No. 49 December 2016

STEEL CONSTRUCTIONTODAY & TOMORROW

http://www.jisf.or.jp/en/activity/sctt/index.html

Special Feature

Steel-structure
Technologies Conducive to
Securing Earthquake andTsunami Safety
1 Initiatives for Establishing

Steel-structure Technologies for
Earthquake and Tsunami Safety

7 Basic Particulars in Structural

Design of Tsunami Evacuation
Buildings

11 Improvement of Tsunami
Evacuation Facilities in
Sendai City

13 Framing-type and Simple

Multi-use Building-type
Tsunami Evacuation Facilities

Serial Article: Latest Design of Steel Buildings in Japan (1)Kunimi Town Office Building
15 New Restoration Center

Designed on Wood-Steel
Hybrid Structures

Back cover JISF Operations

Published Jointly by

The Japan Iron and Steel Federation
Japanese Society of Steel Construction

Special Feature: Steel-structure Technologies for Earthquake and Tsunami Safety

Steel-structure Technologies for
Earthquake and Tsunami Safety
Triggered by the Great East Japan Earthquakeof 2011, the Japan Iron and Steel Federation(JISF) prepared a brochure titled “Earthquake
and Tsunami Safety of Steel-structure Buildings and Application of Steel Products,” via
which JISF promotes proposals to society
pertaining to the construction of buildings
with enhanced earthquake and tsunami safety and to the application of structural steel
products that are useful in the construction of
those buildings.
In this special feature, national initiatives
to secure earthquake and tsunami safety andthe steel-structure technologies that support
safety are introduced in line with the objectives of the brochure, together with the design of tsunami evacuation buildings andtheir practical examples under the following
three themes on pages 1 to 14:• Initiatives for establishing steel-structuretechnologies to secure earthquake and tsunami safety• Basic particulars in the structural design oftsunami evacuation buildings
Practical
examples of tsunami evacuation fa•
cilities employing steel structures

Initiatives for Establishing Steelstructure Technologies for Earthquake
and Tsunami Safety
Committee on Building Construction and Committee on Overseas Market Promotion
The Japan Iron and Steel Federation

Earthquake Disasters and Initiatives for Establishing Steel-structure
Technologies to Secure Earthquake and Tsunami Safety
In Japan, steel structures account for about
30~40% of the total floor area in newbuilding construction starts by structural
method, showing an extremely high rateof steel-structure application compared tosteel-structure applications in foreign nations. When examining the floor area ofsteel-structure building construction starts
by building height, low- and medium-risebuildings with five stories or lower account for more than 90%. Given this situation, in order to build safe and reliabletowns, it is necessary to supply steel products that will help to secure the quality ofsteel-structure building frames and theirresultant seismic resistance.
Earthquake Damage to Steel
Structures and Promoted Countermeasures
In the Great Hanshin-Awaji Earthquake of 1995, while it can be said that
the New Seismic Design Code established in 1981 was practically proven

1 Steel Construction Today & Tomorrow December 2016valid, certain damage occurred in steel-frame structures, in which connection
fractures caused by inferior welding and other damages were found in several steel-structure buildings(Photo 1). The 2000 revision of the Building Stan-

Fracture of brace connection

Fracture of weld
at column end
due to inferior
welding

Fracture at beam
end that occurredprior to its sufﬁcient
deformation*

Fracture of anchor bolts of column base tocause dislocation of column

Photo 1 Damages of steel-frame structures in the Great Hanshin-Awaji Earthquake of 1995(*Photos: Report on Damages to Steel Building Structures in the 1995 Hanshin-Awaji Earthquake,
Steel Committee of Kinki Branch, Architectural Institute of Japan)**

dard Law of Japan, reflecting lessons
from the earthquake thus obtained, established new structural methods forjoints and connections and added new
specifications for steel applications.
In such situations, the Japanese steel
industry has successively put on the market new structural steel products: SN(new structure) standard steel products(steel products exclusively used for building construction), BCR (cold roll-formed
square steel tube) and BCP (cold pressformed square steel tube), high-performance TMCP (thermo-mechanical control process) steel and 590 N/mm2 steel
that meet the needs of seismic design;and H-shape with fixed outer dimension,
low-yield point steel and fire-resistantsteel that conform to diversifying building design methods (Fig. 1).
Then, in the Great East Japan Earthquake of 2011, steel structures suffereddamage due to both earthquakes and tsunamis. In the earthquake, while bucklingand fracturing of the bracing members
and damage to the joints of reinforcedconcrete members occurred, there wasno noteworthy observation of damage tocolumns, beams or other major structuralmembers. However, damage was foundin the ceilings, exterior members andother non-structural steel members usedin gymnasiums and theaters. To mitigate
such damage, a technical standard wasestablished that prevents the falling of
ceiling members.
The effects of the Great East Japan
Earthquake reached the Osaka Prefectural Government Sakishima Office Building, more than 700 km away from the disaster-stricken area of the earthquake. To
that end, examinations were promoted ofcountermeasure against long-period seismic motions.
Among the tsunami-induced damage of the Great East Japan Earthquake,movement, washout, overturning and other similar damages occurred in steel-structure buildings as well as in reinforcedconcrete and other buildings. Meanwhile,
many examples were observed of the steel
framing being left intact in spite of thecollapse and washout of exterior members
during the tsunami attack. (Refer to Photo 2) The lessons from this damage werereflected in the temporary guidelines forthe design of tsunami evacuation buildings prepared by the government agency,
on which additional studies are currently
being conducted.

Fig. 1 Production of Steel Frames and Development of New Steel Products in Japan
Steel-frame fabrication(million tons)

Crude steel production(million tons)

Rolled H-shapes
Extra-heavy H-shape
Tokachi-oki
Earthquake

Miyagiken-oki
Earthquake
New Seismic
Design CodeCold-formed square steel tube

Fire-resistant steel
TMCP (thermos-mechanicalcontrol process) steel forbuilding construction,
H-shape with ﬁxed outerdimension, structural
stainless steel, 590 N/mm2
high-strength steel
Structural stainless steel

Great
Hanshin-Awaji
Earthquake
Revision of
Building
Standard Law

SN standard steel products (steel
products for exclusive use forbuilding construction), BCR (cold rollformed square steel tube) and BCP(cold press-formed square steel tube)
Extra-heavy H-shapeemploying TMCP steel
BCP325T (high-performance coldpress-formed square steel tube)

Great EastJapan
Earthquake

H-SA700 (780 N/mm2 high-strength steel)

Ceiling members fell due to earthquakes.

While exterior members were washedout, the building framing remained intact.

While exterior members were washed out
and fracture of brace was found, thebuilding structure remained intact.

While studs caused deformation due to collisionof drifts, the building framing remained intact.

Photo 2 Earthquake- and tsunami-induced damages to steel-structure buildings in Great East Japan Earthquake(Photos: Surveys of Great East Japan Earthquake in 2011 (Preliminary Report)—National Institutefor Land and Infrastructure Management (Data No. 636), Ministry of Land, Infrastructure, Transport
and Tourism; and Building Research Institute (Data No. 132))

December 2016 Steel Construction Today & Tomorrow 2

Countermeasures against Disasters Forecasted to Occur in Future Great Earthquakes
In the future, several earthquakes are forecasted to occur in various regions of Japan. In order to mitigate the disasters that will
be caused by these earthquakes, the Central Disaster Management
Council of the Cabinet Office is promoting various response measures. The Council sets the protection of people’s lives as its first priority based on the lessons learned from the Great East Japan Earthquake. The Council also estimates the levels of seismic motions
and tsunamis that are forecasted to occur in future Nankai TroughEarthquake (Fig. 2), Tokyo Inland Earthquake and other mega-class
earthquakes and the scale of the resulting disasters in order to reexamine countermeasures against such mega-class earthquakes.
In a report on the huge Nankai Trough Earthquake that is forecasted to occur in the near future, it is reported that disaster-mitigation effects will be brought about by promoting various disaster-prevention
measures. Specifically, it is estimated that the number of completelydestroyed houses due to seismic vibrations will be reduced by about
40% in cases when the current rate of seismic-resistant housing construction at about 80% will be raised to 90%, and that the number ofdeaths due to tsunamis will be reduced by a maximum of about 90%
in cases when early tsunami evacuation is successfully completed
and tsunami evacuation buildings are effectively utilized.

Fig. 2 Profile of Strong Seismic Intensity Scales in the
Great Nankai Trough Earthquake Forecasted to
Occur in the Near Future
Seismic
intensity scale
7
6+
6−
5+
5−
4
3 or lower

Source: Examination Meeting on Great
Nankai Trough Earthquake Models(March 2012, Cabinet Ofﬁce)
Current estimate(Cabinet Ofﬁce,
2012)

Attacked area

Past estimate (Central Disaster Management Council, 2003)

Seismic intensity scale 6− or high About 71,000 km2
Seismic intensity scale 6 or high About 29,000 km
Seismic intensity scale 7
About 4,000 km2+

2

About 24,000 km2
About 6,000 km2
About 400 km2

Seismic Designs in the Building Standard Law of Japan and Mechanical
Properties Required for Steel Products
New Seismic Design CodeIn the New Seismic Design Code introduced in the Building Standard Law and enforced in 1981, seismic design is to be done bychecking seismic resistance of buildings according to two levels of seismic motions and scales (medium-scale earthquakes andgreat earthquakes). For medium-scale earthquakes (seismic intensity scale of 5− on the seven-stage seismic intensity scale of the Japan Meteorological Agency), the aim of the New Seismic Design
Code lies in that buildings do not suffer damage and that the structural members remain within their elastic range; for great earthquakes (seismic intensity scale of 6+), the aim of the New Seismic
Design Code lies in that building collapse is prevented in order toprotect human life while a certain level of damage is allowed tooccur in the structural members.
In particular, the New Seismic Design Code has been establishedbased on the idea that during great earthquakes, damage to steel
structural members is allowed (plasticization of structural mem-

Fig. 3 Energy Absorption during Great Earthquakes
In cases when the area of △OAB
and that of □OCDE are identical,
the seismic resistance or seismicenergy absorption is identical.

Yield
strength

The collapse of building isprevented by means of the energy
absorption when being attacked
by the earthquake.

Deformation

Fig. 4 Effects of Yield Point Deviation on Plasticization of Structural Members

Seismic
force

Pattern B

Collapse pattern A (design)

Pattern A
Pattern C
Seismic
force

When the deviationin yield point is wide:

Collapse pattern B

Plasticizing section
Deformation

3 Steel Construction Today & Tomorrow December 2016

Collapse pattern C

Fig. 5 Effects of Yield Ratio on Plastic Deformation Capacity of Structural Members
Steel product

Frame employing
steel product A

A: Steel product withhigh yield ratio

Frame employing
steel product B

Seismic
force
Stress
B: Steel product withlow yield ratio

As the yield ratio becomes lower,
the plasticizing area of steel products
becomes wider, and thus the plastic
deformation capacity of steel framing
becomes higher.

Strainbers) but the collapse of buildings is prevented by absorbing the seismic energy
through the ductile deformation of structural members (Fig. 3).
As regards steel-frame structures, specifications and detail design methods toprevent buckling and fracturing of joints
are incorporated in the New Seismic Design Code so that the plastic deformation
capacity originally possessed by the steel
framing can be fully demonstrated.
Seismic Design of Steel-frame Buildings and Steel Products Applied
The New Seismic Design Code provides
that the stress occurring in the steel members is designed to be maintained at a level lower than the yield point so that damage to the steel framing can be prevented
during small- and medium-scale earthquakes, and that during great earthquakes
building collapse is prevented by absorbing the seismic energy through the ductile
deformation of structural members.
In order to attain the goal, structural steel products are required to possessa yield point and tensile strength higher
than the commonly specified values. In
addition, the following performances are
required for steel products:
Firstly: Although the plasticizing parts
are designed to be located in the targetedzones at a design stage, there are cases inwhich unexpected members plasticize or
members that should plasticize remain
non-plasticized because of large deviations in the yield point of the steel products, and accordingly the framing does notenter into the designed stage. In order tosolve this problem, it is necessary to suppress the range of yield point deviation by
setting the upper limit for the yield point
as well as its lower limit. (Refer to Fig. 4)
Secondly: Generally the steel framing
is designed to able to treat with seismic
loads by utilizing the large deformation

Seismic
force
Deformation
capacity: Low

Deformation
capacity: High

Absorption of seismicenergy: Low

Absorption of seismicenergy: High

Plasticizing area

Table 1 Mechanical Properties in JIS G3136 Rolled Steels for Building Structures(Reference: Corresponding specifications in EN, ASTM and JIS)
Designation

Tensile strength Yield ratio Elongation (%)(%)(N/mm2)

Yield point or
strength

Charpy impact
energy (J)EN 10025-2
S355J0/J2(16＜t≦40 mm)
Min. 345(40＜t≦63 mm)(t≦100 mm)
Min. 335
Min. 470(63＜t≦80 mm)
Max. 630
Min. 325(80＜t≦100 mm)
Min. 315(t≦40 mm)
Min. 22(40＜t≦63 mm)
Min. 21(63＜t≦100 mm)
Min. 20*Proportional
test piece(S355J0)
0°C/Min. 27(S355J2)-20°C/Min. 27

JIS G3106
SM490B/C(16＜t≦40 mm)
Min. 315
Min. 490(40＜t≦100 mm) Max. 610
Min. 295(16＜t≦50 mm)
JIS＃1A: Min. 21(40 mm＜t)
JIS＃4: Min. 23(SM490B)
0°C/Min. 27(SM490C)
0°C/Min. 47

JIS G3136
SN490B/C*(16≦t≦40 mm)
Min. 325
Max. 445
Min. 490(40≦t≦100 mm) Max. 610
Min. 295
Max. 415(16＜t≦50 mm)
JIS＃1A: Min. 21(40 mm＜t)
JIS＃4: Min. 23

0°C/Min. 27

ASTM A572
Gr. 50Min. 345

Max. 80

Min. 450

ASTM 8”: Min. 18*Through-thickness property of Z25 is specified.

Table 2 Chemical Composition in JIS G3136 Rolled Steels for Building Structures(Reference: Corresponding specifications in EN, ASTM and JIS)
Designation
C

Si

Mn

Chemical composition (%)
P
S(S355J0)(S355J0)(16＜t≦40 mm)
EN 10025-2 Max. 0.20
Max. Max. Max. 0.03
Max. 0.03
S355J0/J2
0.55 1.60 (S355J2)(S355J2)(40 mm‹t)Max. 0.025 Max. 0.025
Max. 0.22
JIS G3106
SM490B/C(t≦50 mm)Max. 0.18
Max. Max. Max.
(50 mm＜t)0.55 1.65 0.035(B) Max. 0.20
(C) Max. 0.18

Max. 0.035

JIS G3136
SN490B/C(t≦50 mm)Max. 0.18(50 mm＜t)Max. 0.20(SN490B)
Max. Max. Max. 0.030
0.55 1.65 (SN490C)
Max. 0.020(SN490B)
Max. 0.015(SN490C)
Max. 0.008

Max. Max. Max.
0.40 1.35 0.040

Max. 0.050

ASTM A572 Max.
Gr. 50
0.23

N

Cu

Ceq**

(S355J0)(t≦30 mm)Max. 0.012 Max. Max. 0.45
0.55 (30＜t≦150 mm)(S355J2)
Max. 0.47(t≦40 mm)Max. 0.44(40 mm＜t)Max. 0.46**Weldability index
EN Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15
JIS Ceq=C+Mn/6+Si/24+Ni/40+Cr/5+Mo/4+V/14

December 2016 Steel Construction Today & Tomorrow 4

♦The concept mentioned above describes
the technical manner to secure the performances required for steel products
used in seismic design and for seismic-

Fig. 6 Seismic-resistant, Base-isolation and Response-control Structures
Seismic-resistant structures

Base-isolation structures

Response-control structures

Isolator
DamperResponse-control damper

Schematic diagram
Featurescapacity of steel members, but the plasticizing area of part of steel framing members becomes narrow in the case when theyield ratio (ratio of yield strength to tensile
strength) is high, and accordingly the sufficient and expected deformation capacity ofmembers and framing cannot be displayed.
To overcome this drawback, it is necessary
to set the upper limit for the yield ratio ofsteel products. (Refer to Fig. 5)
As a steel product that meets not only
the above-mentioned requirements but also has favorable weldability, the SN (newstructure) steel product was standardized
in JIS in 1994. It is specified as JIS G3136(Rolled Steels for Building Structures)that is applied exclusively for building
construction. The kind of steel products
available in SN steel products are plates,
strips, shapes and flat steels, for which
two levels of strength are set: 400 N/mm2
and 490 N/mm2. (Refer to Tables 1 and 2)

Vibration

Vibration

Vibration

During great earthquakes, theseismic energy is absorbedby allowing damage to thebuilding frame in order toprevent collapse of the entire
building from occurring.

Structures in which isolators (laminatedrubber) and dampers are installed
between the building structure and thefoundation structure. Vibrations of thebuilding structure during earthquakes
are greatly mitigated by making thebuilding’s natural period longer byintroducing isolators and by improving
the damping performance of thebuilding by the use of damping devices.

Structures in which responsecontrol dampers (bucklingrestraint braces etc.) areinstalled in the building
structure. Vibrations of thebuilding are mitigated anddamage to columns and beams
is also mitigated solely byabsorbing the seismic energy
by the use of dampers.

resistant structures as well. In addition toseismic-resistant structures, new aseismic structural types called base-isolation structures and response-control
structures have increasingly been ap-

plied. When applying such new structural types, it has become possible to widelyreduce the damage to structural members
such as columns and beams even during
great earthquakes. (Fig. 6)

Design Standards for Tsunami Evacuation Buildings and Proposal for Tsunamiresistant Steel Structures
Guidelines for Structural Designof Tsunami Evacuation Buildings
As regards tsunami evacuation buildings, the Guidelines concerning Tsunami Evacuation Buildings was presented by the Cabinet Office in 2005. Then,based on survey results of the disasters
that occurred in the Great East Japan
Earthquake of 2011, the technical standards for tsunami evacuation buildings
were established-temporary guidelines(Notification No. 1318 of the Ministry ofLand, Infrastructure, Transport and Tourism in 2011), and a separate attachment(New Guidelines: Notification No. 2570
of Director-General of Housing Bureau,
Ministry of Land, Infrastructure, Transport and Tourism in 2011).
In these technical standards, the restrictions by applicable structural typethat were limited to the reinforced-concrete structures and steel-reinforced concrete composite structures in the abovementioned Cabinet Office’s Guidelines
were abolished, and the performance
specifications required for tsunami evacuation buildings were clarified. These
performance specifications now coversteel structures in addition to reinforced5 Steel Construction Today & Tomorrow December 2016concrete structures and steel-reinforced
concrete composite structures.
Further, in computing the tsunami
wave pressure and force, a wave-force
reduction coefficient was introduced thatfacilitates the rational assessment of external forces conforming with the practical conditions of structural plans, suchas whether or not a barrier is installed in

the peripheral area of a building or if apilotis structure is adopted for the building. At the same time, in order to enforce
the stricter examinations of the structural calculations that are made to prevent
overturning and sliding of buildings during tsunamis, the buoyancy of buildings
was recommended to be taken into account. (Refer to Fig. 7)

Fig. 7 Structural Design Method for Tsunami Evacuation Buildings
Flow of structural design*

Calculation of tsunami wave pressure

Calculation of tsunami
wave pressure
Calculation of tsunamic
wave force
Calculation of shear
strength at each layer

Calculation of buoyancya) Buoyancy to
be applied in
the design ofbuilding structureb) Buoyance tobe applied in
the designof foundation

The tsunami wave pressure is
calculated as being the hydrostaticpressure at a height evaluatedby multiplying the design inundation
depth by the water depth coefﬁcient α.

Water depth coefﬁcient
Design inundation depth (m)Unit volume mass of water (t/m3)
Gravity acceleration (m/s2)

Tsunami wave pressure

Design of tsunamipressure-resistant member

Building

Designinundation depth

Examination of drifts
Examination of scouring
Examination of collapse
Examination of overturning
Examination of sliding
Design of foundation beam

Barriers reside in-between
Distance fromcoast of sea,river, etc.
Water depth
coefﬁcient α

No installationof barriers

500 m orlonger

500 m orshorterNotapplicable

1.5

2

3

*Examples of design of tsunami evacuation buildings based on the New Guidelines are published in the following website:
The Japan Building Disaster Prevention Association: Opening of “Commentary on Structural Requirements for Tsunami Evacuation Buildings and Other Structures”
http://www.kenchiku-bosai.or.jp/seismic/tsunami_text.html

Proposal of Tsunami-resistant
Steel Structures
To cope with emerging needs, the Japan Iron and Steel Federation is promoting proposals to construct various types
of facilities employing “New Structural System Buildings Employing Inno-

vative Structural Materials” that canwithstand huge tsunamis and were initially designed and developed with theaim of preventing damage to building
structures even when attacked by a greatearthquake of a seismic intensity scaleof 7 (Fig. 8). The intended applicationof “New Structural System Buildings”
ranges from town block facilities, restoration housing and distribution centers to
disaster-prevention bases to be built by
the use of the pilotis structures employing concrete-filled steel tubes (Fig. 9).

Fig. 8 “New Structural System Buildings Employing Innovative Structural Materials”
Important facilities on raised town block
In order to protect the building fromgreat earthquakes and huge tsunamis,the entire town block is raised, in which
the upper area accommodates
high-function administrative and reginaldisaster-prevention functions, and thelower area houses a parking lot andrental space

1) No damage even when attacked by anearthquake with a seismic intensity scale of 7
Avoiding plasticization of building framing by the use ofhigh-strength steel H-SA700 having a tensile strength twice thatof conventional steel and response-control mechanism as well
Maintaining the main structural section intact when attacked byan earthquake with a seismic intensity scale of 7 so as toprotect human life and to secure continued business operations
after experiencing a disaster••2) Structural planning to resist to huge tsunamis
Securing the structural safety against huge tsunamis and theirbackwashes by means of the “New Structural System Buildings”
Enhanced tsunami measures, reduced tsunami pressure byminimizing the column size and reduced number of columns
and raising an entire town block by the use of high-strength
steel framing••

Restoration housing on raised town block
Raised town block is developed using“New Structural System Buildings
Employing Innovative Structural
Materials,” in which the lower area
houses existing commercial andbusiness facilities as well as newly-located commercial facilities, and theupper area accommodates multi-storied residential buildings constructed
as they encircle a refuge square.
Distribution center
Distribution center with mixed
three-dimensional arrangement ofplants and ofﬁces capitalizing on highceiling heights and large spans andwith ﬂoors that are easily accessible bycars using two ramps3) Buildings with longer service life
Flexibility to allow future change in planning by adopting askeleton-inﬁll (SI) design, in which a building structure and its
exterior-interior structures and equipment are designed as
separate structures, as well as by adopting large spanning forframing structure
Easy restoration of damaged buildings by adopting theexterior/interior members and equipment design in which thesemembers and equipment are designed to be renewed••

4) Resources savings
Realization of environmentally-friendly buildings by adopting
high strength steel, which can lead to the reduction in the total
weight of steel framing and in CO2 emissions
Easy reuse and recycling of steel products by adopting SI design••

Fig. 9 Proposal of Tsunami Evacuation Facilities Employing Steel Structures
Tsunami evacuation towerof lightweight• Realizationbuilding frame with high•seismic and tsunami
resistance that is enabledby the use of square steel
tube-H shape structures
Tower framing, conﬁguration and height that
conform to tsunami height(inundation depth) and thenumber of evacuees

Building serving as disaster-prevention building
a pilotis structure with a• Adopting
height surpassing the assumed•••

Bucklingrestraint
tsunami height to avoid tsunamis thrust brace
Adopting CFT columns with high yieldstrength and rigidity
Adopting response-control structures inwhich buckling-restraint braces are
installed so as to improve the seismic-resistant performance of buildings
Lightweight buildings by the use of steel Concretestructures that can result in less seismic ﬁlled steel
tube structure
force applied to pilotis structures

Responsecontrol
structure
Pilotisstructure“Building National Resilience” Initiatives and the Japanese Steel Industry

Many great earthquakes such as the Great
East Japan Earthquake of 2011 have occurred in Japan, causing serious damages nationwide. Based on the experienceof these earthquakes, the Japan Iron andSteel Federation has promoted surveys
and research on steel structures conducive
to securing earthquake and tsunami safety under tie-ups with related industrial or-

ganizations. As seen in serious accidents
represented by the ceiling collapse on the
Chuo Expressway in December 2012, social infrastructures in Japan are facing the
problem of ongoing superannuation. In order to meet such situations, the “Building
National Resilience” initiative is becoming a pressing task for Japan.
By capitalizing on the steel-structuretechnologies thus far fostered in the Japanese steel industry and enhancing cooperative relations with related organizations, theJapan Iron and Steel Federation is promoting
contributions to the establishment of countermeasures against earthquake, tsunami andother natural disasters and to the “Building
National Resilience” initiatives being tackled by national and local governments. ￭December 2016 Steel Construction Today & Tomorrow 6

Special Feature: Steel-structure Technologies for Earthquake and Tsunami Safety

Basic Particulars in Structural Designof Tsunami Evacuation Buildings
by Kenzo Taga, Professor, Kobe University
The Great East Japan Earthquake that occurred March 11, 2011 was a mega earthquake with a magnitude of 9.0.
While the damage to buildings due toseismic motion was comparatively little, most of the damage to human lifeand buildings was brought about by thetsunamis, which clearly displayed theirdestructive and terror-inducing power. Steel-structure buildings suffered diverse damages from the tsunamis-collapse, overturning, scouring, the loss ofexterior and interior members due to water flow and many others (Photos 1~5).
Triggered by these damages, the Institute of Industrial Science of The University of Tokyo and the Building ResearchInstitute began surveys and research on
tsunami loads, which led to a working

out of temporary guidelines for the design of tsunami evacuation buildings inNovember 2011 by the Ministry of Land,
Infrastructure, Transport and Tourism.
These were the Temporary Guidelines
concerning Structural Requirements for
Tsunami Evacuation Buildings Basedon Tsunami-induced Building Damages in the Great East Japan Earthquake(New Guidelines), a separate attachment of Additional Knowledge (Technical Advice) concerning Design Methods for Buildings That Are Structurally
Safe against Tsunamis1). Information on
the design of tsunami evacuation buildings thus released has been given to local
governments via the Ministry.
In the Guidelines concerning Tsunami Evacuation Buildings (released by the

Photo 1 Steel-structure building destroyed bytsunamis

Photo 3 Building that overturned due to tsunamis

Kenzo Taga: After graduating from Osaka University, he entered Nikken Sekkei Ltd. in 1979. He assumed his current position as Professor, Graduate
School of Engineering, Kobe University in 2011.
Among the major works in which he was involved
are Terminal Building of Kansai International
Airport, Kobe Daimaru Department Store, Kansai
Electric Power Building and Osaka Lawyers’ Hall.

Cabinet Office in June 2005), the tsunami load (the force and pressure working
on a building due to tsunami) is uniformly set at the hydrostatic pressure threetimes the inundation depth. However, it
has recently been assessed that the tsunami load is reduced by whether or not
shelter exists and that it differs depending on the distance from the coast or ariver, and thus the tsunami load thereby
established has rationally been modified.
Tsunami Loads
The horizontal load adopted in the structural design of buildings is generallycomposed of the seismic load and thewind load. At first, the feature of tsunami loads is examined in comparison withthat of seismic load and wind load.

Photo 5 Steel-structure building where exterior
and interior members were washedaway by tsunamis

Photo 2 Steel-structure building with which drifts(ship) collided

7 Steel Construction Today & Tomorrow December 2016

Photo 4 Building that inclined due to scouring• Any seismic, wind or tsunami load isa dynamic loading effect, and in structural design, they are substituted for theequivalent static load to allow simple
design work.
• The seismic force is an inertial force
and is largely affected by the mass. On
the other hand, it can be said that thewind and the tsunami, called the liquid
force, are largely affected by the sizeof the tsunami pressure-receiving area
and the configuration of the buildings.
Accordingly, when the tsunami load is
examined in a comparison of the horizontal load that is dominant for lowand medium-rise buildings, it is easily
assumed that the effect of the tsunami
load will become larger for lightweightsteel structures than for heavyweightreinforced-concrete structures. As
the design inundation depth becomesdeeper, the effect of the horizontal load
due to buoyancy and tsunamis on abuilding becomes larger. To cope withsuch a trend, there seem to be increasing cases in which non-tsunami pressure-resistant members (members thatare subjected directly to tsunami wave
pressure and are expected to break) arearranged as exterior members and a pilotis structure is adopted as a practicalmeasure to mitigate the effect of tsunami loads.
• As the story height increases, the seismic load and the wind load become
high. But the tsunami load is assessedusing the equivalent hydrostatic pressure that becomes larger as the story
height lowers. If the total horizontal
load is identical, it can be understoodthat the overturning moment due to thetsunami load is relatively small. In cases when a pilotis structure is adopted at
the first-story, it can be conceived thatthe tsunami load can greatly be reduced
and the pilotis structure can efficiently
work as a countermeasure against sliding. In this way, effective and appropriate measures to mitigate the tsunami
load can be taken by understanding thefeature of the height-direction tsunami
load distribution profile. Meanwhile,as regards the effect of drifts, it is necessary to make separate examinations.
In the following, an outline of a quantitative assessment of tsunami loads isshown by quoting from the New Guidelines.

Fig. 1 Tsunami Wave Pressure
Building
Designinundation depth

Fig. 2 Tsunami Wave Force
Building

Designinundation depth• Tsunami Wave Pressures

The tsunami wave pressure shall be thehydrostatic pressure distribution obtained by multiplying the design inundation depth by the water depth coefficienta, and it is specified that the numericalvalue 3 conventionally applied is basically adopted as the water depth coefficient; the numerical value 2 can be adopted in cases where an effective shelter
is installed; and the value 1.5 can be adopted in cases where the structure is separated from the coast or a river by 500 m
or more. (Refer to Fig. 1)
From the standpoint of conveniencefor design work, it is specified that thetsunami load is assessed by use of theequivalent hydrostatic pressure. Meanwhile, in the Recommendations for
Loads on Buildings (2015) of the Architectural Institute of Japan, a chapter pertaining to the tsunami load is newly provided where the tsunami load that works
on a building is classified into three conditions depending on the time-dependentchange in which the tsunami works on
the building: tsunami load on the tsunami tip section, that on the non-tip section, and that at the still water stage, andthe method is shown in which the tsunami load is calculated from the inundation
depth and the velocity in these three conditions.
• Tsunami Wave Forces
The tsunami wave force is calculated byintegrating the tsunamic wave pressure
on the tsunami wave force-receiving area.
The running-direction tsunami wave
force for use for structural design iscalculated by assuming that the tsunami wave pressure shown in the tsunami wave pressure calculation formula simultaneously occurs and integrating thetsunamic wave pressure on the tsunami
wave force-receiving area. (Refer to Fig.
2)
• Reduction of Tsunami Wave
Force due to Openings
In cases when openings are provided thatare composed of structural members tobe destroyed by the tsunami wave pressure (non-tsunami pressure-resistantmembers), the tsunami wave pressure
can be reduced to a range that does not
fall short of 70% of the tsunami wave
force calculated in the case of no provision of openings.

December 2016 Steel Construction Today & Tomorrow 8• Effect of a Pilotis Structure on

Reduction of Tsunami Loads
As regards a pilotis structure, the tsunami wave loads can be calculated on thecondition that the tsunami wave pressure
works only on columns, beams and other tsunami pressure-resistant members of
the pilotis structure.
• Directions of Tsunami Horizontal Loads
It is assumed that the horizontal load oftsunamis occurs from every direction.
However, in the case when the running
direction of tsunamis can be assumed
from the forecasted inundation distribution profile obtained by means of simulations and the configuration of coastallines, this shall not apply to the abovementioned assumption. Further, depending on the actual tsunami conditions, thetsunami horizontal load is examined bytaking into account the effect of tsunami
backwashes.
• Buoyancy
While the buoyancy generated by tsunamis basically corresponds to the buoyancy of the volume of the building section that is inundated, it can be calculated
by taking into account the water flowing-in from the opening in conformity
with the rise of the water level. Meanwhile, in cases when the flowing-in oftsunamis into a building’s interior is unclear, it is accepted as desirable that thesafer design be made by taking into account at the stage of design of structural
framings the buoyancy that is calculatedon the condition that water will flow into the building’s interior, and at the stageof discussion about the overturning andsliding of buildings the buoyancy that
corresponds to the submerged building
volume (including the volume of the inner space). (Refer to Fig. 3)

Basic Concepts for Structural
Design of Tsunami Evacuation
Buildings• Design of Tsunami Pressure-resistant and Non-tsunami Pressure-resistant Members
In the structural planning of buildings resistant to tsunami load, the tsunami pressure-resistant members (members thatare subjected directly to tsunami wave
pressure and designed not to break) andthe non-tsunami pressure-resistant members (members that are subjected directly to tsunami wave pressure and expected to break) are clearly distinguishedfrom each other, and then arranged in thebuilding structure.
The strength of tsunami pressure-resistant members is designed so that thestrength does not reach the ultimate
strength even when attacked by tsunamis
and that the tsunami wave force received
by the member can surely been transferred to the structural framing. Further,care should be taken to the water cuttingoff performance of each member if theneed arises.
It is tolerated that non-tsunami pressure-resistant members can break withno damage to the structural framing.
• Design of Structural Framing
It is confirmed that the horizontal
strength of the structural framing exceeds the horizontal load of tsunamis in
every direction and at each story. Further, the strength of tsunami pressureresistant members that also serve as themember of structural framing is designed
so that the strength does not reach the ultimate strength vis-à-vis not only the tsunami load but also the load that combinesother loads when the need arises.

• Examinations of Overturning

and Sliding
It is confirmed that the building will not
overturn or slide due to the tsunami load,taking into account its buoyancy anddead weight (for the piling foundation,
the pull-out force does not surpass thepull-out resistance.)• Scouring
A pile foundation is adopted by taking
into account the occurrence of scouring,or in the case of adopting a spread foundation, measures are taken that prevent
tilting of the foundation due to scouring.
• Collision of Drifts
Taking into account the damage that occurs due to the collision of drifts, it isconfirmed that the structurally importantsections do not collapse due to the collision of drifts, or that, even if some columns and bearing walls are damaged dueto the collision of drifts, the entire building structure does not collapse.
Research is underway on the assessment of the collision force of drifts onbuildings, and thus it is currently difficult
to precisely calculate the collision forceof every kind of drift. Further, in order
to confirm that a building does not collapse due to the collision of drifts, it will
be necessary to assume not only the kind,amount, size, configuration, weight, collision speed and collision direction of thedrifts that will collide with the building
but also the building section that is collided by drifts; but in most cases, it will
generally be difficult to assume such diverse collision factors. To these ends, itwill be important to construct buildings
with sufficient redundancy so that an entire building structure does not easilycollapse by separately adding a structurethat protects the building periphery section or even when the peripheral section
causes local collapse. (Refer to Fig. 4)

Fig. 3 Concept for Buoyancy
Design inundation depth
Water ﬂowing-in
Slab

Slab

Girder

Buoyancy
Accumulated air

Girder

Buoyancy
In the case of water ﬂowing-in
9 Steel Construction Today & Tomorrow December 2016

In the case of no water ﬂowing-inDirections in Tsunami-resistant
Design Employing Steel Structures
The ratio of tsunami load to horizontal
strength, required in seismic design, ishighly likely to become larger for a lightweight steel structure than for a heavyweight reinforced-concrete structure.
The essential factor in the design of asteel-structure tsunami evacuation building is that such a building be appropriately planned and designed after gaining
a full understanding of the features peculiar to the lightweight steel structures
mentioned above.
• Horizontal ResistanceIn seismic design in Japan, the allowablestress design for temporary loading is
adopted for a medium-scale earthquake,and the ultimate strength design for agreat earthquake. In this way, both elastic design and elasto-plastic design are
generally adopted in the seismic design
depending on the load level. The elastic
design means that the building structure
returns to its original state with no damage after an earthquake, and the elastoplastic design allows such conditions as
the occurrence of damage and residual
deformation in a building.
In cases when the plastic design is adopted to treat tsunamis, there is a highpossibility that structural safety after anearthquake and against aftershocks cannot be retained. To remedy such a situation, one effective countermeasure isthat the horizontal load-bearing capacity of a building is raised by applying ultra-high strength steel products in orderto improve the steel-structure building’s
resistance to the seismic load and the tsunami load. (Refer to Fig. 5)• Buoyancy and Measures for
the Overturning and Sliding of
Buildings
If the water does not penetrate into thebuilding, the buoyancy that corresponds
to the building volume will work on thebuilding. Further, in cases when a building is inundated through its exterior walland open sections, if air accumulates inthe section surrounded by beams andslabs, the buoyancy corresponding to
the accumulated air works on the building. To this end, in contrast to a heavyweight reinforced-concrete structure, alightweight steel structure is apt to float,
and thus overturning and sliding are likely to occur.
To improve such a situation, it is feasible that the inundation level of the building is structured using the pilotis systemand that the building finishing members are forcibly collapsed to cause inundation in order to reduce the buoyancy
as much as possible. It has been known

Fig. 4 Collision of Drifts

from past earthquake damage examples
that, when the rigidity and strength of apilotis structure become insufficient interms of seismic design, the building suffers concentrated damages. Accordingly,
due care should be paid to the adoptionof a pilotis structure in seismic design.
In cases when a pilotis structure is adopted as a countermeasure against tsunamis, the most important precondition isof course to secure sufficient seismic resistance.
When applying a steel structure in
the construction of tsunami evacuationbuildings, if the column bases and connections are appropriately designed, theadvantageous toughness peculiar to steel
products is fully demonstrated. In addition, steel structural members are slim,
and in terms of the tsunami pressurereceiving area, an important element inseismic resistance, the area of steel bracing is smaller than that of a reinforcedconcrete bearing wall, which allows the
reduction of the tsunami load itself. To
this end, it is feasible that steel pilotis
structures effective in tsunami-resistant
structural design are easily put into practical use.
As far as the overturning and slidingof buildings due to tsunamis are concerned, a countermeasure can be conceived in which steel piles are used. As ameasure to prevent overturning in particular, it will be appropriate to adopt steel
piles having high pull-out resistance. ￭Reference
1) Additional Knowledge (Technical Advice)concerning Design Methods for Buildings That Are Structurally Safe against
Tsunamis: Notification No. 2570 of Director-General of Housing Bureau, Ministry of Land, Infrastructure, Transport
and Tourism (November 17, 2011)(Separate attachment)
Temporary Guidelines concerning Structural Requirements for Tsunami Evacuation Buildings Based on Tsunami-induced Building Damages in the Great
East Japan Earthquake (New Guidelines)

Fig. 5 Image of Application of Ultra-high Strength Steel

Ultra-high strength steel

December 2016 Steel Construction Today & Tomorrow 10

Special Feature: Steel-structure Technologies for Earthquake and Tsunami Safety

Improvement of Tsunami Evacuation
Facilities in Sendai City
by Masaru Fukurai
Disaster Prevention Planning Section, City of Sendai Crisis Management Department
Huge Tsunamis Attack Sendai City
In the Great East Japan Earthquake of 2011,huge tsunamis with a maximum height of
7.1 m attacked the coastal area of Sendai
City in Miyagi Prefecture. They inundated
an area of more than 45 km2 and caused aheavy loss of life amounting to more than
700 victims (Photos 1 and 2).
Having learned from such tsunami disasters, the Sendai City Office has beentasked with the mission “how to protect
human life from tsunamis,” setting it asa major pillar of the city’s reconstruction
plan. Under the concept of a multi-faceted
defense, diverse countermeasures against
tsunamis are being promoted in Sendai
City. Among the hardware measures are:
• Improvement of coastal and river banks
and of coastal disaster-prevention forests• Measures to control tsunami disasters
by raising road levels• Improvement of tsunami evacuation towers and other evacuation places and evacuation routes so that citizens can smoothly evacuate from tsunami attacks• Mass movement of residential areas witha high risk of suffering a tsunami disasterIn addition, an evacuation plan by area has been worked out, and repeatedtraining exercises for tsunami evacuation have been implemented (Photo 3),
thereby promoting comprehensive coun-

termeasures against tsunamis in terms ofboth hardware and software.
Building Plan for Tsunami Evacuation Facilities in Sendai City
As one of these tsunami countermeasures,
the Sendai City Office plans to build newtsunami evacuation facilities in 13 different locations so that citizens living in the
coastal area can escape a tsunami by foot.
Specifically, the plans call for the construction of tsunami evacuation towers at 6 sites,
evacuation buildings attached to the volunteer fire corps branch station at 5 sites, andevacuation stairs to the rooftops of 2 existing
primary and junior high-school buildings.
In the improvement of these new tsunami evacuation facilities, it was necessary to take diverse factors into account-the wide flat area and relative
unavailability of high-rise buildings to
be used for evacuation peculiar to Sendai City, and the time required for the tsunamis to arrive. To that end, a committee
has been established that is comprised oflearned persons and representatives of theresidents in coastal areas. A full examination has been made regarding evacuation
methods and evacuation facility requirements that would allow for the quick andsure evacuation of citizens, which has led
to the establishment of the tsunami evac-

Photo 1 In the Great East Japan Earthquake, huge damage was brought
about by tsunamis, not by seismic forces.
11 Steel Construction Today & Tomorrow December 2016

Location of Sendai City

SendaiTokyo

Seismic intensity scale
in Great East Japan
Earthquake (2011)
Source: Japan Meteorological
Agency website

7
6+
6−
5+
5−
4
3
2
1

uation facility standards of Sendai City.
Further, exchanges of opinion with local residents have repeatedly been made,and the proposed opinions have been
carefully examined one by one. The results thus obtained have been fully reflected in the improvements of the tsunami evacuation facilities-installationof exterior walls as a countermeasureagainst cold weather and the provisionof ramps to be used for aged persons andwheelchair users to safely evacuate.

Photo 2 Tsunami attacked condition at the Arahama Primary School,
where 350 people were forced to evacuatePhoto 3 Tsunami evacuation training for citizens has been repeatedly implemented in Sendai City.

Further, at both sides of the room, retractable benches have been arranged to meetthe need for a long-term stay. As countermeasures against power failure, it is
now possible to generate electricity employing solar power panels installed on
the rooftop and a cassette gas-type power generator.
In order to meet the need for a stay of
about 24 hours, emergency provisions,drinking water, gas stoves, blankets, simple toilet devices and other necessities
have been stocked in the tower. In addition, in order to secure communications
during a disaster, an emergency wirelessset for use for disaster-prevention administration has been installed.
Tsunami Evacuation Tower Gains
Much Attention
A visit was made to the Nakano 5-chome
Tsunami Evacuation Tower as part of astudy tour during the UN World Confer-ence on Disaster Risk Reduction (2015
Sendai Japan) held in March 2015 (Photo 5). The tower has attracted much attention not only in Japan but abroad, and many interested persons visit the tower for
observation. The Sendai City Office not
only introduces this tower as an effectivemeans to prevent tsunami disasters thatwas developed based on lessons learned
from the Great East Japan Earthquake, butalso is highlighting the importance of tsunami evacuation during earthquakes.
		♦♦♦Firmly establishing the Nakano 5-chome
Tsunami Evacuation Tower as a landmark
for tsunami evacuation, we at the Sendai City Office are promoting measures todisseminate an alarming message regarding tsunami disasters-they are likely tooccur again in the future and many more
lives must be protected from future tsunami attacks.
￭

Fig. 1 Elevation of Nakano 5-chome Tsunami Evacuation Tower
Substructure Superstructure
Evacuation space

Full-scale Tsunami Evacuation Tower
The Nakano 5-chome Tsunami Evacuation Tower, the first of its kind constructedin Sendai City, is a two-story steel-structure tower. It has a total floor area of 398
m2, is equipped with exterior stairways
and ramps and is capable of accommodating 300 persons during tsunami evacuation in the interior section of the second floor (6.6 m aboveground) and on therooftop (9.9 m aboveground). The tower
is designed as a rigid structure that canwithstand ground liquefaction caused byearthquakes, the wave force of tsunamis
and the collision of tsunami drifts. (Refer
to Photo 4 and Fig. 1)
The second-floor evacuation space isdesigned as an enclosed floor surrounded with exterior walls and covered witha roof, taking into account the possibility of hypothermia during intense cold,
thus containing necessary countermeasures against the cold. Inside the room,
partitioned accordion curtains have been
installed so that privacy can be assured.

Photo 5 A study tour to the Nakano 5-chome Tsunami Evacuation
Tower was conducted during the UN World Conference
on Disaster Risk Reduction (2015 Sendai Japan)

Rooftop
9.9 m
Second ﬂoor (also serving as a warehouse) Design tsunami
wave pressure
6.6 m
Tsunami inundation depth
2.0 m
58.9 kN/m2

26.4 mPhoto 4 Two-story steel structure Nakano 5-chome Tsunami Evacuation Tower developed and constructed in Sendai City
December 2016 Steel Construction Today & Tomorrow 12

Special Feature: Steel-structure Technologies for Earthquake and Tsunami Safety

Framing-type and Simple Multi-use
Building-type Tsunami Evacuation
Facilities
Nippon Steel & Sumikin Metal Products Co., Ltd.
In Japan, huge earthquakes such as theTokai Earthquake, Tonankai Earthquake
and Nankai Earthquake are forecasted tooccur in the near future. Given this situation, improvements of tsunami evacuation facilities started in 2004 in Shizuoka
Prefecture, Mie Prefecture, Wakayama
Prefecture, Tokushima Prefecture andother prefectures that are likely to suffer tsunamis associated with such largescale earthquakes. Further, triggered by
the Great East Japan Earthquake of 2011,
improvements of tsunami evacuation facilities are being promoted nationwide.
Tsunami Evacuation Facility of
the Steel Tube Column-H Shape
Structure TypeIn the Great East Japan Earthquake, theSendai Works of Nippon Steel & Sumikin
Metal Products Co., Ltd. was attacked bytsunamis, and it took nearly one year toresume operations of the tsunami-damaged works. During this process, employees proposed to construct a full-scaletsunami evacuation facility at the works.
To this end, based on the latest national design guidelines for tsunami evacuation facilities-Additional Knowledge(Technical Advice) concerning Design
Methods for Buildings That Are Structurally Safe against Tsunamis-and therequest of employees who experienced
the tsunamis, the company has promoted the development of tsunami evacuation towers. The latest development is atsunami evacuation tower that uses columns employing square steel tubes andbeams employing H-shapes (Photo 1) for
its structural members; members that remained intact even after being subjectedto the attack of past tsunamis.
Since 2012, improvements have been
made to the tsunami evacuation towers
based on the tower thus far developed,
and this has led to the construction of a
total of 20 towers (including a tower installed at the company’s Sendai Works)
as of March 2016.
13 Steel Construction Today & Tomorrow December 2016

Safety and Security Required forTsunami Evacuation Towers
Needless to say, it is necessary for tsunami evacuation towers to possess a highlevel of structural safety that can indisputably resist both seismic motions andtsunamis. Specifically, it is required forthese towers to provide not only measures to treat the common horizontal
force (wave force) of tsunamis but alsocountermeasures against drifts, overturning, sliding and scouring that are peculiar
to tsunami. That is, it is important to secure the safety of both the abovegroundstructure and the underground structure.
Further, from the aspect of tower safety, it is indispensable to provide suchmeasures as:• Rapid, sure evacuation of evacuees fromthe ground to the evacuation floor
Preventionof evacuees falling from the•evacuation floor• Responsiveness to the receipt of unforeseen evacuees
In addition, once people evacuatefrom a tsunami, it is highly likely thatthey will need to stay in the evacuation
tower for a certain period, during which
due care must be paid to security and tosafety, including:• Securing protection against rain/windand heat/cold during their stay
Mitigating
uneasiness about darkness at•night and loss of communications• Securing water and food stockpiles
Framing-type and Multi-use Tsunami Evacuation Facilities
Various types of tsunami evacuation facilities can be constructed dependingon the number, age and sex of the target evacuees, site conditions, residents’requests, construction budget and other terms. When examining the recent record of construction, tsunami evacuation
facilities are undergoing the following
evolution, along with an expansion of
the area requiring those evacuation facilities and an increasing need for more effective utilization:• Framing-type evacuation towers without a roof or walls to be built in warm
areas→Evacuation towers with roof andwalls to be fixedly built in cold areasin Tohoku and other regions→Simple,
multi-use evacuation buildings to be built
based on the evacuation tower
Because the Nakano 5-chome Tsunami Evacuation Tower that was completed in Sendai City and introduced on
the previous pages is a tsunami evacuation tower with roof and walls, three examples of representative framing-typetsunami evacuation towers and simple,
multi-use tsunami evacuation buildings
are introduced in the following:
Steel tube column-H-shape structurein which square steel tube is used forcolumn and H-shape for beam• Mihominami Tsunami Evacuation Tower (Framing Type)

This tower was constructed in Miho, Shizuoka Prefecture. It
is a two-story steel-structure tsunami evacuation tower having an evacuation floor of 370 m2 on its roof where about 740
persons can evacuate. Because the construction site is located in a park with ponds and trees and over underground piping, the tower is designed as three independent structures: astructure that supports the evacuation space, a structure that
supports the stairway and a structure that supports the slope.
The square steel tubes used for the columns are 300×300 mm
with a plate thickness of 19 mm, their lower limit for yield
point is 295 N/mm2 and they are filled with concrete. The
tsunami evacuation tower is open and used as an observation tower in normal times.
Design condition

Accommodation capacity

Design inundation depth 3.0 m Evacuation area
Water depth coefficient 3.0
Accommodation

370 m2740 persons• Sonochiku Tsunami Evacuation Tower (Framing Type)

This tower was constructed in Gobo, Wakayama Prefecture.
It is a three-story steel-structure tsunami evacuation tower having an evacuation floor of 450 m2 on the third story
and roof where about 800 persons can evacuate. Taking into account the site configuration, the tower is designed as astructure having an octagonal-shape plane configuration, andthe slope is arranged around the periphery. The square steel
tubes used for the columns are 450×450 mm with a plate
thickness of 22 mm, and have a lower limit for yield point of
295 N/mm2. The tower is designed so that the evacuees canapproach the tower via the park and the neighboring road.

Design condition

Accommodation capacity

Design inundation depth 5.0 m Evacuation area
Water depth coefficient 3.0
Accommodation

450 m2800 persons• Sangochiku Tsunami Disaster-prevention Center (Simple, Multi-use Building Type)

This building was constructed in Toyohashi, Aichi Prefecture. It is a two-story steel-structure tsunami evacuation building having an evacuation floor of 240 m2 on the roof where
about 300 persons can evacuate. A parking lot is provided
on the first story, and a living area on the second story. The
building is designed so that it can be used as an assembly
hall during normal times and its rooftop can be used as anevacuation site during emergencies. The square steel tubes
used for the columns are 300×300 mm with a plate thickness of 12 mm, for which a high-strength steel product having a lower limit for yield point of 365 N/mm2 is adopted.
Design condition

Accommodation capacity

Design inundation depth 1.2 m Evacuation area
Water depth coefficient 1.5
Accommodation

240 m2300 persons

December 2016 Steel Construction Today & Tomorrow 14

Serial Article: Latest Design of Steel Buildings in Japan (1)Kunimi Town Office Building-New Restoration Center Designed on
Wood-Steel Hybrid StructuresJR East Design Corporation
The new Kunimi Town Office Building in Fukushima Prefecture is the firstof the local government office buildingsthat were damaged by the Great East Japan Earthquake (2011) to be rebuilt.
This new building, which serves as theearthquake disaster restoration center for
mountain-encircled Kunimi Town, contains all the elements for reconstructionthat were desired by the town’s citizens
and those involved in construction. It isa bright, warm, relaxing space that was
brought about by the extensive use of local wood and that capitalized on “local
wood-laminated hybrid member of thesteel product built-in type.”

Town Office Building That Merges
into Surrounding Landscaping
The old Kunimi Town Office Building
was completely demolished and rendered unserviceable by the Great East
Japan Earthquake. Since then, the Cultural Hall of Kunimi Town has been substituted as a temporary replacement of
the town office building, which required
urgent new construction. The site chosen for construction of the new building
is open and level and commands a beautiful view of the surrounding mountain
range. To this end, the new building was
designed so that it shows an architectural image of the forest that blends with thesurrounding beautiful scenery; further
the architectural designers aimed at realizing a town office building that offers agentle atmosphere and is encircled withwood that is locally produced for local
consumption. (Refer to Photo 1)
Meanwhile, legal requirements callfor the construction of new town officebuildings to be fire-proof, and this resulted in a careful examination of how to usewood compatibly in fire-proof buildings.
At this stage, JR East Design Corporation noticed that it had previously employed a structural design method thatuses wood for the fire protection of steel
frames. And, based on this, it designed

Photo 1 New Kunimi Town Office Building built capitalizing on the strengths peculiar to wood and steel
15 Steel Construction Today & Tomorrow December 2016

the frame of the new building using thismethod while at the same time aiming
to realize a building space with exposed
framing that is extensively covered withwood. Further, the building was structurally integrated into the surrounding
landscape by promoting a structural feature-the building’s wood-covered inte-

Fig. 1 Plan and Section of Kunimi Town Office Building
Reception counter

Ofﬁce

Multi-purposeroom

Reception counter“Japanese redpine” plaza

Room for consultation
with citizens
Reception counter
Room forbreast-feed baby

Reception counter

Structural core

1st-ﬂoor plan

Section of application of wood-laminatedhybrid member of the steel product built-in type
ColumnBeamAssembly hallCommittee meeting room
Large-size conference
room
Ofﬁce

“Japanese redpine” plaza

Ofﬁce
Ofﬁce

Parking lot

SectionFig. 2 Wood-laminated Hybrid Member of the Steel Product Builtin Type (Column and Beam)rior space could be seen from the outside
through the glass façade.
To this end, the goal targeted by these
design approaches was to “realize a town
office building that would serve as a sitewhere many citizens could get together.”Realization of a Wood-based
Space with Built-in Steel Frames
The town office building has a rectangular 55×20 m shape. Two rows of columns
are installed in the longitudinal direction of the peripheral area of the building. In the center section, the columns
are arranged at a span of 13 m, whichallows provision in the 1st and 2nd stories of a spacious office space with flexible options for use. Reception countersand small rooms are arranged in the sections sandwiched by the two rows of columns, which are called “veranda zones
in contrast to the large area of the center
section. Located in the large space of the
3rd story is an assembly hall and in thenorth-side veranda zone an observatory
lobby is arranged. (Refer to Fig. 1)
While the space appears to be a woodframed structure, it is actually structuredby the use of steel framing with woodframing used as fire protection for the
steel. Specifically, the building frame
is composed of wood-laminated hybrid
member of the steel product built-in typein which the wood members are laminated to the steel members as fire-proofing
materials. These fire protection mem-

Burning-suppression member(Locally-produced larch tree-laminated member)
Steel frame
Connection cover(Locally-produced larch treelaminated member)Fire protection for connection(Wrapping ﬁre protection)
Connection cover(Locally-produced larch treelaminated member)
Burning-suppression member(Locally-produced larch treelaminated member)
Steel frame

Column-beam connection:
Shop covering of laminated member

Photo 2 Wood-laminated hybrid member of the steel product built-in type

December 2016 Steel Construction Today & Tomorrow 16

bers have obtained approval as structural members from the Ministry of Infrastructure, Land, Transport and Tourism.
With this method of fire protection, thewood laminated members function to
suppress burning of the steel framing.

That is, the wood fire protection suppresses the rise of the temperature in thesteel framing during a fire, and when afire is extinguished, the wood fire protection protects the steel framing from thefire due to its self-extinguishing prop-

erty. Laminated Japanese larch trees areused in the burning suppression members. H-shape steel products (300×300mm) are applied for the columns of thewood-steel hybrid sections. (Refer to
Photo 2 and Fig. 2)
Stairways-Structures of Steel Design
While the warmth offered by wood is
pursued in the design of the town office building, the application of steel ishighlighted in the stairway of the atrium and in the stairway to the 3rd-story
observation lobby. Although it is troublesome to structurally highlight theapplication of steel, it can clearly beseen in the stairway sections. In other words, the stairways are exactly ofsteel design.
As imaged in the architectural design, diverse measures were incorporated so that the heavy steel of the stairways looks as light as possible. While
H-shape steel members are used in
the stairway girders, both sides of the
H-shapes are closed employing steel
plates to provide a square box shape.
Two H-shape stairway girders under
the stairway center are placed close together to realize a compact structure,and both sides of the stairway steps are
cantilevered from the stairway girder.
In this way, a lighter-weight image ofthe steel stairway structure was pursued in the design stage. (Photos 3 and4)Photos 3 and 4 Stairways: Highlighted application of steel products

17 Steel Construction Today & Tomorrow December 2016

Full Consideration of the Environment and Preparations for Disasters
A pellet boiler is adopted for air-conditioning, and hardened wood chips areused as a heat source to produce biomass energy. Ignition of the chips requires only a small amount of electricity, and carbon dioxide emissions
are suppressed by means of carbon
neutralization. Because pellets (fuel) produced in Iwaki in Fukushima
Prefecture are used, the pellet boiler
air-conditioning system can be seen as
an environmentally conscious technology in terms of using locally produced
wood materials.
Because the building exterior is ofglass façade construction, citizens expressed some anxiety that it would
be hot in the summer and cold in thewinter. To wipe away such anxieties,

wooden louvers for cutting off sunlight
were adopted to improve the heat-insulation performance of the exterior walland Low-E pair glass with high heatinsulation performance was also adopted. Further, the building is planned sothat the veranda zones work as heat-insulation zones for the large spaces atthe building’s center, which successfully lessens the heat burden of such awide working space.
The recycling of rainwater and theuse of solar power generation havebeen introduced, and thus, even when
the regular electricity supply stops,
building operations can be sustained
for at least three days by using emergency power generators and the solar
power generation system.
Underground Space for Both Car
Parking and Temporarily Receiving Refugees during a Disaster
It has been said that places of refuge wereinsufficient within the Kunimi Town area during past disasters and in the Great
East Japan Earthquake. For that reason,a plan was submitted at the project proposal stage that parking be provided in
the basement, which would be used forthe parking of public-use cars in normal
times and as a place of temporary refugein emergencies. Manhole emergency lavatories can be prepared in the basement.
As a result, a plan was finally acceptedthat allows for the evacuation of citizens.
(Fig. 3)Focusing only on the Strengths of
Steel and Wood
Still the strong point of steel framing isthat it allows for the construction of large
spaces and atrium structures. This performance of steel cannot be substituted
by wooden construction. Above all, theconstruction of fire-proof buildings employing wooden structures is very difficult in terms of both cost and the current
technological level.
As a result, the current hybrid construction method focusing on the strong
points peculiar to the wood or steel members is highly rated-wood materials being used as finishing members and steel
frames as structural members. Further,steel frames are reliable in making thespans between columns larger and in securing considerable space volume. (Refer to Photo 5)
Currently, only comparatively small-

Outline of Kunimi Town Office Building● Location: Kumini Town, Date, Fukushima Prefecture● Project owner: Kunimi Town Office● Application: Town office building● Building site: 1,500.43 m2● Building area: 4,833.39 m2● Structural type: Steel frame structure, partly steel-reinforced concrete structure● No. of stories: 1 basement, 3 stories aboveground, 1 penthouse● Maximum building height: 15,500 mm● Structural design: JR East Design Corporation, Tabata Architect & Design Office● Construction: Joint venture of Ando, Hazama, Andogumi and Sakuma Kogyo● Design period: August 2012~August 2013
● Construction term: September 2013~April 2015

Photo 5 Adoption of wood-steel hybrid structure realizes a large
space with a texture like awooden structure.

size H-shapes are adopted in the steel
frames of hybrid wood-steel members.
However, when we count that it might
become feasible to obtain ministerial
approval for hybrid members that use
square steel tubes or H-shapes with aconstant outer web depth, expectations

are high for the promising developmentof building methods employing “local
wood-laminated hybrid member of thesteel product built-in type.”(Photos and figures: Courtesy of JR East￭
Design Corporation)

Fig. 3 Schematic Diagram for Environmental Plan
Sunlight cutting-off

Reduction of air-conditioning
energy use during spring andautumn periods by means ofautomatic ventilation

Solar power generation

Assembly hall

Low-E
pair glass

Terrace

Highly thermal-insulation
exterior wall
Wood louver
Low-E pair glass

Veranda zone

Ofﬁce zone

Veranda zone

Natural light utilization
by means of sensor control
Floor-shooting air-conditioning
Parking lot(Space for temporarily receiving
refugees during disaster)Pellet boiler

Reuse ofwaste water

Rainwater pit

December 2016 Steel Construction Today & Tomorrow 18

JISF Operations

Two Programs for the Steel Industry Cooperation Program of theJapan-Thailand EPA
The Japan Iron and Steel Federation(JISF) in collaboration with the Iron andSteel Institute of Thailand (ISIT) held
two programs. These programs wereplanned as part of government-initiatedprojects pursuant to the Japan-Thailand
Economic Partnership Agreement (EPA).

sic knowledge.” A total of 20 Thai engineers participated in the program inwhich lectures titled “Bars and Rods
Special Course” were delivered and visits were made to related steel plants. The
program was the second following one
held in 2015.

Newly Recruited and Young Engineer Training Program
The Newly Recruited and Young Engineer Training Program was held for one
week in Osaka in September 2016. The
main aim of the program is for “newly recruited and young Thai engineers
to get necessary and indispensable ba-

Seminar on CO2 Emissions Evaluation Method
A program was held for four days startingfrom July 4, 2016 in Bangkok, Thailand
with the aim of establishing a CO2 emissions evaluation method in the Thai steel
industry. In this program, guidance on a
CO2 emissions evaluation method wasgiven to ISIT staff andrelated persons in theThai steel industry andgovernment agencies. In
addition, the program included the demonstration of CO2 emissions
data collection and anevaluation method during the visit to an electric
furnace steelmaker.

Steel Structure Conference in Cambodia for 2016
The Japan Iron and Steel Federation willhold a conference titled “Recent Technologies for Steel Structures 2016” in PhnomPenh, Cambodia on December 9, 2016. It
will be jointly held by the Ministry of Public Works and Transport of Cambodia andthe Institute of Technology of Cambodia,
and will be supported by the Embassy ofJapan in Cambodia, JICA Cambodia Office, JETRO PHNOMPENH and the Japanese Business Association of Cambodia.
In the conference, three professors
from Japan will participate to deliver lectures in the field of steel construction:• Dr. Osamu Kiyomiya (lecture on
port and harbor facilities)• Dr. Yoshiaki Okui (steel bridges)• Dr. Yasushi Uematsu (building

construction)
Further, two lecturers from Cambodia will participate in the conference by delivering lectures. Subsequently, the Small Group Session of
the conference is scheduled to be heldwith the participation of key persons
from both nations. This conference
will be the fourth in the series, following those held in 2012, 2014 and 2015.

STEEL CONSTRUCTION TODAY & TOMORROW
Published jointly by

The Japan Iron and Steel Federation
3-2-10, Nihonbashi Kayabacho, Chuo-ku, Tokyo 103-0025, Japan
Phone: 81-3-3669-4815 Fax: 81-3-3667-0245
URL http://www.jisf.or.jp/en/index.html
Japanese Society of Steel Construction
Yotsuya Mitsubishi Bldg. 9th Fl., 3-2-1 Yotsuya, Shinjuku-ku, Tokyo 160-0004, Japan
Phone: 81-3-5919-1535 Fax: 81-3-5919-1536
URL http://www.jssc.or.jp/english/index.html

Steel Structure Conference for 2015

© 2016 The Japan Iron and Steel Federation
Edited byCommittee on Overseas Market Promotion, The Japan Iron and Steel Federation
Chairman (Editor): Eiji Katayama
P 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
reproduced with our permission. To download content (PDF format), please go
our website at: http://www.jisf.or.jp/en/activitity/sctt/index.html. We welcome yourcomments about the publication and ask that you contact us at: sunpou@jisf.or.jp.