Searching for Simplicity The Evolution of Wind Provisions in standards and Codes in the United States

This article will provide an historical
overview of the evolution
of wind provisions in standards
and codes in the United States.
From the 1972 edition of the
American National Standards
Institute’s Minimum Design Loads for
Buildings and Other Structures (ANSI A58.1)
— which later became the American Society
of Civil Engineers’ Minimum Design Loads
for Buildings and Other Structures (ASCE 7)
— to the current ASCE 7-05 and the
International Code Council’s 2006
International Building Code (IBC), one
trend is consistent. Through their evolution,
the complexity of wind design has been
steadily increasing.
This article discusses the history of the
wind provisions standards in the United
States, specifically ANSI A58.1 and ASCE 7.
The latter half focuses on the evolution of
wind provisions in the model building codes
in the U.S., such as the IBC and its three
legacy model building codes. In con clusion,
the author makes a plea for action leading
to a way out of this complexity.
[Editor’s Note: This article was originally
published in two parts; it has herein been
incorporated into one article.] WIND PROVISIONS IN STANDARDS
This section traces the evolution of wind
provisions in ASCE 7 and its predecessor
standard, ANSI A58.1.
ANSI A58.1–1972 — Modern wind
design in the United States started with
ANSI A58.1–1972. The new provisions represented
a quantum jump in sophistication
in comparison with codes of practice at that
time. However, the provisions were flawed
with ambiguities, inconsistencies in terminology,
and a format that permitted misinterpretation
of certain provisions.
ANSI A58.1-1982 — A revised ANSI
A58.1-1982 standard contained an innovative
approach to wind forces for components
and cladding of buildings. The wind-load
specification was based on understanding
the aerodynamics of wind pressure around
building corners, eaves, and ridge areas, as
well as the effects of area averaging on pressures.
This standard was largely free of the
ambiguities and inconsistencies of ANSI
A58.1-1972 and began to be adopted by
model code organizations.
ASCE 7-88 — The maintenance and
update of the ANSI A.58.1 standard was
taken over by ASCE in the mid-1980s. The
first minimum-loads standard to appear
under ASCE’s banner was ASCE 7-88, in
which only minor changes and modifications
were made in the wind provisions of
ANSI A58.1-1982.
ASCE 7-93 — No changes whatsoever
were made to the wind provisions in the
next edition of the standard, ASCE 7-93.
ASCE 7-95 — The first significant
updates in the wind provisions since 1982
were made in ASCE 7-95. The most significant
among a number of important changes
was that “three-second-gust” wind speed
rather than “fastest-mile” wind speed
became the basis of design. The averaging
time implicit in fastest-mile wind speed was
the time it takes for a mile of wind to pass
through the measuring instrument called
an anemometer. This typically ranged
between 30 and 60 seconds. The averaging
time changed to a fixed three seconds when
the three-second-gust wind speed was
adopted. Since average wind velocity
increases as the averaging time decreases,
the design wind speed, which for the vast
majority of the country had been 70 miles
per hour (mph), now became 90 mph,
except in the West (roughly in the Pacific
time zone), where it typically became 85
mph. In order not to end up with significantly
greater design wind pressures as a
result of this change, numerous adjustments
had to be made to coefficients. Some
of the more important of these included
velocity pressure exposure coefficients,
gust-effect factors, and internal and external
pressure coefficients that included gust
effects.
Among other significant changes, provisions
were added for wind speed-up over
isolated hills and escarpments by including
a topographic-effect factor in the expression
for the design wind pressure.
New provisions were added for full and
partial loading on the main wind forceresisting
system (MWFRS) of buildings with
a mean roof height greater than 60 ft, thereby
requiring consideration of wind-induced
torsion in all buildings other than low-rise
buildings. Low-rise buildings, for purposes
of the wind design provisions, are those
with mean roof heights up to 60 ft.
Finally, an alternate (low-rise, analytical)
procedure was added for determining
MA R C H 2008 I N T E R FA C E • 13
Reprinted from the December 2006 and January 2007 issues of Structural Engineer, with permission from ZweigWhite.
external loads on the MWFRSs of buildings
having mean roof height not exceeding 60
ft. This procedure had been adopted into
the Standard Building Code (SBC), which
was published by the Southern Building
Code Congress International, from the
Metal Building Manufacturers’ Association
(MBMA) manual and is based on testing
carried out at the University of Western
Ontario, in London, Ontario, many years
earlier.
ASCE 7-98 — In ASCE 7-98, the basic
wind-speed map was updated based on new
analysis of hurricane wind speeds. As a
result, wind speeds became significantly
lower in inland Florida.
A wind-directionality factor, Kd, was
introduced in the expression for the design
wind pressure to account for the directionality
of wind. Directionality refers to the fact
that wind seldom, if ever, strikes along the
most critical direction of a building — basically,
because it cannot. Wind direction
changes from one instant to the next. Wind
can be only instantaneous along the most
critical direction; at the very next instant, it
will not be from the same direction. This
fact used to be taken into account through
a relatively low load factor of 1.3 on the
effect of wind in strength design load combinations.
But then, ASCE 7 received comments
that engineers using allowable stress
design (ASD) could not take advantage of
the directionality of wind. The ASCE 7 decision
to include Kd = 0.85 for buildings in the
definition of the wind pressure was in
response to these comments. In order not to
design using lower-factored wind forces in
strength design, the 1.3 load factor on wind
was adjusted up. A load factor of 1.3/0.85
= 1.53 would have maintained status quo
exactly. However, it was rounded up to 1.6,
which resulted in an effective 5 percent
increase in the wind-load factor. For ASD,
the effect of this change was 15 percent
lower wind forces.
The definitions of Exposures C and D
were changed slightly to allow the shorelines
in hurricane-prone regions to be classified
as Exposure C rather than Exposure D.
A simplified design procedure was introduced
for the first time for relatively common
low-rise (mean roof height not exceeding
30 ft), regular-shaped, simple dia –
phragm buildings. New definitions were
introduced for regular-shaped buildings
and simple diaphragm buildings.
For the first time, the wind design provisions
were organized by the method of
design: Method 1 – Simplified Procedure;
Method 2 – Analytical Procedure; and
Method 3 – Wind Tunnel Procedure. Method
2 contained two separate and distinct procedures
under the same heading — the general
analytical procedure, applicable to
buildings of all heights, and the low-rise
analytical procedure, applicable to buildings
having mean roof height not exceeding
60 ft.
A very important provision was introduced,
requiring that glazing in the lower 60
ft of Category II, III, or IV buildings (all
buildings except those representing a low
hazard to human life in the event of failure)
sited in wind-borne debris regions be
impact-resistant glazing or protected with
an impact-resistant covering, or such glazing
that receives positive external pressure
be assumed to be openings. “Wind-borne
debris region” was defined in ASCE 7-98.
ASCE 7-02 — In ASCE 7-02, the simplified
design procedure, Method 1, of ASCE 7-
98 was discarded. The simplified design
procedure in Section 1609.6 of the 2000
IBC, with only a few relatively minor modifications,
was adopted instead. This simplified
procedure is based on the low-rise analytical
procedure of ASCE 7 and bears
strong resemblance to it. Its applicability is
broader than that of the simplified design
procedure in ASCE 7-98.
ASCE 7-02 required that a ground-surface
roughness within each 45-degree sector
be determined for a distance upwind of
the site. Three surface-roughness categories
were defined as shown in Table 1.
Three exposure categories were defined
in terms of the three roughness categories,
as shown in Table 2. The former Exposure
A (centers of large cities) was deleted.
Method 2, Analytical Procedure for
(MWFRS of) low-rise buildings, was revised
to provide clarification. The different load
cases were clearly delineated.
New pressure coefficients were provided
for determination of wind loads on domedroof
buildings, and provisions for calculating
wind loads on parapets were added.
The design-load cases for the MWFRSs
of buildings designed by the general analytical
procedure (as distinct from the low-rise
analytical procedure) were different in
ASCE 7-98 than in ASCE 7-02. Consider –
ation of wind-induced torsion was now
required for all buildings, not just buildings
having mean roof height exceeding 60 ft.
In the table of roof pressure coefficients
for the design of the MWFRS by the general
analytical procedure, a low-suction coefficient
of 0.18 was added for the windward
roof in all cases where only a high-suction
coefficient had been provided earlier. The
14 • I N T E R FA C E MA R C H 2008
intent of the new low-suction coefficient
was to require the roof to be designed for
zero or a slightly positive (inward-acting)
pressure, depending upon whether the
building is enclosed or partially enclosed,
respectively.
ASCE 7-05 — Several changes are made
in the set of conditions that must be met by
a building for its MWFRS to be qualified to
be designed by Method 1 – Simplified
Procedure. The restriction that the building
not be subjected to topographic effects is
omitted. These are now ac counted for in the
simplified design procedure by including a
topographic-effect factor in the calculation
of the design wind pressure.
The conditions that must be met by a
building for its components and claddings
to be eligible to be designed by Method 1 are
not changed, except that the restriction
concerning topographic effects is lifted, as
in the case of the MWFRS.
Simplified design wind pressures and
net design wind pressures can now be calculated
for basic wind speeds of 105, 125,
and 145 mph.
ASCE 7-05 now explicitly states that the
basic wind speeds estimated from regional
climatic data for special wind regions outside
hurricane-prone areas can be lower
than those given in ASCE 7-05, Figure 6-1.
For estimation of basic wind speeds from
regional wind data in special wind regions
outside hurricane-prone areas, a minimum
criterion is specified.
ASCE 7-02 required Exposure D to
extend inland from the shoreline for a distance
of 660 ft or 10 times the height of the
building, whichever was greater. ASCE 7-05
requires Exposure D to extend into downwind
areas of Surface Roughness B or C for
a distance of 600 ft or 20 times the height of
the building, whichever is greater. The multiplier
of building height by which a certain
terrain category has to extend in the
upwind and the downwind direction of the
building for qualification of an Exposure
Category is changed from 10 to 20, as indicated
above in the specific case of Exposure
Category D. Other controlling distances are
rounded off to the nearest 100 ft.
A definition for “eave height” is added.
Footnote 8 to Figure 6-10 (Low-Rise Analy –
tical Procedure), which concerns delineation
of the boundary between windward
zone pressures and leeward zone pressures,
has been clarified.
Glazing in wind-borne debris regions
that receive positive external pressure can
no longer be treated as openings for design
purposes, instead of making it impact-resistant
or protected.
Provisions for wind loads on parapets
are updated. Values of the Combined Net
Pressure Coefficient are updated from +1.8
and -1.1 to +1.5 and -1.0 for windward and
leeward parapets, respectively. Application
of the provisions to low-slope roofs has been
clarified.
Design wind loads on free-standing
walls and solid signs are revised.
Design wind loads on open buildings
with monoslope roofs are revised. Design
wind loads on open buildings with pitched
or troughed roofs are provided for the first
time.
New provisions are added for rooftop
structures and equipment when the roof
height of the building is less than 60 ft.
Wind-borne debris requirements are
clarified as being applicable to Method 3
(Wind Tunnel Procedure). The requirements
are the same as those for Method 2
(Analytical Procedure).
MA R C H 2008 I N T E R FA C E • 15
Discussion of Changes
from ANSI A58.1-1972 to ASCE 7-05
Of all the changes from ANSI A58.1-
1972 through ASCE 7-05, there are only a
few that are in the direction of more liberalism
in design. The first of these is the adoption
of the low-rise analytical procedure in
ASCE 7-95 as an alternative design
approach for the MWFRS. This procedure
can reduce design wind pressures significantly.
While generalizations are difficult
since so many variables influence the determination
of design wind pressures for a
specific building, use of the alternate procedure
can result in the total wind load being
approximately 30 to 35 percent less than
would be calculated using the primary procedure.
It ought to be remembered that the
low-rise analytical procedure was part of
the Standard Building Code long before it
was adopted by ASCE 7 and is based on
comprehensive testing done at the
University of Western Ontario.
In areas where the basic wind speed is
low, the relative lack of conservatism of the
low-rise procedure is mitigated somewhat
by the requirement that all MWFRS be
designed for a minimum pressure of 10
pounds per square foot applied to the area
of the building projected onto a vertical
plane. However, this provision is widely
ignored and is not rigorously enforced by
local jurisdictions. It needs to be taken
more seriously by practitioners as well as
local jurisdictions.
The second change was the introduction
of the directionality factor, Kd, in ASCE 7-
98. This led to a rounding up of the windload
factor from 1.53 to 1.60 in strength
design, which is conservative. However, this
also decreased the design wind forces when
using ASD methods, which are widely used
in the design of structures made of materials
other than concrete. Also, the three-second-
gust speed map of ASCE 7-95 was prepared
from data accumulated by the
National Weather Service and not converted
from the fastest-mile wind speed map of
ASCE 7-93. While in most areas, 70 mph
fastest-mile wind speed became three-second-
gust speeds of 85 or 90 mph, and so
forth, in certain areas, such as Denver, the
numbers remained virtually unchanged.
This meant that design wind pressures in
those areas went down as ASCE 7-95 was
adopted, even while using strength design,
with incorporation of the rounded-up load
factor of 1.6.
The only other change possibly in the
direction of more liberal design was the
redrawing of the basic wind speed map in
ASCE 7-98, which decreased the basic wind
speeds in inland Florida. Obviously, when
National Weather Service data indicate that
a change is warranted, ASCE 7 has no reason
to resist making that change.
Standard Conclusions
By and large, the changes in ANSI
A58.1/ASCE 7 have not been consistently in
the direction of lower or higher design wind
pressures. If there is a consistent trend to
the changes, it is that the complexity of wind
design has been steadily increasing.
WIND PROVISIONS
IN THE MODEL CODES
The building codes of most jurisdictions
within the United States used to be, and in
some cases still are, based on one of three
legacy model building codes: The BOCA
National Building Code (BOCA/NBC), published
by the Building Officials and Code
Administrators International (BOCA) in
Country Club Hills, Illinois; the Standard
Building Code (SBC), published by the
Southern Building Code Congress
International (SBCCI) in Birmingham,
Alabama; and the Uniform Building Code
(UBC), published by the International
Conference of Building Officials (ICBO) in
Whittier, California. These three model
codes, where still in effect, are in the
process of being replaced by the
International Building Code (IBC), published
by the International Code Council
(ICC), which has absorbed the former model
code groups (BOCA, SBCCI, and ICBO). The
following is an historical summary of wind
design provisions in these model codes.
BOCA/National Building Code — ANSI
A58.1-1972 was adopted by the BOCA/NBC
in its 1978 edition, and retained in the 1981
and 1984 editions. Then, ANSI A58.1-1982
was adopted in the 1987 edition, and
retained in the 1990 edition.
In the 1993 edition, ASCE 7-88 was
adopted, and was retained in the 1996 and
1999 editions. The 1999 edition was the last
edition published before the integration of
BOCA into the ICC.
Standard Building Code — The SBC
adopted ANSI A58.1-1972 in the 1977 revisions
to the 1976 SBC. The adopting language
then appeared in the 1982 edition.
Wind design using ANSI A58.1-1972 was
permitted only for one- and two-story structures,
provided the basic wind pressures
16 • I N T E R FA C E MA R C H 2008
from SBC Table 1205.1 were used. The
1982 SBC also adopted alternate wind-load
provisions (those of the MBMA or Metal
Building Manu fac turers’ Association,
MBMA) in Section 1206. This section was
permitted for the design of buildings with
flat, single-slope, and gable-shaped roofs
with mean roof heights of 60 ft or less, provided
the eave height did not exceed the
least-horizontal dimension of the building.
The 1985 edition had three procedures
that could be used. Two of the procedures
were contained in Section 1205, Wind
Loads, and the third was in Section 1206,
Alternate Wind Loads for Low-Rise
Buildings. The first option allowed under
Section 1205 was use of the provisions
within the section. The second option permitted
by Section 1205 was to use the wind
design provisions of ANSI A58.1-1982, provided
the basic wind pressures of Table
1205.1 were used. Table 1205.1 was based
on the basic wind speed map of Figure
1205.1 (same as the 100-year mean recurrence
interval basic wind speed map contained
in ANSI A58.1-1972), which differed
from the 50-year mean recurrence interval
map in ANSI A58.1-1982.
The alternate wind-load provisions of
Section 1206 (MBMA procedures) were permitted
to be used for the design of buildings
with flat, single-slope, and gable-shaped
roofs with mean roof heights of 60 ft or less,
provided the eave heights did not exceed the
least horizontal dimensions of the buildings.
Section 1206 contained its own basic
wind speed map, which was taken from
ANSI A58.1-1982.
The 1988 SBC permitted any building
or structure to be designed using the provisions
of ANSI A58.1-1982. In addition,
Section 1205.2 had provisions based on the
MBMA procedures for buildings with flat,
single-slope, and gable-shaped roofs whose
mean roof heights were less than or equal to
60 ft. This edition did not require that the
roof eave heights be less than or equal to
the least horizontal dimension of the buildings.
Section 1205.3 applied to buildings
exceeding 60 ft in height, but not more than
500 ft in height, provided the roof slopes did
not exceed 10 degrees or were not arched
roofs. Buildings between 60 and 500 ft in
height and not meeting these limitations,
and all buildings over 500 ft in height, had
to be designed according to ANSI A58.1-
1982. The basic wind speed map within
Section 1205 was the ANSI A58.1-1982
map.
The 1991 edition was essentially the
same as the 1988 edition, except that ANSI
A58.1-1982 was updated to ASCE 7-88. The
basic wind speed map within Section 1205
remained unchanged from the 1988 edition,
because the basic wind speed map did not
change within ASCE 7-88 from what was in
ANSI A58.1-1982.
In the 1994 SBC, ASCE 7-88 was adopted
by reference to apply to all buildings and
structures. An exception continued to permit
the MBMA procedures in Section
1606.2 to be used for buildings with flat,
single-slope, hipped, and gable-shaped
roofs with mean roof heights not exceeding
60 ft or the least-horizontal dimension of
the buildings.
The 1997 edition was essentially the
same as the 1994 edition, except that ASCE
7-88 was updated to ASCE 7-95. The basic
wind speed map within Section 1606.2,
Alternate Wind-Loads for Low-Rise
Buildings, remained unchanged from the
1994 edition. It is necessary to point this
out because the basic wind speed map of
ASCE 7-95 was based on the three-secondgust
wind speed.
The 1999 edition remained unchanged
from the 1997 edition and was the last edition
of the SBC.
Uniform Building Code — The wind
design provisions of the UBC, through its
1979 edition, were based on ANSI A58.1-
1955, the predecessor document to ANSI
A58.1-1972.
The wind design provisions became
based on ANSI A58.1-1972 in the 1982 edition
of the UBC. The calculation procedure
was simplified. Also, important changes
proposed for ANSI A58.1-1982 were incorporated.
Few changes were made in the
1985 and 1988 editions of the UBC.
The UBC wind design provisions
became based on ASCE 7-88 in the 1991
edition. The calculation procedure was once
again simplified. Minor changes were made
in the 1994 edition, and no changes were
made in the 1997 edition, the last edition of
the UBC.
International Building Code — The
first edition of the IBC, the 2000 edition,
adopted ASCE 7-98 for wind design.
However, Method 1, Simplified Design from
ASCE 7-98, was not adopted. Included in
Section 1609.6 of the IBC code was a different,
simplified design procedure based on
the low-rise analytical procedure (part of
Method 2) of ASCE 7-98 and applicable only
MA R C H 2008 I N T E R FA C E • 19
to simple diaphragm buildings, as defined
in the code. For qualifying residential buildings
free of topographic effects, the SBCCI
deemed-to-comply standard SSTD 10,
Standard for Hurricane-Resistant Residen –
tial Construction, and the American Forest
& Paper Association’s (AF&PA) Wood Frame
Construction Manual (WFCM) also were
allowed to be used. The 2000 IBC also
added an alternative way of providing opening
protection in one- and two-story buildings,
included a conversion table between
fastest-mile wind speed and three-secondgust
wind speed, and provided an optional
design procedure for rigid tile roof coverings.
The second edition of the IBC, published
in 2003, adopted ASCE 7-02 for wind
design. There was still a simplified design
procedure, applicable to simple diaphragm
buildings, in Section 1609.6 of the IBC. But
it was now very close to Method 1,
Simplified [Design] Procedure of ASCE 7-02,
because (as mentioned earlier,) ASCE 7-02
discarded Method 1 of ASCE 7-98, and
adopted instead the simplified design procedure
in Section 1609.6 of the 2000 IBC with
some modifications. Qualifying residential
buildings free of topographic effects could
still be designed by SBCCI’s SSTD 10 or
AF&PA’s WFCM. The alternative way of providing
opening protection in one- and twostory
buildings, the conversion table
between fastest-mile wind speed and threesecond-
gust wind speed, and the optional
design procedure for rigid tile roof coverings
remained essentially
unchanged.
ASCE 7-05 is
adopted for wind
design in the third
edition of the IBC,
which was published
in 2006. Simplified
wind design is no
longer in the code; it
is by reference to
ASCE 7-05. Qual i fy –
ing residential buildings
free of topographic
effects can
still be designed by
SBCCI’s SSTD 10 or
AF&PA’s WFCM. The
alternative way of
providing opening
protection in oneand
two-story buildings
is retained in a
modified form in the
2006 IBC. The conversion
table be –
tween fastest-mile wind speed and threesecond-
gust wind speed is revised. The
optional design procedure for rigid tile roof
coverings remains unchanged.
1997 UBC Versus 2006 IBC — A Comparison
Design wind forces at the various floor
levels of an example concrete building, the
plan and elevation of which are shown in
Figures 1 and 2 respectively, were calculated
using the general analytical procedure
(Method 2) of ASCE 7-05 (which has been
adopted into the 2006 IBC) and the wind
design procedure of the 1997 UBC, which is
a simplified version of that in ASCE 7-88.
The building is assumed to be located in
suburban Los Angeles (three-second-gust
wind speed of 85 mph) and the exposure
category is assumed to be B. The simplification
of the analytical procedure of the 1997
UBC was the result of a joint effort by the
Structural Engineers Association of
California (SEAOC) and the Structural
Engineers Association of Washington
(SEAW).
It can be seen in Table 3 that the UBC
procedure produces slightly, but not overly,
conservative results, as it should. The
efforts involved in the two cases were not
comparable, with the ASCE 7-05 design
taking considerably more time and being
more complex (even though the different
load cases in Figure 6-9 of ASCE 7-05,
other than Load Case 1, were not even con-
Figure 1 – Plan of example concrete building.
20 • I N T E R FA C E MA R C H 2008
Figure 2 – Elevation of example concrete
building.
sidered). The primary reason that accounts
for the additional time is that the simplifications
made by SEAOC/SEAW to the provisions
of ASCE 7-88 are not available to
the user of Method 2 of ASCE 7-05. Also, as
outlined in preceding sections, many complexities
have been added to the wind
design provisions of ASCE 7 between the
1988 and 2005 editions. One example of the
added complexity is the prescribed procedure
for the computation of gust-effect factors
for flexible buildings. The example
building being flexible, the gust-effect factor
had to be calculated. The calculation in –
volves a large number of complex equations
and took an experienced engineer more
than an hour and a half to complete.
Ironically, the factor turned out to be 0.87,
which should be compared with the 0.85
prescribed for rigid buildings. While no generalization
is possible on the basis of one
example, the UBC procedure, which has
been in the UBC since 1991, has been used
in the design of a large population of structures
located west of the Mississippi,
in Indiana, and elsewhere. There is no
record of distress that has been attributed
to any deficiency in that design
procedure.
When the state of Oregon adopted
the 2003 IBC as the basis of the 2004
Oregon Structural Specialty Code, it
made an amendment to the 2003 IBC
allowing continued usage of the 1997
UBC wind design procedure (as adopted
into the 1998 Oregon Structural
Specialty Code). The state of
Washington did not make a similar
amendment when it adopted the 2003
IBC as the basis of the state code a few
months ahead of Oregon. A simplification
of the analytical procedures of
ASCE 7-98 and -02 was under development
by the SEAW for quite some
time. The simplified procedure —
SEAW’s Handbook of a Rapid Solutions
Methodology for Wind Design — has
recently been published. This procedure,
however, does not appear ready
for codification.
Conclusion
There is an urgent need for a
design procedure in the IBC that is similar
to the one included in the 1997 UBC. Its
applicability, of course, would be somewhat
restricted. The UBC design procedure itself
cannot be used as it is. It will need to be
updated because, for one thing, it is based
on fastest-mile wind speed, which is no
longer recorded by the National Weather
Service. It is outdated in some other ways,
as well. The most effective way of accomplishing
an update would be through collaboration
among groups, such as the
Structural Engineers Associations of
California, Oregon, and Washington. Early
action to bring about such collaboration is
strongly urged.
Acknowledgements
Much gratitude is expressed to Jim
Messersmith and Steve Skalko of the
Portland Cement Association and Susan
Dowty of S.K. Ghosh Associates Inc. for
their contributions to this paper.
S.K. Ghosh, PhD, is the president of S.K. Ghosh Associates Inc., a seismic and building
code consulting firm located in Palatine, Illinois, and Laguna Niguel, California. He
is active in the development and interpretation of national structural code provisions
and can be contacted at skghosh@aol.com or via www.skghoshassociates.com.
S.K. Ghosh, PhD
Table 3 – Comparison of computed wind forces
for example building.
MA R C H 2008 I N T E R FA C E • 21