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Introduction/Course Description
Introduction
WIND LOADS ON BUILDINGS
IN ACCORDANCE WITH NSCP 2010
SECTION 207
Lecturer ENGR. ADAM C. ABINALES, M.ENG, F.ASEP
Course STRUCTURAL ENGINEERING
Objectives and Results
Objectives
To provide a guide and information on the use of Section 207 of the
NSCP Vol. I Sixth Edition 2010 with some illustrative examples for
the civil engineering graduates, practicing civil/structural engineers,
private and government stakeholders in construction industry and
members of the academe community in the Philippines.
To present the major and significant provisions of Section 207 Wind
Load of Chapter 2 of the NSCP Vol. I Sixth Edition 2010.
Results
Understand and learn the basic wind load calculation as applied to
building using Method 1 or Method 2.
Understand and learn the basic wind load calculation as applied to
tower structure using Method 2.
One of the major and significant revisions of the
NSCP Vol. I Sixth Edition 2010 is Chapter 2
which stipulates provisions on the minimum
design loads to be applied on buildings, towers
and other vertical structures.
Section 207 of the NSCP Vol. I Sixth Edition2010
which discusses the wind load provisions of
Chapter 2 Minimum Design Requirements is one
of the major and significant changes. Wind load
provisions of the NSCP Vol. I 2010 are generally
referenced from the wind load criteria of the
American Society of Civil Engineers (ASCE)
publication, SEI/ASCE Standard 7-05, Minimum
Design Loads for Buildings and Other Structures.
Vocabulary
Basic Wind Speed, denoted by
Basic wind speed is a three-second gust speed at 10 m
above the ground in Exposure “C” and associated with
an annual probability for 2% of being equaled or
exceeded (50-year mean recurrence interval).
Design Wind Force, denoted by
Design wind force is the equivalent static force to be used
in the determination of wind loads for open buildings
and other structures.
Skills developed
Proficiency on wind load derivation for building
Proficiency on wind load derivation for tower structure
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Vocabulary
Design Wind Pressure, denoted by
Design wind pressure is the equivalent static pressure to
be used in the determination of wind loads for buildings
and may be denoted as:
= pressure that varies with height in accordance
with velocity pressure evaluated at height ; or
= pressure that is uniform with respect to the
height as determined by the velocity pressure
evaluated at mean roof height .
Vocabulary
Building, Partially Enclosed
Building, Partially Enclosed is a building that complies
with both of the following conditions:
the total area of openings in a wall that receives
positive external pressure exceeds the sum of the
areas of openings in the balance of the building
envelope (walls and roof) by more than 10%; and
the total area of openings in a wall that receives
positive external pressure exceeds 0.5 m2 or 1% of
the area of that wall, whichever is smaller, and the
percentage of openings in the balance of the
building envelope does not exceed 20%.
Vocabulary
Building, Enclosed
Building, Enclosed is a building that does not comply with
the requirements for open or partially enclosed
buildings.
Building, Open
Building, Open is a building having each wall at least 80%
open.
Vocabulary
Building, Low-rise
Building, Low-rise is an enclosed or partially enclosed
building that comply with the following conditions:
mean roof height less than or equal to 18 m; and
mean roof height does not exceed least horizontal
dimension.
Building, Envelope
Building Envelope consists of cladding, roofing, exterior
wall, glazing, door assemblies, window assemblies,
skylight assemblies and other components enclosing the
building.
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Vocabulary
Building, Flexible
Building, Flexible is a slender building that has a
fundamental natural frequency less than 1 Hz.
Building, Rigid
Building, Rigid is a building or other structure whose
fundamental natural frequency is greater than or equal
to 1 Hz.
Vocabulary
Components and Cladding (C&C)
Components and Cladding (C&C) are elements of the
building envelope that do not qualify as part of the main
wind-force resisting system. Cladding receives wind loads
directly and generally transfers the load to other
components or to the MWFRS.
Main Wind-Force Resisting System (MWFRS)
Main Wind-Force Resisting System (MWFRS) is defined as
the overall structure receiving wind loading from more
than one surface.
Vocabulary
Wind Engineering
Wind Engineering is best defined as the
rational treatment of interactions
between wind in the atmospheric
boundary layer and man and his works
on the surface of the Earth. - Dr. Jack
Cermak (1975)
Highlights of Significant Provisions in
Section 207 – Wind Loads
Previous Editions of NSCP Volume I
The wind load criteria of NSCP 1992 Fourth Edition were
essentially different from that of NSCP 2001 Fifth Edition;
the basic wind speed averaging time was changed from
the fastest-mile to 3-second gust. This in turn
necessitated significant changes in boundary-layer profile
parameters, gust effect factor, and some pressure
coefficients.
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Highlights of Significant Provisions in
Section 207 – Wind Loads
NSCP Volume I, Sixth Edition
In the latest version NSCP 2010 6th Edition, there are
numerous significant provisions that involve expansion of
the simplified procedure, load cases for main wind-force
resisting systems, and introduction of surface roughness
length to define exposure coefficients.
The basic approach to assessing and determining wind
loading has not been changed (relative to the NSCP 2001
5th Edition), but new parameters, such as roughness
surface length, wind directionality factor, are added to
provide more flexibility to designers.
Highlights of Significant Provisions in
Section 207 – Wind Loads
Introduction of wind directionality factor
(Section 207.5.4.4)
Highlights of Significant Provisions in
Section 207 – Wind Loads
The significant provisions that may affect the design
process are listed as follows:
Introduction of the simplified procedure, which is
expanded (Section 207.4)
Highlights of Significant Provisions in
Section 207 – Wind Loads
Introduction of surface roughness length to define
exposure coefficients (Section 207.5.6.2)
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Highlights of Significant Provisions in
Section 207 – Wind Loads
Exposure A is deleted from the tabulated values
(Section 207.5.6.3)
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Load cases are applied to buildings of all heights for
main wind-force resisting system (MWFRS)
(Figure 207-9)
Highlights of Significant Provisions in
Section 207 – Wind Loads
New pressure coefficients are provided to determine
wind loads for domed roof buildings (Figure 207-7)
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Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Provisions for calculating wind loads for parapets
(MWFRS and C&C) are added (Section 207.5.12.2.4)
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
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Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
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Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
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Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
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Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
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Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
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Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Reduction factor is allowed for partially enclosed
building containing large volume
(Section 207.5.11.1.1)
Gust effect factors are more defined for rigid and
flexible structures (Section 207.5.8).
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Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Gust effect factors
for other structures
such as poles,
masts, trussed
towers, billboard
structures, freestanding wall and
solid signs are also
defined.
(Section 207.7)
Table 207-5.
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Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
Highlights of Significant Provisions in
Section 207 – Wind Loads
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Highlights of Significant Provisions in
Section 207 – Wind Loads
Wind loads on all
structures
supporting
antennas, cables
and other
attachments and
appurtenances shall
be referred to TIA222-G (2005)
(Section 207.5.15.2)
Calculation Procedure
Calculation Procedure
Sixth Edition of NSCP Volume I, 2010
Sections 207.4 through 207.6 of the NSCP 2010 prescribe
the provisions for the design procedure that may be
adopted in the calculation of wind forces on the structure
MWFRS and its components and cladding (C&C).
Method 1 – Simplified Procedure
Calculation Procedure
Method 1 – Simplified Procedure
as specified in Section 207.4 the simplified
procedure may be applied to buildings
meeting certain specific requirements
which are set for MWFRS and C&C,
respectively
generally used for evaluating design loads
for common regular shaped low-rise
buildings
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Calculation Procedure
Method 2 – Analytical
Procedure
Calculation Procedure
Method 3 – Wind
Tunnel Procedure
Calculation Procedure
Method 2 – Analytical Procedure
as specified in Section 207.5 analytical
procedure is applicable to buildings and
other structures – buildings of all heights;
alternate low-rise buildings with mean
roof height less than or equal to 18 m; or
open buildings and other structures not
susceptible to across wind loading or
other special considerations due to
location
Calculation Procedure
Method 3 – Wind Tunnel
Procedure
must meet certain
test conditions as
specified in
Section 207.6 for
the proper
conduct of such
tests
particularly useful
for obtaining
detailed
information about
pressure
distributions on
complex shapes
and the dynamic
response of
structures
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Design Wind Pressure / Force
Rigid Buildings of All
Heights
Design Wind Pressure / Force
Flexible Buildings
Design Wind Pressure / Force
Low-Rise Buildings
Design Wind Pressure / Force
Components & Cladding
elements of Parapets
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Design Wind Pressure / Force
Open Buildings with
Monoslope, Pitched or
Trough Slope
Design Wind Pressure / Force
Other Structures
Design Wind Pressure / Force
Solid Free-standing Walls and Solid Signs
Velocity Pressure
Velocity Pressure
47.3 10
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Velocity Pressure
Velocity Pressure
47.3 10
Velocity Pressure
Velocity Pressure
47.3 10
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Velocity Pressure
Velocity Pressure
Velocity Pressure
Velocity Pressure
47.3 10
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Velocity Pressure
Velocity Pressure
47.3 10
Velocity Pressure
Velocity Pressure
Wind Zone Map of
the Philippines
Wind Zone for the
Different Provinces
of the Philippines
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Velocity Pressure
47.3 10
Exposure Category
Exposure Category
Exposure
Exposure Category
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Exposure Category
Exposure Category
Example Scenario of
Exposure Category B
Exposure Category
Exposure Category
Example Scenario of
Exposure Category C
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Exposure Category
Example Scenario of
Exposure Category C
Pressure and Force Coefficient
Pressure and Force Coefficient
Internal Pressure Coefficient
Pressure and Force Coefficient
External Pressure Coefficient
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Pressure and Force Coefficient
Pressure and Force Coefficient
Refer to Figure 207-6 of NSCP v1 2010
Pressure and Force Coefficient
Pressure and Force Coefficient
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Pressure and Force Coefficient
Pressure and Force Coefficient
Refer to Figure 207-7 of NSCP v1 2010
Pressure and Force Coefficient
Pressure and Force Coefficient
Refer to Figure 207-8 of NSCP v1 2010
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Pressure and Force Coefficient
Gust Effect Factor
Gust Effect Factor
Gust Effect Factor
Gust Effect Factor
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Gust Effect Factor
Gust Effect Factor
Example Problem 1
Example Problem 1
Given a 60-m x 75-m Gable Roof Warehouse
Building with dimensions and framing as shown
below:
Design parameters:
Location: The Fort Global City, Taguig City
Topography: Homogeneous
Terrain: Flat, open terrain
Dimensions: 60-m x 75-m in plan
Eave height = 6 m
Roof slope 4:12 (18.4°)
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Example Problem 1
Example Problem 1
Framing configuration:
Framing: Rigid frames span the 60-m direction
Rigid frame bay spacing = 7.5 m
Lateral bracing in the 75-m direction is
provided by a “wind truss” spanning the 60m to side walls and cable/rod bracing in the
plane of the walls
Girts and purlins span between rigid frames
(7.5 m)
Girt spacing = 1.6 m
Purlin spacing = 1.2 m
Solution and Discussion to Example
Reference /
Problem 1
Notes
Exposure
and Building
Classification
The building is located on flat and
open terrain. It may not fit
Exposure Category B or D;
therefore, Exposure Category C
is considered.
The building function is commercial
- industrial. It is not an essential
facility or likely to be occupied
by 300 persons at one time.
Occupancy Category IV is
appropriate; therefore, = 1.0
Sections
207.5.6.2 and
207.5.6.3
Section
207.5.6
Table 207-3
Framing configuration:
Cladding: Roof panel dimensions = 0.6 m
Roof fastener spacing on purlins = 0.3 m on
center
Wall panel dimensions = 0.6 m x 6 m
Wall fastener spacing on girts = 0.3 m on
center
Openings are uniformly distributed
Solution and Discussion to Example
Reference /
Problem 1
Notes
Basic Wind
Speed
Calculation
Procedure
The building location is in Metro
Manila (NCR) which in Zone II
of the Philippine Wind Zone
Map. Therefore, the basic
wind speed is = 200 kph.
Method 2, Analytical Procedure,
will be used in this example. In
addition, provisions of
buildings of all heights, given
in Section 207.5.12.2.1 for
MWFRS will be used.
Table 207-1 or
Figure 207-24
Section 207.5
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Solution and Discussion to Example
Reference /
Problem 1
Notes
Wind
Directionality
Velocity
Pressure
Wind directionality factor
= 0.85 for MWFRS and C&C.
The velocity pressures are
computed using the following
equation:
47.3 10
where
=?
= 1.0 (no topographic effect)
= 0.85
= 1.0
= 200 kph
Section
207.5.4.4 or
Table 207-2
Design wind pressures for MWFRS of this
building can be obtained using Section
207.5.12.2.1 for buildings of all heights or
Section 207.5.12.2.2 for low-rise
buildings. In this example, pressures are
determined using buildings of all heights
criteria:
&
where
for windward wall at height above
ground
for leeward wall, side walls, and roof at
height
for enclosed buildings
= gust effect factor
= external pressure coefficient
= internal pressure coefficient
Velocity
Pressure
Section
207.5.10
Equation 20715
Table 207-4
Section
207.5.7
Section
207.5.4.4 or
Table 207-2
Substituting the values into
Equation 207-15 yields:
47.3 10
1 0.85 200
Height
Elev. (m)
4.50
6.00
9.00
11.00
12.00
15.00
16.00
Eave
*
1
N/m2
1608.2
Ridge
Solution and Discussion to Example
Reference /
Problem 1
Notes
Design Wind
Pressure
Solution and Discussion to Example
Reference /
Problem 1
Notes
0.85
0.90
0.98
1.02
1.04
1.09
1.10
1608.2
(N/m2)
1367
1447
1576
1640*
1673
1753
1769
is based on
Note 2 of
Table 207-4.
Values for
are the same
for Cases 1
and 2 for
Exposure C.
Mean roof
height = 11
m.
N/m2
Solution and Discussion to Example
Problem 1
Section
207.5.4.4 or
Table 207-2
Section
207.5.12.2.1
Equation 20717
Figure 207-6
Figure 207-5
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Solution and Discussion to Example
Problem 1
Solution and Discussion to Example
Reference /
Problem 1
Notes
Design Wind
Pressure
Solution and Discussion to Example
Reference /
Problem 1
Notes
External
Pressure
Coefficient
on Wall
The pressure coefficients for the
Figure 207-6
windward wall and for the
side walls are 0.8 and -0.7,
respectively, for all '/(
ratios.
The leeward wall pressure
coefficient is a function of
'/( ratio. For wind normal to
the ridge, '/( = 60/75 = 0.8;
therefore, the leeward wall
pressure coefficient is -0.5.
For this example, when the wind is
normal to the ridge, the windward
roof experiences both positive and
negative external pressures.
Combining these external
pressures with positive and
negative external pressures will
result in four loading cases when
wind is normal to the ridge.
When wind is parallel to the ridge,
positive and negative internal
pressures result in two loading
cases. The external pressure
coefficients
for θ = 0° apply in
this case.
Figure 207-6
Solution and Discussion to Example
Reference /
Problem 1
Notes
External
Pressure
Coefficient
on Wall
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Solution and Discussion to Example
Reference /
Problem 1
Notes
External
Pressure
Coefficient
on Wall
For wind parallel to the ridge, '/( =
Figure 207-6
75/60 = 1.25; the value of ,
obtained by linear interpolation, = 0.45.
In summary, the wall pressure coefficients
are:
Surface
Windward wall
Leeward wall
Side wall
Wind direction
All
Normal to
ridge
Parallel to
ridge
All
'/(
All
0.80
0.8
-0.50
1.25
-0.45
All
-0.70
Solution and Discussion to Example
Reference /
Problem 1
Notes
External
Pressure
Coefficient
on Roof
Figure 207-6
Solution and Discussion to Example
Reference /
Problem 1
Notes
External
Pressure
Coefficient
on Roof
The roof pressure coefficients for
the MWFRS are determined
and shown below:
Surface
Windward
roof
Leeward
roof
15°
18.4°
20°
-0.5
-0.36*
-0.3
0.0
0.14*
0.2
-0.5
-0.57*
-0.6
Figure 207-6
*Values obtained by linear interpolation. For
wind normal to ridge, /' = 11/60 = 0.186.
Solution and Discussion to Example
Reference /
Problem 1
Notes
Internal
Pressure
Coefficient
Values for
for buildings are
addressed in:
Section
207.5.11.1
Figure 207-5
The openings are evenly
distributed in the walls
(enclosed building). The
reduction factor of Section
207.5.11.1.1 is not applicable
for enclosed buildings;
therefore,
= ±0.18
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Solution and Discussion to Example
Reference /
Problem 1
Notes
Gust Effect
Factor
For rigid structures (where the ratio of
to the least width of building =
16/60 = 0.18 < 4), hence, rigid
building, can be calculated using
Equation 207-4:
1 * 1.7+, ̅ .
0.925
1 * 1.7+/ ̅
where
+, = +/ = 3.4
̅ 0.6 = 0.6(11) = 6.6 m or ̅
4.5 m
2 = 0.2
ℓ = 150 m
ε5 = 1/5
01 =
Section
207.5.8.1
Then, compute the other notations
̅
2
67 6/
0.2
̅
̅
67 6/
.
.
1 * 0.63
(*
'̅
7. 8
in which
'̅
ℓ
̅ 9̅
10
'̅
Section
207.5.8.1
Equation 2075
0.214
1
6.6
10
138.04
150
6/;
Table 207-5
Gust Effect
Factor
Table 207-5
Solution and Discussion to Example
Reference /
Problem 1
Notes
Gust Effect
Factor
Solution and Discussion to Example
Reference /
Problem 1
Notes
Equation 2076, use ( = 60
m (the smaller
value gives
larger value of
)
Equation 2057
Solution and Discussion to Example
Reference /
Problem 1
Notes
Gust Effect
Factor
Then,
.
6
=>?@@ >.=A
Equation 2076
6<7. 8 @AB.>C
. 0.84
Substituting the computed
values to evaluate :
0.925
1 * 1.7 3.4 0.214 0.84
1 * 1.7 3.4 0.214
Equation 2074
0.883
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Solution and Discussion to Example
Reference /
Problem 1
Notes
Net Wind
Pressures on
MWFRS
Wind pressure on the MWFRS is
determined as
&
0.883
& 1640 D0.18
Solution and Discussion to Example
Reference /
Problem 1
Notes
Net Wind
Pressures on
MWFRS
Equation 20717
On the windward wall from 0 –
4.5 m, wind normal to ridge:
1367 0.883 0.8 & 1640 D0.18
670 N/m2 with (+) internal pressure
1261 N/m2 with (-) internal pressure
Net Wind
Pressures on
MWFRS
From previous calculation, note
that = 1640 N/m2;
=
±0.18; therefore, the quantity
(
) = ±295 N/m2
*Two loadings on windward roof Refer to
Figures 1-1
and two internal pressures
through 1-2 in
next slides
yield a total of four loading
cases.
Net pressure (N/m2) with
Surface
(m)
(N/m2)
Windward
wall
4.50
6.00
1367
1447
0.883
0.883
0.80
0.80
(+
)
670
727
()
1261
1317
All
1640
0.883
-0.50
-1019
-429
All
1640
0.883
-0.70
-1309
-719
-0.36
-816
-226
0.14
-92
498
-0.57
-1120
-530
Leeward
wall
Side walls
Windward
roof*
Leeward
roof
Solution and Discussion to Example
Reference /
Problem 1
Notes
In summary, the net pressures
for the MWFRS (wind normal
to ridge) are shown in table:
-
1640
0.883
-
1640
0.883
Solution and Discussion to Example
Reference /
Problem 1
Notes
Net Wind
Pressures on
MWFRS
Figure 1-1 – Net Design Wind Pressures for MWFRS
when Wind is Normal to Ridge with Negative
Windward External Roof Pressure Coefficient
Net pressure (N/m2) with
Surface
(m)
(N/m2)
Windward
wall
Leeward
wall
Side walls
Windward
roof*
Leeward
roof
4.50
6.00
1367
1447
0.883
0.883
0.8
0.8
670
727
()
1261
1317
All
1640
0.883
-0.5
-1019
-429
All
1640
0.883
-
1640
0.883
-0.7
-0.36
0.14
-1309
-816
-92
-719
-226
498
-
1640
0.883
-0.57
-1120
-530
(+
)
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Solution and Discussion to Example
Reference /
Problem 1
Notes
Net Wind
Pressures on
MWFRS
Figure 1-2 – Net Design Wind Pressures for
MWFRS when Wind is Normal to Ridge with
Negative Windward External Roof Pressure
Coefficient
Surface
(m)
(N/m )
2
Windward
wall
Leeward
wall
Side walls
Windward
roof*
Leeward
roof
Net Wind
Pressures on
MWFRS
Net pressure (N/m2) with
4.50
6.00
1367
1447
0.883
0.883
0.8
0.8
(+
670
727
)
()
1261
1317
All
1640
0.883
-0.5
-1019
-429
All
1640
0.883
-
1640
0.883
-0.7
-0.36
0.14
-1309
-816
-92
-719
-226
498
-
1640
0.883
-0.57
-1120
-530
Solution and Discussion to Example
Reference /
Problem 1
Notes
Net Wind
Pressures on
MWFRS
Figure 1-4 – Net Design Wind Pressures for
MWFRS when Wind is Normal to Ridge with
PositiveWindward External Roof Pressure
Coefficient
Surface
(m)
(N/m )
2
Windward
wall
Leeward
wall
Side walls
Windward
roof*
Leeward
roof
Solution and Discussion to Example
Reference /
Problem 1
Notes
Net pressure (N/m2) with
4.50
6.00
1367
1447
0.883
0.883
0.8
0.8
(+
670
727
)
()
1261
1317
All
1640
0.883
-0.5
-1019
-429
All
1640
0.883
-
1640
0.883
-0.7
-0.36
0.14
-1309
-816
-92
-719
-226
498
-
1640
0.883
-0.57
-1120
-530
Figure 1-3 – Net Design Wind Pressures for
MWFRS when Wind is Normal to Ridge with
Positive Windward External Roof Pressure
Coefficient
Surface
(m)
(N/m )
2
Windward
wall
Leeward
wall
Side walls
Windward
roof*
Leeward
roof
Net pressure (N/m2) with
4.50
6.00
1367
1447
0.883
0.883
0.8
0.8
(+
670
727
)
()
1261
1317
All
1640
0.883
-0.5
-1019
-429
All
1640
0.883
-
1640
0.883
-0.7
-0.36
0.14
-1309
-816
-92
-719
-226
498
-
1640
0.883
-0.57
-1120
-530
Solution and Discussion to Example
Reference /
Problem 1
Notes
External
Pressure
Coefficient
on Roof
(Wind
Parallel to
Ridge)
For wind parallel to ridge, /' = 11/75
= 0.147 and θ < 10°. The values of
for wind parallel to ridge are:
Surface
Roof
/'
≤ 0.5
Distance from
windward edge
0 to
to 2
>2
Figure 207-6
-0.9, -0.18*
-0.5, -0.18*
-0.3, -0.18*
*The values of smaller uplift pressures
on the roof can become critical
with roof live load; load
combinations are given in Sections
203.3 and 203.4.
35
8/14/2013
Solution and Discussion to Example
Reference /
Problem 1
Notes
Figure 207-6
External
Pressure
Coefficient
on Roof
(Wind
Parallel to
Ridge)
Solution and Discussion to Example
Reference /
Problem 1
Notes
The net pressures for the MWFRS
(wind parallel to ridge) are:
External
Pressure
Coefficient
on Roof
(Wind
Parallel to
Ridge)
Surface
(m)
(N/m2)
Windward wall
0 - 4.50
6.00
9.00
12.00
15.00
16.00
All
All
0 to h*
h to 2h*
> 2h*
1367
1447
1576
1673
1753
1769
1640
1640
1640
1640
1640
Leeward wall
Side walls
Roof*
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
= 1640 N/m2;
= ±0.18;
= ±295 N/m2
*Distance from windward edge.
Solution and Discussion to Example
Reference /
Problem 1
Notes
External
Pressure
Coefficient
on Roof
(Wind
Parallel to
Ridge)
Figure 1-5 –Net Design Wind Pressures for MWFRS when Wind
is Parallel to Ridge with Positive Internal Pressure
Surface
(m)
(N/m2)
Windward wall
0 - 4.50
6.00
9.00
12.00
15.00
16.00
All
All
0 to h*
h to 2h*
> 2h*
1367
1447
1576
1673
1753
1769
1640
1640
1640
1640
1640
Leeward wall
Side walls
Roof*
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.80
0.80
0.80
0.80
0.80
0.80
-0.45
-0.70
-0.90
-0.50
-0.30
Net pressure (N/m2) with
(+
)
()
670
1260
727
1317
818
1408
886
1476
943
1533
954
1544
-947
-357
-1309
-719
-1598
-1008
-1019
-429
-729
-139
0.80
0.80
0.80
0.80
0.80
0.80
-0.45
-0.70
-0.90
-0.50
-0.30
Net pressure (N/m2) with
)
()
(+
670
1260
727
1317
818
1408
886
1476
943
1533
954
1544
-947
-357
-1309
-719
-1598
-1008
-1019
-429
-729
-139
Refer to
Figures 1-5
through 1-6 in
next slide
Solution and Discussion to Example
Reference /
Problem 1
Notes
External
Pressure
Coefficient
on Roof
(Wind
Parallel to
Ridge)
Surface
(m)
(N/m2)
Windward wall
0 - 4.50
6.00
9.00
12.00
15.00
16.00
All
All
0 to h*
h to 2h*
> 2h*
1367
1447
1576
1673
1753
1769
1640
1640
1640
1640
1640
Leeward wall
Side walls
Roof*
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.80
0.80
0.80
0.80
0.80
0.80
-0.45
-0.70
-0.90
-0.50
-0.30
Net pressure (N/m2) with
(+
)
()
670
1260
727
1317
818
1408
886
1476
943
1533
954
1544
-947
-357
-1309
-719
-1598
-1008
-1019
-429
-729
-139
36
8/14/2013
Solution and Discussion to Example
Reference /
Problem 1
Notes
External
Pressure
Coefficient
on Roof
(Wind
Parallel to
Ridge)
Figure 1-6 –Net Design Wind Pressures for MWFRS when Wind
is Parallel to Ridge with Negative Internal Pressure
Surface
(m)
(N/m2)
Windward wall
0 - 4.50
6.00
9.00
12.00
15.00
16.00
All
All
0 to h*
h to 2h*
> 2h*
1367
1447
1576
1673
1753
1769
1640
1640
1640
1640
1640
Leeward wall
Side walls
Roof*
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.80
0.80
0.80
0.80
0.80
0.80
-0.45
-0.70
-0.90
-0.50
-0.30
Net pressure (N/m2) with
(+
)
()
670
1260
727
1317
818
1408
886
1476
943
1533
954
1544
-947
-357
-1309
-719
-1598
-1008
-1019
-429
-729
-139
Solution and Discussion to Example
Reference /
Problem 1
Notes
Design Wind
Load Cases
Section 207.5.12.3 requires that
any building whose wind
loads have been determined
under the provisions of
Sections 207.5.12.2.1 and
207.5.12.2.3 shall be
designed for wind load cases
as defined in Figure 207-9.
Solution and Discussion to Example
Reference /
Problem 1
Notes
External
Pressure
Coefficient
on Roof
(Wind
Parallel to
Ridge)
Figure 1-6 –Net Design Wind Pressures for MWFRS when Wind
is Parallel to Ridge with Negative Internal Pressure
Surface
(m)
(N/m2)
Windward wall
0 - 4.50
6.00
9.00
12.00
15.00
16.00
All
All
0 to h*
h to 2h*
> 2h*
1367
1447
1576
1673
1753
1769
1640
1640
1640
1640
1640
Leeward wall
Side walls
Roof*
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.883
0.80
0.80
0.80
0.80
0.80
0.80
-0.45
-0.70
-0.90
-0.50
-0.30
Net pressure (N/m2) with
(+
)
()
670
1260
727
1317
818
1408
886
1476
943
1533
954
1544
-947
-357
-1309
-719
-1598
-1008
-1019
-429
-729
-139
Solution and Discussion to Example
Reference /
Problem 1
Notes
Design Wind
Load Cases
Section
207.5.12.3 has
exception that
if a building is
designed with
flexible
diaphragm,
only load cases
1 and 3 need
to be
considered.
Figure 207-9
p.2-47
37
8/14/2013
Solution and Discussion to Example
Reference /
Problem 1
Notes
Design Wind
Pressures on
Components
& Cladding
(C&C)
The following equation is used to obtain
the design pressures for components
and cladding (C&C):
&
1640
& D0.18
where
values are obtained
from Figure 207-11A
38