Wind Engineering in 2006 - Huston

8/10/2019 Wind Engineering in 2006 - Huston

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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)



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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..




Changes in ASCE 7Changes in ASCE 7--0505

SEAWSEAWss Rapid Solutions MethodologyRapid Solutions Methodology (RSM)(RSM)


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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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)


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)


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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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)


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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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


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.


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


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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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.


Building withBuilding with

center core,center core,

torsionallytorsionally

weak.weak.



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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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



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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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



p=qGCp=qGCpp--qqii(GC(GCpipi)) Eqt. 6Eqt. 6--1717

q = Velocity pressure evaluated at various locationsq = Velocity pressure evaluated at various locations


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






CCpp = External pressure coefficient from Fig. 6.6= External pressure coefficient from Fig. 6.66.86.8



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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.


Dependent on building geometry.Dependent on building geometry.

Roof pressures decrease along length of roof.Roof pressures decrease along length of roof.


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






CCpp = External pressure coefficient from Fig. 6.6 thru 6.8= External pressure coefficient from Fig. 6.6 thru 6.8



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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 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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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


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


Read theRead the

Footnotes!Footnotes!


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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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.


Read theRead the

Footnotes!Footnotes!


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


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)



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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


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



Where:Where:






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



Where:Where:







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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


1010

Cp =Cp = -- 0.90.9

h/L = 0.5h/L = 0.5



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LL

hh


1010

Cp =Cp = -- 1.31.3

h/Lh/L 1.01.0


These areThese are

graphicalgraphical

representationsrepresentations

of L/H, toof L/H, to

make it easiermake it easier

to visualize.to visualize.


= 0= 0 (Flat Roof)(Flat Roof)


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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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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


--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



Where:Where:







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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



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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


Wind Speed Up EffectsWind Speed Up Effects

FinalFinal

Questions?Questions?

Documents

Wind Engineering in 2006 - Huston