WIND LOAD CALCULATION FOR WIND LOAD CALCULATION FOR SHELTER STRUCTURE AS PER SHELTER STRUCTURE AS PER

ASCE7ASCE7

PRESENTINGPRESENTINGM.Azeem SuddalM.Azeem Suddal

WHAT IS SHELTER WHAT IS SHELTER STRUCTURE ?STRUCTURE ?

Shelter is a structure having a pair Shelter is a structure having a pair of end frames, and a canopy frame of end frames, and a canopy frame interconnecting the end frames.interconnecting the end frames.

Main Parts of a Shelter StructureMain Parts of a Shelter Structure

•Main Wind Force Resisting System (MWFRS)Main Wind Force Resisting System (MWFRS)

• Components and Cladding (C & C)Components and Cladding (C & C)

WHAT IS MWFRS?WHAT IS MWFRS?

An assemblage of structural elements assigned to An assemblage of structural elements assigned to provide support and stability for the overall provide support and stability for the overall structure. The system generally receives wind structure. The system generally receives wind load from more than one surface.load from more than one surface.

WHAT IS C & C?WHAT IS C & C?

Elements of the Elements of the building envelopebuilding envelope that do not that do not qualify as part of the main wind force -resisting qualify as part of the main wind force -resisting systemsystem..

LOAD CALCULATION FOR MWFRS LOAD CALCULATION FOR MWFRS & COMPONENTS AND CLADDING& COMPONENTS AND CLADDING

Factors Affecting the Wind Load CalculationFactors Affecting the Wind Load Calculation

Building CharacteristicsBuilding Characteristicsa ) Roof Geometrya ) Roof Geometryb ) Building Geometryb ) Building Geometryc ) Height above Gradec ) Height above Grade

METHODS OF CALCULATIONMETHODS OF CALCULATION

a ) :Simplified Procedurea ) :Simplified Procedure

b ) : Analytical Procedureb ) : Analytical Procedure

c ) : Wind Tunnel Procedurec ) : Wind Tunnel Procedure

There are three methods for calculation There are three methods for calculation the wind load on a structure.the wind load on a structure.

Wind LoadWind LoadMethod Presented Method Presented

ASCE 7 – 02ASCE 7 – 02

““Method 2 – Analytical Procedure”Method 2 – Analytical Procedure”

Wind Load ProcedureWind Load Procedure

DetermineDetermine

Basic wind speed, V (6.5.4)Importance factor, I (6.5.5)Exposure category (6.5.6)Topographic factor, Kzt (6.5.7)Gust factor,G (6.5.8)Enclosure classification (6.5.9)Internal pressure coefficient GCpi (6.5.11.1)

Wind Load Procedure Wind Load Procedure (Con’t)(Con’t)

External pressure coefficients Cp or GCpi,or force coefficient Cf (6.5.11.2 or 6.5.11.3)

Velocity pressure qz or qh (6.5.10) Design wind load P or F ( 6.5.12 and 6.5.13)

WIND LOAD CALCULATION AS PER ASCE

Definitions

Building Envelop

Cladding,roofing,exterior walls,glazing,door ,window, skylight assemblies and other components enclosing the building.

Open Building

A building having each wall at least 80% open i-eAo ≥0.8AgAo = Total area of openings in wall that receives positive external pressure (m²)Ag = The gross area of that wall in which Ao is idendified (m²)

WIND LOAD CALCULATION AS PER ASCE

Partially Enclosed BuildingPartially Enclosed Building

A building that complies with both of the following conditions1- The total area of openings in a wall that receives positive external pressure exceed the sum of areas of openings in the balance of the building envelop ( walls & roof) by more than 10%. i-eAo > 1.10 Aoi

WIND LOAD CALCULATION AS PER ASCE

2- The total area of openings in a wall that receives positive external pressure exceeds 4ft² or 1% of the area of that wall,whichever is smaller. i-eAo > 4ft² or >0.01AgWhereAo,Ag are as defined for open buildingAoi = The sum of areas of openings in building envelop (walls & roof) not including Ao (m²)

WIND LOAD CALCULATION AS PER ASCE

The design wind force for open building and other The design wind force for open building and other structures shall be determined by the following structures shall be determined by the following formula.formula.

F = qF = qzzGCGCffAAf f (N)(N)

WhereWhere

qqzz = Velocity pressure evaluated at height z = Velocity pressure evaluated at height z

1- Design Wind Load on 1- Design Wind Load on Open Open Building and Other Building and Other StructuresStructures

Design Wind Load on Open Design Wind Load on Open Building and Other Structures Building and Other Structures (Con’t)(Con’t)

G = Gust effect factorG = Gust effect factor

Cf = Net force coefficient from figure 6-18 Cf = Net force coefficient from figure 6-18 through 6-22through 6-22

Af = projected area normal to the wind Af = projected area normal to the wind except where Cf is specified for the actual except where Cf is specified for the actual surface area (m²)surface area (m²)

Adobe Acrobat Document

2- 2- Design Wind Load on Design Wind Load on Enclosed Enclosed and and Partially Partially Enclosed BuildingsEnclosed Buildings

Design wind pressures for the main wind force-resisting system of enclosed and partially enclosed buildings of all heights shall be determined by the following equation:

p = qGCp-qi(±GCpi) (N/m²)

Where

q =qz for windward walls evaluated at height z above the ground;

q = q = qqhh for leeward ,side walls and for leeward ,side walls and roofs,evaluated at height h;roofs,evaluated at height h;

qqii = = qqhh for windward,leeward ,side walls and for windward,leeward ,side walls and roofs of enclosed buildings and for roofs of enclosed buildings and for negative internal pressure evaluation in negative internal pressure evaluation in partially enclosed building partially enclosed building

qqii = = qqzz for positive internal pressure for positive internal pressure evaluation in partially enclosed buildings evaluation in partially enclosed buildings where height “z” is the highest opening where height “z” is the highest opening in the building.in the building.

Design Wind Load on Enclosed Design Wind Load on Enclosed and Partially Enclosed and Partially Enclosed Buildings (Con’t)Buildings (Con’t)

G = Gust effect factorG = Gust effect factor

CCpp = External pressure coefficient from Fig = External pressure coefficient from Fig 6-6 or 6-8;6-6 or 6-8;

(GC(GCpipi) = Internal pressure Coefficient from ) = Internal pressure Coefficient from Fig 6-5 Fig 6-5

Design Wind Load on Enclosed Design Wind Load on Enclosed and Partially Enclosed Buildings and Partially Enclosed Buildings (Con’t)(Con’t)

GCpi Cp

ASCE 7 Method 2ASCE 7 Method 2

EXAMPLE• Example wind load analysis of a low

rise structure:-

30'

h = 15'

40'

ASCE 7 Method 2ASCE 7 Method 2

•Example of ASCE Method 2–Basic wind speed: V – 125 mph–Exposure Category: C–Building classification I: 1.15 (Importance Factor)–Enclosure classification: Enclosed

• Velocity Pressureq = 0.00256Kz Kzt KdV² I

ASCE 7 Method 2ASCE 7 Method 2

• Velocity Pressureq = 33.1 psfqz, qh, and qi = q, for h = 15 feet

ASCE 7 Method 2ASCE 7 Method 2

ASCE 7 Method 2ASCE 7 Method 2

• Wind pressures – MWFRS

Buildings of all heightsp = qGCp – qi(±GCpi)

•External pressure coefficients MWFRS

Windward Wall Cp = 0.8

Side Wall Cp = – 0.7

ASCE 7 Method 2ASCE 7 Method 2

ASCE 7 Method 2ASCE 7 Method 2•External pressure coefficients MWFRS

Leeward wallL/B = 0.75 Wind parallel to 30'Cp = – 0.5L/B = 1.33 Wind parallel to 40'Cp = – 0.43 (interpolated)

ASCE 7 Method 2ASCE 7 Method 2

• Vertical pressure coefficients MWFRSh/L = 0.5 h/L = 0.38Cp0 to h : –0.9 h to 2h : –0.5 >2h : –

0.3

ASCE 7 Method 2ASCE 7 Method 2•Windward wall p = 22.5± 5.06 psf•Side wall p = –19.7± 5.06 psf•Leeward wall p = –14.1± 5.06 psf

–wind normal to 40 ft

•Leeward wall p = –12.2± 5.06 psf–wind normal to 30 ft

ASCE 7 Method 2ASCE 7 Method 2•Roof p = –25.4 ± 5.06 psf 0 to h/2 ft

•Roof p = –25.4 ± 5.06 psf h/2 to h ft

•Roof p = –14.1 ± 5.06 psf h to 2h ft

•Roof p = –8.5 ± 5.06 psf > 2h ft

ASCE 7 Method 2ASCE 7 Method 2

p = –8.5p = –14.1

p = –25.4

p = 22.5 p = –12.2

MWFRS

± internal p = 5.06

p = –14.1

p = –14.1

p = –25.4

p = 22.5 ± internal p = 5.06

MWFRS

ASCE 7 Method 2ASCE 7 Method 2