CHAPTER 26 WIND LOADS: GENERAL REQUIREMENTS

130(58)

140(63)150(67)

165(74)

Figure 26.5-1B Basic Wind Speeds for Occupancy Category III and IV Buildings and Other Structures.Notes:1. Values are nominal design 3-second gust wind speeds in miles per hour (m/s) at 33 ft (lOrn) above ground for

Exposure C category.2. Linear interpolation between contours is permitted.3. Islands and coastal areas outside the last contour shall use the last wind speed contour of the coastal area.4. Mountainous terrain, gorges, ocean promontories, and special wind regions shall be examined for unusual wind

conditions.5. Wind speeds correspond to approximately a 3% probability of exceedance in 50 years (Annual Exceedance

Probability = 0.000588, MRI = 1700 Years).

248a

MINIMUM DESIGN LOADS

m~*>;l:~; u: f-c 150(67):1 ~'''l ~4~~~160(72)

K 170(76)...7'" .,.170(76) 180(80) ~~" 180(80)

....::5~V190(85)

~200(89)

.' 200(89)

WI120(54)'lJ-/;1ffi\I

130;~~~\ 160(72)140(63)150(67)

_ Special Wind Region

Vmph210175170145

LocationGuamVirgin IslandsAmerican SamoaHawaii -

(rn/s)(94) 1.60.(72~<.!6)

(78) ~180(80)

(76)(65)

Puerto Rico

Figure 26.5-1B (Continued)

248b

CHAPTER 30 WIND LOADS - COMPONENTS AND CLADDING

- Gust Effect Factor (Section 26.9)- Enclosure classification (Section 26.10)- Internal pressure coefficient (GCp;) (Section 26.11).

30.2.2 Minimum Design Wind PressuresThe design wind pressure for components and

cladding of buildings shall not be less than a netpressure of 16 lb/tr' (0.77 kN/m2) acting in eitherdirection normal to the surface.

30.2.3 Tributary Areas Greater than 700 ftl (65 m')Component and cladding elements with tributary

areas greater than 700 ft2 (65 nr') shall be permitted tobe designed using the provisions for MWFRS.

30.2.4 External Pressure CoefficientsCombined gust effect factor and external pressure

coefficients for components and cladding, (GCp), aregiven in the figures associated with this chapter. Thepressure coefficient values and gust effect factor shallnot be separated.

30.3 VELOCITY PRESSURE

30.3.1 Velocity Pressure Exposure CoefficientBased on the exposure category determined in

Section 26.7.3, a velocity pressure exposure coeffi-

316

cient K, or Kh, as applicable, shall be determined fromTable 30.3-1. For a site located in a transition zonebetween exposure categories, that is, near to a changein ground surface roughness, intermediate values ofK;or Ki, between those shown in Table 30.3-1, arepermitted, provided that they are determined by arational analysis method defined in the recognizedliterature.

30.3.2 Velocity PressureVelocity pressure, qz, evaluated at height z shall

be calculated by the following equation:4 qz = 0.00256 KzKztKdV2 (lb/fr') (30.3·1)

[In SI: qz = 0.613 KzKztKdV2 (N/m2); V in m/s]

where

Kd = wind directiona1ity factor defined in Section 26.6K, = velocity pressure exposure coefficient defined in

Section 30.3.1Kzt = topographic factor defined in Section 26.8V = basic wind speed from Section 26.5

qh = velocity pressure calculated using Eq. 30.3-1 atheight h

The numerical coefficient 0.00256 (0.613 in SI)shall be used except where sufficient climatic data areavailable to justify the selection of a different value ofthis factor for a design application.

MINIMUM DESIGN LOADS

Velocity Pressure Exposure Coefficients, Kh and Kz ITable 30.3-1 I

1. The velocity pressure exposure coefficient K, may be determined from the following formula:

For 15 ft. $ Zs Zg For Z< 15 ft. 0.'

K, = 2.01 (zlZJ2/a. K, = 2.01 (l5/Zg)21a.·

Note: Z shall not be taken less than 30 feet in exposure B.

2. a. and Zgare tabulated in Table 26.9.1.

3. Linear interpolation for intermediate values of height Z is acceptable.

4. Exposure categories are defined in Section 26.7.

Height above Exposure

ground level, Z

B C Dft (m)

shall0-15 (0-4.6) 0.70 0.85 1.0320 6.1 0.70 " 0.90 1.0825 7.6 0.70 0.94 1.12

30.3-1) 30 9.1 0.70 0.98 1.1640 12.2) 0.76 I 1.04 1.22

5] 50 15.2) 0.81 1.09 1.2760 (18) 0.85 1.13 1.31~ (21.3 0.89 1.17 1.34

ion 26.6 80 (24.4 0.93 1.21 1.38fined in 90 27.4 0.96 1.24 1.40

100 30.5 0.99 1.26 1.43.8 120 36.6) 1.04 1.31 1.48

140 42.7 1.09 1.36 1.520.3-1 at 160 48.8 1.13 1.39 1.55

180 54.9 1.17 1.43 1.58200 61.0 1.20 1.46 1.61

3 in SI) 250 76.2 1.28 1.53 1.68c data are 300 91.4 1.35 1.59 1.73nt value of 350 (106.7 1.41 1.64 1.78

400 121.9 1.47 1.69 1.82450 137.2 1.52 1.73 1.86500 152.4 1.56 1.77 1.89

Notes:

317

CHAPTER 30 WIND LOADS - COMPONENTS AND CLADDING

Figure 30.4-2A External Pressure Coefficients,

Enclosed, Partially Enclosed Buildings

10 100

l3) Roof'-'-'-(2) '", ,

1"0... \...•..."

\..1)

~

-3.2

-3.0-2.8-2.6-2.4

E -2.2_~ -2.0.- -1.8~ -1.6

8 -1.4e -1.2

~ -1.0en -0.8eQ. -0.6as -0.4E -0.2

~ 0~ +0.2

+0.4

+0.6E1 10 20 50 100 200 5001000

(0.1) (0.9) (1.9) (4.6) (9.3) (18.6) (46.5)(92.9)

Effective Wind Area, ft2 (nf)

c..(,J~

-2.8

h s 60 ft.

Gable Roofs e ~ 7°

10 100

-2.8

-1.7-1.6

-1.1

-0.8

-1.8

-1.1-1.0-0.9

+0.2.+0.3

(3) OverhanaI\.\.,

\...(i)J.(2). "", ,

~ "-" ..." ~,

-3.2

...: -3.0~ -2.8'u -2.6

=0; -2.4-2.2

(,J -2.0e::::3 -1.8~ -1.6e -1.4Q. -1.2

as -1.0c•.• -0.8

~ -0.6W 1 10 20 50 100 200 500 1000

(0.1) (0.9) (1.9) (4.6) (9.3) (18.6) (46.5)(92.9)

Effective Wind Area, ft2 (nf )

Notes:

l. Vertical scale denotes GCp to be used with qh.2. Horizontal scale denotes effective wind area, in square feet (square meters).3_ Plus and minus signs signify pressures acting toward and away from the surfaces, respectively.4. Each component shall be designed for maximum positive and negative pressures.5. If a parapet equal to or higher than 3 ft (0.9m)is provided around the perimeter of the roof with e ~ 7°,

the negative values of GCp in Zone 3 shall be equal to those for Zone 2 and positive values of GCp inZones 2 and 3 shall be set equal to those for wall Zones 4 and 5 respectively in Figure 30.4-1.

6. Values of GCp for roof overhangs include pressure contributions from both upper and lower surfaces.7. Notation:

a: 10 percent of least horizontal dimension or O.4h, whichever is smaller, but not less than either 4% ofleast horizontal dimension or 3 ft (0.9 m).

h: Eave height shall be used for e ~ 10°.B: Angle of plane of roof from horizontal, in degrees.

336

MINIMUM DESIGN LOADS

h s 60 ft.

GablelHip Roofs 7°< e s 27°

--n-- -TtT- --n--t ~!---~-->(j;~@--!@, ", ", ", ", ", ", ", "

0: <D :Q:; CD! <D 10, ,, ,, ,,, ,, ,,,, ,_-'- or.,; - - J - - - - - - -'- -

0: 0 :~0: 0 :0

10 100-2.8-2.6-2.4-2.2

-2.0-1.8-1.6-1.4-1.2

-1.0-0.8-0.6-0.4-0.2

o+0.2+0.4+0.6+0.8

1(0.1)

-2.80..(.)(9-EQ)-0

-1.7 ~-1.6 Q)

0(.)

-1.1 ~:::3en

-0.8 en~Cl..

a co) c::'-

~w

(3) ................•.. Roof

1"0.

~ r--....~

-0

...(i){2).&.(3} +0.3+0.5

-2.6

-2.0

-1.7

10 20 50 100 200 500 1000(0.9) (1.9) (4.6) (9.3) (18.6) (46.5)(92.9)

Effective Wind Area, ft 2(m2)

8'(9~ -4.0Q) -3.8-0 -3.6~ -3.48 -3.2

~ -3.0:::3 -2.8~ -2.6~n, -2.4

co -2.2c:: -2.0Q; 1 10 20 50 100 200 500 1000xw (0.1) (0.9) (1.9) (4.6) (9.3) (18.6) (46.5)(92.9)

Effective Wind Area, ft 2(m2)

10 100

~ 0\ erM ha

"I\..

""'I"<.2)

-1.2

-0.9-0.8

-3.7

-2.5

-2.2

Notes:

1. Vertical scale denotes GCp to be used with qh.2. Horizontal scale denotes effective wind area, in square feet (square meters).3. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively.4. Each component shall be designed for maximum positive and negative pressures.5. Values of GCp for roof overhangs include pressure contributions from both upper and lower surfaces.6. For hip roofs with 7° < e ~ 27°, edge/ridge strips and pressure coefficients for ridges of gabled roofs shall

apply on each hip.7. For hip roofs with e ~ 25°, Zone 3 shall be treated as Zone 2.8. Notation:

a: 10 percent of least horizontal dimension or O.4h, whichever is smaller, but not less than either 4% ofleast horizontal dimension or 3 ft (0.9 m).

h: Mean roof height, in feet (meters), except that eave height shall be used for e ~ 10°.e: Angle of plane of roof from horizontal, in degrees.

CHAPTER 30 WIND LOADS - COMPONENTS AND CLADDING

Figure 30.4-2CEnclosed, Partially Enclosed Buildings

CD2

h s 60 ft.

It 10 100" -3.0.,;- -2.8

~ ·2.6:§ -2.4

=i -2.2

8 -2.0 -2.0G) -1.8 -1.8:s -1.6~. -1.4~ -1.2a.._ -1.0~ 1 10 20 50 100 20.0 5001000

..' Gi (0.1) (0.9) (1.9) (4.6) (9.3) (18:6) (46.5)(92.9)

;H' Effective Wind Area, ft2 (nf )

overnang

\.2J&13)~

Notes:L Vertical scale denotes GCp to be used with qh-2_ Horizontal scale denotes effective wind area, in square feet (square meters).3_ Plus and minus signs signify pressures acting toward and away from the surfaces, respectively.4_ Each component shall be designed for maximum positive and negative pressures.5. Values of GCp for roof overhangs include pressure contributions from both upper and lower surfaces.6. Notation:

a: 10 percent ofleast horizontal dimension or OAh, whichever is smaller, but not less than either 4% ofleast horizontal dimension or 3 ft (0.9 m).

h: Mean roof height, in feet (meters).9: Angle of plane of roof from horizontal, in degrees.

CD

c. 10 100g -1.6.,;- -1.4

~ -1.2 -1.2·u -1.0 -1.0

~ ~ ~

8 ~::~::l -0.2

~ 0~ +0.2a.. +0.4

asc +0.6Gi +0.8 +0.8>< +1.0 +0.9W 1 10 20 50 100 200 5001000

(0.1) (0.9) (1.9) (4.6) (9.3) (18.6) (46.5)(92.9)

Effective Wind Area, ft2 (nf)

C2)&(3) Roof•••••••••

(i') -•........ -

~

MINIMUM DESIGN LOADS

h s 60 ft.Figure 30.4-SA External Pressure Coefficients, Monoslope Roofs

3°< e::; 10°oofs

Enclosed, Partially Enclosed Buildings

I ® :0 lIIr ~ ® L...------.l-r-

II a.I 0I CJ

® CD tt .:c::::Q)

I 'ua I

==I

. IQ)0

I 0·2.6 ~ ® r-------.-L- l

Q)·2.5 •..

I ® :0 :::JI tntn·2.0 Q)•..

·1.7 0..

a;C

·1.1 •..Q)-><w

10 100-3.0- .8-2.6-2.4-2.2

-2.0-1.8-1.6-1.4

-1.2-1.0

-0.8-0.6-0.4-0.2

o+0.2+0.4

+0.61

(0.1) (0.9) (1.9) (4.6) (9.3) (18.6) (46.5)(92.9)

Effective Wind Area, ft2 (m2)

1J~

""' '""(3) """,(2') '" "~

""'-~

KD~

ALLWNES

-2.6

-1.8-1.6-1.5-1.3-1.2-1.1

+0.2+0.3

50 100 200 500 100010 20

~3-II- w

Notes:

1. Vertical scale denotes GCp to be used with qh.2. Horizontal scale denotes effective wind area A, in square feet (square meters).3. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively.

t4 .. Each component shall be designed for maximum positive an~egative pressures.5. For e ~ 3°, values of GCp from Fig. 30A-2A shall be used.6. Notation:

a: 10 percent of least horizontal dimension or OAh, whichever is smaller, but not less thaneither 4 percent of least horizontal dimension or 3 ft (0.9 m).

h: Eave height shall be used for e ~ 10°. 'W: Building width, in feet (meters).e: Angle of plane of roof.from horizontal, in degrees.

y.

341