No. 50 April 2017

STEEL CONSTRUCTIONTODAY & TOMORROW

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

Special Issue

Japanese Society of
Steel Construction
JSSC Commendations for Outstanding Achievements in 2015

• Outstanding Achievement Awards

1 Long-span

Pedestrian
Suspension Bridge“Mishima
SKYWALK”

2 Suita City Football

Stadium-Seismicisolation Structure
for Roofing

Photo:Hiroyuki Oki

3 Outer Frame CFH

Method for the
Framing of Steel-frame Multi-storied Housing• Thesis Awards

4 Mechanism of Damage to Steel Finger Joints of Highway Bridges
5 Strength of Weld Joints of Framing Employing High-strength

Built-up H-shapes Produced by Means of Undermatching Welding

Special Feature: Seismic Retrofitting of Buildings and Bridges

6 Earthquake Damages and Transition in Seismic-resistantStandards in Japan

8 Kawaramachi Multi-storied Housing
9 Yakumo Gakuen School Building
11 Shikoku Bank Headquarters Building

10 Asakusa Station Building©Koji Fujii / Nacasa &Shinjuku
Nomura Building
Inc.
12Partners

13 Katashinagawa Bridge 15 Nishiike Bridge
Special Article: Stainless Steel

17 High-strength Welding Materials for SUS304A
18 JSSC Operations
Published Jointly by

The Japan Iron and Steel Federation
Japanese Society of Steel ConstructionJSSC Commendations for Outstanding Achievements in 2016: Outstanding

Long-span Pedestrian Suspension
Bridge “Mishima SKYWALK”
Prize winners: Kawada Industries, Inc. and Chodai Co., Ltd.
Longest Pedestrian Suspension
Bridge in JapanThe Hakone Seiroku Mishima Suspension Bridge is a pedestrian suspension
bridge constructed in Mishima, Shizuoka Prefecture. Named “Mishima SKYWALK,” it has a main span length of 400

m and is the longest pedestrian suspension bridge in Japan (Fig. 1).
Because the bridge is in a place ofscenic beauty that commands a panoramic view of Mt. Fuji and Suruga Bay,plans for the bridge were worked out thatcultivate various tourist attractions by

Fig. 1 General Drawing of Mishima SKYWALKElevation

Plan

Photo 1 Full view of Mishima SKYWALKPhoto 2 Wind tunnel tests

1 Steel Construction Today & Tomorrow April 2017

Fig. 2 Section of Mishima SKYWALK

capitalizing on this fine location, with
Mishima SKYWALK as the main facility. Further, the bridge project was promoted with private funds, a rare case in
the construction of large-scale structures.
(Refer to Photo 1)
Advanced Wind-resistant Design
and Erection Method
To construct a bridge suitable for thisbeautiful scenery and to emphasize landscaping to create a new place of interest,
minute care was paid at every stage ofthe design work using Mt. Fuji as a motif-from the configuration and color of
the main towers to the configuration of
the hand rails and the coloring of the thinpavement.
In examining the wind resistance ofthe bridge, the characteristics of windconditions were found by means of onsite observation and by numerical fluid
analysis using modeling of the peripheral
topography at the bridge’s erection site,
the design wind velocity was then prescribed, and wind tunnel tests were conducted. (Photo 2)
As a result of these wind-tunnel tests,
torsional flutter was found to occur in thestandard section on which fairings witha tip angle of 90° were installed and 500
mm-wide gratings were provided at thecenter of the bridge width. To cope withthis situation, the width of the gratings
was expanded to 630 mm and 20 mmwide slits were provided in the vicinity of the curbs, which successfully suppressed the flutter. (Refer to Fig. 2)
After installation of the main towers,
stretching of the pilot rope, installationof the catwalks and erection of the cables, the bridge superstructure was erected by means of the cable crane methodthat was selected because of the topographical conditions of the valley at thebridge erection site.
While the bridge erection was carried out under the severe climatic conditions peculiar to mountain foothills, suchas winds blowing up from Suruga Bay,dense fog and snowfall during the winter months, the bridge was safely put in￭
to service in December 2015.

Achievement Awards

Suita City Football Stadium-Seismicisolation Structure for Roofing
Prize winner: Takenaka Corporation
The Suita City Football Stadium is thehome stadium of GAMBA OSAKA, aclub team of the Japan Football Association (J-League). It is the first stadium inJapan constructed with donations fromsupporters and private enterprises.
At the design stage, a European-style
stadium that would be simple and compact was chosen. Regarding the roof
structure, a configuration was selectedthat images players standing shoulderto-shoulder, and the frame was designed

so that the design concept harmonizes
well with the structural framing. (Refer
to Photos 1 and 2)
3D Truss and Seismic-isolation
Roof Structures
A “3D truss structure” and a seismic-isolation roof structure were adopted forthe roof structure of the stadium. The
3D truss structure is a framing system inwhich the truss is installed in three directions: long-side, short-side and 45° directions. In contrast to a framing system inwhich the trusses are arranged in parallel crosses, the 3D truss structure allows
for shorter-span truss installation (Fig.
1), thereby greatly reducing the weightof the steel frames. For the seismic-isolation members, 8 high-damping laminated rubber bearings and 8 linear-motion
sliding bearings were adopted.
Fig. 2 Profile of Maximum Response
Acceleration (mm/s2)(X-direction component at x-direction level 2 seismic motion)

Photo 1 Full view

X-direction

Photo 2 Inner view

Max 1,788

Fig. 1 Parallel-cross Truss Arrangement and 3D Truss Structure
T1 truss(span: 98.6 m)

T2 truss(span: 95.1 m)

T3 truss(span: 52.3 m)

Reduced Response Acceleration
and Thrusting Force
Fig. 2 shows a comparison of the maximum response acceleration of the x-direction components during a long-side
direction (x direction) earthquake between a seismic-isolation structure and anon-seismic-isolation structure. As a result of this comparison, it became clearthat the response acceleration of a seismic-isolation structure (a) can be reduced to about 10% that of a non-seismic isolation structure (b). Further it
became clear that the response acceleration at the z-direction component cantilevered beam ends can also be reduced toabout 10% and that the seismic-isolation
structure offers a great improvement in
the seismic safety of not only the framing
but the catwalks and the lighting equipment.
Fig. 3 shows the axial force diagram
obtained from the static analytical results(long period+temperature load (+30°C)).
While a thrusting force of about 5,867
kN is generated in the non-seismic-isolation structure, the horizontal-direction
support reaction force reaches nearly 0
in the seismic-isolation structure, whichleads to a greater reduction of sectionsof truss-support columns in the lower
framing structure from 1.5 m×6 m to 1.5
m×1.5 m.
♦(a) Seismic-isolation

X-direction

T4 truss(span: 37.4 m)

Max 23,491

In the current project, a compact floor
planning, rational structural planningand the latest in contemporary technology have extensively been incorporated tosecure the highest level of structure quality, construction efficiency and cost per￭formance.

(b) Non-seismic-isolation

High-damping laminated rubber bearing
Linear-motion sliding bearing

Fig. 3 Static Analytical Results(Axial force diagram: Long period+Temperature load (+30°C), kN)
Thrusting force:
5,867 kN

220 m

Thrusting force: Nearly 0

Axial force

Thrusting force: 29 kN

90 m
Column Truss beam(a) Parallel-cross truss (b) 3D truss structurearrangement

Non-seismic-isolation

Seismic-isolation
April 2017 Steel Construction Today & Tomorrow 2

Outer Frame CFH Method for the Framingof Steel-frame Multi-storied Housing
Prize winners: Takenaka Corporation and Nippon Steel & Sumitomo Metal Corporation
In the construction of conventional medium- and high-rise multi-storied housing,
reinforced-concrete structures have commonly been adopted as the structural typebecause the required performance can easily be secured and economic merits can beobtained. However, this structural systemdoes raise concerns about the measures totreat environmental issues and labor shortage. Consequently, we developed the “outer frame CFH®” method, a steel-structure
framing system that eliminates these fears
and creates new attractiveness. The outer
frame CFH method has already been applied in practical housing projects.
Targets and Features of the Outer
Frame CFH Method
Among the tasks targeted in the development of this new steel-frame housing method are: a shorter-term housing supply notgoverned by labor conditions, high seismic
resistance during great earthquakes, application flexibility that can meet changes inlife stages, expansion of effective indoor
space, flatter finishing of indoor space andeconomic advantages similar to those ofcommon RC-structure multi-storied housing. This has led to the development of the“outer frame CFH method” and the “outer/inner framing method” as the new housing construction technology that offers ma-

ny advantages over RC-structure housing.
This new technology assures indoor spacewith protrusion-free installation of columns and beams, and broad views.
A more notable feature of these two
methods is not only the provision of highrigidity and high seismic resistance but enhanced freedom in floor planning and highly improved construction efficiency, all ofwhich are attained by the adoption of concrete-filled H-shapes (CFH) for the outer
frame and the separation of seismic-resistant elements into two orthogonal directions.
These advantages allow greater reductionof the construction term over RC-structure
housing, no protrusion of beams into theceilings inside the rooms, and the provisionof comfortable living spaces in which a wide
opening section can be secured up to the fullceiling height. (Refer to Figs. 1 and 2)

Short-side direction: H-shape
Column 500×250

Beam 500×200(Photo: Hiroyuki Oki, Blue Hours)

Outline of Practical Projects andAchievements
The outer frame CFH method was appliedin the reconstruction housing projects of theKamaishi area that suffered damage in the
Great East Japan Earthquake of 2011. Underthe restricted labor conditions in disasterstricken Kamaishi and other Tohoku areas,a housing project consisting of an 8-story
and a 5-story medium-rise buildings (Photo 1) was completed in a construction term

Fig. 1 Outline of Outer Frame CFH Method▐ Inner frameof only 1 year, about 2/3 the assumed termfor RC-structure housing. In practical application, corrugated steel plate panel walls
were installed in the short-side direction andthe fittings of CFH beam-CFH column connections and other structural methods were
newly devised to further improve seismic
resistance and construction efficiency.
We consider the outer frame CFH
method to have attained many achievements in response to the calls of local
governments and citizens for the immediate completion of reconstruction projects.
We are striving to promote social contributions through further improvements ofthis new steel-frame housing method. ￭Photo 1 Appearance seen from courtyard▐ Outer frameFig. 2 Detail of Outer Frame CFH Method

Outer long-side direction:
Concrete-ﬁlled steel frame
member (CFH member)
ColumnBeam
650×300
600×300▐ Detail of framing structure
Outer frame column
Lower-story section:
CFH member
Upper-story section:
ALC ﬁreproof covering

Outer frame CFH beam
(hot-dip galvanized)
Concrete placement at
adjacent execution yard
Hollowed composite
slab+Cast-in-place
concreteTie-beam for installation
Rust-preventive paint▐ Spread foundation
Independent footing foundation
Elimination of pile foundation due tolightweight structure▐ Corrugated steel plate wall panel
Short-side direction:
Securement of rigidity
Improvement of seismic
resistance

3 Steel Construction Today & Tomorrow April 2017

CFH beam end
Non-bracket method:
No concrete ﬁlling for beam
end, temporary installation
using bolt, on-site weldingof beam end

Inner frame column
ALC, lining rockwool andother ﬁreproof coverings

JSSC Commendations for Outstanding Achievements in 2016: Thesis Awards

Mechanism of Damage to Steel Finger
Joints of Highway Bridges

Prize winners: Shuhei Sakai, Central Nippon Expressway Company Limited, Shuichi Ono, Japan
Construction Method and Machinery Research Institute, and Kazuo Tateishi, Professor, Nagoya University
Shuhei Sakai(representative author)
1996: Graduated from Graduate
School of Gifu University
1996-2005: Engineer, Japan Highway Public Corporation
2005-2010: Chief Researcher, Nippon Expressway Research Institute Company Limited (seconded)2010-: Subleader, Construction Department, Central
Nippon Expressway Company Limited

The expansion joints installed on bridges
frequently suffer damage, and there arerare cases in which this damage leads toserious traffic accidents.
Fig. 1 shows an example of damage
to a steel finger joint that was installedin the 1950s and suffered damage aftera lapse of 40 years. When implementing
inspections, repairs and other maintenance operations on expansion joints, it isnecessary to regulate road traffic. These
maintenance operations bring about traffic congestion and there is some risk ofminor collisions of maintenance workers
with vehicles, always a headache for expressway administrators.
Damages Common to Many ofDamaged Joints
We have conducted surveys of the appearance and fractured surfaces of nuFig. 1 Example of Damage to
Steel Finger Joint

merous damaged steel finger joints andconducted their component analysis. As
a result, we have found damages that arecommon to many of the damaged joints.
Steel finger joint members fracturein the following procedure due to wheelloading and corrosion:• Around the weld of plate-shaped anchorsthat are weld-joined to the face-plate andare embedded into the reinforced-concrete slab
Aroundthe weld of rib that are weld•
joined to the face-plates and the web• Around the weld of the face-plates of web• In the face-plate around the cracking
tips of the web
Further, the filled mortar under theface-plates were crushed and washed out
due to wheel loading. Beach mark patterns were found in the fracture surfacesof face-plates as shown in Fig. 2, wherein fatigue crack occurred from the root of
weld, piled up in the vicinity of the faceplate surface, spread in lateral directions,and finally led to the face-plate fracture.
In addition, sectional loss was found insteel products in the neighborhood of respective fractured members.
It is clear from these survey resultsthat the main causes of damage to steel
finger joints are the corrosion caused bystagnant water that drained from the roadsurface between the damaged mortar andthe face-plate and the fatigue of steel
products caused by the face-plate deformation due to the wheel loading. And thesteel members suffer from damage in thedamaging processes mentioned above.

Verification of Damage Mechanism
Further, in the current survey, FEM analFig. 2 Fracture Surface of Face-plateysis of damaged steel finCracking expands in the surface
ger joints was conducted toplate excluding its surface section
grasp the range of vehicle
traffic-induced stress in the
Beach markdamaged member sections
patternso as to verify the damage
Grinding andmechanism.
polishingFig. 3 shows the relation
between the stress range
in the face-plate and the
Root gap
Pitted corrosion
FPlength of web cracking. It
can be understood from thefigure that, as web cracking
Slab side
expands, the possibility inWP
creases of face-plate fracture due to the fatigue. ￭Face-plate: 35 kg in weight,
about 1 m in length

Stress range at face-plate (N/mm2)

Fig. 3 Web Cracking Length and Stress Range at Face-plate200.0

e section
f sectiong section

150.0

h sectione section

f section

100.0
Slab side

50.0

0.0

0

200
400
600
800
Web cracking length (mm)g section

Finger side

h section

April 2017 Steel Construction Today & Tomorrow 4

Strength of Weld Joints of Framing
Employing High-strength Built-up
H-shapes Produced by Means ofUndermatching Welding

Prize winners: Gento Yamamoto, Graduate School of Engineering, Kyoto University, andKeiichiro Suita, Professor, Graduate School of Engineering, Kyoto University
Gento Yamamoto

2014: Graduated from the master’s course at the Graduate School of Engineering, Kyoto University
2014: Entered Tohata Architects& Engineers, Inc.

Application of H-SA700 Highstrength SteelThe current study targets H-SA700, a highstrength steel grade developed for use inbuilding structures. While H-SA700 has
a tensile strength about twice that of conventional steel, its yield ratio is specified
at 98% or lower and a key premise for its
application is within an elastic range.
Because it is difficult to produce rolled
H-shapes employing high-strength steel,there are cases in which H-shape members employing high-strength steel are
to be produced by means of welded assembly. According to the guidelines forthe welding of H-SA700 high-strength
steel for building structures, it is specified
that the welding material used to weld HSA700 will have a tensile strength lower
than that of the base metal, and therefore
it is considered appropriate that built-up
H-shapes employing H-SA700 be produced by means of fillet welding in which
an undermatched weld joint is formed inorder to apply these high-strength steel
products in the building structural system.
Method to Verify Strength ofUndermatched Weld Joints
In cases when seismic force works on abuilding structure for which built-up Hshapes produced by means of undermatching welding are used for the columns andbeams, because the yield stress of the weld
joint is lower than that of the H-SA700
base metal, panel connections are subjected to large shear force, and thus the peripheral side fillet welds are likely to fracture.
Further, because large stress concentrates
locally on the columns due to the tension
Fig. 2 Fracture Mechanism 1 Set
Based on 4-point Bending Test
Results (damage to peripheralside fillet weld)Qu

ws

force occurring from the beam flanges, thefront fillet welds of built-up H-shape columns are also likely to fracture.
Then, in order to prevent damage tothese fillet welds from occurring, a 4-point
bending test and local tension test wereconducted to examine a method to verify
the strength of the fillet welds. In addition,
based on the results of these tests, a cruciform framing test specimen was prepared
to conduct the experiments for columnbeam connections under conditions close
to those of practical column-beam connections, and a method to verify the strengthof the weld joints was examined. (Refer to￭Figs. 1~3, and Photo 1)
Fig. 3 Fracture Mechanism 2 Set Basedon 4-point Bending Test Results(damage to front fillet weld)

Qu

wf

Rs

Rf

θs
ρs

ρf

θf

Fig. 1 Loading Device Used for Cruciform Framing Test (unit: mm)

- Q

Q

Pin

Column ﬂange

Laterally stiffening
jig

Linking member

5 Steel Construction Today & Tomorrow April 2017

Panel

Photo 1 At the stage of maximum strength of peripheral fillet weld of cruciform framing test
specimen (fracture of peripheral fillet weld)

Special Feature: Seismic Retrofitting of Buildings and Bridges

Earthquake Damages and Transition in
Seismic-resistant Standards in Japan

Revision of Building Standards
Japan is a prominent earthquake-prone
country. Even when looking back upon thelast half century, numerous earthquakes
have occurred. Based on the examples ofearthquake damage thus far suffered, seismic design methods and legal restrictions
have been reinforced and revised (Table 1).
In the Tokachi-oki Earthquake that
occurred in 1968, much damage occurred in reinforced-concrete (RC)structure buildings. In the quake, shear
fractures of thick but short columns, socalled short columns, were found particularly in school buildings. Triggered bythis damage, the Building Standard Law
of Japan was revised in 1971 to makethe spacing between column hoop reinforcements narrower to prevent the occurrence of shear fractures in columns.

New Seismic Design CodeDue to the development of analyticaltechnologies, there was a growing tendency toward switching to a seismic design method that incorporates dynamic properties. Then, the “Developmentof a New Seismic Design Method,” acomprehensive technology development
project of the Construction Ministry atthat time, was promoted for five years
starting from 1972. In this regard, thevalidity of this new design method wasproven by the damage caused by the Miyagiken-oki Earthquake of 1978, basedon which the Building Standard Law wasradically revised in 1981 to establish the
New Seismic Design Code.
The New Seismic Design Code presents technical standards based on the following two aims:• That buildings suffer no damage in medium-scale earthquakes that are highly
likely to encounter once or more during
their service life.
• That buildings suffer neither destruction nor
collapse in a rare mega-scale earthquake thatmight occur once during their service life.
Specifically, two-stage design methods are adopted in the New Seismic
Design Code: for medium-scale earthquakes, an elastic stress design is adopted so that the framing will suffer no damage; and for mega-scale earthquakes, anultimate stress design is adopted thatconsiders the elasto-plastic performance

Table 1 Major Earthquakes and Enforcement of Building Standards in Japan
1968
1971
1978
1981
1995
2000
2003
2011-

Tokachi-oki Earthquake (M7.9, serious damages to RC structures)
Enforcement of the revised Building Standard Law(Severer restriction on column hoop reinforcement spacing)
Miyagiken-oki Earthquake (M7.4)
Enforcement of the revised Building Standard Law (New Seismic Design Code)Great Hanshin Earthquake (M7.3, serious damages to buildings constructed
before 1981, enforcement of New Seismic Design Code)
Enforcement of the Law for Promotion of Seismic Retrofit of Buildings
Enforcement of the revised Building Standard Law(Implementation of performance-based design methods)
Tokati-oki Earthquake (M8.0, oil tank damage by long-period earthquake motions)Great East Japan Earthquake & Tsunami (M9.0, serious damages to buildings by
tsunamis, building response by long-period earthquake motions)
Amendment of the Law for Promotion of Seismic Retrofit of Buildings; Implementationof tsunami design; Study of long-period earthquake motions

specified in the New Seismic Design Codewas highly assessed. (Refer to Photo 1)
In RC structures, numerous instances ofserious and destructive damage occurred inbuildings constructed before 1971. While
Serious Damage in the Great
bending fractures of columns occurred in
Hanshin Earthquake
In 1995, the Great Hanshin Earthquake oc- buildings constructed between 1972~1981,
curred, and many buildings suffered from there were many cases in which the damdestruction, collapse and other serious age did not lead to the collapse of building
damage. In steel-frame structures, numer- structures. Most buildings constructed afous fractures occurred in the brace joints ter 1981 experienced only slight damage.
and in the column-beam connections of Photo 2 shows the earthquake-inducedbuildings constructed before 1981, thus damage of RC-structure buildings over thethe importance of the connection design developing course of seismic-resistant regulations, by which the distinctive features of damage depending on the construction
period can be understood.
Fig. 1 shows an example of the level of damage
to RC school buildings byconstruction period in the
Fracture of brace joint
Fracture of column-beam
Great Hanshin Earthquake.
connection
In the figure, the construcPhoto 1 Damages of steel structural members in the Greattion period is divided inHanshin Earthquake
to three terms: before 1971,
of framing in order to protect human life.
This Code has extensively been appliedin the design of buildings in Japan.

1971
Former Building Standard Law

Former Building Standard
Law (revised)

1981
New Seismic Design CodePhoto 2 Relation between earthquake damages and seismic-resistant standards
April 2017 Steel Construction Today & Tomorrow 6

1972 to 1980 and after 1981, and the level of damage is also divided into threeterms: no damage/minor damage, intermediate damage and major damage/destruction or collapse. Destruction or collapse occurred extensively in buildings
constructed before 1971. On the other hand, almost no damage occurred inbuildings constructed in 1981 and later,which clearly shows wide recognition of
the effectiveness of the New Seismic Design Code enforced in 1981.
In those days, various moves arosesuch as recognition of the economic loss
caused by various disasters, assessmentof the value of building structures as asocial asset and the steady diffusion of
the BCP (business continuity planningduring disasters) concept. Given this situation, the government enforced in 1995
a new law known as the “Law for Promotion of Seismic Retrofit of Buildings”
Fig. 1 Level of Damages to School
Buildings by Construction Term

Number ofbuildings
200
150
100

No damage, minor
damage500Before From 1972 After1971
to 1980 1981

Intermediate damage
Major damage,destruction or collapase

Source: Architectural Institute of Japan

Fig. 2 Seismic Retrofitting Methods(a) Wall or bracing(b) Outer frame

for the sake of promoting the seismic retrofitting of existing buildings.
Seismic Retrofitting of Existing
Buildings
The aim of seismic retrofitting is to provide existing buildings with seismic resistance equal to that specified in the currently prevailing New Seismic Design
Code to enhance the value of existingbuildings. In most seismic retrofitting,the target buildings were constructed before 1981, and their seismic resistance is
to be improved to a level similar to or
higher than that specified in the New
Seismic Design Code.
Seismic retrofitting methods areroughly divided into the following twoclasses:• Methods to add strength-Shear walls,
bracing or outer framing is added to an
existing building (Fig. 2 (a) and (b)).
• Methods to mitigate the external force tobe borne by the building-Two methods
are applied: vibration control in whichdampers are assembled in existing framing(Fig. 2 (c)), and base isolation in which
seismic isolators are provided on the basement (Fig. 2 (d)).
Meanwhile, among the conventional methods to increase the strength andtoughness of structural members of steelstructure buildings are the reinforcementof structural member sections using cover plates and shapes and the addition of
stiffeners. For RC-structure buildings, a(c) Vibration control(d) Base isolation

Fig. 3 Increasing Adoption of Vibration-control and Base-isolation Buildings
Cumulative total

No. of buildings

Cumulative total

No. of buildings
Cumulative total

Vibration-control buildings

7 Steel Construction Today & Tomorrow April 2017

Base-isolation buildings

Source：The Japan Society of Seismic Isolation

method is applied that retrofits the columns by wrapping of the columns withcarbon fiber and steel plate.
Fig. 3 shows the trend in the number of applications of vibration-control
and base-isolation structures. Vibrationcontrol structures have shown a rapid
increase in application since the Great
Hanshin Earthquake and have been adopted for nearly all high-rise buildings inJapan. The cumulative total of buildings
employing vibration-control structures
amounts to about 1,000. Base-isolation
structures have been applied in wideranging fields from government buildings and office buildings to multi-storied
housing since the Great Hanshin Earthquake, and the cumulative total of buildings employing base-isolation structures
amounts to about 3,000.
Countermeasures against
Tsunamis and Long-period
Seismic Motions
In 2011, the Great East Japan Earthquake
generated huge tsunamis that brought
about serious damage to a wide area centered around the Tohoku and Kanto areas. Specifically, dead and missing persons totaled nearly 20,000 and more than
100,000 buildings were fully destroyed
or washed away, causing us once again torecognize the terrible power of tsunamis.
In the wake of such huge disasters, local governments have planned the construction of tsunami evacuation buildings. To cope with such a situation,
design standards for buildings that facilitate safe evacuation from tsunamis arebeing examined, and practical tsunami
evacuation buildings are being proposed.
Another important task prompted by
the disastrous effects of the Great East
Japan Earthquake is how to treat “longperiod seismic motion.” In this earthquake, high-rise and base-isolationbuildings with long natural periods experienced large-scale shaking over a longtime due to the long-period, long-durable seismic motions that occur in thegreat earthquake of the subduction-zone
type. It will be necessary in the future topromote further examinations of these“long-period seismic motions.”♦
To enhance the value of existing buildings, seismic retrofitting is being extensively promoted by capitalizing on
advanced seismic designs and technologies. The latest retrofitting projects in thefield of buildings and bridges are intro￭
duced on the following pages.

Seismic Retrofitting of Buildings: Kawaramachi Housing

Seismic Retrofitting System Using
Mega Response-control Frame and Two
Buildings Connection
by Shigekazu Suzuki and Daijiro Ogata, Obayashi Corporation
There are about 25,000 multi-storied
apartments or 18% of all the 133,000
apartments constructed in conformity
with the former Seismic Design Code(enacted before 1981), which require
seismic retrofitting, according to the actual situation surveys of multi-storied
apartments made by the Tokyo Metropolitan Government in August 2011.
However, the implementation of seismic
retrofitting has been difficult because of
its high costs and an impairment of openness and livability. Currently, there isstrong demand to prolong the service lifeof buildings, to utilize housing stock effectively and to respond to issue of global environment.
Fig. 1 Arrangement of Kawaramachi
Housing
Structural connectionof opposite buildings

VIEW

VIEW

Outer steel
frame

VIEW

VIEW

Photo 1 Kawaramachi housing after seismic retrofitting

Photo 2 “Skip arrangement” of mega response-control frame

Connection of Two Apartment
Buildings
Our ambition for a retrofitting project of
the Kawaramachi municipal multi-storied housing in Kawasaki is “harmonizing the retrofitting device with the original design concept of Otani Associates”
and also “making the space attractive.”
Two buildings that require seismic reinforcement stand close to and parallelwith each other. In order to make full useof this arrangement, response-control
braces for longitudinal direction and horizontal connections of the two buildings
for lateral direction were installed in the
courtyard. (Refer to Photo 1 and Fig. 1)
As the response-control braces were
installed only outside the corridor, lighting and ventilating conditions weremaintained and there was no influenceon the appearance and residence space.
In addition, “skip arrangement” of themega response-control frame, where a
two-floor frame was prepared as one
unit, reduced the number of structuralmembers and the joints with the existingbuildings (Photo 2). And even while retrofitting work was going on, this retrofitting method minimized the influence on
circulation of residents and allowed residents to stay in their apartments.
New Attractive Common Space
The courtyard between those two buildings had served as a children’s play-

Photo 3 A kind of near-future space createdbetween two housing buildings

ground and as a place of rest and relaxation. Although the courtyard became aspace surrounded by steel frames in thecurrent retrofitting, the residents who
pass the corridor can be seen throughthe frame as before. The steel frame
dynamically overlaps with the original concrete corridor handrail, which
composes a near-future space in a sense￭(Photo 3).
April 2017 Steel Construction Today & Tomorrow 8

Seismic Retrofitting of Buildings: Yakumo Gakuen School Building

Parallel Structural Method Using PC
Steel Members
by Tomofumi Sekiguchi and Motoaki Hiruma, Kajima Corporation
How the Parallel Structural
Method Works?
The parallel structural method is a seismic
retrofitting method to improve the seismic
resistance of existing buildings. Specifically, foundations and precast columns are
newly installed outside the existing buildings, PC steel members are then arranged towhich tension is applied, and finally the existing buildings are joined with these foundations and columns (joining of the foundation is with hole-in anchors, pressure joiningof the aboveground structures is with PC
steel members). In the parallel structural
method, the principle of cable-stayed bridges is utilized for seismic retrofitting.
The prescribed prestressing is introduced in advance into the PC steel members on both the left and right sides ofthe precast column. When an earthquake
occurs, the tension force of the PC steel
member on one side is increased and thaton another side is released due to the hor-izontal deformation of the buildings sothat the PC steel members on both sides
resist the seismic force. (Refer to Fig. 1)
Seismic Retrofitting Plan for the
East School Building of Yakumo
GakuenIn addition to the parallel structural
method (seismic retrofitting on the longside of the rectangular building), seismic retrofitting by means of the new installation of an RC reinforcing wall, theadditional concrete placement for existing walls and the closing of openings inexisting walls (in both the long-side andshort-side directions) was carried out tosatisfy the seismic resistance required of
the school facilities.
In particular, as a symbol in the current
seismic retrofitting of Yakumo Gakuen,
an application condition for the parallel structural method on the west side of
the East School Building was presented

Outline of East School Building

No. of stories: 3 stories aboveground and 1
penthouse
Total floor area: 957.88 m2
Structural type: Reinforced-concrete structure
Completion: 1958

to feature a “lightweight-image retrofitting design in spite of the use of steel reinforcing members” (Fig. 2 and Photo 1).
Further, the effect of retrofitting on theclassroom layout was kept to a minimum
level to realize an open and bright schoolbuilding that secures fine views from theclassrooms, and good ventilation andlighting in the classrooms as well.
On top of this, a retrofitting plan was
worked out that suppressed the effect ofthe plan on school life to a minimum byreducing on-site work that would be accompanied by noise and vibration. As aresult, the retrofitting work was completed during the summer vacation period (48￭days) of Yakumo Gakuen.

Fig. 1 Principle of Seismic Retrofitting by Means of Parallel Structural Method
Horizontal
resistance
Increase in
Reduction intension stress tension stress

Seismic force

Photo 1 Appearance of East School Building
after seismic retrofitting by means ofParallel Structural Method

PC steelbar φ26
PC鋼棒
φ26

1,200

4,750

PC steelbar φ26PC鋼棒
φ26
3P1：1C-19T12.7(SWPR7BL)(F360)

4

Integrated slab
一体化スラブ

PC鋼棒
φ26
PC
steel
bar (4 sections)4箇所
Precastcolumn柱

一体化 slab
Integrated
スラブ

,6

74.
2

,3
9

4.

2P1：1C-19T12.7(SWPR7BL)(F360)

6,
95

41.

11

▽2FL

16

3,740
3,710

4,750

X2

2,200
1,000 1,640 60

▽RFL

▽3FL

500

Precast柱column

▽PHFL

3,740

2,700

Fig. 2 Elevation and Section of Seismic Retrofitting by Means of Parallel
Structural Method

▽1FL
▽GL

Foundation基礎部
section9 Steel Construction Today & Tomorrow April 2017

1P1：1C-19T12.7(SWPR7BL)
Reinforcing
補強梁
beam

Newly-installed
pile
杭新設

Seismic Retrofitting of Buildings: Asakusa Station Building

Seismic Retrofitting Harmonized with
Function and Façade Design
by Hideharu Ushiba, Shimizu Corporation
Restoration of a Town Symbol
The Tobu Asakusa Station Building was
designed by Misao Kuno, then the first
construction chief of the Japanese Ministry of Railways, and was built by Shimizu Gumi (currently Shimizu Corporation) in 1931. A department store wasestablished on all floors other than thesecond one, which serves as the platform floor of the Tobu Railway’s Asakusa Station. The building opened as thefirst full-scale railway terminal buildingin the Kanto area.
Along with the opening of the worldclass broadcasting tower TOKYO SKYTREE® in May 2012, retrofitting of theterminal building was planned. However, in light of its application as a stationbuilding that would be difficult to reconstruct, a full-scale restoration plan was
promoted that involved not only prolongation of the building’s service life due
to seismic retrofitting but also remodeling of the building’s façade. To that end,
the old station building was restored as a
new commercial facility named EKIMISE (station square). (Refer to Photo 1)

Outline of Seismic Retrofitting
In order not to suspend operations ofboth the station and the department store,
it was necessary to implement safe andsecure retrofitting work. The work on theplatform was carried out on a detailed
minute-by-minute schedule. All steel
frames were prepared in a unit member
to keep on-site assembly work to a minimum. The major retrofitting work is outlined below:• Wheel-type Arch Braces
The wheel-type arch braces were manufactured so as to respect the design of theoriginal station building (Photo 2). These
braces not only improve the building’s
seismic resistance but also revive, by theuse of contemporary technology, the rolethat has been played by the building in
Asakusa, a prominent traditional downtown area of Tokyo.
• Steel Plate Shear Walls
The steel plate shear walls were sandwiched between the existing building
and the newly-installed exterior members by reducing the thickness of wall
system, so its application is invisible interms of both inner and outer appearance(Photo 2).

Wheel-type arch brace

Photo 1 EKIMISE (station square) after restoration and seismic retrofitting• Carbon Fiber Wrapping ofColumns
Shear walls and braces could not be installed for the platform area because of
the need to maintain passenger route, so
it was necessary to retrofit internal columns using retrofitting members withthicknesses as thin as possible. To meetthis need, the major part of seismic resistance was secured by other frames andthe platform columns were retrofitted bymeans of carbon fiber wrapping. (Refer
to Photo 3 and Fig. 1).
♦

In spite of a short construction term of
only 15.5 months and the high work difficulty within the railway terminal building, restoration and seismic retrofittingof the building were successfully completed by fully implementing advanced
technologies. Wishes submitted by boththe engineers at the initial construction
stage and the project owner for restoration have successfully been realized andthe restored building again serves as a￭symbol of downtown Asakusa.

Steel plate shear wall

Photo 2 Wheel-type arch brace and steel plateshear wall

Photo 3 Seismic retrofitting of platform columns
by means of carbon fiber wrapping

Fig. 1 Seismic Retrofitting Methods Applied to 2nd-story Platform Floor
Retroﬁtting of columns by means of carbon ﬁber wrapping
Retroﬁtting using wheel-type brace
Retroﬁtting using braces within framing
Retroﬁtting using additional shear wall

April 2017 Steel Construction Today & Tomorrow 10

Seismic Retrofitting of Buildings: Shikoku Bank Headquarters Building“T-Grid” Method for Attractive Seismic
Design of Façade
by Takenobu Koga, Taisei Corporation
The headquarters building of the Shikoku Bank, Ltd. is an office building
constructed facing the Harimaya-bashi
crossing in the center of Kochi City (Photo 1). The current seismic retrofitting has
been implemented as a link in a number of countermeasures provided in anticipation of the Nankai Earthquake thatis forecasted to occur in the future. The
main goal of the retrofitting is to protect client and employee lives and to secure continuous bank operations during
the outbreak of Nankai Earthquake. The
specific measures involve seismic retrofitting of three sections: building structure, exterior curtain wall and the ceilingof the banking business space.
In addition to securing the enhanced
safety of these structural sections, another important task was to suggest to the
local citizenry the refined presence of the
Shikoku Bank Headquarters.
Directions in Seismic Retrofitting
The headquarters building constructed in
1963 is a steel-reinforced concrete structure

Photo 1 Appearance of the building (after retrofitting)of lattice construction. The first floor facing
the street is the banking business space withan atrium structure up to the ceiling of thesecond floor, and the third to sixth floors
are for office space. The seismic-resistantelements are arranged as shown in Fig. 1.
It is a typical structurally eccentricbuilding in which seismic-resistant elements are eccentrically arranged in the coreside. Thus, it is believed that damage due tosignificant twisting will occur in the sectionthat faces the street during a great earthquake. To that end, seismic retrofitting has
been required that not only controls structural eccentricity but also offers an attractive design in harmony with the street while
retaining the openness necessary for firstfloor banking operations (Photo 2).
Attractive Façade Design
Because of the formation of the surrounding streets that feature Japanesestyle architecture, a retrofitting method using a vertical-grid steel plate shear
wall (T-Grid) was developed with a “vertical grid” theme that is frequently adopted in Japanese traditional architecture. In
order to suppress twisting of the building
structure, in five structural planes of thefirst-floor corner sections, T-Grid members with an opening ratio of 50% werearranged that apply 25 mm-thick flatbars as the grid members and 16 mmthick flat bars as the panel members.
Steel products were applied for the vertical and lateral grids. A rectangular grid
was adopted with dimensions of 400×600

mm, the same ratio as that of the existing openings, and the depth of the verticalmembers was set at 200 mm, and that of
the lateral members at 175 mm. This led toa structural design with a striking verticalline. The glass curtain wall was arranged
shifting from the T-Grid to stress the transection of the simple and strong steelframe grid. How to obtain finely finishedand safe weld joints was a primary concern at every stage from design to manufacture and installation. (Refer to Photo 3)
Highly Effective Seismic Retrofitting
The seismic resistance diagnosis was
carried out based on the rigidity andstrength of the T-Grid that was obtained
from an incremental analysis of FEM
models. The result showed that seismic
retrofitting, by improving the strengthand the eccentricity ratio of the building,was successfully carried out to secure an￭
Is value of 0.6 or more.

Photo 2 Interior view of banking business space(after retrofitting)Fig. 1 Arrangement of Seismic-resistant Elements

AtriumEccentric arrangement ofgrid-type shear wall

11 Steel Construction Today & Tomorrow April 2017

Section of installation ofgrid-type shear wall

Photo 3 Details of façade

Seismic Retrofitting of Buildings: Shinjuku Nomura Building“Dual TMD-NT” Devices as a Measureagainst Long-period Seismic Motion
by Hiroki Nakayama and Kei Mutou, Takenaka Corporation
The Shinjuku Nomura Building is a highrise steel structure constructed in 1978. It
has a height of about 210 m and a planeconfiguration of about 51×33 m.
In the current seismic retrofitting of
the building, as a countermeasure against
long-period seismic motion, two units ofa new-type of TMD (tuned mass damper)
were installed within the machine roomon the topmost 53rd story with the aim
Fig. 1 Framing Elevation and Installation Location of Tune Mass
Dampers
Mass damper(new installation)

209,350 (GL～RFL)
3,800 (6FL～46FL)

Ribbed steel
RFL plate wallof having no effect on tenants or building appearance (Figs. 1 and 2, Photo 1).
Steel Weight Response-control
Device of Japanese Development:“Dual TMD-NT”
A feature of the Dual TMD-NT is the
structuring of a compact system for installing steel weight response-control devices within a machine room with limited space. Specifically, the stroke wassuppressed by setting the damping ratio by TMD to be particularly high andthe height of the device was suppressedby adopting a slider system that supports
the steel weight using a linear guide anddouble-layered rubber. (Refer to Fig. 2)
7,000-kN steel weight

40FL
6FL
1FL
⑨
H
Framing elevation diagram

Photo 1 Appearance of “Dual TMD-NT”

Fig. 2 Outline of New-type Response-control Device “Dual TMD-NT”
5,5

Weight(7,000 kN)

00

m
0m

,80

11

mm

The mass of the TMD is made fromsteel (composed of steel plate to facilitate easy transport), and its total weight
is about 7,000 kN. The ratio of the mass
weight (covering 2 units) to the building’s aboveground weight is about 2.4%,
and the mass weight is supported by a
two-step response-control mechanism
composed of 4 units of double-layered
rubber and 4 units of bi-direction movable linear guides.
The rigidity of the TMD is to dependon the double-layered rubber and damping is to depend on a velocity dependent-type oil damper. A feature of thetwo-step response-control mechanism isthat the steel weight is supported using
the double-layered rubber in the case ofsmall deformations, for example, caused
by wind-induced shaking, and that thesteel weight is supported using the linear guide in the case of large deformation
during earthquakes (Fig. 3). These supporting systems allow for the mechanism
to stably make compatibility with thelarge mass deformation not only without being affected by the friction of thelinear guide during strong winds but also
during earthquakes.
Reduction of Shaking Width andTime
It is now possible by the installationof Dual TMD-NTs to reduce not only
earthquake-induced building responseby about 20~30% but wind-induced￭
shaking response by about 40%.

1,500 mmFig. 3 Two-step Response-control
Mechanism by the Use of Double-layered Rubber and Linear
Guide

Linear guideOil damper

Gap:
A few mm

Small deformation
Flow of mass load
Linear guideDoublelayered
rubberOil buffer

Large deformation
Flow of mass load

Existing frame of building
Double-layered rubber
Double-layered rubber(For adjustment of periods)

Linear guide+ Single-layered rubber

Gap iseliminatedApril 2017 Steel Construction Today & Tomorrow 12

Seismic Retrofitting of Bridges: Katashinagawa Bridge

Introduction of Base-isolation andResponse-control Structures in a
Truss Bridgeby Syuji Kashimoto, Hitachi Zosen Corporation
The Katashinagawa Bridge is a longtruss bridge composed of a series ofthree 3-span continuous trusses, which
is located on the Kanetsu Expresswaythat opened in 1985. It has a total extension of 1,034 m, and its maximum span
length is about 169 m. Its distinctive feature is its main trusses spaced 16 m apartbecause of the up and down lane integrated structure, a high structural heightof main trusses with heights of 14~25 m,
and the continuous arrangement of highbridge piers with heights of 50~70 m, excluding the P1 pier. (Refer to Photo 1)
Seismic Retrofitting of a Long
Truss Bridge
Seismic retrofitting was implemented
for the superstructure of this long truss
bridge based on the latest seismic-resistant standard. The commonly-applied seismic retrofitting method wasbasically adopted. Specifically, the seismic response was reduced by adopting abase-isolation structure for the bearings(replacement with base-isolation bearings), and then the structural members
were seismically reinforced.
On the other hand, in the P4 and P5
piers of the center-span intermediate
support section, where the span length isgreatest, the vertical reaction of the bearings is extremely high (35,000 kN/pier/bearing), and therefore a technical study
was made of how to secure the spacenecessary for installing the jacks, how to
retrofit the main trusses and the possibility of expanding the pier width in orderto adopt a base-isolation structure.
As a result of the study, it became
clear that the safe retrofitting of the P4
and P5 piers employing a base-isolation structure would be difficult. Then,in place of the base-isolation structure
method, another method was adopted
in which the seismic energy is absorbed
by assembling seismic-response dampers into the bearing sections and their peripheral areas.

13 Steel Construction Today & Tomorrow April 2017

Adoption of Friction Dampers
In adopting seismic-response dampers,
priority was placed on ease of maintenance and sure damping performance.
As a result, friction dampers (damping
capacity: 2,600~9,800 kN) were selectedthat facilitate not only easier inspection
but easier confirmation of whether or not

deformation occurs during an earthquake
than the buckling-restraint braces thus
far commonly applied. (Refer to Fig. 1)
Major features of friction dampers are
as shown below:• Friction dampers have a structure inwhich stainless steel plates and friction
plates slide over each other as shown

Photo 1 Katashinagawa Bridge, a long truss bridge, on the Kanetsu Expressway

Fig. 1 Installation of Friction Dampers (P3~P6)
Installation section of friction damper
Sway bracing section
Lower lateral bracing section
Intermediate lateral bracing section
Range of lining concrete placement

Fig. 2 Friction Damper and Its Basic Components (double-surface friction)

High-strength bolt set

WasherPlate washer
Outer plate (split plate, etc.)

Coned disc spring
Plate washer
Friction surface(sliding surface)

Friction plate
Stainless steel plate

Inner plate (bracing
member, etc.)
Longhole

WasherAsphalt pavement t=75 mm
RC slab t=210 mm

Photo 2 Installation of friction damper in sway bracing gusset section

Table 1 Performance Requirements for Friction Dampers
Allowable deformation

Response velocity

Friction damper for Katashinagawa Bridge±120 mm

120 cm/s(Reference) Friction damper for buildings±45 mm40 cm/sin Fig. 2, and allow easy confirmationof whether deformation occurs during
an earthquake.
• Because these dampers are compact insize and only 3 m in length, they canbe inspected from the inspection pathby installing them in the vicinity of theupper gusset sections of the sway bracing and thus maintenance can easily be
carried out (Photo 2).
Friction dampers have conventionallybeen applied as response-control devices mainly in building construction, andthere has been no record of their application in long bridges. Thus, after clearly determining the performance required
for the dampers (allowable deformation and response velocity) by means ofa time-history dynamic response analysis of the entire Katashinagawa Bridge
system, these dampers were adopted thatwere developed to satisfy the required
performance (Table 1), and further improvements were added that could secure
the corrosion resistance needed for outdoor applications peculiar to a civil engineering structure. These endeavors haveallowed application of the friction dampers into the Katashinagawa Bridge.
♦
As stated above, in addition to theadoption of base-isolation structures
for bearing, response-control dampers
were applied that facilitate easy maintenance, which has led to the successful seismic retrofitting of the long truss
Katashinagawa Bridge that satisfies thelatest seismic-resistant standard. (Refer￭
to Fig. 3)

Fig. 3 General Drawing of Katashinagawa Bridge
Total length
Bridge section B

Bridge section C• Horizontal member• Diagonal member• Cover-plate reinforcement • Cover-plate reinforcement• Sway bracing,lateral bracing• Friction damper• Vertical member• Cover-plate
reinforcement• Displacement
control device• Bearing replacement• Lining concrete• Vertical member• Cover-plate reinforcement• Bearing
replacement• Lining concrete• Bearing replacement• Lining concrete• Gusset plate
reinforcement• Bearing replacement• Lining concrete• Gusset plate
reinforcement• Bearing replacement• Lining concrete• Response-control damper

April 2017 Steel Construction Today & Tomorrow 14

Seismic Retrofitting of Bridges: Nishiike Bridge

Retrofitting Design of Steel Deck-type
Langer Bridge with Seismic Dampers
by Shuhei Yasumoto, West Nippon Expressway Company Limited, and Tomoaki Nakamura,
Yokogawa Bridge Corp.

Outline of Nishiike Bridge
Nishiike Bridge was constructed in 1974.
The arch span is 75 m and the arch riseis 14 m. It stands on the Type 1 ground(Bedrock). Fig. 1 shows the generaldrawing of the bridge.
Present State Analysis
Fig. 2 shows the result of the present
state analysis.
It shows that the strains in the stiffening girder and columns exceeded
their yield strain (maximum 19 εy inthe compressed side) in the longitudinal direction. In the transverse direction, the strains in the arch lateral bracing and column sway bracing exceeded
their yield strain (maximum 72 εy in thecompressed side). And at the arch support, the huge lifting force of maximum
2,300 kN was generated.
Selection of Seismic Dampers
The present state analysis reveals theseismic performance of this bridge. Twocases for decreasing seismic response are
given in Table 1.
For the longitudinal direction, in
CASE1, “filled-spandrel of arch crown”
and “unbuckling brace” are adopted toincrease in-plane stiffness of arch. In ad15 Steel Construction Today & Tomorrow April 2017

Fig. 1 General Drawing of Nishiike Bridge

P1(P13)
Cross section

Bridge length 122000
Span length 121800
74873

25561

20676

4.40%

Mov.
Mov.

700

100
354

10400
9000 700

13648(13551)

100
339

Wakayama

Osaka
A-LINE

Fig. 2 The Result of the Present State Analysis
Earthquake in thelongitudinal direction

Earthquake in thetransverse direction

Damaged area of local buckling
Damaged area of total bucklong
Damaged area for other reasons

Fiber elements(arch rib section)

Table 1 Case of Seismic Retrofit
Direction of countermeasureLongitudinal direction
Transverse direction
CASE1(Model of placement of order)

Filled-spandrel of arch crown+ Unbuckling brace

CASE2(Model added viscous damper)

CASE1+ Viscous damper

dition, “viscous damper” is installed at
the end-abutment in CASE2.
For the transverse direction, “shear
damper” is installed at gusseted connection of end-column and lower-lateral (Fig. 3). Fig. 4 shows the placement of
those devices.
Functional Overview of “Shear
Damper”
This section describes about shear damper, which is one of the devices adopted at
this retrofitting.
Shear damper is a damping damper
using low-yielding steel at its shear panel. It exerts a damping effect against thetransverse directional seismic wave by
setting it at gusseted connection.

Shear damper

Fig. 3 Image of Shear Damper

13602(13721)

Side view

14000 594

Nishiike Bridge on the Hanwa Expressway, which is managed by the West Nippon Expressway Company Limited, is asteel deck-type Langer bridge and it has
been in service for over 40 years. The
bridge site is located within 200 km of
the Nankai Trough where magnitude 8
scale earthquake occurs repeatedly every
100 to 150 years.
Nishiike Bridge was designed according to the steel highway bridge design
specification in 1964, which did not assume a large-scale earthquake.
With the aim of not dynamically exceeding the elastic range during large
earthquake, various seismic dampers
were adopted and nonlinear time history
analysis was applied in the seismic retrofit design of Nishiike bridge, an outlineof which is reported in this article.

Fig. 4 Summary of Retrofit Measures on Nishiike Bridge
Viscous damper

Filled-spandrel

End-column
Unbuckling bracea) Full view of the bridgeb) Filled-spandrel of arch crownLower lateral of the arch rib

Shear damperc) Unbuckling bracee) Shear damper-1f) Shear damper-2

It takes a fixing behavior in the elastic range until the occurrence of Level
1 Earthquake (with high probability ofoccurrence). During the Level 2 Earthquake (with less probability of occurrence but strong enough to cause criticaldamage), it absorbs seismic energy byyielding its shear panel. (Refer to Figs.
5 and 6)
Additionally, shear damper can be replaced independently after a quake because of the isolation structure with bolted joint.
Fig. 5 Actuation Mechanism of Shear
DamperNormal time,
Level 1 Earthquake
Fixing behavior

Level 2 Earthquake
Shear yielding→Absorption ofseismic energy

Shear panel(low-yielding steel)Fig. 6 Situation of Frame
Model Experimentation for
Shear Damperg) Shear damper-3d) Viscous damperh) Shear damper-4

Seismic Retrofit State Analysis
Fig. 7 shows the comparison of contour
figure which illustrates the response in
CASE1 and 2.
In CASE1, there were still a large
amount of reaction forces remaining atarch rib base and end-column. Therefore, the thickness of reinforcing plate
was also increased. The more the reinforcement, the more intensify the reaction force. In CASE2, a viscous damper was added, which reduced the axial
displacement of bridge. As a result, thestress of the members of the bridge did
not exceed the elastic limit (σmax/σy<1.0)
and the reinforcement was suppressed toa realistic amount.

i) Reinforced by cover plate

Conclusion
In recent years, due to the technological advances of seismic damper, various products have been put into practical use. In this case, the response of theentire bridge could be reduced within theelastic limit by using dampers. However,
the total weight of reinforcement is still
not a small amount.
It is expected that more economical
seismic retrofitting will be able to leadthrough a design for plasticity with close
consideration of the seismic behavior. ￭Fig. 7 Comparison of Contour Figure
The earthquake in longitudinal direction
CASE1: Filled-spandrel of arch crownPresent state+ Unbuckling brace

T=0.6869

The earthquake in transverse direction
Present state

T=0.5010

CASE2: CASE1+ Viscous damper

T=0.3498※ T: Natural Period (sec)
CASE1 and 2: Shear damper

Horizontal support member

April 2017 Steel Construction Today & Tomorrow 16

Special Article: Stainless SteelDevelopment of High-strength Welding
Materials for SUS304A

by Working Group on Welding, Stainless Steel Technology Standardization Committee, JapaneseSociety of Steel Construction
Large Plastic Deformation Capacity to Resist Earthquakes
The framing of steel-frame structures in thefield of building construction is composedof column and beam members, and thetype of column-beam connection shownin Fig. 1 is commonly applied. Columnbeam connections are prepared by meansof full-penetration welding, and thus they
are formed with structures in which fullypenetrated welds are concentrated.
In earthquake-prone Japan, the frequency of large-scale earthquakes ishigh. When a building is subjected togreat seismic forces, large tension force
works on the weld joints. To cope withsuch a situation, in the construction ofsteel structures in Japan, plastic design isadopted that premises the plasticization
Fig. 1 Type of Column-Beam Connections Widely Applied

ColumnBeam-end weld
BeamPhoto 1 Examples of stainless steel structuresof beam ends in order to treat the external forces of large-scale earthquakes.
More specifically, during large-scale
earthquakes, building collapse is avoided
by the maximum use of the plastic deformation capacity (seismic energy absorption capacity) of steel products.
Overmatched Weld Joints Are Required to Demonstrate Deformation Capacity
In order to make steel structural members fully demonstrate their plastic deformation capacity, it is required to take into account the relative strength of the basemetal and the weld metal and as a result toadopt so-called overmatched weld joints(tensile strength of the base metal<tensile
strength of the weld metal).
In the construction of stainless steel-

SUS304stainless steel

TS308 weld metal

Tensile strength (MPa)17 Steel Construction Today & Tomorrow April 2017

Data frequency of TS308 weld metal

Data frequency of SUS304 stainless steel

Fig. 2 Comparison of Tensile Strength between SUS304 Base Metal
and TS308C Weld Metal in Practical Use

structures (Photo 1), SUS304A stainlesssteel (equivalent to ANSI Type 304) ismost commonly used for building structural members and E308T flux-coredwire, the most popular welding material in building construction, is used. However, when comparing the respective
strengths of SUS304A and E308T, thetensile strength of SUS304A surpasses
that of E308T by about 50 MPa (Fig. 2)
and, as a result, when such undermatchedweld joints are used, the weld joints would
be fractured in the weld metal. Therefore,
weld joints using E308T cannot be applied as weld joints specified in a seismic design that is established to cope withlarge-scale earthquakes.
Development of Overmatched TS308MoJ Flux-cored Wire
As a measure to cope with this situation, the Japanese Society of Steel Construction (JSSC) conducted diverse surveys on the effects of the main chemicalcompositions of weld metal on tensile
strength (Fig. 3). The main aim was todevelop high-strength flux-cored wire inwhich fractures occur in the base metalof SUS304A weld joints.
As a result of these surveys, it became
clear that in cases when an acicular-state
ferrite structure (Fig. 4) is utilized that is
obtained from F-mode solidification (solidified primary crystal: ferrite phase),
weld metal with stabilized strength andno considerable reduction of elongation
can be obtained (Fig. 5). Thereafter, JSSC
registered in the Japanese Industrial Standards the newly-developed TS308MoJ
flux-cored wire for which the composition
range of AWS E308MoT is slightly mod-

Fig. 4 Microstructure of Acicular-state
FerriteStructure of weld metal
Austenite+Ferrite
Austenite+Ferrite+Martensite

Ferrite contents
DeLong:>18FN
WRC: 19.3FN
Scope: 14.4FN

ther, it became clear that the occurrenceof the phenomenon is largely affected by
the size of the test specimens and the difference in strengths becomes dominant
as a factor to decide fracture position inpractical weld joints having a large width
to thickness ratio.
To this end, it can be assessed that
SUS304A weld joints employing TS308MoJ appropriately function as overmatched weld joints in the preparation of￭
weld joints practically applied.
Fig. 5 Weld Metal with Stabilized
Strength and No Considerable
Reduction of Elongation
Acicular-state
ferriteEstimated value obtained from chemical composition (MPa)(−37Ni+27Cr+40Mo+225N+400)

Elongation (%)

Measured value (MPa)Fig. 3 Analytical Results for Tensile
Strength Obtained from ChemicalComposition Regression Equation

In order to confirm the strength of
SUS304A weld joints employing TS308MoJ, a joint tensile test was conducted. This test made clear that, although
the strength solely of the weld metal surpassed that of the base metal, a phenomenon was observed in which weld joint
fractures occurred in the weld metal. As
a result of an analysis of this phenomenon by means of numerical simulation,
it became clear that, when there arises a great difference in uniform elongation between the base metal and the weld
metal in a tension test, such a phenomenon occurs under certain conditions. Fur-

Tensile strength（MPa）

ified to the high-ferrite composition side.
Further, it became clear that the composition system of TS308MoJ offers afeature in which its sensitivity to embrittlement that occurs due to σ-phase
precipitation at high temperatures is far
lower than that of high-alloy, high-ferrite
content weld metals such as TS309Mo
and TS2209.

Ferrite content (WRC FN）

JSSC Operations

2016 China-Japan-Korea Tall Building ForumThe 2016 China-Japan-Korea Tall Building Forum was held on July 8, 2016 at
the Tokyo Institute of Technology in Japan. It was organized jointly by the CTBUH Japan Structures Working Group,
the International Committee of the Japanese Society of Steel Construction andthe Laboratory for Materials and Structures, Institute of Innovative Research of
the Tokyo Institute of Technology. The
Forum is an international conference thatis held as a link in the Asian operations of
the Council on Tall Buildings and Urban
Habitat (CTBUH) and intended mainly
for structural engineers and learned persons in China, Korea and Japan. The current 2016 Forum is the third session ina series that follows the 2014 Forum inShanghai and the 2015 Forum in Seoul.
At the 2016 Forum in Tokyo, Professor Kazuhiko Kasai of the Tokyo Instituteof Technology delivered a keynote address
titled “Performance of Seismic Protective
Systems for Super-Tall Buildings and Their
Contents,” which was then followed bynine presentations given by the representatives of the three participating nations.
The presentations from China covered
the structural design of the 500 m-classhigh-rise China Zun Tower, the seismic
engineering of ultra-tall mega framing andthe structural shear wall system reinforced
with steel members. Two presentations forthe 555 m-high Lotte World Tower andanother one for 400 m-high supertall RC
building constructed in Pusan were given by Korea. Two examples of the seismic
retrofitting of existing buildings and thedesign of the GINZA KABUKIZA (kabuki theater) were presented by Japan.
More than 150 engineers, researchers and students participated in the Forum, where positive discussions continued
throughout the day. At the closing of theForum, Professor Emeritus Akira Wada of
the Tokyo Institute of Technology (Chair-man, CTBUH Japan) made an address ofgratitude, and it was announced that thenext Forum will be held in Beijing, China
in September 2017. The 2016 Forum cameto an end with many successful results.
On July 7, the day before the Forum, atechnical tour was organized mainly for
CTBUH members to inspect two highrise construction sites in Tokyo. In thetour, high evaluations were given to Japanese advanced seismic-resistant technologies, such as the tuned mass dampers
installed across three consecutive stories
and the isolation system at the intermediate 25th story of the 40-floor building.

Keynote address by Professor Kazuhiko Kasaiof Tokyo Institute of Technology

Technical tour at the day before the Forum(by Hideo Oka, Takenaka Corporation)

April 2017 Steel Construction Today & Tomorrow 18

11th Pacific Structural Steel Conference
The 11th Pacific Structural Steel Conference (PSSC) was held for 2 days starting from October 30, 2016 at the Crowne
Plaza, Shanghai, China under the sponsorship of the Chinese Society of Steel
Construction. Many countries participated in the conference-11 member countries of the Pacific Council of Structural
Steel Association (PCSSA) and 18 countries from Europe. A total of 209 theses,
keynote lectures and others were submitted, and a total of 123 individuals presented their theses in Topics 1~8. Presentations from Japan totaled more than 30.
The proceedings by topic at the 11th

PSSC are shown in the figure below. As
seen in the figure, many theses were presented in the fields of connection andmember behaviors. At the conference,
11 keynote lectures were delivered by
the representatives of the 11 PCSSA
member countries, and representing Japan, a lecture titled “2016.4 Kumamoto
Earthquake in Japan and Its Damage on
Structures” was delivered by Yozo Fujino, President of the Japanese Society of
Steel Construction.
Since the first PSSC in 1986 in New
Zealand, the participating countries havealternated in holding the conference every three years. The next conference is tobe held in 2019 in Japan. This, the 12th
conference in the series, will be the first
one held in Japan since the third one 27
years ago in 1992. Because it is to beheld in the year prior to the 2020 Tokyo Olympic Games, it will be possible
to observe the construction of the newathletic facilities. To this end, the positive participation and cooperation by our
younger generations are expected in the
preparation work for the 12th PSSC to beheld in 2019 in Japan.

Proceedings at 11th Pacific Structural Steel Conference by Topic(Total number of theses submitted: 194)
Topic 1: High-rise Building and Space
Structure (10)Topic 2: Bridge, Tower, Marine and Boiler (10)Topic 3: Composite Structure (16)

No. of theses submitted
No. of presentations given
Of which, theses andpreservations from Japan

Topic 4: Connection Behavior (35)Topic 5: Member Behavior (41)Topic 6: Analytical and Experimental
Methods (39)

Delivery ceremony for PSSC flag from China toJapan

Topic 7: Design Concept and Method (18)Topic 8: New Technology and Material (25)

Message from Chairman of International Committee
Hiroshi Katsuchi, Chairman, International
Committee of JSSC (Professor, Yokohama
National University)

JSSC has conducted
a wide range of activities in the form ofsurvey, research andtechnological development aimed at promoting the spread ofsteel construction and at improving associated technologies, and at the sametime it has extended cooperation to related organizations overseas. Aimed at
spreading steel construction technologies of Japan and developing overseas
markets, the International Committee of
the Japanese Society of Steel Construc-tion (JSSC) was responsible for the edition of No. 50 issue.
No. 50 issue introduces 2016 JSSC
awards of outstanding achievement insteel construction and excellent thesis. In
addition, this issue features seismic retrofit of steel structures. Following theoverview of earthquake damages in Japan, revisions of seismic design codes,
the law on promotion of renovation forearthquake-resistant structures, spread ofseismic base isolation and control, andclassification of seismic retrofit methods,
examples of seismic retrofitting of buildings and bridges are introduced, which
are not only structural reinforcement but
also a wide range of seismic control/baseisolation devices. In addition, recent re-

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
3F Aminosan Kaikan Building, 3-15-8 Nihonbashi, Chuo-ku, Tokyo 103-0027, Japan
Phone: 81-3-3516-2151 Fax: 81-3-3516-2152
URL http://www.jssc.or.jp/english/index.html

search results of welding materials forstainless steel are introduced.
International activities in 2016 that are
the Tall Building Forum of the Council on
Tall Buildings and Urban Habitat held at
Tokyo Institute of Technology in July organized by JSSC and the 11th Pacific Structural Steel Conference (PSSC) in Shanghai, China in October are reported. The
next 12th PSSC was decided to be hosted by JSSC in Japan in 2019. JSSC would
like to invite many participants to the 12th
PSSC in Tokyo where the Tokyo Olympic
Games is waited one year later in 2020.
Finally, we would like you to continuously understand for activities of JSSC
and we would also like to hear your opinions at any time.
© 2017 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.