WIND LOADING ANALYSIS - MWFRS and Components/Cladding
Per ASCE 7-02
Code for Low-Rise, Enclosed Buildings with h <= 60' and Roof q <= 45 o
Using Method 1:
Simplified Procedure (Section 6.4)
Input Data:
Wind Speed, V =
mph?? (Wind
Map, Figure 6-1 )
Bldg.
Classification =
(Table 1-1)
Exposure Category =
(Sect. 6.5.6)
Ridge Height, hr =
ft. (hr >= he)
Eave Height, he =
ft. (he <= hr)
Building Width, W =
ft. (Normal to Building Ridge)
Building Length, L
=
ft. (Parallel to Building Ridge)
Roof Type =
(Gable or Monoslope)
Wall C&C Name =
Girt
Siding
Wall
Fastener
(Girt, Siding, Wall, or Fastener)
Wall C&C Eff.
Area =
ft.^2 (for Component/Cladding)
Roof C&C Name =
Purlin
Joist
Decking
Fastener
(Purlin, Joist, Decking, or Fastener)
Roof C&C Eff.
Area =
ft.^2 (for Component/Cladding)
Overhang Eff. Area
=
ft.^2 (for Component/Cladding)
Hurricane Region?
Y
N
Resulting
Parameters and Net Design Pressures:
For Transverse Direction:
(wind perpendicular to
ridge)
Roof Angle, q =
deg.
Mean Roof?? Ht., h =
ft.?? (h = he for q < 10 deg.)
Adjustment Factor, l =
(adjusts for height and
exposure)
Importance Factor, I =
(Table 6-1)
Wall & Roof End
Zone Width, a =
ft.?? (use: "2*a"?? for MWFRS,??
"a"?? for C&C)
Transverse
MWFRS Net Pressures (psf)
Location
Direction
Zone
Load Case 1
A = end
zone of wall
Horizontal
A
B = end
zone of roof
Horizontal
B
C =
interior zone of wall
Horizontal
C
D =
interior zone of roof
Horizontal
D
E = end
zone of windward roof
Vertical
E
F = end
zone of leeward roof
Vertical
F
G =
interior zone of windward roof
Vertical
G
H =
interior zone of leeward roof
Vertical
H
For Longitudinal
Direction:
(wind parallel to ridge)
Roof Angle, q =
deg.??
(assumed)
Mean Roof?? Ht., h =
ft.?? (h =
(hr+he)/2)
Adjustment Factor, l =
(adjusts for height and exposure)
Longitudinal
MWFRS Net Pressures (psf)
Location
Direction
Zone
Load Case 1
A = end
zone of wall
Horizontal
A
B = end
zone of roof
Horizontal
B
C =
interior zone of wall
Horizontal
C
D =
interior zone of roof
Horizontal
D
E = end
zone of windward roof
Vertical
E
F = end
zone of leeward roof
Vertical
F
G =
interior zone of windward roof
Vertical
G
H =
interior zone of leeward roof
Vertical
H
Total
Design MWFRS Horizontal Load (kips)
Transverse
Longitudinal
Load Case 1
Load Case 2
Min. Load
Load Case 1
Load Case 2
Min. Load
Formulas:
Ph(Trans) =
((Pc*(L-4*a)+Pa*4*a)*he+(Pd*(L-4*a)+Pb*4*a)*(hr-he))/1000
Ph(Trans)(min) =
P(min)*L*hr/1000?? ,?? where: P(min) = 10.0 psf on projected area
Ph(Long)(min) =
P(min)*W*(hr+he)/2/1000?? ,?? where: P(min) = 10.0 psf on full area
Components
& Cladding Net Pressures (psf)
Item
Location
Zone
Pos. (+)
Neg. (-)
4 =
interior zone of wall
4
5 = end
zone of wall
5
1 =
interior zone of roof
1
2 = end
zone of roof
2
3 = corner
zone of roof
3
Roof
Overhang
2 = end
zone of o.h.
2
---
3 = corner
zone of o.h.
3
---
Notes:???? 1.
For Method 1: Simplified
Procedure of Section 6.4 to be used for an enclosed low-rise building??
to determine the design
wind loads, all of the following nine conditions of 6.4.1.1 must be met:
???? a. Building is a simple diaphragm
building, in which wind loads are transmitted through floor??
???????????? and roof diaphragms to the vertical
Main Wind-Force Resisting System (MWFRS).
???? b. Building is a low-rise building where
mean roof height, h <= 60 ft., and h <= min. of L or W.
???? c. Building is enclosed and conforms to
wind-borne debris provisions of Section 6.5.9.3.
???? d. Building is a regular shaped building,
having no unusual geometrical irregularity.
?????? f. Building is not classified as a
flexible building so it is considered "rigid".
???? g. Building is not subject to across-wind
loading, vortex shedding, etc.
???? h. Building has no expansion joints or
separations.
?????? i. Building is not subject to topographic
effects, no abrupt topographic changes.
?????? j. Building has an approximately
symmetrical cross section in each direction with either a??
???????????? flat roof, or gable roof with q <= 45 degrees.
Wind pressures ( p s30) in Figures 6-2 and 6-3 were prepared based on following
assumptions:
???? a. Mean roof height, h = 30 ft.?? ,??
Exposure category = B?? ,?? Importance factor, I =1.0
???? b. Velocity pressure exposure coefficient,
Kz = 0.70
???? c. Directionality factor, Kd = 0.85?? ,??
Topographic factor, Kzt = 1.0
???? d. Internal pressure coefficients, GCpi =
+0.18, -0.18 (enclosed building)
???? e. MWFRS pressure coeff's. from Figure
6-10, and C&C pressure coeff's. from Figure 6-11.
?????? f. Design wind pressure, Ps = l * I * p s30 , in
psf.
Design wind pressures are
net pressures (sum of external and internal pressures).
Wall net pressure for
MWFRS is total for both windward and leeward walls.
(+) and (-) signs signify
wind pressures acting toward & away from respective surfaces.
If pressures for Zones
"B" and "D" < 0, assume = 0.
For the design of the longitudinal MWFRS use
roof angle, q = 0 degrees.
Both load cases 1 and 2 are be checked for
roof angle, 25 degrees < q
<= 45 degrees.
The total design MWFRS horizontal load is the
total horizontal wind load on either the length (L)??
or the width (W) of the
building respectively assuming one end zone of a width = 2*a.
Minimum wind load for
MWFRS design shall be 10 psf applied on projected vertical plane.
Minimum wind load for
C&C shall be 10 psf acting in either direction normal to surface.
References:??
???? a. ASCE 7-02 Standard, "Minimum
Design Loads for Buildings and Other Structures".
???? b. "Guide to the Use of the Wind Load
Provisions of ASCE 7-02"
???????????? by: Kishor C. Mehta and James M.
Delahay (2004).
(continued)
MWFRS -
Wind Zones
Components
and Cladding - Wind Zones