 ft or 2020times thetimes the
height of the building (6.5.6.3)height of the building (6.5.6.3)
For velocity pressure, a transition zone betweenFor velocity pressure, a transition zone between
exposure categories is allowed (6.5.6.6)exposure categories is allowed (6.5.6.6)
Changes from ASCE 7Changes from ASCE 7--02 to ASCE 702 to ASCE 7--0505
Clarifies that for a topographic effect to apply, allClarifies that for a topographic effect to apply, all
5 of the conditions must be met. (6.5.7.2)5 of the conditions must be met. (6.5.7.2)
In wind borne debris regions the standards thatIn wind borne debris regions the standards that
must be met are specified (6.5.9.3)must be met are specified (6.5.9.3)
The combined net pressure coefficient,The combined net pressure coefficient, GCGCpnpn forfor
parapets has been reduced (6.5.12.2.4)parapets has been reduced (6.5.12.2.4)
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Changes from ASCE 7Changes from ASCE 7--02 to ASCE 702 to ASCE 7--0505
Design loads for open buildings withDesign loads for open buildings with monoslopemonoslope,,
pitched orpitched or troughedtroughed roofs has been added.roofs has been added.(6.5.13)(6.5.13)
Forces on rooftop structures and equipment forForces on rooftop structures and equipment forbuildings with hbuildings with h 60 feet has been added60 feet has been added(6.5.15.1)(6.5.15.1)
In wind tunnel tests glazing in wind borne debrisIn wind tunnel tests glazing in wind borne debrisregions shall be protected (6.6.5)regions shall be protected (6.6.5)
Changes from ASCE 7Changes from ASCE 7--02 to ASCE 702 to ASCE 7--0505
Clarification to footnote 8 for lowClarification to footnote 8 for low--rise walls andrise walls and
roofs (Figure 6roofs (Figure 6--10)10)
Clarification to footnote 5 for Gable roofs withClarification to footnote 5 for Gable roofs with
77 (Figure 6(Figure 6--11B)11B)
Figures for open buildings withFigures for open buildings with monoslopemonoslope,,
pitched orpitched or troughedtroughed roofs have been addedroofs have been added
(Figures 6(Figures 6--18 A18 A -- D, 6D, 6--19 A19 A -- C)C)
Figure for solid freestanding walls & solidFigure for solid freestanding walls & solid
signs has been changed (Figure 6signs has been changed (Figure 6--20)20)
ASCE 7 Design OptionsASCE 7 Design Options
See Page 84 of Commentary Volume 1
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ASCE 7 & IBC Design OptionsASCE 7 & IBC Design Options
Option 1Option 1Simplified LowSimplified Low--Rise ProcedureRise Procedure
(ASCE 7(ASCE 7--02, IBC 2003, ASCE 702, IBC 2003, ASCE 7--05)05)
UsesUses MBMAMBMA MethodMethodGood for selected buildingsGood for selected buildings
Tables give Design Pressures for MWFRS and Components andTables give Design Pressures for MWFRS and Components andCladding matching code design forcesCladding matching code design forces
Simple adjustments for different exposuresSimple adjustments for different exposures
Minimal Calculations requiredMinimal Calculations required
Not in the 2006 IBC, still in ASCE 7Not in the 2006 IBC, still in ASCE 7--0505
ASCE 7 Design OptionASCE 7 Design Option
Simplified and LowSimplified and Low--
Rise Provisions basedRise Provisions based
onon PseudoPseudo PressurePressure
CoefficientsCoefficients
Based on StructuralBased on Structural
ActionsActions
Correlated LoadingCorrelated Loading
Simple Diaphragm BuildingsSimple Diaphragm Buildings
ConceptsConcepts
Applicable when the MWFRS isApplicable when the MWFRS isprimarily a base shear problem.primarily a base shear problem.
Internal pressure cases create theInternal pressure cases create thedifferent proportions of loads ondifferent proportions of loads onthe windward and leeward faces.the windward and leeward faces.
Internal pressures cancel out in baseInternal pressures cancel out in baseshear calculationsshear calculations
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Simple Diaphragm BuildingsSimple Diaphragm Buildings
ConceptsConcepts
If the wind forces are delivered to theIf the wind forces are delivered to theMWFRS via floor slabs and roofMWFRS via floor slabs and roofdiaphragms, the windward and leewarddiaphragms, the windward and leewardloads are combined into a shear at eachloads are combined into a shear at eachstory.story.
Only if members in the MWFRS areOnly if members in the MWFRS areloaded directly by the wind do theloaded directly by the wind do theinternal pressure cases come intointernal pressure cases come intoplay.play.
Simplified ProvisionsSimplified Provisions
Not allowed in the 2003 IBC if:Not allowed in the 2003 IBC if:
Site is on a hill or escarpmentSite is on a hill or escarpment 6060 inin
Exposure B or 30Exposure B or 30 in Exposure C, andin Exposure C, and
Maximum average slope > 10%, andMaximum average slope > 10%, and
Unobstructed upwind for a distance of 50Unobstructed upwind for a distance of 50
times the height of the hill or 1 mile.times the height of the hill or 1 mile.
ASCE 7ASCE 7--05 allows K05 allows Kztzt
topographic effectstopographic effects
Simple Diaphragm BuildingsSimple Diaphragm Buildings
Good examplesGood examples
Houses with plywood shear walls.Houses with plywood shear walls.
Typical TiltTypical Tilt--Up or Masonry wall buildings.Up or Masonry wall buildings.
Concrete frames.Concrete frames. Steel frames with vertically spanning walls andSteel frames with vertically spanning walls and
diaphragm floors and roofs.diaphragm floors and roofs.
Bad examplesBad examples
Metal building frames with horizontally spanningMetal building frames with horizontally spanninggirts.girts.
Unsymmetrical buildings.Unsymmetrical buildings.
Any building with an expansion joint in theAny building with an expansion joint in theMWFRS.MWFRS.
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DonDont use Low Rise on This!t use Low Rise on This!
Table 1609.6.2.1(4)
Height and Exposure
Adjustment Coefficients
Exposure
Mean
roof
ht
B C D
15 1.00 1.21 1.47
20 1.00 1. 29 1 .55
25 1.00 1. 35 1 .61
30 1.00 1.40 1.66
35 1.05 1.45 1.70
40 1.09 1.49 1.74
45 1.12 1.53 1.78
50 1.16 1.56 1.81
55 1.19 1.59 1.84
60 1.22 1.62 1.87
Note: Alltable values shallbeadjustedf or
other exposures andheights by multiplyng
by theabovecoefficients.
Simplified Provisions
for MWFRS
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11
22
33
44
55
SimplfiedSimplfied DesignDesign
Simplified design wind pressures for theSimplified design wind pressures for the
MWFRSsMWFRSs of lowof low--rise simple diaphragmrise simple diaphragm
buildings represent the net pressures (sum ofbuildings represent the net pressures (sum of
internal and external) to be applied to theinternal and external) to be applied to thehorizontal and vertical projections of buildinghorizontal and vertical projections of building
surfaces.surfaces.
For the horizontal pressures (zones A, B, C, D),For the horizontal pressures (zones A, B, C, D),
this net pressurethis net pressure is the combination of theis the combination of the
windward and leeward net pressures.windward and leeward net pressures.
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SimplfiedSimplfied DesignDesign
Minimum Pressures: The load effects of theMinimum Pressures: The load effects of the
design wind pressures shall not be less than thedesign wind pressures shall not be less than theminimum load case from assuming the pressuresminimum load case from assuming the pressures
for the wall zones A, B, C, and D are all equal tofor the wall zones A, B, C, and D are all equal to
+10 psf, while assuming the pressures for the+10 psf, while assuming the pressures for the
roof zones E, F, G, and H are all equal to 0 psf.roof zones E, F, G, and H are all equal to 0 psf.
ASCE 7 Design OptionsASCE 7 Design Options
Option 2Option 2LowLow--Rise ProcedureRise Procedure
UsesUses MBMAMBMA MethodMethodApplicable to all building shapesApplicable to all building shapes
PseudoPseudo Pressure CoefficientsPressure Coefficients
Limited to buildings less than or equal to 60Limited to buildings less than or equal to 60 in heightin height
Eight Load Cases to ConsiderEight Load Cases to Consider
Hip roofs configurations in commentaryHip roofs configurations in commentary
ASCE 7 Design OptionsASCE 7 Design Options
P = qP = qhh[(GC[(GCpfpf))(GC(GCpipi)])]Eqt. 6Eqt. 6--1818
qqhh = Velocity pressure evaluated at mean roof height.= Velocity pressure evaluated at mean roof height.
q = 0.00256 Kq = 0.00256 KzzKKztztKKddVV22II
(GC(GCpfpf) = External Pressure Coefficient from Fig. 6) = External Pressure Coefficient from Fig. 6--10 (below)10 (below)
(GC(GCpipi) = Internal Pressure Coefficient from Fig. 6) = Internal Pressure Coefficient from Fig. 6--5.5.
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ASCE 7 Design OptionsASCE 7 Design Options
ASCE 7 Design OptionsASCE 7 Design Options
ASCE 7 Design OptionsASCE 7 Design Options
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Torsion ProvisionsTorsion Provisions
Torsion RequirementsTorsion Requirements
ASCE 7ASCE 7--02 included new02 included newLoad cases forLoad cases for LowLow
RiseRise methodmethod
Ignored in ASCE 7Ignored in ASCE 7--0202
Method 1Method 1
Simplified (Method 1) canSimplified (Method 1) can
not be used in ASCE 7not be used in ASCE 7--0505
if torsion controls!!if torsion controls!!
Torsional provisionsTorsional provisions
This load case is specially designed to affectThis load case is specially designed to affect
Torsionally SensitiveTorsionally Sensitive structures, but not tostructures, but not to
affect regular buildings.affect regular buildings.
Building withBuilding withperimeter shearperimeter shearwallswallsok.ok.
Torsional ExamplesTorsional Examples
Building withBuilding withdistributeddistributedbracingbracingok.ok.
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TorsionallyTorsionallyirregularirregular
Buildings inBuildings in
rotationrotationok.ok.
Torsional ExamplesTorsional Examples
Building withBuilding with
center core,center core,
torsionallytorsionally
weak.weak.
Torsional ExamplesTorsional Examples
ASCE 7 Design OptionsASCE 7 Design Options
Option 3Option 3All HeightsAll Heights ProcedureProcedure
Applicable to all building shapes and heightsApplicable to all building shapes and heights
Analytical procedure requiring determination of wind designAnalytical procedure requiring determination of wind design
pressurespressures
Similar to 1997 UBC requirementsSimilar to 1997 UBC requirements
Basis for SEAWBasis for SEAWss Rapid Solution MethodologyRapid Solution Methodology
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ASCE 7 Design OptionsASCE 7 Design Options
Main Wind Force Resisting SystemMain Wind Force Resisting System
p=qGCp=qGCpp--qqii(GC(GCpipi))Eqt. 6Eqt. 6--1717 q = Velocity pressure evaluated at various locationsq = Velocity pressure evaluated at various locations
G = Gust effect factor, equal 0.85 for rigid buildingsG = Gust effect factor, equal 0.85 for rigid buildings
CCpp = External pressure coefficient from Fig. 6= External pressure coefficient from Fig. 6--6 thru 66 thru 6--88
(GCp(GCpii) = Internal pressure coefficient from Fig. 6) = Internal pressure coefficient from Fig. 6--55
Velocity PressureVelocity Pressure
q = 0.00256q = 0.00256 KKzz KKztzt KKdd VV22 IIEqt. 6Eqt. 6--1515
KK zz = velocity pressure exposure coefficient, Table 6= velocity pressure exposure coefficient, Table 6--33
KK ztzt= topographic factor, Figure 6= topographic factor, Figure 6--44
KK dd = wind directionality factor, Table 6= wind directionality factor, Table 6--44
VV 22 = basic wind speed, Figure 6= basic wind speed, Figure 6--11
II = importance factor, Table 6= importance factor, Table 6--11
All Heights Method Simplified Method
Difference in Pressure DistributionDifference in Pressure Distribution
Vertical VariationVertical Variation
Horizontal VariationHorizontal Variation
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Terrain EffectsTerrain Effects
Terrain EffectsTerrain Effects
Terrain EffectsTerrain Effects
Wind speed increase at cliffs,Wind speed increase at cliffs,escarpments and the crests ofescarpments and the crests ofisolated hills and ridges.isolated hills and ridges.
Key Factor is that the terrainKey Factor is that the terrain
constitute abrupt changes inconstitute abrupt changes inthe general topography.the general topography.
Wind Speed up effects canWind Speed up effects canincrease the wind speed at aincrease the wind speed at abuilding site by as much asbuilding site by as much as200%.200%.
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Terrain EffectsTerrain Effects
Wind SpeedWind Speed--Up Effects shall apply if:Up Effects shall apply if:
Site is on the upper half of a hill, ridge or nearSite is on the upper half of a hill, ridge or nearthe crest of an escarpmentthe crest of an escarpment andand
The hill, ridge or escarpment isThe hill, ridge or escarpment is 6060 inin
Exposure B or 15Exposure B or 15 in Exposure C or D,in Exposure C or D, andand
Unobstructed upwind for a distance of 100Unobstructed upwind for a distance of 100
times the height of the hill ortimes the height of the hill or 22 miles,miles, andand
Maximum average slope > 5.7%,Maximum average slope > 5.7%, andand
Protrudes 2 times above terrainProtrudes 2 times above terrain
ASCE 7 Design OptionsASCE 7 Design Options
Main Wind Force Resisting SystemMain Wind Force Resisting System
p=qGCp=qGCpp--qqii(GC(GCpipi)) Eqt. 6Eqt. 6--1717
q = Velocity pressure evaluated at various locationsq = Velocity pressure evaluated at various locations
G = Gust effect factor, equal 0.85 for rigid buildingsG = Gust effect factor, equal 0.85 for rigid buildings
CCpp = External pressure coefficient from Fig. 6= External pressure coefficient from Fig. 6--6 thru 66 thru 6--88
(GC(GCpipi) = Internal pressure coefficient from Fig. 6) = Internal pressure coefficient from Fig. 6--55
ASCE 7 Design OptionsASCE 7 Design Options
Main Wind Force Resisting SystemMain Wind Force Resisting System
p=qGCp=qGCpp--qqii(GC(GCpipi)) Eqt. 6Eqt. 6--1717
q = Velocity pressure evaluated at various locationsq = Velocity pressure evaluated at various locations
G = Gust effect factor, equal 0.85 for rigid buildingsG = Gust effect factor, equal 0.85 for rigid buildings
CCpp = External pressure coefficient from Fig. 6.6= External pressure coefficient from Fig. 6.66.86.8
(GC(GCpipi) = Internal pressure coefficient from Fig. 6) = Internal pressure coefficient from Fig. 6--55
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CCpp, External Pressure Coefficient, External Pressure Coefficient
Varies with height on windward surface.Varies with height on windward surface.
Constant pressures on leeward and side wall surfaces.Constant pressures on leeward and side wall surfaces.
CCpp, External Pressure Coefficient, External Pressure Coefficient
Dependent on building geometry.Dependent on building geometry.
Roof pressures decrease along length of roof.Roof pressures decrease along length of roof.
CCpp, External Pressure Coefficient, External Pressure Coefficient
InterpolationInterpolation
between valuesbetween values
allowed.allowed.
Reductions forReductions forlarge areaslarge areas
allowed.allowed.
Read Footnotes!Read Footnotes!
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Rear Wall Suction depends on L/BRear Wall Suction depends on L/B
Does not reDoes not re--attachattach
ReRe--attachesattaches
Large suction forceLarge suction force
Small suction forceSmall suction force
Flow separationFlow separation
Front Roof Suction depends on L/HFront Roof Suction depends on L/H
ReRe--attachesattaches
if long roofif long roof
Smaller averageSmaller average
suction force becausesuction force because
of reof re--attachmentattachment
Flow separationFlow separation
ASCE 7 Design OptionsASCE 7 Design Options
Main Wind Force Resisting SystemMain Wind Force Resisting System
p=qGCp=qGCpp--qqii(GC(GCpipi)) Eqt. 6Eqt. 6--1717
q = Velocity pressure evaluated at various locationsq = Velocity pressure evaluated at various locations
G = Gust effect factor, equal 0.85 for rigid buildingsG = Gust effect factor, equal 0.85 for rigid buildings
CCpp = External pressure coefficient from Fig. 6.6 thru 6.8= External pressure coefficient from Fig. 6.6 thru 6.8
(GC(GCpipi) = Internal pressure coefficient from Fig. 6) = Internal pressure coefficient from Fig. 6--55
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(GC(GCpipi), Internal Pressure), Internal Pressure
CoefficientCoefficient Values for Open,Values for Open,
Partially Enclosed,Partially Enclosed,
and Enclosedand EnclosedBuildingsBuildings
G cannot beG cannot beseparated from Cseparated from Cpi.pi.
Typically buildingsTypically buildingsgo from Enclosed togo from Enclosed toPartially Enclosed toPartially Enclosed toOpen to EnclosedOpen to Enclosed(6.9.5.4).(6.9.5.4).
EnclosureEnclosure
Buildings are defined as;Buildings are defined as; Enclosed,Enclosed,
Partially Enclosed,Partially Enclosed,
OpenOpen
Windows with nonWindows with non--impactimpactresistant glazing orresistant glazing orprotection in wind borneprotection in wind bornedebris regions, need to bedebris regions, need to betreated as openings whentreated as openings whenassessing enclosureassessing enclosureclassification.classification.
Torsion ProvisionsTorsion Provisions
Torsion RequirementsTorsion Requirements 2000 Research found2000 Research found
underestimation for bothunderestimation for bothAnalyticalAnalytical andand LowLow--
RiseRise methodsmethods ASCE 7ASCE 7--02 included new02 included new
load cases forload cases forAnalyticalAnalytical methodmethod
Unchanged in 7Unchanged in 7--0505
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Torsion ProvisionsTorsion Provisions
Design Wind Load Cases, 6.5.12.3Design Wind Load Cases, 6.5.12.3
All buildings, all heights (7All buildings, all heights (7--02 requirement)02 requirement) Exceptions: One story, hExceptions: One story, h 30 ft30 ft
Figure 6Figure 6--99
Four load casesFour load cases
MMtt, e, exx, e, eyy equationsequations
Figure 6Figure 6--10 Low Rise, ASCE 710 Low Rise, ASCE 7--02 added two torsional02 added two torsional
load cases. Unchanged in 7load cases. Unchanged in 7--05.05.
Transverse, longitudinal directionsTransverse, longitudinal directions
ASCE 7 Design OptionsASCE 7 Design Options
Components and Cladding LoadsComponents and Cladding Loads
Low Rise Buildings & Buildings hLow Rise Buildings & Buildings h
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Cladding PressuresCladding Pressures
Picture from AWCPicture from AWC
ASCE 7 Design OptionsASCE 7 Design Options
Read theRead the
Footnotes!Footnotes!
ASCE 7 Design OptionsASCE 7 Design Options
Components and Cladding LoadsComponents and Cladding Loads
Buildings h > 60Buildings h > 60
p = q(GCp = q(GCpp))qqii(GC(GCpipi))
qq== qqzz for windward walls calculated at height zfor windward walls calculated at height z
q = qq = qhh for leeward walls, side walls & roofs, evaluated at meanfor leeward walls, side walls & roofs, evaluated at mean
roof heightroof height
qqii= q= qhhfor windward walls, side walls, leeward walls, and roofsfor windward walls, side walls, leeward walls, and roofs
for enclosed buildings and negative internal pressure in partialfor enclosed buildings and negative internal pressure in partiallyly
enclosed buildingsenclosed buildings
qqii= q= qzz for positive internal pressure in partially enclosedfor positive internal pressure in partially enclosed
buildings, evaluated at the highest opening in the building.buildings, evaluated at the highest opening in the building.
Conservatively evaluated at height h.Conservatively evaluated at height h.
(GC(GCpp) = External Pressure Coefficients, Figure 6) = External Pressure Coefficients, Figure 6--1717
(GC(GCpipi) = Internal Pressure Coefficient, Figure 6) = Internal Pressure Coefficient, Figure 6 --55
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ASCE 7 Design OptionsASCE 7 Design Options
For h > 60For h > 60values for wallsvalues for wallsand roofand roofcontained oncontained onone graph.one graph.
For other thanFor other thanflat roofs, useflat roofs, useroof chartsroof chartsfrom Fig. 6from Fig. 6--11.11.
ASCE 7 Design OptionsASCE 7 Design Options
Read theRead the
Footnotes!Footnotes!
ASCE 7 Design OptionsASCE 7 Design Options
Parapet ProvisionsParapet Provisions Very common design element that was not covered byVery common design element that was not covered by
the standardthe standard
Before ASCE 7Before ASCE 7--05 there was no research available on05 there was no research available on
parapet loadsparapet loads For ASCE 7For ASCE 7--02 the Wind Task Group developed a02 the Wind Task Group developed a
rational method based on judgmentrational method based on judgment
Subsequent research has confirmed the approachSubsequent research has confirmed the approachslight tweak (downward) of numbers for 2005slight tweak (downward) of numbers for 2005
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Parapet Design ProcedureParapet Design Procedure
MWFRS, CCMWFRS, CC
Components and cladding:Components and cladding:P = qP = qpp (GC(GCppGCGCpipi))
P = combined net pressureP = combined net pressure
GCGCpp = external pressure coefficient= external pressure coefficient
GCGCpipi = internal pressure coefficient= internal pressure coefficient
Two load cases:Two load cases: Case A: + pressure to front surfaceCase A: + pressure to front surface
Case B: + pressure to back surfaceCase B: + pressure to back surface
Parapet Design ProcedureParapet Design Procedure
MWFRS, CCMWFRS, CC
MWFRS:MWFRS:
PPpp = q= qppGCGCpnpn
PPpp = combined net pressure= combined net pressure
GCGCpnpn ==
+1.8, windward parapet (ASCE 7+1.8, windward parapet (ASCE 7--02)02)
--1.1, leeward parapet1.1, leeward parapet (ASCE 7(ASCE 7--02)02)
+1.5, windward parapet (ASCE 7+1.5, windward parapet (ASCE 7--05)05)
--1.0, leeward parapet1.0, leeward parapet (ASCE 7(ASCE 7--05)05)
Parapet Design ProcedureParapet Design Procedure
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Wind Engineering SeminarWind Engineering Seminar
WhatWhats new in Wind Designs new in Wind Design -- 2006 IBC2006 IBC
ProvisionsProvisions Changes in ASCE 7Changes in ASCE 7--0505
SEAWSEAWs Rapid Solutions Methodologys Rapid Solutions Methodology
(RSM) Provisions(RSM) Provisions
Which Code to use?Which Code to use?
For quickest results and lowest values, use theFor quickest results and lowest values, use the
Simplified Provisions,Simplified Provisions,
If you building does not meet simplifiedIf you building does not meet simplified
requirements, userequirements, use Rapid Solution Method,Rapid Solution Method,
Source ofSource of LegacyLegacyWind CodesWind Codes
ANSI/ASCE 7ANSI/ASCE 7 MBMA / CanadaMBMA / Canada
NBC SBC
UBC
Simplification by TriSimplification by Tri--State SEAState SEAss
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Source of IBC Wind ProvisionsSource of IBC Wind Provisions
NBC /ASCE 7NBC /ASCE 7 SBCSBC
All-Heights Low-Rise
RSM
Simplification by SEAWSimplification by SEAW
ASCE 7ASCE 7 -- 20022002
Basis of SEAWBasis of SEAWss RapidRapid
Solution MethodSolution Method
RSM: the Simplification of ASCERSM: the Simplification of ASCE--77
PrePre--solved thesolved the qqss Equation.Equation.
Included External & Internal PressuresIncluded External & Internal Pressures Graphical Basis (Simplified Interpolation)Graphical Basis (Simplified Interpolation)
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ASCE 7 vs. SEAW RSMASCE 7 vs. SEAW RSM
Pressure EquationPressure Equation
ASCE 7:ASCE 7:
ppAA=0.00256 V=0.00256 V 22 KKdd I [I [KKzz KKztzt GCGCppKKziziKKztizti ((GCGCpipi)])]
SEAW RSM:SEAW RSM:
pprsmrsm == qqss KKzz CCrsmrsm [[IIww KKtt]]
1997 UBC:1997 UBC:
p =p = qqss CCee CCqq IIww
Interior Pressure/SuctionInterior Pressure/Suction
We havenWe havent had to deal with this before in thet had to deal with this before in theWest (UBC).West (UBC).
The UBC hid it, and assumed interior pressure,The UBC hid it, and assumed interior pressure,since that condition usually controls.since that condition usually controls.
SEAW RSMSEAW RSM
Pressure EquationPressure Equation
pprsmrsm == qqss KKzzCCrsmrsm [[IIww KKtt]]
Where:Where:
qqss depends on geographical location,depends on geographical location,
KKzz depends on height and exposure,depends on height and exposure,
CCrsmrsm depends on location on building,depends on location on building,
IIww depends on building occupancy, anddepends on building occupancy, and
KKtt depends on topographydepends on topography
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SEAW RSMSEAW RSM
Pressure EquationPressure Equation
pprsmrsm == qqss KKzzCCrsmrsm [[IIww KKtt]]
Where:Where:
qqss depends on geographical location,depends on geographical location,
KKzz depends on height and exposure,depends on height and exposure,
CCrsmrsm depends on location on building,depends on location on building,
IIww depends on building occupancy, anddepends on building occupancy, and
KKtt depends on topographydepends on topography
ASCE 7ASCE 7 KKzz --Velocity PressureVelocity Pressure
Exposure CoefficientExposure Coefficient Relates the wind profileRelates the wind profile
for various sitefor various site
exposures.exposures.
Similar to CSimilar to Cee in thein the 9797UBC.UBC.
DoesnDoesnt contain the gustt contain the gust
factor like Cfactor like Cee..
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We took theWe took the KKzzheight factor table, andheight factor table, and
put it on a graphical background.put it on a graphical background.
SEAW RSMSEAW RSM
Pressure EquationPressure Equation
pprsmrsm == qqss KKzzCCrsmrsm [[IIww KKtt]]
Where:Where:
qqss depends on geographical location,depends on geographical location,
KKzz depends on height and exposure,depends on height and exposure,
CCrsmrsm depends on location on building,depends on location on building,
IIww depends on building occupancy, anddepends on building occupancy, and
KKtt depends on topographydepends on topography
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What is theWhat is the CCrsmrsm ??
This is the heart of our simplification.This is the heart of our simplification.
Equating the ASCE 7 pressure equation and theEquating the ASCE 7 pressure equation and the
SEAWSEAWs RSM equation yields:s RSM equation yields:
CCrsmrsm = K= Kdd [[GCGCpp ++ ((GCGCpipi)])]
Wall PressuresWall Pressures
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This half of figure
This portion of
ASCE Table
Wall PressuresWall Pressures
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Windward Wall PressureWindward Wall Pressure
From ASCE 7 Table CFrom ASCE 7 Table Cpp = 0.80= 0.80
CCrsmrsm = K= Kdd [[GCGCpp ++ ((GCGCpipi)])]Where:Where:
KKdd = 0.85 (Directionality Factor)= 0.85 (Directionality Factor)
G = 0.85 (Gust FactorG = 0.85 (Gust FactorWe are dealing with gust windWe are dealing with gust wind
speeds)speeds)
((GCGCpipi) =) = ++ 0.18 (Enclosed Building)0.18 (Enclosed Building)
CCrsmrsm = 0.85 [0.85(0.80)= 0.85 [0.85(0.80) ++ (0.18)](0.18)]
== +0.42, +0.73+0.42, +0.73
Wall MainWall Main--Frame PressuresFrame Pressures
Leeward wallLeeward wall
depends ondepends on
L/BL/B
A figure wasA figure was
added to help.added to help.
Leeward WallsLeeward Walls
Values fromValues from
ASCE 7ASCE 7
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BB
LL
WidthOf
WidthOf
Sepa
ration
Sepa
ration
Cp =Cp = -- 0.50.5
1997 UBC VALUE1997 UBC VALUE
L/BL/B 0 TO 10 TO 1
ROOF
BB
LL
WidthOf
WidthOf
Separation
Separation
Cp =Cp = -- 0.30.3
L/B = 2L/B = 2
ROOF
BB
LLCp =Cp = -- 0.20.2
L/B = 4L/B = 4
ROOF
Reattachment
Point
WidthOf
WidthOf
Separation
Separation
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Worst case isWorst case is
0.5 rear wall0.5 rear wall
pressure.pressure.
indward Roofindward Roof
PressurePressure
Values fromValues from
ASCE 7ASCE 7
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Roof PressuresRoof PressuresVary w/ HeightVary w/ Height
to Width Ratioto Width Ratio
LL hh
= Angle Of Separation= Angle Of Separation
1010
Cp =Cp = -- 0.70.7
h/Lh/L 0.250.25
Windward RoofWindward Roof
LL hh
= Angle Of Separation= Angle Of Separation
1010
Cp =Cp = -- 0.90.9
h/L = 0.5h/L = 0.5
Windward RoofWindward Roof
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LL
hh
= Angle Of Separation= Angle Of Separation
1010
Cp =Cp = -- 1.31.3
h/Lh/L 1.01.0
Windward RoofWindward Roof
These areThese are
graphicalgraphical
representationsrepresentations
of L/H, toof L/H, to
make it easiermake it easier
to visualize.to visualize.
Windward RoofWindward Roof
= 0= 0 (Flat Roof)(Flat Roof)
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Windward RoofWindward Roof
0
(Gable Roof Or(Gable Roof Or
Steep Slope)Steep Slope)
Leeward RoofLeeward Roof
PressuresPressures
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Leeward RoofLeeward Roof
Pressures VaryPressures Vary
Slightly w/Slightly w/
Height toHeight to
Width RatioWidth Ratio
and Roof Slopeand Roof Slope
Another wrinkle for Roof Angles < 10Another wrinkle for Roof Angles < 10
Windward RoofWindward Roof < 10< 10
--0.3,0.3, --.18.18>2h>2h
--0.5,0.5, --0.180.18h To 2hh To 2h
--0.9,0.9, --0.180.18h/2 To hh/2 To h
--0.9,0.9, --0.180.180 To h/20 To h/2
CpCp
LL
hh
h/Lh/L 0.50.5
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Windward RoofWindward Roof < 10< 10
Varies,Varies, --0.180.18> h/2> h/2
Varies,Varies, --0.180.180 To h/20 To h/2
CpCp
LL hh
0.50.5 h/Lh/L 1.01.0
Windward RoofWindward Roof < 10< 10
--0.7,0.7, --0.180.18> h/2> h/2
--1.3,1.3, --0.180.180 To h/20 To h/2
CpCp
LL hh
h/Lh/L 1.01.0
You can evenYou can even
just use the worstjust use the worst
case linecase line
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Component andComponent andCladding PressuresCladding Pressures
Next:Next:
C&CC&C
tablestables
C & CC & C
These figures include interior pressure (orThese figures include interior pressure (or
suction) !suction) !
Also the Directionality FactorAlso the Directionality Factor
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ICONsICONs Tell AllTell All -- C&CC&C
Cover everything on Facing PagesCover everything on Facing Pages
SEAW RSMSEAW RSM
Pressure EquationPressure Equation
pprsmrsm == qqss KKzzCCrsmrsm [[IIww KKtt]]
Where:Where:
qqss depends on geographical location,depends on geographical location,
KKzz depends on height and exposure,depends on height and exposure,
CCrsmrsm depends on location on building,depends on location on building,
IIww depends on building occupancy, anddepends on building occupancy, and
KKtt depends on topographydepends on topography
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Also:Also:
Discussion and diagrams forDiscussion and diagrams for
edge pressure patterns & howedge pressure patterns & how
to handle roof overhangs.to handle roof overhangs.
SEAW Wind Engineering CommitteeSEAW Wind Engineering Committee Committee MembersCommittee Members
Don Scott, ChairmanDon Scott, Chairman
Jerry Barbera, CommentaryJerry Barbera, CommentaryChairmanChairman
Ahmad AisilliAhmad Aisilli
Scott BeardScott Beard Ed HustonEd Huston
Ed LebertEd Lebert
John LoscheiderJohn Loscheider
Bill MoosekerBill Mooseker
Tony TschanzTony Tschanz
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SEAW Wind Engineering CommitteeSEAW Wind Engineering Committee Principal AuthorsPrincipal Authors
Jerry Barbera, HandbookJerry Barbera, HandbookChairmanChairman
Ahmad AsilliAhmad Asilli Scott BeardScott Beard
Ed HustonEd Huston
Ed LebertEd Lebert
Tony TschanzTony Tschanz
Review and SupportReview and Support Don Scott, ChairmanDon Scott, Chairman
John LoscheiderJohn Loscheider
Bill MoosekerBill Mooseker
Commentary Chapter OneCommentary Chapter One
Technical & Historical OverviewTechnical & Historical Overview
of Wind Codesof Wind Codes
Commentary Chapter TwoCommentary Chapter Two
Quality AssuranceQuality Assurance
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Commentary Chapter ThreeCommentary Chapter Three
OverviewOverview -- IBC, IRC & ASCE 7IBC, IRC & ASCE 7
Commentary Chapter FourCommentary Chapter Four
Basic Wind SpeedBasic Wind Speed
Commentary Chapter FiveCommentary Chapter FiveImportance FactorsImportance Factors
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Commentary Chapter SixCommentary Chapter SixExposure & Topographic EffectsExposure & Topographic Effects
Commentary Chapter SevenCommentary Chapter Seven
Gust ResponseGust Response
Commentary Chapter EightCommentary Chapter Eight
Main Wind Force Resisting SystemMain Wind Force Resisting System
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Commentary Chapter NineCommentary Chapter Nine
Component & Cladding PressuresComponent & Cladding Pressures
Commentary Chapter TenCommentary Chapter Ten
Glass and GlazingGlass and Glazing
Commentary Chapter 11Commentary Chapter 11
Prescriptive DesignsPrescriptive Designs
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Additional ChaptersAdditional Chapters
TwelveTwelveMiscellaneous StructuresMiscellaneous Structures
ThirteenThirteenQ&AQ&AUnusual Wind ConditionsUnusual Wind Conditions FourteenFourteenHigh WindsHigh WindsHurricanesHurricanes
TornadoesTornadoes
FifteenFifteenA Case for Drift ControlA Case for Drift Control
SixteenSixteenWind Tunnel Design PracticeWind Tunnel Design Practice
SeventeenSeventeen-- Equipment & Structure DesignEquipment & Structure Design
Commentary Problem SolutionsCommentary Problem Solutions
Volume TwoVolume Two
IBC & ASCE 7 Wind Load ProvisionsIBC & ASCE 7 Wind Load Provisions
Main Wind Force Resisting PressuresMain Wind Force Resisting Pressures
Component and Cladding PressuresComponent and Cladding Pressures
Miscellaneous StructuresMiscellaneous Structures
Torsion ProvisionsTorsion Provisions
Wind Speed Up EffectsWind Speed Up Effects
FinalFinal
Questions?Questions?