No. 52 December 2017

STEEL CONSTRUCTIONTODAY & TOMORROW

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

Feature Articles

Advanced Design of Structural
Steel Buildings in Japan
Publication of English Translation of the 2005 AIJ DesignStandards for Structural Steel Buildings1• Organization of Design Standards and Recommendations for3• Now Available: English Translation of the 2005 AIJ Design

Structural Steel Buildings in Japan
Standard for Steel Structures

5 Seismic Retrofittingof Long-span Steel
Structures Using
Viscosity Dampers

9 Guidebook for Preventing Brittle Fractures of Inner DiaphragmElectro-slag Welds

13 Latest Information about Steel Products for Building Structures inJapan

Serial Article: Latest Design of Steel Buildings in Japan (2)ROKI Global Innovation Center
15 Bright, Vast

Space Design
Employing
Steel FrameWood Hybrid
Trusses

Back cover JISF Operations

Published Jointly by

The Japan Iron and Steel Federation
Japanese Society of Steel Construction

Design Standards for Structural Steel Buildings

Publication of English Translationof the 2005 AIJ Design Standards for
Structural Steel Buildings

Organization of Design Standards and Recommendationsfor Structural Steel Buildings in Japan
Motohide Tada: After finishing the master’scourse of the Graduate School of Engineering,Osaka University, he entered Nikken Sekkei Ltd.
in 1982. He became assistant professor of the
School of Engineering, Osaka University in 1989
and assumed his current position as professor of
the School of Engineering, Osaka University in2007. His specialization is building structures.

by Motohide Tada
Professor, Osaka University
Three Design Methods for Structural Steel Buildings
Fig. 1 illustrates the organization of design standards and recommendations forstructural steel buildings prescribed by
the Architectural Institute of Japan (AIJ).
The structural design methods adopted in Japan is classified into three distinct methods-allowable stress design,
plastic design and limit-state design.
For structural steel buildings, one design standard and two recommendations
are prescribed by AIJ in compliance withthese three methods as follows:• Allowable stress design addressed by
Design Standard for Steel StructuresBased on Allowable Stress Concept
For each member comprising the structure, the stresses computed for temporary and sustained load combinations(the two load intensities defined basedon frequency of occurrence) must be
no greater than the respective allowablestresses. Implicit in this design method
is the premise that the building structure
remains elastic for temporary and sustained loads.
• Plastic design (ultimate load design method) addressed by Recommendations for
the Plastic Design of Steel Structures
The members are designed so that the loadthat causes frame collapse (collapse load)surpasses the ultimate load obtained bymultiplying the design load by a load factor. This design method permits controlled
damage caused by the structural systemdeforming beyond its elastic limit.
• Limit-state design addressed by Recommendations for the Limit State Design
1 Steel Construction Today & Tomorrow December 2017

Fig. 1 Organization of AIJ Design Standards and Recommendations for
Structural Steel Buildings• Allowable stress design:
Design Standard for Steel Structures-Based on Allowable Stress Concept• Plastic design:
Recommendations for the Plastic Design of Steel Structures• Limit-state design:
Recommendations for Limit State Design of Steel Structures

Recommendations that address astructural type
• Recommended Provisions for
Seismic Damping Systems
applied to Steel Structures• Recommendations for the
Design and Fabrication ofLight Weight Steel Structures

Recommendations that address
structural components• Recommendations for Designof Connections in Steel
Structures• Design Recommendations for
Composite Constructions• Recommendations for the
Design and Fabrication of
Tubular Truss Structures in
Steel

Recommendations that address
load effects• AIJ Recommendations for Fire
Resistant Design of Steel
Structures

Recommendations that address
structural behavior• Recommendations for
Stability Design of Steel
Structuresof Steel Structures
This method is established based on two
key features. First, design requirements are
specified for limit states. Limit states areconditions beyond which functionality ofthe structural system or member cannot be
maintained or fundamental assumptions areinvalid. Second, design loads and member strengths are determined based on aprobabilistic approach. There are two fundamental limit states: the “strength limit state” which addresses structural safety under extreme loading conditions; and“serviceability limit state” which address-es usability, functionality and habitabilityof the building for daily use.
Supplementary Recommendations to the Three Major Design
Systems
AIJ provides a number of design recommendations that supplement the design
standard and recommendations mentioned above. The design recommendations may be categorized into the following four types:• Recommendations that address a specific structural type (Recommended Provisions for Seismic Damping Systems
Applied to Steel Structures, and Recommendations for the Design and Fabrication of Light Weight Steel Structures)
Recommendations
that address specif•
ic structural components (Recommendations for Design of Connections in Steel
Structures, Design Recommendations for
Composite Constructions, and Recommendations for the Design and Fabrication of Tubular Truss Structures in Steel)Recommendations
that address specific•load effects (AIJ Recommendations forFire Resistant Design of Steel Structures)
Recommendations
that address a specif•
ic structural behavior such as buckling(Recommendations for Stability Designof Steel Structures)
Characteristic features and roles ofeach design recommendation are summarized in the following by excerpting
and quoting from the preface of each recommendation.

• Recommended Provisions for Seis-

mic Damping Systems Applied to
Steel Structures
This document addresses steel structures employing columns and beams asa primary structural system and buckling-restrained braces and/or shear panels as supplemental damping systems.
The provisions present performance assessment methods for commonly usedsteel dampers, analytical modeling procedures for dampers and response-controlled steel structures, and design methods that assure that the story-drift angles
of response-controlled steel structures
remain within the target limit under design ground motions. (Excerpted from
preface of the first edition)• Recommendations for the Design

and Fabrication of Light Weight
Steel Structures
This document addresses steel structureswith three or fewer stories composed ofsteel whose plate thickness is no greater than 6 mm. The 1985 revision assures
the same structural performance and reliability expected from the capacity design
method introduced by the 1981 revisionof the Building Standard Law of Japan.
Based on the realization that plastic analysis is not directly applicable to lightgage steel structures, the recommendations propose to adjust the first-stage
design procedure (achieved by allowablestress design, and whose primary purpose is to assure no damage from smaller and frequent earthquake loads) to replace the second-stage design procedure(achieved by ultimate-strength design,
and whose purpose is to assure formation of a controlled energy dissipating
mechanism against extreme earthquake
loads). (Quoted from preface of the 1985
edition)• Recommendations for Design ofConnections in Steel Structures
Provisions and requirements for welded connections, bolted connections, andcolumn bases, which had been stipulated in separate AIJ standards and recommendations, are assembled in this single document with a comprehensive andextensive commentary. Two strengths
are specified for each connection type:the elastic-limit strength and ultimate
strength. The elastic-limit strength is adequate for allowable stress design for
temporary loads. The ultimate strength
represents the maximum force that theconnection can transfer. In combination
with an adequate design methodology,
these connection strengths provide thefundamental design basis for structuralsteel buildings. (Excerpted from prefaceof the first edition)• Design Recommendations for Com-

posite Constructions
This document is composed of four parts,
Part 1: Structural Design Recommendations for Composite Beams; Part 2: Structural Design Recommendations for Deck
Composite Slabs; Part 3: Design Recommendations for Steel Frame-Reinforced
Concrete Load-Bearing Wall Composite
Structures; and Part 4: Design Recommendations for Anchor Bolts. The recommendations have responded to immediate needs for rational design methods
and seismic upgrade schemes employing
composite construction. (Excerpted from
preface of the first edition)

and Fabrication of Steel Tubular
Truss Structures
This document addresses design and fabrication requirements that are specific tosteel pipes and tubes comprising truss
structures. Because members for thiscommittee have been active in the X-VE
Technical Sub-commission of the International Institute of Welding, fundamental elements of the recommendations
agree with many overseas specifications.
(Quoted from preface of the 2002 edition)• AIJ Recommendations for Fire Re-

sistant Design of Steel Structures
This document reexamined the fire-resistant design provisions prevailing in
the Japanese laws and ordinances (as of1999) that are based on allowable member temperature and required fire endurance duration. The recommendations
present a rational, simple, and realistic
design framework that is based on the ultimate strength concept which compares
structural strength against load effects.
(Excerpted from preface of the first edition)• Recommendations for Stability De-

sign of Steel Structures
This document serves four purposes: first, to clarify the technical basis ofbuckling-related provisions contained invarious specifications on structural steelbuildings; second, to explain the concepts related to buckling phenomena andto clarify how the phenomena relate todesign; third, to serve user convenienceby compiling equations and design methodologies that enjoy popular practicalusage; and fourth, to aid starting engineers and students by presenting practical examples. (Excerpted from prefaceof the first edition)♦♦♦

The organization, role, and contents of
the AIJ standards and recommendations
on structural steel buildings was introduced in this article. ￭• Recommendations for the Design
December 2017 Steel Construction Today & Tomorrow 2

Now Available: English Translation of the 2005 AIJ DesignStandard for Steel Structures

by Taichiro Okazaki
Professor, Hokkaido University
An English translation of the 2005 AIJ
Design Standard for Steel StructuresBased on Allowable Stress Concept,
hereinafter referred to as the Standard, isavailable for download from the DigitalContents Distribution webpage (https://www.aij.or.jp/eng/publish/index_ddonly.htm) of the Architectural Institute ofJapan (AIJ). The translation (front cover shown in Photo 1) was produced by
the Sub Committee to Prepare English
Versions of Design Provisions for Steel
Structures whose members include researchers in structural steel buildings andrepresentatives of Japanese steel producers. AIJ intends to make this translation
the first of a series of English editionsof its design specifications for structuralsteel buildings described in the first halfof this article.
The Standard prescribes the most fundamental design rules for structural steelbuildings constructed in Japan. Since
1981, the building regulations in Japan
have comprised a two-level design procedure requiring allowable stress designfor moderate earthquake loads and ultimate strength design for severe earthquake loads. As implied by the title, theStandard applies to the former design
procedure which dictates the proportionof structural members for the vast majority of ordinary steel buildings. Whilethe ultimate strength design is requiredfor high-rise, long-span and other special
buildings, the allowable stress design is a
general rule that is required for all buildings regardless of height or structural
type or configuration.
The translation includes the main
body of the Standard and Special Commentaries for the English Edition. The
Special Commentaries are intended toaid readers who are not familiar with theregulations, codes and provisions, or design and construction practice in Japan.
Therefore, the translation may be used
not only as a stand-alone design standard
but also as a source of information for
3 Steel Construction Today & Tomorrow December 2017

Taichiro Okazaki: After finishing the doctor’s course at the Graduate School of Engineering, Kyoto University in 1996 and receiving
Ph.D. from the University of Texas in 2004, he became assistantprofessor, University of Minnesota in 2005. Then he served as
researcher, National Research Institute for Earth Science and Disaster Resilience in 2009 and assumed his current position as professor, Hokkaido University in 2016. His specialization covers steel
structures and earthquake engineering.

structural steel buildings in Japan. For
example, the relationship between legal design regulations and AIJ technicaldocuments are described in the preface
and elsewhere as appropriate. The different types of structural steel, listed in Table 1, and the definition of F value, or
standard allowable stress, are explainedin the Special Commentaries of Section
5.1. The allowable strengths of structuralbolts are described in Section 5.2.
The Standard was first published in1970 and updated in the latest edition
published in 2005. The Sub Committee
recognizes that the Standard owes significantly to the Specification for the Design, Fabrication and Erection of Structural Steel for Buildings published by theAmerican Institute of Steel Construction (AISC), in particular to the 1963
and 1967 editions. The chapter organization and many provisions of the first edition of the Standard were taken from the
AISC Specification. The primary difference of the AIJ Standard from the AISC
Specification has been the premise thatseismic loads are dominant at any geographic location in Japan.
The 2005 edition incorporates up-todate scientific knowledge and current
Japanese practice in member strength(Chapter 5), design for fatigue (Chapter 7), bolts (Chapter 15), welds (Chapter 16), and column bases (Chapter 17).
Unique features of the Standard that may
not be seen in other international design

Photo 1
Front cover of 2005 AIJ
Design Standard for Steel
Structuresstandards and regulations include comprehensive coverage of built-up sections with web openings (Section 9.2 forbeams, Section 11.6 for general compression members, and Section 11.10 forcolumns) and design requirements forthe three general types of column bases(Section 17.2 for exposed type, Section
17.3 for encased type, and Section 17.4
for embedded type).
We are hopeful that the English translation of the Standard will prove itself
valuable for engineers designing structural steel buildings in Japan or applying Japanese technology outside of Japanand to fulfill general interest in Japanesedesign and construction. ￭Fig. 1 Sample Page Excerpted from 2005 AIJ Design Standard for
Steel Structures

F (N/mm2)
Yield-to-tensile
Designation
Thickness (mm) strengths ratio,
Steel typeand grade≦40>40 max, %
235
215
400
Rolled steels for general structure
325
295
490
SS
375
540
400
235
215
490
325
295
Rolled steels for welded structure
SM
520
355
335#
570
400
400
400
80
235
215
SN
Rolled steels for building structure
80
325
295
490
Welded light gauge steel H section for general structure SWH 400
235
215
Carbon steel square and rectangular
235
215
400
STKR
tubes for general structure
490
325
295
400
235
215
STK
Carbon steel tubes for general structure
325
295
490
235
215
400
80*
STKN
Carbon steel tubes for building structure
325
295
490
80*
235
215
400
Rolled steel bars for building structure
SNR
490
325
295
Light gauge steel sections for structure

SSC

Hot-rolled atmospheric corrosion resisting
steels for welded structure

SMA

235
235

215
215

-

490
325
#
2
* Max. 85% for arc-welded pipe. 315 N/mm for thickness over 75 mm.

295

-

400
400

Plate
Section
Bar
RHS
CHS
Cold
formedsectionTable 1 Structural Steel Products Applied in Building Construction-

December 2017 Steel Construction Today & Tomorrow 4

Seismic Retrofitting of Plant Building

Seismic Retrofitting of Long-span Steel
Structure Using Viscosity Dampers
byHideki Idota
Professor, Nagoya Institute of Technology
Yukimori Yanagawa
KOZO KEIKAKU ENGINEERING Inc.
Hitoshi Niimi
TOYOTA INDUSTSTRIES CORPORATION
Need for Seismic Retrofitting of
Buildings in Long Service
In Japan, a number of long-span steelstructure plant buildings that were constructed in the high economic growth
period in the 1960s and 1970s are stillin use. The Building Standard Law
of Japan was revised in 1979 and requires many buildings constructed before 1979 to be seismically retrofitted.
However, the seismic retrofitting ofthese buildings shows no steady progress due to the following reasons:• To implement the seismic retrofittingthat would satisfy the provisions in thecurrent Building Standard Law, it would
be necessary to temporarily suspend
plant operations, and this would bringabout great economic loss.
• While if a plant were moved to another site, the suspension of operations
could be avoided, but this would require securing a new plant site and ahuge sum of cost for movement.
• Because a clear relation has not yet
been established between the parameters (Is: seismic index of structures)
applied for the seismic retrofitting design currently in use and the level ofdamages caused by an earthquake, seismic retrofitting based on performancebased design cannot be applied.
In order to handle these issues, retrofitting by the use of viscosity dampers was successfully applied to a steelstructure large-span building (Figs. 1
and 2, Table 1), an outline of which is
introduced in this article.
Estimating of Responses under
Expected Seismic Waves
In order to examine a method for seismic retrofitting of the target building,dynamic response analysis was conducted using various earthquake mo5 Steel Construction Today & Tomorrow December 2017

Hideki Idota: After finishing the doctor’s course of
the Tokyo Institute of Technology in 1988, he became
assistant professor of the Faculty of Engineering, Nagoya Institute of Technology in 1998. He assumed his
current position as professor, the Graduate School ofEngineering, Nagoya Institute of Technology in 2009.
He received the Architectural Institute of Japan Prize2015 (Research Themes Division).

Table 1 Outline of the Plant Building Targeted for Retrofitting
No. of stories

1 story aboveground, no underground floor and penthouse

Total building area

About 33,600 m2

Plane shapeLong side: 13 spans, about 200 m; Short side: 12 spans, about 160 m

Eaves height,
building height

Eaves height: GL=8.2 m; Building height: 11.5m

Year of design

1966 (based on the former Seismic Design Code)ColumnBuilt-up column using rolled H-shapes

BeamTruss beam using L-shapes

Roof

Saw-tooth configuration, slate covering

Foundation

Independent foundation, steel pipe pile, exposed column base

Earthquake load

Unit load that reflects latest equipment load: 1.84 kN/m2

Seismic resistancediagnosis result

Minimum value of seismic index of structure (Is value): 0.17;

Natural period (s)Average value: 0.30
No retrofitting Long side: 1.21; Short side: 0.89
Extremely rare equivalence Long side: 1.78; Short side: 1.70

Fig. 1 Perspective Drawing of 3D Analysis ModelEstimation of Ultimate Deformation and Settlement of Design
Criteria
A conference with the owner pertaining
to the criteria in the retrofitting design
was held based on the characteristic

Fig. 2 Detailed Configuration of Saw-tooth Roof

Fig. 3 Maximum Response Spectrum
Simulated earthquake motion for structural design(85% in scale of motions of extremely rarely occurring earthquake)
Simulated earthquake motion for structural design(100% in scale of motions of extremely rarely occurring earthquake)
Earthquake motions estimated to occur in Tokai, Tonankai and Nankai Earthquakes
Initial-stage primary natural period (south-north direction)
Initial-stage primary natural period (east-west direction)
Equivalent primary natural period in rarely extremely occurring earthquake(south-north direction, east-west direction)

Maximum response acceleration (cm/s/s)

Damping coefﬁcient h=5%

Natural period (s)Damping coefﬁcient h=5%
Maximum response displacement (cm)tions. The earthquake motions adopted for examination are the following
three:• Wave 1: Simulated Earthquake
Motion for Structural Design
This is ground surface motion amplified by reflecting the results of surveysof the ground at the target building site
conducted based on the motion on theengineering bedrock that is provided in
the Building Standard Law. The return
period of the simulated earthquake motion is 500 years.
• Wave 2
This is an earthquake motion obtainedby reducing the peak ground velocityof Wave 1 to 80%. The return periodof the earthquake motion is 300 years.
• Wave 3
This is an earthquake motion expected to occur in the Great Nankai-TroughEarthquake. The occurrence probability for this ground motion is 10% in
coming 30 years.
Fig. 3 shows the maximum acceleration response spectrum and the maximum displacement response spectrumof each of these three waves. The figure also shows the primary natural period for the target building obtained byusing a 3D analysis frame model.
According to the figure, the natural
period of the target building is about
1.1 seconds in the east-west direction,
and about 0.9 seconds in the southnorth direction. When the natural period is made shorter-cycled by applying seismic retrofitting to this building,the natural period of the target building approaches the predominant period, and thus it is estimated that earthquake motions input into the building
rapidly increases.
Under such conditions, in cases
when retrofitting is examined that aims
at improving the strength of a building,the scale of retrofitting that maintains
the building within an elastic range
against a response acceleration surpassing 500 (cm/m2) tends to becomelarge. Accordingly, it was judged not
rational for this building to apply a retrofitting method that leads to a shorter
natural period.

Story drift angle 1/50

Story drift angle 1/100

Natural period (s)December 2017 Steel Construction Today & Tomorrow 6

Outline of Seismic Retrofitting
Seismic retrofitting by the use of buttress framing was undertaken for thetarget building taking into accountthe judgement that, as mentioned earlier, seismic retrofitting by means ofstrength improvement is not rational
for the target building. Specifically,as shown in Fig. 6, steel-structure buttress framing was newly installed on
the steel pipe supporting piles driven
7 Steel Construction Today & Tomorrow December 2017

Fig. 4 Concept of Push Over Analysis of Phased Strength Loss Type5)
Shear force

First fracture in truss connection

First push over analysis

Second fracturein truss connection

Third push over analysis in the caseof deleting the fractured truss

Second push over analysis in the caseof deleting the fractured truss

Deformation

Fig. 5 Results of Push Over Analysis
Long-side direction

Story shear force (kN)P-Δ effectjudgement
gradient

Axis A
Axis C
Axis E
Axis G
Axis I
Axis K
1/ 70

Axis B
Axis D
Axis F
Axis H
Axis J
Axis L
1/47

Axis 1
Axis 3Axis 5
Axis 7
Axis 9Axis 11
Axis 13
1/70

Axis 2
Axis 4
Axis 6
Axis 8
Axis 10
Axis 12
Axis 14
1/41

Story displacement (mm)Short-side direction

Story shear force (kN)features peculiar to the target building
introduced in the above. The intensionsof the owner were as follows:• Design criterion 1
The plant building should not collapse
in an earthquake that is extremely rare.
• Design criterion 2
Damage to a building by a rarely occurring earthquake is allowed, but continued plant operations must be secured even when subjected to such anearthquake.
• Design criterion 3
Plant operations are not to be suspended during retrofitting work.
In criterion 1, because the building
is in a limit state that targets the occurrence of building collapse, a push overanalysis was conducted that takes into account the occurrence of fracturesin truss connections. In the analysis,
the restoring force characteristic4) similar to that in the skeleton curve under
the cyclic loading was given to handle
buckling. Fig. 4 shows the concept for
the analytical method.
Fig. 5 shows the results of push overanalysis. In the analysis, the first breakpoint of most framings occurs due toyielding caused by the out-of-planebending at anchor bolts or the baseplate of exposed column bases.
In the long-side direction of framing, the truss connections of mostframings fracture when the story drift
angle surpasses 1/70, and after lowering the strength of framings by about
15% due to truss connection fracture,
the strength of the framings shows nonegative gradient up to around 1/50 of
the story drift angle even when taking
the P-Δ effect into account.
In the short-side direction of framing, while a connection fracture occurs
in an early stage in the existing braceof axis 14, strength lowering does notoccur up to around 1/40 of the story
drift angle in the axes other than axis 14.

P-Δ effectjudgement
gradient

Story displacement (mm)Story displacement (mm)Fig. 6 Response-control Buttress Framing Installed Outside of Plant

Estimating of Maximum Response after Seismic Retrofitting
In order to estimate the maximum response occurring after retrofitting of
the target building, a seismic response
analysis was made using a 3D model
to which the response-control buttressframing was added.
Analytical results show that the
maximum response displacement could
be set at its specified criteria (within
1/70 of the story drift angle) when subjected to earthquake motions in waves
2 and 3 mentioned earlier. In the casewhen subjected to the earthquake motion in wave 1, while the story drift angle in which the maximum response
displacement surpasses its specified
criterion occurs, it was confirmed thatbuilding collapse and beam fallingcaused by the fracture of chord members do not occur. The fracture occurrence in chord members discussed here
was judged based on the fracture occurrence criterion in which the axial
strain at the tension side does not surpass 1% as shown in Fig. 7.
Attainments of Retrofitting
The following useful results and futuretasks were obtained in the current retrofitting project:• Seismic retrofitting that satisfies thebuilding performance desired by theowner was realized with extreme economy by allowing the buckling of chordmembers.
• In the seismic retrofitting of steel-structure large-span buildings that require
sustained business operations, it will
be necessary to develop a seismic retrofitting technology that effectively improves seismic resistance by retrofitting only from outside the buildings.
• It is important to clarify the relation
between the scale of earthquake motion input for retrofitting design andthe resulting damage estimated to occur, and to devise technology for easily
explaining such a relation to owners.
￭

Fig. 7 Hysteresis of Axial Strain-Axial Stress of the Truss that Causes Buckling
300
Axial stress (N/mm/mm)

outside the building, and the building
and the buttress framing were connected using viscosity response-control
dampers7). The buttress framing was
installed on both sides of the structuralplanes of the building.

Tension side

250
200

Restoring force characteristic in the caseof ignoring buckling
Hysteresis of time-story analysis

150

Fracture strength at connection

100
0
50
-50

-100

Compression side
-150
-0.010 -0.008 -0.006 -0.004 -0.002 -0.000 0.002
Axial strain (−)

Photo 1 Response-control buttress framing employing viscosity damper

References
1) Notification No. 184 of the Ministryof Land, Infrastructure, Transport andTourism: Basic Policies to Promote Seismic Resistance Diagnosis and Seismic
Retrofitting of Buildings, Jan. 2006
2) Central Disaster Management Council, Cabinet Office: Preparation of Disaster-prevention Map, Mar. 2005
3) Ministry of Land, Infrastructure, Transport and Tourism: Recommendations forTechnical Standards relating to Building Structures for 2015, Section 8.1
Structural Calculation of High-rise
Buildings
4) Management Committee on Reinforced
Concrete Structures, Architectural Institute of Japan: Assessment Method
for Seismic Resistance of Existing

Medium-rise RC Buildings Employing Equilibrium Linearization Method, AIJ Annual Convention in 20145) Shibata, Wakabayashi et al: Formularization of Hysteresis Characteristics of Steel-frame Diagonal Bracing(1-2), AIJ Transactions No. 316, June
1982
6) Architectural Institute of Japan: Various Problems concerning to Bucklingof Steel Structures for 2013, Assessment of Braces That Cause Buckling
Subjected to Cyclic Axial Forces, p. 6
7) Shingaki, Kuroda, Arima, Inoue andBaba: Development of Response-control Device Using Ball Screws, AIJ
Journal of Technology and Design (8),239-244, June 1999

December 2017 Steel Construction Today & Tomorrow 8

Prevention of Brittle Fracture Occurrence in Welds

Guidebook for Preventing Brittle Fracturesof Inner Diaphragm Electro-slag Welds-For Use in the Manufacture of Built-up Box Section Columnsby Takahiko Suzuki, Nippon Steel & Sumikin Technology Co., Ltd., and Takumi Ishii, JFE Techno-Research Corporation
Increasing Need for Preparation of
Guidebook
The Japanese Society of Steel Construction published in 2016 the Guidebook forPreventing Brittle Fractures of Inner Diaphragm Electro-slag Welds1) for use in
the manufacture of built-up box section
columns. The research for the preparation of the Guidebook was commissionedby the Japan Iron and Steel Federation.
Built-up box section columns are
manufactured by weld-assembling four
steel plates (hereinafter referred to as“box columns”). Box columns have been
extensively adopted for construction of
the low-rise stories of high-rise officebuildings, and the thickness of the steel
plates used ranges from 25 mm to 100
mm. The standard welding practice adopted for joining the inner diaphragms ofbox columns is electro-slag welding, andthere are cases in which the maximum
heat input in welding reaches 1,300 kJ/
cm. (Refer to Fig. 1)
It is believed that the toughness of thecolumn skin plate is greatly lowered due
to such a large heat input and stress isconcentrated on the slit (Fig. 2) between
the backing metal of the electro-slag
weld (hereinafter referred to as “ESW”)
and the skin plate of the box column, andas a result brittle fracture occurs in the
ESW. While there are no examples offractures occurring in steel frames damaged in past earthquakes, fractures occurring in ESW (Fig. 3) have been foundin research being promoted on the fracture of column-bean connections2).
In the Hyogoken-Nanbu Earthquake(Great Hanshin Earthquake) of 1995,
fractures occurred in the CO2 weld connections of steel-frame beam ends, andas a countermeasure against such fractures, the Guidelines for Preventing Brittle Fracture in Beam-end Welded Connections was published by the Building
Center of Japan3). In the Guidelines,
steel-frame beam ends are required topossess a toughness of 70J or higher
9 Steel Construction Today & Tomorrow December 2017

Fig. 1 Manufacture of Built-up Box Section Column (Box Column)
by Means of Large Heat-input Welding
Corner weld

Inner diaphragm weld

Submerged arc welding (SAW)Heat input: 150~650 kJ/cm

Electro-slag welding (ESW)Heat input: 400~1,300 kJ/cm

Position of anxiety over brittle
Fig. 2 Outline of Column-Beam Connectionof Box Column and Anxiety overBacking metal fracture occurrence
Brittle Fracture Occurrence
Built-up box
section column

Inner diaphragmH-section beam
ESW

SAW

ColumnMicrostructure of column-beam weld joint section

Condition of fracture occurring from
Fig. 3 Brittle Fracture Occurring from
Backing Metal Slit Tip and Cause backing metal slit tip
of Fracture Occurrence
Diaphragm

Beam flange
Crack

CO2 weld metal

Beam flange
fracture surface

Slit tip
Skin plate

ESW
Crack

Columnskin plate

Backingmetal

(70J: Charpy absorbed energy at a test
temperature of 0°C). However, because
welding heat that is several tens of times
more than that in CO2 welding is input
during electro-slag welding, it is difficult

to secure a toughness of 70J for ESW.
To cope with such a situation, highperformance steel has been developed inwhich the lowering of toughness in large
heat-input welding is suppressed (highFig. 4 Understanding of Fracture Occurrence Condition
by Means of Structural Testing
Loading test for T-shaped section framing

Tension test for cruciform joint

Skin plate

Charpy impact test for ESW

Arrangement and analysis of correspondence relation between fracture strengthand Charpy impact value at ESW joint

Fig. 5 Partial Framing Test: Example of Fracture Condition

Outline of the Guidebook
According to the Guidebook for Preventing Brittle Fractures of Inner Diaphragm Electro-slag Welds, the tensile
force (tensile stress) working on ESW is
suppressed to lower levels based on the
toughness of practical ESW, capitalizing
on which ESW fractures are prevented
from occurring. This is because both thefracture strength (upper-limit stress) of
ESW and the toughness of ESW simultaneously lower, as shown in Figs. 7 and8. In the following, the methods to prevent ESW fractures from occurring are
introduced:

Fig. 6 Relation between Fracture Strength andToughness Level of ESW Joint

Fracture strength/design yieldstrength of ESW joint

HAZ toughness steel4)). However, because the plate thickness of column skinplate tends to be thinner due to the recent
wider application of concrete-filled steel
tube columns, it has become difficult tosecure an appropriate toughness of ESW
even with the use of high HAZ toughness steel. Meanwhile, when electro-slag
welding is replaced with CO2 welding,steel-frame productivity is greatly reduced.
Given these circumstances, it has
been required to discover a means to prevent the occurrence of brittle fracturethat takes into full account the currentlyapplied steel products, welding materials
and weld execution conditions as well.
The Japan Iron and Steel Federation
conducted structural testing (Fig. 4) that
adopts as parameters the toughness of
welds and the tensile stress of column
skin plate to reproduce the conditions for
ESW fracture (Fig. 5). The relation between the ESW toughness and the ESW
fracture strength was found from the test
results (Fig. 6). Further, the local stressat the fracture initiation point (equivalent maximum main stress) was foundby means of FEM analysis (Fig. 7) thereby confirming the relation between the
ESW toughness level (Charpy impact
value) and the upper-limit stress (Fig. 8).
A series of the results obtained from theabove (for example, the reference 5) areorganized in the current Guidebook forPreventing Brittle Fractures of Inner Diaphragm Electro-slag Welds.

• Method by Means of Easy Ex-○ Partial model test
△ Partial framing test

Toughness level of ESW (J)aminations of Fracture Prevention
Fig. 9 shows the flow of easy examinations required for ESW fracture prevention. As seen in the flow, at first the
toughness level of ESW is determined,
and then fractures are prevented from
December 2017 Steel Construction Today & Tomorrow 10

Δt: Penetration width (mm) *Sum of

occurring by setting the macroscopic
stress working on the diaphragm at thelevel lower than the upper-limit value forapplied stress shown in Table 1. The applied stress dσ is calculated using the following equation.
σ=dM( d t+Δt )・( bH+bf t )・( bB+2st )cf

M: Bending moment working on beamend (column face) (N･mm)
dt: Thickness of inner diaphragm (mm)cfpenetration width at both sides
bH: Beam height (mm)bft: Beam flange thickness (mm)bB: Beam flange width (mm)st: Thickness of column skin plate (mm)In the calculation of the applied stress
σ, the standard toughness of ESW is set
at 27J. However, in cases when the applied stress dσ surpasses 240 N/mm2 orin cases when the standard toughness
27J cannot be secured, the upper-limd

Fig. 7 Understanding of Fracture Occurrence Condition
by Means of FEM Analysis

Cruciform joint test

T-shaped joint test
Arrangement and analysis of correspondence relation between local stress andCharpy impact value at slit tip

Equivalent maximum main stress
at fracture initiation point (N/mm2)

Fig. 8 Relation between Equivalent Maximum Main Stress
at Fracture Initiation Point and Toughness Level

it applied stresses corresponding to thetoughness levels vE=15J and vE=47J,
which are shown in the table, are applied.

• Method by Means of Detailed

Examinations of Fracture Prevention
In the method by means of detailed examinations of fracture prevention, fracture prevention is examined based on thelocal stress occurring in the slit between
the backing metal and the column skinplate of ESW. This method takes into
account the tensile stress of the column
skin plate, and thus a more rational fracture prevention design becomes available compared to the fracture prevention
design using the easy examination method mentioned above.
Fig. 10 shows the flow of detailed examinations required for ESW fracture
prevention. The examination flow consists of three procedures: 1) calculationof the stress occurring in the inner diaphragm, 2) calculation of the maximum
main stress working on the fracture initiation point, and 3) determination of thetoughness required for avoiding the occurrence of brittle fracture. The required
strength γreq is calculated from the design conditions employing the procedures 1), 2) and 3), and the calculated
value is compared with the upper-limit strength γlim calculated from the toughness of ESW. In cases when the comparison result is γreq≦γlim, the examinations
end, and in cases when comparison result is γreq＞γlim, the connection detail andthe toughness shown in the design conditions are reexamined.

• Assessment Method for the○ Partial model test
△ Partial framing test

Toughness level of ESW (J)

Table 1 Standard for Upper-limit Value of Applied Stress of Inner Diaphragm
Toughness level of ESW ( vE )15J or higher

27J or higher

47J or higher

Standard for upper-limit value
for applied stress ( d )160 N/mm2
or lower (0.5×F)

240 N/mm2 orlower (0.75×F)

325 N/mm2 orlower (1.0×F)

11 Steel Construction Today & Tomorrow December 2017

Toughness of ESW
The toughness of ESW is assessed bymeans of impact tests in the weld execution tests that are conducted using actual
steel products and welding materials andunder practical welding conditions. It is
known that the toughness of ESW greatly differs depending on the notch position of the test specimens. While a uniform procedure for the extraction andpreparation of test pieces has thus far not
been adopted, the Guidebook has prescribed such a test procedure shown below.
According to the Guidebook, the test
specimen is extracted from the position
shown in Fig. 11, and the impact test
is implemented in three different notch
positions. This is because the initiation
point of the fracture is the fusion zone of

Fig. 9 Flow of Easy Examinations Required for
ESW Fracture Prevention
Settlement of
toughness level of ESW

・Reference of existing
performance data
・Conﬁrmation bymeans of advancewelding test as
the need arises

Reexamination ofconnection detail(Reduction ofstress by meansof width
expansion, etc.)

No

Conﬁrmation of appliedstress of inner
diaphragm based on
toughness level

Applied stress:
Upper limit or lower

Fig. 10 Flow of Detailed Examinations Required for
ESW Fracture Prevention
Settlement ofdesign condition(detail, external
force)

Standard toughnesslevel: 27J (0°C)

1 ) Calculationof stress
occurring ininner diaphragmStandard(corresponding to 27J)
upper limit for appliedstress: 240 N/mm22 ) Calculation of
maximum mainstress working on
fracture initiation
point3 ) Decision of
toughnessrequired to avoid
brittle fracture
occurrence

Future Plans pertaining to the
Guidebook
The current Guidebook targets the ESWof 490 N/mm2-grade steel. Meanwhile,
recent trends show that 590 N/mm2grade steel is increasingly being adopted for the construction of buildings thatare tending to become gigantic. To that
end, it is considered necessary to makeexaminations similar to those mentioned
above in the application of high-strength

Calculation of
maximum mainstress reqσm at
fracture initiation
point
Calculationof required
strength γreq

Calculation of upperlimit strength γlim

γreq ≦ γlim

No

Yes

End

ESW at the slit tip, and the fracture occurs in the weld metal or the heat-affected zone (HAZ) of ESW. Specifically, thethree notch positions are:
• Bond: Fusion zone of the column skinplate and the weld metal• HAZ1: A position 1 mm from the bondsection to the column skin plate side
• Depo1: A position 1 mm from the bondsection to the weld metal side
Three impact tests are conducted ateach of the three notch positions to findthe average value for Charpy absorbed
energy. Of the average values thus found,the lowest value is set at the toughness of
ESW. The test temperature to be basically adopted for the impact test is 0°C, but
in cases when the steel-frame application
environments and conditions greatly differ one from the other, the test temperature is changed.

Calculation of
applied stress dσof inner diaphragm

No

Yes

Settlement of
welding condition(toughness level vE )End

Fig. 11 Procedure for Extraction and Preparation of Test Specimens

steel with tensile strength ratings of 490
N/mm2 or more. ￭References
1) Japanese Society of Steel Construction:
Guidebook for Preventing Brittle Fractures of Inner Diaphragm Electro-slag
Welds, JSSC Technical Report, No. 110,20162) H. Akiyama, S. Yamada, Y. Matsumoto, T. Takeuchi and H. Sugimoto: Full
Scale Shaking Table Test on Ultimate
Seismic Resistance of Advanced Typeof Beam-to-Column Connections, AIJ
Journal of Structural and Construction
Engineering, No. 551, pp. 141-148, Jan.
20023) The Building Center of Japan: Guidelines for Preventing Brittle Fracture of
Beam-end Welded Connections, Sept.
2003 (Related article: Design to Prevent

Brittle Fracture in Beam-end Connections, SCT&T No. 6)4) The Japan Iron and Steel Federation:
High Toughness Steel-HAZ Toughness in the Welded Joints of Box Columns, SCT&T No. 6
5) YH Song, T. Ishii, H. Shimokawa, T.
Suzuki, Y. Kayamori, Y. Harada and K.
Morita: Research on Fracture Behavior of Electro-slag Weld of ColumnBeam Partial Framing Model, Journalof Japanese Society of Steel Construction, Vol. 17 No. 68, Dec. 2010 (Related
article: JSSC Thesis Prizes 2012 Studyof the Fracture Behavior of Electro-slag
Welds in Beam-Column Framing Models, SCT&T No. 38)

December 2017 Steel Construction Today & Tomorrow 12

Advanced Standards and Guidelines for Structural Steel

Latest Information about Steel Products
for Building Structures in Japan
Committee on Overseas Market Promotion, The Japan Iron and Steel Federation
The Japan Iron and Steel Federation(JISF), jointly with steelmakers who are
JISF member companies, is promoting
research on advanced product standards

and application technologies pertaining
to structural steel products developed inJapan. This article introduces information on the recent results of joint researchon the standardization of structural steel
products and the revision of guidelines
regarding four steel products destined forbuilding construction.

Publication of Guidelines for Application Technologies for H-SA700 (780 N/mm2grade High-strength Steel for Building Structures)

Table 1 Features of H-SA700 in Mechanical Properties
Yield
Tensile Yield Impact
Designa- Thickness strength strength ratio energy（mm） （N/mm2）（N/mm2）（%） （J）
tion

Ceq
（%）

PCM
（%）

‒
6≦t＜12
325≦[0℃ ] （t≦40）≦0.44
SN490B 12≦t＜40 325～445 490～610≦0.29
27≦ （40＜t）≦0.46≦80
40≦t≦100 295～415[0℃] 47≦≦0.65 ≦0.32
H-SA700A
6≦t≦50 700～900 780～1000 ≦98[-20℃] 47≦ ≦0.60 ≦0.30
H-SA700B*SN490B: Conventional steel product for building construction

ventional Guidelines for Welding but the
Design Guidelines for H-SA700 (draft),which incorporate the achievements attained in joint research with related organizations. The new Guidelines are compiled as a technical document relating
to both the design and application of HSA700. (Refer to Fig. 1)

Fig. 1 Member Downsizing Attained by
the Use of H-SA700, and Resulting
Steel Weight Reduction
Dimension

800

SN490B H-SA700

Fy（yield strength）（N/mm2） 295

700

85
40
Web thickness t1
（mm）
t1
35
=85 Flange thickness t2（mm） 100
2）
Section
area
（
cm
2578
1085
t2=100

Steel weight ratio (%)
Weight/Equivalent strength(Refer to Table 1)
The Guidelines for Welding of HSA700 prepared by JISF has thus far been
available as a technical document for theapplication of H-SA700. In March 2017,
JISF issued the Guidelines for Application Technologies for H-SA700. The
new Guidelines cover not only the con-1350

H-SA700 is a steel product that was certified by the Ministry of Land, Infrastructure, Transport and Tourism in 2012and marketed as the product having astandard common for steelmakers. Two
designations have been adopted for the
steel: H-SA700A for use for non-welding and H-SA700B for use for welding.

100

(%)

80
60
40

100%

20
0

42%
SN- H-SA490B 700

Revision of Guidelines for the Design and Welding of SA440 (590 N/mm2-grade
High-performance Steel for Building Structures)

Table 2 Features of SA440 in Mechanical Properties
Yield
Tensile Yield Impact
Designa- Thickness strength strength ratio energy
PCM
Ceq
tion
（mm） （N/mm2）（N/mm2）（%） （J）（%） （%）‒
325≦
6≦t＜12[0℃ ] （t≦40）≦0.44≦0.29
SN490B 12≦t＜40 325～445 490～610
27≦ （40＜t）≦0.46≦80
40≦t≦100 293～415
SA440C 19≦t≦100 440～540 590～740 ≦80

13 Steel Construction Today & Tomorrow December 2017

[0℃ ] （t≦40）≦0.44 ≦0.28
47≦ （40＜t）≦0.47 ≦0.30

The current revision of the Guidelines
made in March 2016 has two purposes:
reflection on the Guidelines, the establishment and revision of related laws and ordinances and the revision of JIS specifications for welding materials made after
2000; and the addition to the Guidelinesof amendments and postscripts in order toreflect the application of large heat-input
welding for built-up square columns andother new technological knowledge andinformation about accumulated results of
the application of SA440 thus far attained.

Fig. 2 Member Downsizing Attained by
the Use of SA440, and Resulting
Steel Weight Reduction
Dimension

800

SN490B SA440

Fy（yield strength）（N/mm2）
Web thickness t1
（mm）

295

440

85

65

t1
50
=85 Flange thickness t2（mm） 100
2
Section area（cm ）2578 1711
t2=100

Steel weight ratio (%)
Weight/Equivalent strength

the sectional dimensions and the weight ofstructural members applied but also the fabrication work needed. (Refer to Fig. 2)
JISF issued in October 1996 the first edition of Guidelines for Design and Application of High-performance 590 N/mm2grade Steel for Building Structures (SA440).
It was revised in August 2004 to incorporate new information such as measures to
respond to the revision of both the Building Standard Law of Japan and JIS specifications for welding materials in June 2000,
straightening technology and stud welding.

1350

SA440 is a steel product that is not only highin tensile strength (590~740 N/mm2) but low
in yield ratio (80% or lower), and, further,features less deviation in mechanical properties. Its chemical composition is designed sothat the weld-crack sensitivity is suppressed
to a minimum, and its weldability is greatly improved over conventional 600 N/mm2grade steel. (Refer to Table 2) To that end,
it is a steel product that is easy to apply interms of both design and construction. Design by using SA440 high-strength steel facilitates a remarkable reduction in not only

100

(%)

80
60
40

100%
66%

20
0

SN490BSA440

Establishment of Standards MDCR0016 and 0017-2016 for TMCP Steel Products
for Building Structures
TMCP (thermo-mechanical control process) steel products for building structures have been developed to meet theincreasing size of framing member whilebuildings are getting higher and larger.
The product was certified by the Ministry of Land, Infrastructure, Transport andTourism for marketing and has been extensively applied in the field of building
construction.
JISF has established its own standard for TMCP steel products for building structures with the aim of further promoting their application by the following

Table 3 Features of TMCP Steel in Mechanical Properties
Designation

Thickness
（mm）

Yield
Tensilestrength
strength2（N/mm ） （N/mm2）

SN490B6≦t＜12325≦
12≦t＜40 325～44540≦t≦100 295～415

490～610

Yield
ratio
（%）
‒
≦80

means: setting of common designations
and specifications, enhancement of application technologies and promotion of
R&D conducive to improving the competitiveness of steel-frame manufacturing technologies. (Refer to Table 3 andFig. 3)Fig. 3 High Strength and Good
Weldability Offered by TMCP Steel

Impactenergy（J）

Weldability
Ceq
（%）

[0℃ ]
27≦

（t≦40）＜0.44（40＜t）＜0.46

700

Tensile strength
N/mm2）

TMCP325B（MDCR0016） 40≦t≦100 325 ～445 490～610

≦80

[0℃ ]
27≦

（t≦50）＜0.38（50＜t）＜0.40

600

TMCP355B（MDCR0016） 40≦t≦100 355～475

520～640

≦80

[0℃ ]
27≦

（t≦50）＜0.40（50＜t）＜0.42

500

TMCP385B（MDCR0017） 19≦t≦100

≦80

[0℃ ]
70≦

（t≦50）＜0.40（50＜t）＜0.42400

550～670385～505

TMCP steel（air cooling）

TMCP steel（water cooling）

As-rolled steel
0.20

0.30

0.40

Ceq
（%）

0.50

JIS Standardization of H-beams with Fixed Outer Dimensions
JIS (Japanese Industrial Standards) re- • Flange width: 200~400 mm
tion of the number of stiffeners to be inFixed beam depth and fixed flange
width in an identical size series enablesimple design and fabrication. The application of H-beams with fixed outerdimensions offers two practical advantages-reduction of the number of filler
plates to be applied in bracket-beam bolt
connections, made available by making the beam height uniform; and reduc-Fig. 4 Comparison between
Conventional H-beam and H-beamwith Fixed Outer Dimensions

Fig. 5 Optimal Structural Design and Construction Cost Savings
Attained by the Use of H-beam with Fixed Outer Dimensions

Fixed beam depth

lating to H-beams was revised in 2014,
with the new incorporation of standard
dimensions for H-beams with fixed outer dimensions. H-beams with fixed outerdimensions are a kind of H-beam having
fixed beam depth and fixed flange width
in an identical size series (Fig. 4). Standard dimensions incorporated in JIS are:
• Web height: 400~1,000 mm

Conventional H-beamstalled on the columns in column-beamconnections, made available by making
the height of the beam to be joined withthe column uniform (Fig. 5). These application advantages lead to not only improved connection fabrication efficiency but also to the simple design of entire
steel-frame buildings.

H-beam with fixed outer dimensions
Bracket-H beam connection

Filler plate:2 types and5 pieces

Fixed flange width
Conventional H-beam
H-beam with
（Fixed inner dimension） fixed outer dimensions

Filler plate:1 type and2 pieces

Column-beam connection

Stiffener:
Different in top
and bottom

Stiffener:
Identical in top
and bottom

December 2017 Steel Construction Today & Tomorrow 14

Serial Article: Latest Design of Steel Buildings in Japan (2)ROKI Global Innovation Center-Bright, Vast Space Design Employing Steel FrameWood Hybrid TrussesTetsuo Kobori Architects and Arup
The ROKI Global Innovation Center(ROGIC) is an R&D building of ROKI Co., Ltd., a global company with advanced filtration technology. What ROKI required of this project was that the“site encouraged creativity” for further
development of filtration technology.
The huge airy grid-patterned roof, thatis made by steel frame trusses restrained
buckling by wood members, made it possible to open the work space upon naturallight (Photo 1).
Spatial Imaging Makes Optimum
Use of Building Site Abundantwith Nature
The building site is located in a mountainous area with the Tenryu River flowing below. The site consists of tieredlevel ground that was left intact after residential land development carried out 30
years ago, and a regulating reservoir islocated there as it is hidden from the surrounding area. It is also blessed with awild environment awash with waterfowl
and other inhabitants.
Strongly inspired by these site conditions, we imagined a large single
room-like space that integrates the natural environment and the architecturea spacious area that is brought about by
making the most of the topographicalconditions that overlook the reservoir
and in which the building floors are located as they rise from the ground (Fig. 1
and Photo 2).
Spacious Single Room-like Area
with Overlapping Floors
ROGIC has four floors that, capitalizing on the topographical conditions peculiar to the site, are linked to each other in tiers from the south-side reservoir
to realize a spacious single room-likespace. The building measures 64 m inthe east-west direction and 54 m in thesouth-north direction. The total floor area is 9,000 m2, where work spaces andlaboratory rooms are laid out, in addition
to a coffeehouse and terrace, and accom15 Steel Construction Today & Tomorrow December 2017

Photo 1 Full view of ROKI Global Innovation Center

Fig. 1 Concept Sketch for ROGIC Building Proposed at Initial Design Stage
Air duct (elevator)

Sky

Filter zone
(semi-external space)

Sky light

Mechanicalpod

Mountainside

ShieldinglouverOpen
Tree

Ceiling film
Elevator
shaft, air duct

Regulating
reservoir

modating around 150 workers.
The main entrance is located on thenorth side of the fourth floor (mountainside). The first thing that you encounter
when entering the ROGIC building is aview overlooking the entire work space
and the regulating reservoir on the south
side. From this perspective, everyone in
the room sees and be seen by everyone
else, thus making this perspective usefulfor researchers.

Photo 2 Peripheral area of ROGIC where theriver flows and trees grow thickPhoto 3 Entire working space seen from 4th floor

The building interior is structured sothat researchers and workers go downfrom the entrance toward the lower
working spaces. The tiered floors fromthe second to the fourth are for work
spaces, while the first floor contains theexperimental area on the north side andthe terrace facing the reservoir on thesouth (Photo 3).
Because we intended to provide asemi-outdoor space in which the indoors
feel as if it were outdoors, we planned
the entire roof to be composed of a structure like a thin film that is floating lightly
in the air. Further, we chose not to installcolumns within the indoor space, and as aresult, the roof, composed of wood-steel
hybrid double-skin trusses, was made tocover the entire building structure.
The south side of the roof is entirely composed of glass, and a slit sky
light is arranged at the top of the folded-plate roof. A filter produced by ROKI is spread as the ceiling material beneath the lower chord members of theroof. The filter is a non-woven fabric thatat first glance seems like Japanese paper.
The filter has a sound-absorbing performance, and at the same time diffuses the
sunlight so that lighting is not required
during the daytime in the indoor space.
When it is light outside, the indoor spaceis light due to the filter performance, andwhen it gets dark outside, it becomesdark inside. That is, the filter is designed
so that it reflects on the indoor space theclimatic changes and cloud movements
just as they are.

Equipment
A wood-steel frame hybrid structure isadopted for the construction of the hugeroof, and steel-reinforced concrete structures for the other building structures.
Taking into account the characteristics ofthe space and the connections between
heavy equipment and devices, the structural type was decided based on the concept of suitable materials for the rightplaces.
The Building Standard Law of Japan
specifies the adoption of fireproof construction in the case of wooden buildings
having a total floor area of more than
3,000 m2 regardless of region. However,in the case of a steel-structure building, it
specifies the adoption of quasi-fireproof
construction depending on the region
and does not specify the adoption of fireproof construction for the roof structure.
Therefore, in the ROGIC project, we interpreted these specifications to meanthat the wooden members served just as
finishing members that restrain bucklingof the steel-frame lower chord members,

and as a result the wooden members
were omitted from the list of structural members used for the main structural sections.
Structuring of a Roof Free
Curvature by the Use of Wood-Steel
Hybrid Trusses
The huge roof is a wood-steel frame hybrid structure. The beams are installed in
two directions to the roof’s free curvature at a pitch of 3.2 m.
H-shapes (H-194×150×6×9; SN490)
are used as the upper chord members. Tshapes (T-149×149×5.5×8; SN490) areused as the main members of the lower chords. Built-up H-shapes are used
for the structural sections in the periphery of the roof supports where stress isconcentrated. The wooden members areattached to the lower chord steel framein order to restrain buckling of the lower
chord steel frame.
The lower chord members are installed at a pitch of 3.2 m, which however cannot offer sufficient structuralFig. 2 Structure of Huge Roof Employing Steel Frame-Wood Hybrid Members
Upper chord member: H-194×150×6×9
V-shapedcolumnDiagonal member: 2L-75×75×6
Lower chord member: T-149×149×5.5×8
Buckling-restraint member: Laminated wood

V-shapedcolumnStructural Plan for Space andDecember 2017 Steel Construction Today & Tomorrow 16

strength, and thus a sub-frame that stiffens the lower chord is additionally installed at a pitch of 3.2 m. T-shapes (T100×100×5.5×8; SS400) are used as the
sub-frame members, and wooden members are likewise used as members that
restrain buckling of the sub-frame members. To that end, the lower chord surfaceof the roof naturally forms a 1.6 m wooden grid due to the application of the lower chord members and sub-frame members in the roof truss. (Refer to Fig. 2)
Because the roof configuration has a
two-direction free curvature, configurational twisting and bending occur in thetruss beams that span the roof. The roof
configuration is symmetrical, and thus
two identical members are naturally used
for the roof.
As regards the H-shapes used as upper chord members, the flange plate at
6-junction connections is gently folded to match the specified roof curvature.
As regards the web plate, tolerance of the
web is absorbed by the use of round bars
(60 mm dia.) arranged at the center of theconnections.
For the connection of the T-shapes
used as lower chord member, 7 mm thick
diaphragm plates and 6 mm thick web
plates, having more thickness than thelower chord members, are adopted to absorb the tolerance occurring in the flanges and webs between each member due
to the twisting. Bolt-joining was adopted for the upper chord members to securehigher installation accuracy. Because
wooden members are inserted into thelower chord members to restrain buckling, weld-joining was adopted for the
lower chord members. (Refer to Fig. 3)
Steel-frame manufacturing accuracy for the truss beams and accuracy intheir installation are linked directly to thecompletion accuracy for the huge roof.
Shop manufacturing accuracy for the
steel frames was confirmed at the stageof assembly inspection, where workers
were engaged in temporary assembly
while at the same time securing due manufacturing accuracy for the plates, one byone, using jigs and taking a long time.

Fig. 3 Detail of Steel Frames Used for Roof Truss

Huge Roof Installation Method
Requiring High Accuracy
In the assembly of the huge roof, thetruss beams were separated into their respective units, which were then subjected to field assembly. After confirmationof the assembly accuracy, these units
were hoisted and assembled into specified positions. Further, after assembly of

Photo 6 Wood-grid roof structure after jacking down

17 Steel Construction Today & Tomorrow December 2017

Photo 4 Hoisting and welding of field-assembled
roof truss beam units

the huge roof, assembly accuracy wasconfirmed using surveying instruments.
In the installation of the huge roof, after first placing crawler cranes on boththe mountain and reservoir sides, thesteel frames were installed using thesetwo cranes from the reservoir side to-

Photo 5 Fixing wood members to lower chordmemberward the mountain side. Because Vshaped column head connections using
clevis pins were adopted, strict accuracy
was required to install the V-shaped columns, for which enhanced accuracy was
secured. (See Photo 4)

Fig. 4 Detail of V-shaped Column

Outline of ROGIC Building

Location: Hamamatsu, Shizuoka Prefecture
Project owner: ROKI Co., Ltd.
Main application: R&D facility
Site area: 67,510.58 m2
Building area: About 5,000 m2(incl. 1,500 m2 of existing headquarters building)
Total floor area: About 9,000 m2(incl. 4,500 m2 of existing headquarters building)
Structural type: RC structure(partly steel frame-RC composite structure)
No. of stories: 4
Maximum height: 14,978 mm
Architect: Tetsuo Kobori Architects
Structural engineer: Arup
Mechanical and electrical engineer: Arup
Landscaping: studio on siteLighting design: Izumi Okayasu Lighting Design
Office design: Okamura Corporation
Construction: Taisei Corporation
Design term: Jan. 2009~Oct. 2010
Construction term: Jan. 2011~Sept. 2013

Photos and figures

Photos 1, 3 and 7: Takahiro Arai
Photo 2: Kawazumi . Kenji Kobayashi Photo Office
Photos 4, 5 and 6; Figs. 1, 2, 3 and 4: Tetsuo
Kobori Architects

After completion of the roof’s steelframe installation, the wooden members
were attached, and then the completedroof was jacked down. The deformationlevel at each stage coincided well with thecalculated values. (See Photos 5 and 6)
Certain approaches were incorporated
in the design stage so that the columns
to support the roof could not be seen in
the work space, among which were thearrangement of the columns outside of
the work space and their housing in the
shutter rails and walls. The V-shaped

columns to support the roof on the south
side were also arranged outside of thework space.
Particular care was paid in the aesthetic design of the V-shaped columns.
A cross section of these columns has arhombus shape in which the box section is rotated by 45° to match the gridconfiguration of the roof. In elevation(Fig. 4), the column has a tapered shape(350×350 square in column base and175×175 square in column head). Seamwelds and on-site welds of the V-shaped

columns were grinder-finished to impartthese columns with a sculptural image.
In the connection between the roof
and the columns, cast steel members
were adopted to transfer the load acting on the roof to the columns. Also, particular care was paid to the configuration of the gusset plates inserted into thecast steel members so that the beautiful
rhombus shape of the columns could beseen. (Refer to Fig.4 and Photo 7) ￭Photo 7East-side look of the hugeroof that spans an entire
building

December 2017 Steel Construction Today & Tomorrow 18

JISF Operations

Seminar in Seven Cities for the Wider Application of
Structural SteelIn order to promote the wider applicationof steel structures in building construction, the Japan Iron and Steel Federation(JISF) has yearly held a “Seminar on Steel
Products for Building Construction and
Their Application Technologies.” From
November to December 2016, JISF helda seminar in seven major cities in Japan:
Tokyo, Osaka, Nagoya, Sapporo, Fukuoka, Hiroshima and Sendai. A total of about
450 persons from construction companies, design offices, fabricators, government agencies and universities attended.
In the respective seminar sites, lectures were delivered by experts in fourareas-the JISF Committee on Building Construction, university professorsof the seminar’s host city, and researchers from the National Institute for Landand Infrastructure Management and the
Building Research Institute.
Among the technical lectures delivered by the JISF Committee on Building Construction were “Guidebook forPreventing Brittle Fractures of Inner Diaphragm Electro-slag Welds” and the recently revised “Guidelines for the Design
and Welding of SA440 (high-strength
steel for building structures).” Their outlines are introduced in the current No. 52

JISF seminar in Tokyo

issue of Steel Construction Today & Tomorrow.
JISF plans to hold the seminar in 2017as well.
In September 2016, the Japanese Society of Steel Construction also held inTokyo and Osaka a course that gives detailed explanations on the “Manual forStandard Tests for Mechanical Propertiesof Welds of Steel-frame Buildings” andother latest publications relating to design of steel-frame welds and executionof steel-frame welding. JISF and the Japan Steel Constructors Association participated in the course as co-sponsors.

JISF seminar in Osaka

Presentation at SEAISI Conference underan Environmental ThemeThe South East Asia Iron and Steel Institute (SEAISI) held the 2017 SEAISI
Conference and Exhibition in May 2017
in Singapore. The JISF International Environmental Strategic Committee dispatched Committee Chairman Ken-ichiro
Fujimoto and a member of the JISF staff
to present two papers at the conference.
In the Cost & Energy Management
II session of the conference, Committee
Chairman Ken-ichiro Fujimoto presented a paper titled “Voluntary Energy Management in the Japanese Steel Industry,”
in which he discussed “Commitment to a

Low Carbon Society,” a program for voluntary energy savings and CO2 emission
reduction being promoted in the Japanese steel industry.
In the Environmental Management
session of the conference, the JISF staff
member delivered a paper titled “Life Cycle Assessment of Steel Products Incorporating Steel Recyclability,” in which
he introduced the development of international standardization of the LCI (Life
Cycle Inventory) Calculation Methodology for Steel Products that the Japanese
steel industry proposed in July 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
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

Presentation by Chairman Ken-ichiro
Fujimoto of JISF International Environmental Strategic Committee© 2017 The Japan Iron and Steel Federation
Edited byCommittee on Overseas Market Promotion, The Japan Iron and Steel Federation
Chairman (Editor): Hiroyuki Tanaka
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.