No. 43 December 2014

STEEL CONSTRUCTIONTODAY & TOMORROW

http://www.jisf.or.jp/en/activity/sctt/index.html【 k a z e 】“風 (kaze)” in Japanese, or wind in English

Serious building damage, particularly to exterior members,that is caused by the strong winds of typhoons
and tornadoes occur worldwide.
How to deal wind load and how to mitigate strong
wind-induced damage are discussed in this issue, No. 43.

In this issue.....
Special Feature: Wind Resistance of Buildings
1 Advances in Wind-resistant Design andWind Resistance Evaluation in Japan

4 Strong Wind-induced Damage to
Buildings and Concepts for
Mitigating Such Damage

6 Wind Load Provisions in the

Building Standard Law of Japan

9 Evaluation of Habitability Related

to Wind-induced Building Vibration

11 Performance-based Wind-resistantPublished Jointly by

The Japan Iron and Steel Federation

Design for 300-m Vertical City

Photo: SUZUKI hisao

15 Steel Application Technology: Basic Details about High-strength
Bolt Joining

Japanese Society of Steel Construction

Back cover JISF Operations

Wind-resistant Design

Advances in Wind-resistant Design andWind Resistance Evaluation in Japanby Yasushi Uematsu, Professor, Tohoku University
Establishment of the Enforcement Order of the Building Standard Law
In Japan, the Enforcement Order of the Building Standard Law of Japan was establishedin 1950. It was the first legal regulation thatspecified the wind-load evaluation method tobe adopted in building design, which regulated the calculation of wind load P by use of
the following equation:
where
C : wind force coefficient
A : building area or tributary area of component under consideration (m2)q : velocity pressure (calculated by using
Equation (2))
Meanwhile, the wind force coefficient C
refers to the difference between external andinternal pressure coefficients. Note that thesetwo coefficients are not specified separately.
whereh : height above ground level (m)The equation is based on a maximum instantaneous wind velocity of 63 m/s that wasobserved at the top of the steel observation
tower (15 m above ground level) of the Muroto Meteorological Observatory during the
Muroto Typhoon in 1934. The equation wasderived by assuming that the vertical distribution (profile) of the maximum instantaneous wind velocity is proportional to 1/4th
the power of the height above ground level,and by substituting the above-mentioned observation value.
Incidentally, it is well accepted that thepower exponent for the profile of the maximum instantaneous wind velocity during typhoons and other synoptic winds is about 1/2
the value for the mean wind velocity. Thus,
the above-mentioned power exponent of 1/4
implies that the power exponent for the mean
wind velocity profile corresponds to about
1/2. In those days, such a large value of power exponent was not used in any country in
the world, which in fact did not reflect actual conditions. However in Japan, no so-called
high-rise buildings had been constructed,
and there were few buildings for which windloads dictated the structural design, thereby
causing no substantial problems. The wind
1 Steel Construction Today & Tomorrow December 2014

force coefficients C were obtained from windtunnel tests using uniform smooth flow, inwhich the effects of turbulence were not considered. Further, the social background that
led to the establishment of Equation (2) included the following issues:• In those days, because the Muroto Typhoon
was of unprecedented scale in Japan, it was
expected that, if wind loads of that level wereadopted, buildings would have some safetymargin for future typhoons.
• Unlike earthquakes, typhoons can be forecasted to a certain extent, and thus it is possible to take countermeasures against them.
Therefore, it was considered that, even iflower wind loads were adopted for reasonsof economic advantage, no serious problems
would result.
Increasing Building Height Prompts
Reexamination of Wind Load Calculation Method
Following the popularization of TV sets
among general households during Japan’s
period of high economic growth, the nation’s
first large-scale television tower with a heightof 180 m was constructed in Nagoya in June
1954. During the tower’s design stage, the inadequacy of Equation (2) was pointed out. As
a result, the profile of the maximum instantaneous wind velocity was reexamined in reference to the building codes and standards inforeign countries. This produced the following equation, which assumed a power exponent of 1/8 and was used in the design of thetower:
After completion of the Nagoya television
tower, full-scale measurements taken during
typhoons demonstrated that the measured results agreed relatively well with Equation(3). As a result, Equation (3) has played agreat role in the blossoming of subsequent
high-rise building construction in Japan.
Following the revision of the BuildingStandard Law in 1963, Japan’s first full-scale
high-rise building, the Mitsui-Kasumigaseki Building (36 stories above ground, 156 m
in height), was completed in Tokyo, marking
the dawn of the high-rise building age in Japan. In addition, the National Indoor Stadi-

um with a 126-m main span was constructed
for the Tokyo Olympic Games held in 1964,
marking the beginning of large-span buildings in Japan.
As the height or clear span of buildings
increases, the natural frequency generally decreases, thereby causing the significant
dynamic effect of wind. That is, the contribution of the resonance component (resonanceeffect) in the dynamic response of buildings
becomes more significant. On the other hand,when the scale of a building increases, thenet wind load acting on the building decreases due to scale effect. In the case of a smallscale building, the load effect (for example,
the stress involved in the structural members)
becomes the maximum when the maximum
peak wind velocity occurs. In the case of alarge-scale building, on the other hand, thewind pressures acting on the structural members do not reach the maximum peak values
at the same time for all members, and thus theload effect does not become the maximum at
the moment of the maximum peak wind velocity.
Emerging from this background was a
gradually increasing understanding of the dynamic load effects on buildings, which led tomany surveys and researches on the turbulent
structure of wind, wind tunnel test methods,
the actual conditions of wind pressure, windinduced vibration and other factors.
Along with the appearance of high-risebuildings, it was urgently required to establish a reasonable wind-resistant design method for curtain walls, particularly to establish a method for testing the wind resistanceof glass plate and the water proof of curtain
walls. During that period, Japan was successively struck by super typhoons, such as theIse-bay Typhoon (1959) and the Second Muroto Typhoon (1961), causing great damage
to roofing, exterior walls and other exterior members. The damage to these exterior
members frequently triggered severe damage
to the main wind resisting systems (structural frames), thereby pointing out the importance of preventing damage to cladding/components and promoting safe design.
In such situations, Notification No. 109,
the first regulation concerning the wind-re-sistant design of exterior members, was issued by the Ministry of Construction in 1971.
This regulation focused mainly on the following two topics:
1) Design velocity pressure is sorted into twoclasses respectively for roofing materials
and for external walls, which are calculated by using the following equations:• For roofing materials:• For external walls of buildings higher
than 31 m:

2) The areas of local wind pressures in eaves,
overhanging roofs, verges and wall surface
corner sections are specified, where the design wind force coefficient is specified as
C = –1.5.
Fig. 1 shows the profiles of velocity pressure provided by Equations 5(a) and 5(b).
The curves of the two equations cross at aheight of 16 m, and the lower value of thesetwo curves at each height is used for evaluating wind loads.
Efforts to Establish a More Rational
Method of Evaluating Wind Loads
Because the fluctuation of wind velocity isquite random in nature, the time-space correlation of wind velocity should be consideredappropriately based on a statistical and probabilistic approach, when evaluating the windloads on buildings. Prof. Alan G. Davenportof the University of Western Ontario, Canada
proposed in 1967 a new approach, known as

the gust loading factor method (Fig. 2). According to this method, the design wind load
P is provided by the following equations:where
U : mean wind velocity at height z above
ground levelG : gust loading factor defined by the following equation:where: mean displacement of building due tothe mean wind force: maximum value of dynamic displacement (= ・ ): standard deviation of dynamic displacement: peak factor.
Comparison of Equations (6) to (8) withthe corresponding provision in the Enforcement Order of the Building Standard Law
shows the following features:• When considering the wind-induced vibration of structure, the maximum instantaneouswind velocity does not always give the maximum load effects (i.e., stress, displacement
and other loading effects).

• The maximum peak wind force at each pointon the building does not occur simultaneously. Therefore, the net wind force acting
on the entire building decreases with an increase in the size of building.
In light of such conditions, the gust loading factor method adopts a probabilistic andstatistical approach to evaluate the design
wind loads on buildings by considering the
temporal and spatial fluctuation characteristics of wind velocity. Further, the method
provides the “equivalent static wind load”
that gives the maximum load effect. Therefore, the commonly used conventional static analysis can be applied in the structuraldesign, nevertheless the wind loading is dynamic.
When comparing Equations (1) and (6)each other, it is found that the design windvelocity is specified based on the maximum
instantaneous wind velocity in Equation (1),while it is based on the average wind velocity in Equation (6). Further, the dynamic effect of fluctuating wind velocity on the load
effects is taken into consideration by using
the maximum instantaneous wind velocity inEquation (1), while it is taken into consideration by using the gust loading factor G thatis based on the maximum peak value of thebuilding response.

Fig. 2 Definition of Gust Loading Factor (Recommendations for Loads on
Buildings 1981 Edition)
Displacement of building
Wind velocity

Wind force

Fig. 1 Comparison of Design Velocity
Pressure
Height

60

50
4

120 h

30

60 h

Time

h (m)

40

20

10

0

0

100

200

300

400

500

(Mean wind velocity)(Mean displacement)(Mean wind force)(Maximum displacement)q (kg/m 2)

December 2014 Steel Construction Today & Tomorrow 2

The building response depends not only
on the wind velocity but also on many factors relating to the building; that is, the shape,
scale and the dynamic characteristics, such as
natural frequency and damping factor. All ofthese factors are reflected in the equation for
G. In the case of small-scale buildings, it isthought that the maximum load effect occurs
at the moment of the maximum peak wind velocity. Here, the ratio of the maximum peakwind velocity to the mean value is defined as
the gust factor Gv. Because the wind force is
proportional to the square of the wind velocity, Equations (1) and (6) imply that G = Gv2.
It does without saying that the wind load
evaluation by using Equation (6) is far morerational than the use of Equation (1). As a result, the use of Equation (6) to evaluate windloads has been incorporated into the provisions of codes and standards in many countries. In Japan, the Architectural Institute ofJapan (AIJ) published Recommendations for
Loads on Buildings in 1981, in which thewind load evaluation was based on the Davenport method.
Then, because several inadequacies were
found in the AIJ Recommendations, it was revised in 1993 to correct these inadequacies.
The features of the revised Recommendations
are as follows:• The wind load calculation equation takes
two forms: one for the main wind force resisting systems (structural frames) and theother is for cladding/components. This is because the scale and vibration characteristicsof the structural frames are quite different
from those of the cladding/components, anddue considerations are made on the different
ways that wind load works on the structural
frames as opposed to cladding/components.
The• design wind velocity is settled by taking into account the frequency of the occurrence of strong winds and the safety levelof the building during the service life of thebuilding in respective areas. That is, the return period is settled according to the safety level required for the building, and thebuilding is designed based on the wind velocity that corresponds to the return period
thus settled. Meanwhile, the design wind velocity is evaluated by using the annual maximum wind velocity.
The• design velocity pressure qH is to be set
as the velocity pressure at a reference height
H corresponding to the building (commonly
the average height of the roof). Accordingly,
the vertical distribution of the wind load istreated as the distribution of the wind force
coefficient (or wind pressure coefficient).
3 Steel Construction Today & Tomorrow December 2014

• The effect of the time-space correlation ofwind pressures on the building is evaluated using the probabilistic and statistical approach, which is expressed as the gust effectfactor. While the gust effect factor is similar
to the gust loading factor defined by Prof.
Davenport, the gust effect factor is appliedin a wider context as a factor that expresses
the dynamic load effect of wind pressures
and wind forces.
• The conditions of wind blowing at the site
are classified according to “surface roughness,” and the features of these conditions
thus classified were reflected in the profiles ofmean wind velocity and turbulence intensity.
Then in 2000, the Enforcement Order ofthe Building Standard Law was fully revised.
The Order incorporated a wind load evaluation method that was based on the probabilistic and statistical approach, as in the caseof many other countries. Although the method defined in the Order was simplified by
imposing several restrictions, such as limiting the applicable building height to 60 m orless, the basic method of wind load evaluation used is almost the same as that provided
in the AIJ Recommendations (1993).
The AIJ plans to revise the Recommendations approximately every 10 years by actively incorporating the latest information. Inline with this policy, revisions were made in
2004 and preparations are being promoted to
publish the 2015 revised version. In this revision, in order to allow more reasonable evaluation of design wind loads, due consideration is being given to many factors, such as
the effect of local topography on wind velocity, the wind direction coefficient and seasonal coefficient, aerodynamic instability, andload combinations. Further, the revision will
also employ the use of computational fluid
dynamics (CFD) together with wind tunnel
experiment.
The appearance of high-rise buildings
has posed new and unexpected problems. In
1979, Typhoon No. 20 struck the Tokyo metropolitan area with winds of a strength seen
only once every ten years. Also, it brought attention to the issue of wind-induced vibrationof high-rise buildings, especially in the Shinjuku new urban center. Building vibration did
not cause any serious problems to the structures. However, because of the typhoon’s
long duration and incessant blowing, a considerable number of people had discomfort
and queasiness as they experienced in seasickness.
Triggered by such situations, the issueof habitability of high-rise buildings has re-ceived a great deal of attention, which led tothe publication of Guidelines for the Evaluation of Habitability to Building Vibrationin 1991 by AIJ. The Guidelines was thenrevised in 2004 by incorporating the latest
available knowledge. In the Guidelines, thecriterion for evaluating the habitability isgiven by use of the relationship between the
maximum response acceleration for the windvelocity with a 1-year return period and thenatural frequency of building.
Evaluation of Wind Resistance
In June 1998, the Building Standard Law
was revised. In this revision, the design concept was widely shifted to the “performancebased design” while remaining the conventional concept of specification design. In
building design, three limit states are generally assumed-serviceability, damage andsafety limits, and the design criteria are given
to each of these limit states. For example, theserviceability limit for high-rise buildings isdetermined by taking wind-induced vibration(habitability) into account.
In this regard, based on the Guidelines
for the Evaluation of Habitability to Building Vibration mentioned above, the criterion
for evaluating habitability is given employing the relation between the maximum response acceleration for wind velocity with a
1-year return period and the natural frequency of buildings. Particularly in the response
and limit strength calculation in the Enforcement Order of the Building Standard
Law, it is stipulated that, when determining
damage limit, structural members should
remain in the elastic range when subjected
to rare strong winds with an approximately 50-year return period, and that, when determining safety limit, buildings should notcollapse even when subjected to extremelyrare strong winds with a 500-year return period. However, neither the Guidelines nor
the Enforcement Order offers a clear prescription for cladding/components suffering great damage due to strong winds. Because of this, the AIJ has provided specificdesign approaches in its publication Manual for Cladding Wind Resistance Evaluation
for Designers and Engineers published in2013.
￭
Reference
1) A.G. Davenport, Gust loading factors, Proc.
of ASCE, Struc. Div., 1967.

Mitigation of Strong Wind-induced Building Damage

Strong Wind-induced Damage to
Buildings and Concepts for Mitigating
Such Damage
by Hitomitsu Kikitsu, Building Research Institute
Serious Damage to Buildings Causedby Strong Wind
It is recently reported that serious tornado damage has frequently occurred both in Japan andabroad with great social impact. The scenes arestill fresh in our memory of the damage inflicted by tornadoes in several Japanese cities, centering on Tsukuba in Ibaragi Prefecture in 2012
(Photo 1) and Koshigaya in Saitama Prefecture
in 2013. Meanwhile, it is also true that damage
is caused by typhoons, but this damage is liable to be obscured by the scale of the damage
caused by tornadoes (Photos 2~3).

Among a building’s various structures, it is
the roofing members, exterior walls, openings
and other external claddings and componentsthat are vulnerable to the effect of strong wind.
The primary measure for preventing wind-induced building damage is to mitigate the damage to them.
Concepts Conducive to Mitigating
Damage to External Claddings andComponents• Specific Damage Conditions
When a building is subjected to strong windof typhoon, the wind force attributable to theturbulence of approach flow generates on thewindward roof and wall, and this results in localized peak negative pressure occurring along
the edges of roof and sidewall. The BuildingStandard Law of Japan prescribes the method for calculating localized peak pressure. According to this method, the action of wind gusts
generated by a translating tornado can be considered to follow those of a typhoon. However, unlike a typhoon, particularly as the whirling center of a tornado approaches closer toa building, the force produced by the updraft
works on the building to increase the damage(refer to Fig. 1), to which due attention shouldbe paid.
The damage caused by strong wind can beunderstood as the apparent damage of the mostvulnerable section among wind-induced load
paths in a building. Most of the damage can befound in the external cladding and componentsof the building. Accordingly, in order to mitigate such wind damage, it is important to settle the design load after gaining an appropriate understanding of how wind force will workon the building and, then, to give due consideration when selecting the specifications for theexternal cladding and components.

Photo 1 Example of damage caused by tornado (Tsukuba in 2012)

Photo 2 Example of damage caused by typhoon (Miyakojima, Okinawa in 2003)

Photo 3 Example of damage caused by typhoon (Miyakojima, Okinawa in 2003)

December 2014 Steel Construction Today & Tomorrow 4

Fig. 1 Working Form of Load and External
Force due to Tornado

Vertical updraft

Flying debris

Translationof tornado• Sharing of Information about Mem-

Horizontal
swirling ﬂow

Upward force
Impact force
by ﬂying debris

Dead load andstrength of building• Concepts for Verification of theStrength of External Members
When verifying the strength of external cladding and components, two approaches arecommonly applied: structural design basedon the standard specification of the members
and structural design based on their allowablestrength.
In the former approach, the wind pressure
resistance is secured by selecting standard
specifications (distance between supports,
plate thickness, etc.) from a product catalog
according to the necessary level of the designload, and thus structural calculations are not required and wind pressure resistance can be easily verified.
In the latter approach, the wind pressure resistance is verified by calculating the allowablestrength of each structural section based on thestrength test results (Photo 4). In this verification process, for example in the case of steel
roofing and walls, it is common that a value of
2.0 or higher be settled as the safety factor required to find the allowable strength of suchmembers.
Based on the results of these verification
processes, due care is taken in the design work,
such as increasing the plate thickness or narrowing the fastening and installation spaces ofthe supporting members, in order to reduce thepossibility of damage occurrence.
Further, there are many cases of production
and commercial facilities that are large in scale
and that require asset security and the preservation of building functionality. Facilities of this

5 Steel Construction Today & Tomorrow December 2014

level of a facility, by assigning incremental
wind loads to external members that are basedon levels surpassing those in the Law and thenverifying the wind pressure resistance of thesemembers.
Currently, the wind force of tornadoes is
not taken into account in common wind resistance design, but it is considered that the concepts mentioned above can, to a certain degree,
mitigate tornado-induced building damage as
well.

Lateral force

nature can be forecasted to incur several typesof wind-induced damage. That is, when roofing and other exterior members are stripped off
and scattered about, the resulting inflow of rain
can extensively damage indoor equipment andmake the entire facility functionally useless. In
important facilities that house highly advanced
functions, even if the main structures are intact, it is possible that striped-off and scatteredroofing and other external claddings and components could cause enormous economic loss.
Related to wind resistance design in the
Building Standard Law of Japan, return periods of approximately 50 years are supposed. It
can be said that damage caused by strong windcan be mitigated, depending on the importanceber Applications
Because the performance appraisal of external cladding and components is commonly
entrusted to construction companies and the
manufacturers of these members, how to assign appropriate roles in any structural verification is liable to be unclear. Therefore, it isimperative that information about the strengthand other properties of these external members be adequately shared among the designers, construction companies and member manufacturers throughout the process from design
to construction.
Further, studies of recent damage illustrates
that the damage is often caused by secular deterioration of structural members and a subsequent loss of their strength and by the adoptionof inappropriate repair methods. These examples suggest that appropriate maintenance of
external cladding and components and proper
repairs are indispensable in mitigating damage
to members caused by strong wind.
￭

Reference
Japan Metal Roofing Association and JapaneseSociety of Steel Construction: Standard of
Steel Roofing, SSR 2007 (published in 2008)

Photo 4 Example of strength test for the connection of folded roofing (SSR2007)

Wind Load Provisions

Wind Load Provisions in the BuildingStandard Law of Japanby Yasuo Okuda, National Institute for Land and Infrastructure Management
Introduction
Article (1) Purpose of the Law and System of the Building Standard Law of Japan
states, “The objective of this law is to establish minimum standards regarding the site,
structure, facilities, and use of buildings inorder to protect the life, health, and property of the nation, and thereby to contribute topromoting the public welfare.” As stated, theLaw regulates the construction of every typeof building in Japan, and provides the minimum standard to be observed in building
construction.
In 2000, the Enforcement Order of the
Building Standard Law [Law] and its Notifications were widely revised, and the windload-related provisions in the Enforcement
Order and its Notifications were also widely revised based on Recommendations for
Loads on Buildings (1993) [hereafter, Recommendations] issued by the Architectural Institute of Japan. The wind load values
adopted with the establishment of the Law
in 1950 were uniform throughout the nation and went unchanged for 50 years, but
in the revision of the Law in 1998 and of the
Enforcement Order and its Notifications in
2000, the wind load values were changed so
as to take into account local and ancillary
conditions. Further, in 2007, the Enforcement Order of the Building Standard Law
was also revised to require the submition ofa structural calculation document for exterior members at the time of building confirmation, a step that had formerly been exempted.
Meanwhile, the Architectural Institute ofJapan has been revising Recommendations
nearly every 10 years since it was first issued in 1981, and the latest version is scheduled for publication in February 2015.
In discussing the standards and specifications for wind-resistant design of buildings
in Japan, an outline of the wind load specifications prescribed in the Building Standard
Law and in Recommendations is introducedin this article. Also introduced is an outlineof diverse guidelines conforming to the windload provisions of the Building Standard
Law as prepared by the respective industry
organizations.

Wind Load Provisions of the BuildingStandard Law
While Recommendations has been revised
nearly every 10 years by the Architectural Institute of Japan to reflect the latest advances in research, the wind load provisionsof the Building Standard Law have not been
so frequently revised since the Law’s establishment in 1950. However, following the revision of the Law in 1998 (introduction of
performance-based design in building standards), widely-ranging revisions and newlyestablished requirements were made to the
Law’s Enforcement Order and to related notifications in 2000. As this was happening,
the wind load provisions of the Law were also widely revised based on Recommendations (1993). As regards the wind load values that were uniformly enforced nationwide
following the establishment of the Law in1950, it has recently become possible to prescribe more rational wind loads that reflect
local and ancillary conditions and the structural characteristics of individual buildings.
Among the specific approaches to determine
more rational loads are:• Clarification of separate wind loads for structural framing and exterior members
Introductionof a standard wind velocity Vo•
Introductionof ground roughness classifi•
cations• Introduction of gust loading factors• Settlement of two load levels of damage criterion and safety criterion in the calculationof response and limit strength
Adoptionof SI units•
Enhancementof wind force coefficients, etc.
•
Difference between the BuildingStandard Law and Recommendations
for Loads on Buildings• Basic Principles Applied in the
Building Standard Law and Recommendations for Loads on Buildings
Although the wind load provisions of the
Law currently in use are based on Recommendations (1993), there are fundamental differences between them. Because the
Building Standard Law has binding legal
force, any judgment contrary to the Law
would not be legally permissible. Further,while the minimum standard load level issettled, any design that uses a load level lower than the minimum standard prescribed in
the Law is impermissible, but designs thatuse load levels surpassing the minimum
standard are permissible. On the other hand,
Recommendations itself has no legally binding force and shows its concept and parameters required to conduct structural design
to structural designers so that it has become
possible for the structural designer to selectthe necessary load level (the basic wind load
is settled to meet a strong wind having a return period of 100 years, and the structuraldesigner can select his optional load levelobtained by use of the conversion coefficient
more than the level of the Building Standard
Law).
As stated above and in contrast to the
Building Standard Law, Recommendations
is not a legally binding document. Nevertheless, Recommendations is frequently referenced when specific evaluation methods
in the Law are not applicable, such as windforce coefficients for buildings with a special
architectural configuration, increased windvelocity caused by landforms, or a vibration
response characteristic of high-rise buildings
taller than 60 m. It can be said that Recommendations serves to complement the windload provisions prescribed in the Law.

• Specific Differences in Wind Load

Specifications between the Building Standard Law and Recommendations for Loads on Buildings-Clarification of separate wind loads
for structural framing and exterior
members
While partially-common wind force coefficients were applied for both structural framing and exterior members in the BuildingStandard Law before its revision in 2000,
wind loads were not so clearly distinguishedbetween the two categories. But after revision of the Law in 2000, wind loads forstructural framing and exterior members
were more clearly distinguished in conformance with Recommendations, which were
included in the Enforcement Order and related Notifications.
December 2014 Steel Construction Today & Tomorrow 6

-Introduction of standard wind velocity Vo
Before its revision in 2000, the Building Standard Law defined velocity pressure q as 60 √hand made wind load uniform throughout thenation. Following the 2000 revision, velocity pressure q has been determined using thestandard wind velocity Vo, the vertical distribution of wind velocity based on groundroughness classification, the gust effect factor
and other influences and, further, takes into
account local and ancillary conditions and thestructural characteristics of individual buildings.
Fig. 1 shows the standard wind velocity
Vo in Japan, which is settled at “30~46 m/s
depending on the rate of occurrence of winddamages based on the recorded history of pasttyphoons and associated wind properties.”
The value of 30~46 m/s is obtained by converting the annual maximum wind velocities
recorded by meteorological offices nationwide to wind velocities with a return periodof 50 years (10-minute average wind velocity at a height of 10 m over ground with a surface roughness classification II). The figure
shows respective standard wind velocities inTable 1 Ground Roughness Classifications and Ground Conditions in
Recommendations for Loads on Buildings
Classification ofground roughness
I

Flat area with nearly no obstacles

Coastal zone

II

Area with obstacles such as agricultural
products, area where tress and low-risebuildings lie scattered

Rural zone

III

Area with dense trees and low-risebuildings, area where medium- and high-risebuildings (4~9 stories) lie scattered

Forest zone
Industrial zone
Housing zone

IV

Area with dense medium- and high-risebuildings (4~9 stories) in wider range

Medium- and high-riseurban zone

V

Area with dense high-rise buildings(10 or more stories)

High-rise urban zone

Fig.2 Vertical Distribution of Wind Velocity Prescribed by the Building Standard Law
70
60
50
40
30
20
10
0
0.4

Fig. 1 Drawing of Standard Wind Velocity Vo

the cities, towns and villages of Japan in 2000
that were divided into nine areas classified bywind velocity level. The standard wind velocity thus obtained has allowed the dominantwind characteristics of each area to be reflected in the design wind velocity.
-Introduction of ground roughnessclassifications
In Recommendations, the specified groundroughness is selected by the structural designer from among the five classifications and7 Steel Construction Today & Tomorrow December 2014

Representative
examplesGround conditions at peripheral areas

H[m]The wind load for structural framing is thewind force that works on an entire building
structure, and differs depending on the winddirection. The load on exterior members is
the wind force that works on roofing materials and other exterior members (area: about
1~5 m2), and shows maximum and minimum
values in all wind directions. Accordingly, thewind pressure per area has a relation: the loadon exterior member ≥ the load on structural
framing.

0.6

0.8

1

Er

1.2

1.4

1.6

photos shown in Table 1 based on his judgment. On the other hand, the Building Standard Law adopts a vertical distribution ofwind velocity (Fig. 2) that is similar to thatin Recommendations, but in the Law, groundroughness is clearly divided to four classifications depending on the specified area (Table2) in order to eliminate as much vagueness inthe classification as possible. Because groundroughness classifications I and IV are settled
by specified administrative agencies based on
the regulations, classifications II and III areto be adopted in most areas (refer to Table 2).
-Introduction of gust loading factor
The gust loading factor Gf was introduced in
the 2000 revision of the Law and conforms
to Recommendations. The numerical value of the gust loading factor Gf is settled according to the ground roughness classificationand the building height while taking into account wind turbulence and building scale andstructural characteristics. On the other hand,in the method adopted in Recommendations,Table 2 Classification of Ground
Roughness Prescribedby the Building Standard Law
Groundroughnessclassification

Inside urban Outside urban
planning
planning
area
area

◎

I
II

○

○

III

○

○

IV

◎

the structural designer finds the value of gusteffect factor by taking into account wind turbulence, building scale and structural characteristics and by using the calculation formula.
-Settlement of two load levels ofdamage criterion and safety criterion in the calculation of response
and limit strength
Before being revised in 2000, the BuildingStandard Law used allowable stress calculations and retained horizontal strength calculations to settle load levels; but, after its revision in 2000, the Law introduced criticalstrength calculations, too. In critical strength
calculations, two criteria-damage criterion and safety criterion-were provided andtheir respective loads were settled. For thewind load, two load levels having 50-year and
500-year return periods respectively were settled, and loads conforming to the safety criterion were set at 1.6 times the loads conforming to the damage criterion.
-Adoption of SI (International System of Unit)
Before the Building Standard Law was revised in 2000, it had employed an engineering unit system, but following the adoption of
SI (International System of Unit) in the Japanese Industrial Standards in 1991, SI was also adopted in the Law. In the system of engineering units that had been in use, both mass(kg) and force (kgf) were employed, but they
were barely distinguishable and sometimes
caused misunderstanding. However, in the SI
system, mass (kg) and force (N) are clearly
distinguished, and the force relationship is 1
kgf = 1 kg × g (gravitational acceleration) ≒9.8 N. As a result, wind pressure that had been
expressed using kgf/m2 is now expressed in SI
units as N/m2, and a numerical value of about
9.8 times the conventional value is adopted in
the SI unit system. Meanwhile, SI units wereintroduced in Recommendations in 2004.

(Building height)(Building height)

Ⅱ

31 m

13 m

Ⅲ

0 m 200 m

13 m

Ⅱ
Ⅲ

500 m

(Distance from sea coastal line or lake coastal line)**Sea coastal line or lake coastal line is to be set tohave a distance of 1,500 m or more from the line
to the opposite shoreline.
Inside the urban
planning area

Outside the urban
planning area

-Enhancement of wind force coefficients, etc.
In the Building Standard Law before its revisionin 2000, the wind coefficient and wind pressure
coefficient were diagrammatically expressedusing a two dimensional building section, but
after the Law’s revision in 2000, the two-dimensional section was changed to a three-dimensional expression. Further, from 2008, thebuilding standard improvement subsidy project
began implementing wind tunnel and other tests
to derive wind force coefficients for hip roofs,
rooftop advertising plates, porch handrails andother members. In 2013 it became possible forstructural designers to reference these coefficients.
Wind-resistant Design Guidelines of
Various Industrial Organizations
Structural designers have been obliged to submit a structural calculation document for exterior building members (roofing materials, exterior walls, openings, etc.) at the time of building
confirmation, but often the design and installation of these members are trusted to people specializing in the particular structural members.
Given such a situation, the industrial organizations of the exterior members industry have independently prepared the guidelines shown below. These guidelines aid structural designers,
project owners and supervisors in confirmingthat the wind resistance of exterior members
conforms to the wind load provisions of the
Building Standard Law.
Roofing materials• Japan Roof Tile Industry Association and others: Guideline for Tile Roof Standard Design
and Installation (2001)• NPO Japan Exterior Furnishing TechnicalCenter: Guideline for Decorative Slate Covering for Housing Roof and Roof Wind-resistant Design and Installation (2002)• Japan Metal Roof Association and JapaneseSociety of Steel Construction: Steel Sheet
Roof Structure Standards SSR2007• Japan Copper Development Association:
Copper Sheet Roof Structural Manual (revised in 2004)• Architectural Institute of Japan: Japanese Architectural Standard Specification JASS12,
Roofing Work (2004)
Exterior walls• Architectural Institute of Japan: Japanese Architectural Standard Specification JASS27,
Dry Exterior Wall Work (2004)• Japan Fiber Reinforced Siding Manufacturers Association: Fiber Reinforced-type Siding
and Standard Execution (2nd version 2009),
Improvement of Housing Quality and Durability and Exterior Wall Ventilation Structure(2001)
Japan
Metal Siding Industry Association: Ex•ecution Manual of Japan Metal Siding Industry Association (2008)• Extrusion Cement Plate Association: Standard
Specifications for ECP Execution (2010)• Architectural Institute of Japan: Japanese Architectural Standard Specification JASS21
ALC Panel Work (2005)• Autoclaved Lightweight Aerated Concrete
Panel Association: ALC Panel Structure Design Guideline (2004), ALC Thin Panel Design and Construction Guideline (October2002), ALC Attachment Structure Standards(2004)
Architectural
Institute of Japan: Japanese Ar•
chitectural Standard Specification JASS14
Curtain Wall Work (1996)
Curtainwall
Fire Window’s Association: Cur•
tain Wall Performance Standards (2006)• Precast Concrete System Association: Guidance for Design, Precast Curtain Wall Calculation Examples (Temporary revised version)
Openings (door, window glass, etc.)• Japan Rolling Shutters & Doors Association:
Wind Pressure-resistant Strength Calculation
Standards for Shutters and Overhead Doors(2003)
Architectural
Institute of Japan: Japanese Archi•
tectural Standard Specification JASS17 GlassWork (2003)*****

An outline of the wind loads on buildings adopted in Japan is introduced by comparing thewind load provisions in the Building Standard Law and the guidelines in Recommendations for Loads on Buildings of the Architectural Institute of Japan. Further, the guidelines
for wind-resistant design pertaining to exterior building members, prepared by related industrial organizations, were introduced.
￭
December 2014 Steel Construction Today & Tomorrow 8

Wind-induced Building Vibration

Evaluation of Habitability Related toWind-induced Building Vibration
by Osamu Nakamura, Wind Engineering Institute Co., Ltd.
It is known that the wind can cause buildings to vibrate. When wind-induced vibration occurs, it causes discomfort, queasiness, seasickness and other adverse effects
that can lead to complaints and to building
deterioration. Further, in cases when a building vibrates more violently, panic can occur
and lead to a state of chaos. How vibrations
are felt differs depending on social environment and personal sensitivity, and cannot be
objectively evaluated; further, criteria related
to building vibration differ in different countries. Meanwhile, when people recognize thata building is safe even when it does vibrate,
their uneasiness is mitigated and their sensitivity to the vibrations decreases.
The main topics of discussion in this article are: how a building vibrates when subjected to the wind, how people feel wind-induced vibration, how wind-induced vibrationis treated in different countries, and whatcountermeasures against wind-induced vibration are taken in Japan.
Wind-induced Building Vibration
When the wind causes a building to vibrate,
the vibrations that move in the along-wind
direction are dominant in low-rise buildings,
but in high-rise buildings, the vibration pattern is more complicated and is composedof translational vibrations consisting of two
horizontal components (along-wind direction and across-wind direction) and rotational vibration caused by torsion. Thus, because such random vibrations are the resultof external forces that change irregularly interms of both time and space, they consist of
responses of various frequency components
and, therefore, cannot be evaluated using only a single frequency.
However, in common high-rise buildings,
the primary natural frequency component of
the translational vibrations appears prominently. In particular, the time history of theacceleration, which is the target for evaluation in this article, can be deemed to be theharmonic vibration of just the primary natural frequency that is accompanied by random
and comparatively gentle amplitude modulations, as shown by the example in Fig. 1. Inpractice, vibrations occur that are composedof bi-directional translational vibrations andtorsional vibration. However, these major
types of vibration appear alternately, and it
is seldom that the maximum response to thetranslational bi-directional vibrations and thetorsional vibration appear simultaneously.
Accordingly, even when any maximum
acceleration of the translational bi-directional vibrations and the torsional vibrations
is considered to be in close agreement withthe maximum acceleration composed of thetranslational and torsional vibrations, there
is not a large difference in the evaluation
results. Further, when the natural frequency in the vibration-direction differs, the level of one’s perception of vibration differs depending on the frequency, and accordingly an
evaluation of habitability can be made basedon the vibration direction.

Perception of Vibrations
While a person’s perception of and sensitivity to vibration are closely tied to displacement, velocity, acceleration, jerk and otherfactors, it is not truly known which of thesefactors is the most significant element for theperception of and sensitivity to vibration. A
person’s perception of and sensitivity to vibration differs according to the amplitude
targeted in the evaluation, but, when evaluating habitability related to wind-induced vibration, acceleration is the frequently adopted factor.
While there is no firm reason why acceleration is frequently adopted, if anything, it
can be said that a person’s perception of vibration is greatly affected by one’s physicalresponse to floor vibration. However, building vibrations that take habitability into account can be accepted as single-period vibrations in most cases, and displacement,
velocity, acceleration and jerk are in a proportional relation via frequency. Accordingly, when either of these is used, the evaluation results are substantially identical.
Fig. 2 shows the discussion results pertaining to the relation between accelerationand the average threshold at which vibrations are perceived. The figure is based on
major survey results obtained from laboratory tests and of actual buildings subjected
to strong winds; in both cases, the questionnaire results were statistically evaluated. The
plot indicates the average values of the vibration perception threshold with personal de-

Fig. 1 Acceleration Time History at Top of the Building

Acceleration (cm/s2)

Peak acceleration

Time (sec)

9 Steel Construction Today & Tomorrow December 2014

Fig. 2 Average Vibration Perception Thresholds

Peak acceleration (cm/s2)

the determination of return period will differ
depending on the social environment and theconcept of different nations.

Frequency (Hz)viations, or a perception probability of 50%.
Specifically, for example, a peak accelerationof about 5 cm/s2 in the neighborhood of a frequency at 0.2 Hz is shown in Fig. 2, whichmeans that 50% of people perceive vibrations
when subjected to a frequency at 0.2 Hz having a peak acceleration of 5 cm/s2.
It is found in the figure that the averagevibration perception threshold shows differences (different symbols in the figure) depending on the examining organization; but
the same trend in vibration perception threshold having relatively few deviations is shownin the figure, in spite of survey results obtained from different organizations. That is,
the perception of vibration depends on frequency, and the tendency is shown in which
the vibration is most highly perceived in theneighborhood of frequencies of 1~3 Hz.

and 90% of perception probability, and determination of the level of perception probability to which a return period of 1 year is set
is entrusted to the judgment of the structuraldesigners. Buildings in Japan are commonly
designed targeting a perception probability of
50%. In the Australian criteria, plural return
periods are given.
In the case of short return periods, how todeal with routine vibration is to be taken into
account, and in the case of long return periods, how to handle great vibrations that occur
only rarely is to be taken into account; but,

Countermeasures against Wind-induced Building Vibration
In order to mitigate wind-induced building
vibration, the method that improves building
rigidity is used. However, as can be seen in
Figs. 2 and 3, in the low frequency zone of 1
Hz or less, even if vibration is mitigated by
improving rigidity, this results in an increasein natural frequency which, in turn, increases
the likelihood that vibration will be perceived
and that habitability will not be improved in
the end. To correct this, methods that enhance
vibration-damping performance are adopted
in most cases. In this case, because a low acceleration level is usually targeted in order toimprove habitability, it is necessary to adopt
a damping system that is effective even in the
low-acceleration zone. Currently, many highrise buildings have been constructed in which
vibration-damping devices are installed.
On the other hand, from an architectural planning perspective, there is a method toplan the floor and plane position according toa building’s expected use and frequency. Further, in order to prevent both visual and auditory perception of vibration, measures are adopted that will prevent creaking in partition
walls and other secondary structural members and that will prevent the vibration of
window shades and pendant lights.
￭

Fig. 3 Comparison of Occupant Serviceability Criteria for Tall Buildings
Japan (1 year, H-10)
Japan (1 year, H-30)
Japan (1 year, H-50)
Japan (1 year, H-70)

Peak Acceleration (cm/s2)

Occupant Serviceability Criteria in
Different Nations
To cope with issues relevant to wind-inducedbuilding vibration, occupant serviceability
criteria have been standardized in several nations. Fig. 3 shows a comparison of representative criteria for certain nations. In some nations, the standard deviation for accelerationis adopted instead of the peak value for acceleration, but in this figure, the criteria areshown replacing the peak values.
These criteria are standardized so that thepeak acceleration during their respective return periods does not surpass the value for abuilding’s natural frequency. However, theJapanese criteria show levels at 10, 30, 50, 70

Japan (1 year, H-90)
ISO (1 year, ofﬁce)
ISO (1 year, residence)
Canada (10 years, ofﬁce)
Canada (10 years, residence)EURO (5 years, ofﬁce)
EURO (5 years, residence)
Australia (10 years)
Australia (5 years)
Australia (1 year)

Frequency (Hz)

December 2014 Steel Construction Today & Tomorrow 10

Advanced Wind-resistant Design

Performance-based Wind-resistant
Design for 300 m Vertical City
by Kiyoaki Hirakawa, Takenaka Corporation
Outline of Building and Structure
ABENO HARUKAS (hereinafter HARUKAS) is Japan’s tallest skyscraper, standing at 300 meters, which was completed in
March 2014 (Photo 1).
The building site is situated in Abeno,
Osaka, which is a city representative of Japan and the world’s seventh largest metropolitan area. This area has been growing fast anddrawn the most attention in recent years.
HARUKAS is a superhigh-rise vertical city with the gross floor area of approx.
212,000 square meters. Rising 60 stories

above the ground and 5 underground stories, this tower incorporates diverse functions: a terminal station, a department store,
an art museum, offices, a hotel, an observatory, parking spaces and more. No other building of this scale has been built above a stationin any place of the world.
Japan is one of the most earthquake andtyphoon-prone countries in the world. Details of the performance-based seismic design for this building are summarized in Ref.
1. This paper focuses on the performancebased wind-resistant design for HARUKAS

as below.
When a strong wind blows on a building,a Karman vortex is generated on the leewardof the building and lets the building shakein the direction orthogonal to the wind. The
illustrations as indicated in the Fig. 1 show
the visualized statuses of Karman vortexes,
which indicate that the effect of a Karmanvortex is minimized in the case of HARUKAS (below right) compared with a rectangular solid building (below left).
Fig. 1 Statuses of Karman Vortexes

Photo: SUZUKI hisao

Photo 1 Northwest view

11 Steel Construction Today & Tomorrow December 2014

The quality of aerodynamic characteristics is extremely critical in wind-resistant design of a skyscraper as high as 300 meters.
A “setback” type building like HARUKAS is
a building shape with excellent aerodynamic performance that efficiently reduces overturning moment acting on a building affectedby a Karman vortex.
As shown in Fig. 2, the superstructure iscomposed of three “blocks” having setbacks
on the north side. The lower block is for the
department store, the middle one for offices and the upper one for a hotel. The upper
block has a large atrium in the center. Located between the blocks and at the top of theupper one are transfer-truss floors. In orderto enhance horizontal and torsional rigidity
against strong earthquakes and wind excitation, outrigger mega-trusses are placed in thetransfer floors and the middle block.
A total of four types of dampers, both viscous and hysteresistic, are placed mainly at
the four corners in the lower block, aroundthe central core in the middle block andaround the atrium in the upper block in order
to absorb energies input by earthquakes orwind. In addition, two kinds of mass damp-

Fig. 2 Structural Planningers (AMD and ATMD) are installed on the56th floor in order to improve the habitability
mainly of the hotel in the upper block. Evaluation of habitability against wind load will
hereinafter be described in detail.
The robust structure using outriggers andshear studs helps reduce the natural period of
the building to prevent occurrence of an aerodynamic unstable vibration (phenomenon of
shaking causing greater shaking) which islikely to be generated by a soft building witha longer period. Moreover, use of vibration
control dampers enhances damping performance to restrain the building shaking caused
by a strong wind and settle it down in a shortperiod of time.
Outline of Wind-resistant Design
Table 1 shows the design wind speeds, crite-

Table 1 Study Items for Wind-resistant Design
Study item

Structural
framework
SafetyWind load

Designwind speed

Average load

Vo=34 m/s (Level 1)
Vo=42.5 m/s (Level 2)(to comply with
Notification)Windtunnel test
(measured windpressure )Aerodynamic 1.2 times windspeed forunstable
structural
vibrationframework

Fluctuation
component

Designcriteria

Spectrum modal;
Structural members shall
Load combination
be within elastic range
to comply with
Guidelines for Loads on and story drifts shall be
Buildings (Architectural 1/100 or less for Level 2.
Institute of Japan)
Aerodynamic
vibration test using
MDOF modelNo aerodynamic unstablevibration shall occur at not
more than 1.2 times Level
2 design wind speed.

Exterior
claddings

1.10 times windspeed specified
in Notification

Wind tunnel test
(measured windpressure )Glass shall not be
broken.

Habitability
Comfort study

V=17 m/s(recurrence
interval of one
year)

Wind tunnel test Spectrum modal;(measured wind (frequency of windpressure )direction to beconsidered )“H-30” (about 30% of
habitants feel quakes)
or moreDecember 2014 Steel Construction Today & Tomorrow 12ria and other items studied in developing theperformance-based wind-resistant design forthis building.
Outline of Wind Tunnel Tests
Wind pressure measurement tests were conducted to determine the wind pressures acting on this building. The scale of the windtunnel test model for that purpose was 1/500,
and the modeling range was a radius of 700
meters (Photo 2). Approximately 600 measuring points were embedded in an acrylic
model to measure the wind pressures.
Base shears were calculated by spectrum

Photo 2 Wind tunnel test

modal response analyses taking only the firstmode into consideration. The relationship between the base shears at the wind speed for“Level 2” corresponding to the return period of 500 years and wind angles are shown in
Fig. 3. The maximum base shear in the northsouth (Y) direction, a narrow side of the building, appears at wind angle 85°, which is nearly the east-west (X) direction.
Calculation of Wind Loads
The wind loads on all the stories when the baseshear is largest at wind angles 175°and 85°for
X-direction and Y-direction, respectively, arePhoto 3 Aerodynamic vibration experimentFig. 3 Relations between Base Shears and Wind Angles
mean

max

max-meanmean

40,0000-40,000-80,000

max-mean

80,0000-80,000-160,000

Wind direction (degree)

Wind direction (degree)

Fig. 4 Comparison between Wind Loads and Seismic Loads
Wind load

Seismic loads

R floor60

R floor
60

50

50

40

40

30

30

20

20

10

10

1

1

B5

B5

50,000100,000
150,000
Shear force (kN)(a) X-direction

Studies of Aerodynamic Unstable Vibration
The wind speed at which the frequency generated by Karman vortex calculated by the windpressure measurements coincides with thebuilding’s natural frequency (0.169 Hz) in the
Y-direction is 97.9 m/sec., which is more than
1.4 times the wind speed (66.6 m/sec.) withthe recurrence interval of 500 years.
It seems that this building has a configuration in which aerodynamic unstable vibration is unlikely to occur, because the building
width varies with building height in the Y-direction with a larger wind pressure area corresponding to the orthogonal directions for winddirections of 90° and 270°.
Nevertheless, aerodynamic vibration experiments were conducted considering thatthe upper block is thin and possibly vulnerable
to torsional vibration. The experiments used a
5-lumped-mass 3D model which has the same
mass, eigenvalue and damping (0.03 for translational mode and 0.014 for torsional mode)as the design values (Photo 3). As a result, it
is confirmed that aerodynamic unstable vibration does not occur at less than 1.2 times thedesign wind speed with the recurrence intervalof 500 years, as shown in Fig. 5.

(b) Y-direction

Design loads

Fig. 5 Aerodynamic Vibration Test
0.8

RMS. acceleration (m/s2)(a) X-direction0

max

160,000

Base Share (kN)

Base Share (kN)

80,000

shown in Fig. 4 in comparison with the seismic loads for “Level 2.”
The seismic loads exceed the wind loads
on all stories in the X-direction and almost all
stories except for a few lower stories in the Ydirection. Loads that incorporate both types ofloads were established as the external loads for
sectional design.

X-direction (ana.)
Y-direction (ana.)

0.6

X-direction (exp.)
Y-direction (exp.)

0.4

0.2

0.0

0

20

40

60

Mean wind speed (m/s)

050,000100,000
150,000
Shear force (kN)(b) Y-direction

13 Steel Construction Today & Tomorrow December 2014

80

100

Conclusion on Performance-based
Wind-resistant Design
This section introduces the performancebased wind-resistant design of the first 300
m-high building in Japan. The building configuration, superstructure systems and various damping devices are sophisticatedly integrated to ensure a higher level of safety andcomfort against wind load.
￭

Fig. 6 Mechanism of Active Tuned Mass Damper

Fig. 7 Habitability Evaluation of Hotel Guest Room at 55th Floor
10.00

Maximum Accelerationon the 55th Floor(cm/s2)

Evaluation of Habitability
There will be a hotel in the upper block of thisbuilding (see Photo 4), for which comfortable
habitability has to be provided by keeping
the response accelerations less than approximately 3 cm/sec2, at Class H-30 (about 30%
of occupants present perceive tremor) withthe recurrence interval of one year. For that
purpose, two kinds of active mass dampers
were installed on the 56th floor to reduce response accelerations in case of strong winds.
Two active mass dampers work only when
their period is synchronized with the natural period of the building, which is as longas about 6 seconds. One active mass damper(AMD) at the east side is a conventional pendulum. The other active tuned mass damper (ATMD) at the west side is a conventional
suspended pendulum combined with an inverted pendulum so as to minimize the suspended length (2.2 m) and avoid exceeding
ceiling height as shown in Fig. 6.
Habitability in the hotel rooms is improved with mass dampers for the narrowside (north-south; Y-direction) of the building as shown in Fig. 7. However, the vibration in the wide side (east-west; X-direction)is sufficiently small without mass dampers.
The building ensures a high level of habitability by reducing the acceleration of shaking in a short direction to about a half whena strong wind blows, which is as frequent
as approximately several to ten-odd times a
year.

Improved by
ATMD AMD

1.00

0.100

X-direction
Y-direction
Torsional direction
Y-direction (with AMD)
Torsional direction (with AMD)

Frequency (Hz)

H-10
H-30
H-50
H-70
H-90
1.000

Note: Torsional vibrations were maeasured at
3,500 m from the center of the building.

Reference
1) Nakai, M., Koshika, N., Kawano, K., Hirakawa, K., and Wada, A. (2012). ”Performance-Based Seismic Design for High-Rise
Buildings in Japan” International Journal of
High-Rise Buildings.

Photo 4 Top of HARUKAS
December 2014 Steel Construction Today & Tomorrow 14

Steel Application Technology

Basic Details about Highstrength Bolt Joining

ly applied in Japan.

The Japan Iron and Steel Federation
In joining steel-frame members with high-strength bolts, two methods
are commonly used: friction joining and tension joining. The two typesof high-strength bolts in primary use are: high-strength hexagonal bolts
and high-strength torque shear bolts. Depending on the application environment, in addition to bolts manufactured using general-purpose ordinary steel materials, hot-dip galvanized bolts and bolts manufactured
using fire-resistant steel, weathering steel and stainless steel are available. Nominal diameters of commonly applied bolts are M16, M20, M22
and M24. In addition, some bolt makers offer bolts having larger diameters, such as M27 and M30.
Currently, the grade of high-strength bolts most commonly used in
the building construction in Japan is F10T (tensile strength: 1,000 N/mm2), and the grade of high-strength hot-dip galvanized bolts is F8T(tensile strength: 800 N/mm2). In the past, F13T bolts (tensile strength:
1,300 N/mm2) were manufactured but were later prohibited due to theoccurrence of delayed fractures. Further, regarding Japanese Industrial Standards (JIS) grades F8T, F10T and F11T (tensile strength: 1,100
N/mm2), the application of F11T bolts was prohibited for the most part.
Further, F11T is not described in Guidebook on Design and Fabricationof High Strength Bolted Connections issued by the Architectural Institute of Japan.
Table 1 shows the high-strength bolts that, currently, are common-

Kinds of High-strength Bolts• High-strength Hexagonal Bolts
The high-strength hexagonal bolts used to join ordinary steel products
are specified in JIS: JIS B 1186 (Sets of high strength hexagon bolt,
hexagon nut and plain washers for friction grip joints) and 1 set is definedas containing 1 bolt, 1 nut and 2 washers (see Photo 1). The reason why
the bolts are specified in sets is to guarantee the mechanical properties,
shape and dimensions of the bolt, nut and washers that constitute a set
and, further, to specify the introduction of axial force.
Three kinds of hexagonal bolts are available according to the mechanical properties of the set to which they belong: Type 1 (F8T), Type 2(F10T) and Type 3 (F11T). In Type 1 (F8T) sets, the joining efficiency is
bad and there are not any JIS-certified production plants; and in the Type
3 (11T) sets, delayed fractures have occurred. Because of this, these
two bolt sets are no longer in use. Currently, only Type 2 (10T) sets produced at JIS-certified production plants are in use.
Further, high-strength hexagonal bolts are classified as Type A or B
according to the torque coefficient of the bolt set.

Photo 1 Set of high-strength hexagonal bolt

Table 1 High-strength Bolts Commonly Applied in Japan
Name

Standard

Grade

NominaldiameterBolt
product

Tensilestrength(N/mm2)Hardness(HRC)

Reference

High-strength
hexagonal bolt

JIS B 1186

F10T

M12~M30Bolt

1,000~1,200

27~38

JIS-certified productionplant

Nut

–

16~35

High-strength
torque shear bolt

JSS II 09

S10T

High-strength
hot-dip galvanizedbolt

Conformingto
JIS B
1186

F8T

High-strength
fire-resistant steelbolt

JIS B 1186
JSS II 09

F10T-FRS10T-FR

High-strength
hot-dip galvanizedfire-resistant steel
bolt

Conforming
to JIS B
1186

F8T-FR

High-strength
weathering steelbolt

JIS B 1186
JSS II 09

F10T-W
S10T-W

High-strength
stainless steel bolt

SSBS 301

10T-SUS

15 Steel Construction Today & Tomorrow December 2014

M16~M30

M16~M30

M16~M24

M16~M24

M16~M24

M12~M24

Washer

–

35~45

Bolt

1,000~1,200

27~38

Nut

–

16~35

Washer

–

35~45

Bolt

800~1,000

18~31

Nut

–

16~35

Washer

–

25~45

Bolt

1,000~1,200

27~38

Nut

–

16~35

Washer

–

35~45

Bolt

800~1,000

18~31

Nut

–

16~35

Washer

–

25~45

Bolt

1,000~1,200

27~38

Nut

–

16~35

Washer

–

35~45

Bolt

1,000~1,200

27~38

Nut

–

16~35

Washer

–35~45

Approval by Minister of Land,
Infrastructure, Transport and Tourism
Approval by Minister of Land,
Infrastructure, Transport and Tourism
JIS-certified production plant
S10T-FR: Approval by Minister ofLand, Infrastructure, Transport andTourism
Approval by Minister of Land,
Infrastructure, Transport and Tourism

JIS-certified production plant
S10T-W: Approval by Minister ofLand, Infrastructure, Transport andTourism
Approval by Minister of Land,
Infrastructure, Transport and Tourism

Table 2 Examples of Chemical Composition of Steel Materials Used for High-strength Bolts, Nuts and Washers (%)
C

Si

Mn

P

S

Cu

Ni

Cr

B

Al

Ti

Bolt

0.21

0.12

0.83

0.021

0.009

–

–

0.38

0.0016

0.032

0.021

Nut

0.34

0.17

0.75

0.030

0.021

–

–

–

–

–

Washer

0.22

0.27

1.04

0.020

0.006

–

–

–

0.0016–High-strength
fire-resistant steel
bolt

Bolt

0.22

0.24

0.82

0.018

0.013

0.01

0.02

1.04

–

0.025

Nut

0.22

0.20

0.78

0.016

0.016

–

–

1.09

–

High-strength
weathering steel
bolt

Bolt,
nut,
washer

0.22

0.19

0.74

0.014

0.024

0.30

0.37

0.63

High-strength
stainless steel
bolt

Bolt,
nut,
washer

0.07

0.30

0.84

0.037

0.006

3.30

4.23

15.67

High-strength
ordinary steel bolt

Mo

Nb

–

–

–

0.022

–

–

–

0.36

–

0.035

–

0.36

–

0.0018

0.042

–

–

–

–

–

–

–

0.37

The steel materials that are commonly used to manufacture bolt
products are: low-carbon steel with added chromium (Cr) and boron (B)for the bolts; carbon steel for the machine structure for the nuts; and carbon steel, or low carbon steel with added manganese (Mn) or B, for themachine structure for the washers (Table 2).

room temperature.
Because high-strength torque shear bolts are not standardized in
JIS, bolt makers have obtained general approval from the Minister ofLand, Infrastructure, Transport and Tourism to manufacture this type ofbolt.

• High-strength Torque Shear Bolts
High-strength torque shear bolts are specified by the Japanese Society of Steel Construction in JSS II 09. One bolt, 1 nut and 1 washer are
specified as 1 set (Photo 2), and only a single set is specified in JSS II
09, namely, Type 2 (S10T). High-strength torque shear bolts are denoted as grade S10T and are distinguished from high-strength hexagonalbolts that are denoted as F10T.
Torque shear bolts feature a bolt configuration with a round bolt head
and the provision of the pin tail at the bolt tip via the break-off groove(refer to Photo 2). These bolts also feature that the required axial force
for high-strength torque shear bolts is obtained by fastening the bolt until when the pin tail causes fracture and accordingly finishing of bolting
work can easily been confirmed. Meanwhile, the required fastening axial
force of the bolt set is specified in the standards for high-strength torqueshear bolts. Table 3 shows the tension required for fastening bolts set at• High-strength Hot-dip Galvanized Bolts
In order to provide rust prevention or corrosion protection for steel-frame
members, high-strength hot-dip galvanized hexagonal bolts (Photo 3)
are used to join sections of steel frames manufactured using hot-dip galvanized products of ordinary steel. Because sets of high-strength hotdip galvanized hexagonal bolts are not standardized in JIS and because
the F value (strength rating) is not settled in the Building Standard Law
of Japan, bolt makers have obtained general approval for “high-strength
hot-dip galvanized bolt joining” from the Minister of Land, Infrastructure,
Transport and Tourism, based on Article 37 of the Building Standard Law.
To this end, high-strength hot-dip galvanized hexagonal bolts are manufactured conforming to the standard in JIS.
Galvanizing of bolts, nuts and washers is conducted at HDZ55 (coating mass: 550 g/m2 or more), and over-tapping of the nut threads is conducted prior to galvanizing.
Conventionally, the strength rating of hot-dip galvanized bolts was
set at the F8T level, taking into account the drop in strength and the occurrence of delayed fractures that are attributable to the galvanizing bathtemperature being higher than the tempering temperature for F10T highstrength bolts. However, high-strength bolts having an F12T strength,that are manufactured using recently developed, ultrahigh-strength bolt
technology, have been put into practical application.
The friction surfaces after galvanizing are given a slight blastingtreatment to improve the surface roughness to 50 micron Rz or higher.
When special surface treatments other than blasting are applied, a slip
strength test is conducted to confirm surface friction.

Photo 2 Set of high-strength torque shear bolt

Table 3 Introduction Tension for Sets of High-strength
Torque Shear Bolts (Room Temperature)
Nominal diameter

Average value of bolt introduction tension
per 1 production set(kN)

M16

110~133

M20

172~207M22

212~256M24

247~298M27

322~388M30

394~474

Photo 3 Set of high-strength hot-dip galvanized bolt

December 2014 Steel Construction Today & Tomorrow 16

Design and Joining of High-strength Bolt Joints• Allowable Strength of High-strength Bolts
The allowable strengths prescribed for the friction joining and tension
joining of high-strength bolts (F10T and S10T) are stipulated in the
Enforcement Order of the Building Standard Law, and the allowablestrengths of high-strength hot-dip galvanized bolts (F8T) are specified
according to the approval of the Minister of Land, Infrastructure, Transport and Tourism. The allowable strengths, listed by the nominal bolt diameter, are summarized in Table 4.
The allowable shear strengths of high-strength hot-dip galvanizedbolts (F8T), shown in Table 4, are found from the formula: “allowable
shear strength = 0.40 × Bo (design bolt tension),” in which the slip coefficient is set at 0.40. On the other hand, the allowable shear strengthof high-strength hexagonal and torque shear bolts (F10T and S10T) is
calculated using a slip coefficient set at 0.45. Meanwhile, the allowable
shear strength and the allowable tensile force for F10T and S10T are
similar to those prescribed in Design Standard for Steel Structures of theArchitectural Institute of Japan.
• Fastening Operations
High-strength bolt fastening is undertaken by a group of bolts and in thefollowing order: primary fastening → marking → final fastening. Meanwhile, the instruction of work procedure for ultrahigh-strength bolts issimilar to that for high-strength bolts, but the primary torque for ultrahighstrength bolts is different from that of high-strength bolts.

-Primary fastening
The primary fastening of high-strength hexagonal bolts, high-strength
torque shear bolts and high-strength stainless steel bolts is undertaken using the primary fastening torque values shown in Table 5; highstrength hot-dip galvanized bolts are fastened using the primary fastening torque values shown in Table 6.
-Marking
After the primary fastening is completed, all the bolts, nuts and washers of all the bolt sets, as well as the structural members, are marked.
-Final fastening
After a bolt set has undergone primary fastening and marking, final fastening is conducted by rotating the nuts. High-strength hexagonal bolts
are fastened using the prescribed torque to obtain the standard bolt tension. High-strength torque shear bolts are fastened using a dedicatedelectric wrench until the break-off groove fractures.
Final fastening of high-strength hot-dip galvanized bolts and highstrength stainless steel bolts is performed by rotating the nut 120° fromthe mark made at the completion of primary fastening and marking.
-Inspection
After final fastening, any excess bolt length and nut rotation are visually inspected to confirm whether or not fastening is normally undertaken.
Meanwhile, for high-strength hexagonal bolts and high-strength torqueshear bolts that are fastened by means of the torque method to the standard bolt tension, or bolt elastic range, the degree of nut rotation at thetime of final fastening will show a slight change depending on the lev-

Table 4 Allowable Strength of High-strength Bolts (Sustained Load)
Grade according tomechanical property of bolt

F8T
F8T-FR

F10T (S10T)and F10T
(S10T)-FR (M16~M24)
F10T (S10T)-W(M16~M24)
10TSUS (M12~M24)

Nominaldiameter

Design bolt
tension(kN)

Standard bolt
tension
(kN)

M16

85.2

M20

133

M22

Allowable shear
strength (kN)

Allowabletensile force(kN)

1-surfacefriction

2-surfacefriction

93.7

22.7

45.4

50.3

146

35.4

70.8

78.5

165

182

44.0

88.0

95.0

M24

192

211

51.2

102

113

M27

250

275

66.6

133

143

M30

305

335

81.3

163

177

M16

106

117

30.2

60.3

62.3

M20

165

182

47.1

94.2

97.4

M22

205

226

57.0

114

118

M24

238

262

67.9

136

140

M27

310

341

85.9

172

177

M30

379

417

106

212

219

Table 5 Primary Fastening Torque for High-strength
Bolts

Table 6 Primary Fastening Torque for High-strength
Hot-dip Galvanized Bolts

Grade

Nominal diameter

Fastening torque (N・m)

Grade

F10T
S10T

M16

Approx. 100

M16

Approx. 100

M20

Approx. 150

M20

Approx. 150

M22

Approx. 150

M22

Approx. 150

M24

Approx. 200

M24

Approx. 200

M27

Approx. 300

M27

Approx. 200

M30

Approx. 400

M30

Approx. 250

10T-SUS(M16~M24)

17 Steel Construction Today & Tomorrow December 2014

F8T

Nominal diameter

Fastening torque (N・m)el of primary fastening, but the change will remain within a few tenths ofa degree.
On the other hand, for high-strength hot-dip galvanized bolts andhigh-strength stainless steel bolts that are fastened using the nut rotation method to a point close to the bolt strength, the final nut rotation
amounts to 120° (the prescribed rotation amount). Because the postfastening relaxation of high-strength hot-dip galvanized bolts and highstrength stainless steel bolts is greater than that of high-strength hexagonal bolts and high-strength torque shear bolts, the required fastening
bolt tension is increased to the bolt’s yield area.
In cases when it is found by visual inspection that both the bolt andwasher cause their co-rotation and axial rotation due to marking provided after primary fastening and that abnormality is observed in the nut rotation amount, the bolt set is replaced with the new one. In such cases, once a high-strength bolt has been used, it should never be reused.
-Fastening operation control
In order to confirm whether or not a friction surface has been correctly treated or if proper fastening has been undertaken, the Architectural Steel Framing Quality Control Organization of the Japanese Societyof Steel Construction has issued instructions titled “Qualification System for Engineers for Architectural High-strength Bolt Joining Control”
for high-strength bolts in general and “Qualification System for Highstrength Bolt Execution Engineers” for high-strength hot-dip galvanizedbolts and high-strength stainless steel bolts. Based on the instruction ofwork procedures described in these two qualification systems, engineers
engaged in high-strength bolt joining operations can exercise good execution control.
Because these engineers are highly knowledgeable about the execution of high-strength bolt work, they can be expected to ensure a highdegree of quality execution work when installing high-strength bolt connections.
Recent Developments in High-strength Bolts
As stated above, the strength rating of commonly used high-strength
bolts has been increased to F10T grade (1,000 N/mm2). This is attributable to the unavoidable risk of delayed fractures that are associated withthe use of high-strength bolts of F11T or higher grades.
However, as the size and strength of steel-frame members have increased in recent building construction, the adoption of the commonly
applied F10T bolts has led to an excessive increase in the size of joining members and in the number of bolts required. To cope with this situation, the need is growing for more compact bolt joints, or for stronger
high-strength bolts. In answer to this need, several bolt makers havesuccessively hurdled the problems associated with delayed fracture thatis caused by higher bolt strength, and have developed and put into prac-

tical use ultrahigh-strength torque shear bolts having a tensile strength of
1,400 N/mm2, as well as ultrahigh-strength hot-dip galvanized bolts having a tensile strength of 1,200 N/mm2.

• Ultrahigh-strength Torque Shear Bolts

Ultrahigh-strength torque shear bolts are now in practical use thanks to
the development of steel materials with high delayed-fracture resistanceand to improved thread configurations that relax stress concentration(Photo 4). The basic configuration and dimensions conform to the standard JSS II 09 of the Japanese Society of Steel Construction. Ultrahighstrength torque shear bolts offer a high design strength that is about 1.5
times that of conventional bolts (F10T), and the corresponding bolt joints
are compact, about 2/3 the size of conventional bolt joints.
Because of these characteristics, users can obtain many advantages
from the application of ultrahigh-strength torque shear bolts: reductionsin the expense and term of construction work and high efficiency and labor savings of bolting work. Because of this, the application of thesebolts is increasing in the construction of high-rise buildings that use large
structural members, shopping centers that feature wider column-to-column spans, and production plants and warehouses with heavy floor
weights. Table 7 shows examples of ultrahigh-strength torque shear
bolts.
■

Photo 4 Set of ultrahigh-strength torque shear bolt

Table 7 An Example of Ultrahigh-strength Bolts
Name

Ultrahighstrength torqueshear bolt

Standard

Grade-

Specified originally by
respective bolt
makers(Ex: SHTB, STCB,USSB)

Nominaldiameter

Product

Tensilestrength(N/mm2)Hardness(HRC)

M16~M24Bolt

1,400~1,490

39~47

Nut

-

30~40

Washer-40~50

Reference
Approval by
Minister ofLand, Infrastructure,
Transport andTourism

December 2014 Steel Construction Today & Tomorrow 18

JISF Activities

Preparation of Reference Materials on Steel Construction
Technologies in JapanThe Japan Iron and Steel Federation (JISF) has prepared a list ofreference materials on steel construction technologies in Japan. In
order to encourage wider use of Japanese steel construction technologies overseas and at the request of the Ministry of Land, Infrastructure, Transport and Tourism. JISF introduces in these reference materials 27 kinds of steel construction technologies andsteel construction products that are widely applied in Japan in thefields of building construction and civil engineering.
These technologies and products help to improve the functionsof buildings, port/harbor facilities and other infrastructures andare demonstratively effective in disaster prevention. These reference materials are now available at our website (http://www.jisf.
or.jp/en/activity/sctt/index.html). The technologies and products
introduced are:
• New Structural System Buildings Employing Innovative Steel Materials• SN Steel - Structural Steels for Buildings• Cold-formed Rectangular Steel Tubes for Buildings - BCR/BCP• Low Yield-point Steel for Building Structures• Buckling Restrained Brace - BRB• Concrete-Filled Tube - CFT• Thermo-Mechanical Controlled Process - TMCP Steel• High Strength Steel for Buildings - SA440/H-SA700• Port Renovation Method Employing Steel Materials• Seismic Retrofitting of Quays, Seawalls and Breakwaters Employing Steel Materials• Method of Reinforcing Existing Bridge Foundation with Steel Pipe, Sheet Piles
and Steel Pipe Piles• Lateral Flow Control for Revetment• Steel Framed House• Liquefaction Control Earthquake Resistance Measures Using Steel Sheet Piles• Debris Flow Control Method Employing Steel Materials• Landslide Disaster Control Method with Cribbing Structure (Steel Cribbing)• Falling-stone Prevention and Slope Protection Work Using Steel Materials• Steel Structure Disaster Protection Center Building• High Tide and Tsunami Wave Control with Steel Materials• Water Shield Revetment Using Steel Piles and Steel Pipe Sheet Piles• School Facility Built with a Steel Structure (Multipurpose Institution)• Floating Disaster Management Base (Mega-float)• Fire Resistant Steel (FR)• Ultra-High-Strength Bolt
• H-beam with Fixed Outer Dimensions• Steels for Bridge High-performance Structure (SBHS)• Weathering Steel for Bridges

Request for Participation in Survey of
Steel Construction Today & Tomorrow
Steel Construction Today & Tomorrow, a joint periodical of the Japan Iron
and Steel Federation (JISF) and the Japanese Society of Steel
Construction, is published three times a year. It is the only English
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© 2014 The Japan Iron and Steel Federation
Edited byCommittee on Overseas Market Promotion, The Japan Iron and Steel Federation
Chairman (Editor): Keiji AndoP u b l i s h e d t h r e e t i m e s p e r y e a r, S T E E L C O N S T R U C T I O N TO D AY &TOMORROW is circulated to interested persons, companies and publicorganizations to promote a better understanding of steel products and theirapplication in the construction industry. Any part of this publication may be
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