No. 65 August 2022

STEEL CONSTRUCTIONTODAY & TOMORROW

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

Feature Article

Towards Highly Resilient andLonger-lasting Steel Bridges
1 Bridge Technologies ofHanshin Expressway Wangan
Route and Structural Plans for
Osaka Wangan Expressway
Western Extension Project4 Activities of the Research Committee on Steel Bridges with Higher
Resilience and Longer Service Life (2nd Term)

6 Report of the Working Group on Rationalized Design
9 Report of the Working Group on Fatigue Strength
12 Report of the Working Group on Corrosion and Durability
Special Topic

15 SBHS-High-performance

Steel for Bridges Originatedin Japan

19 JISF Operations

Published Jointly by

The Japan Iron and Steel Federation
Japanese Society of Steel Construction

Feature Article: Towards Highly Resilient and Longer-lasting Steel Bridges (1)Bridge Technologies of Hanshin
Expressway Wangan Route andStructural Plans for Osaka Wangan
Expressway Western Extension Project

by Hidesada Kanaji
Corporate Executive Officer
Hanshin Expressway Company Limited

Hanshin Expressway Wangan
Route and Osaka Wangan
Expressway Western Extension
Project
The Osaka Wangan Expressway is atrunk line with a total extension of about
80 km, which runs along the coastal area (wangan) of Osaka Bay. It connectswith the Honshu-Shikoku Connecting
Expressway at Myodanicho in Kobe
City, passes through a reclaimed area between Kobe and Osaka and finally connects with the Kansai International Airport at Matsubara in Izumisano City. It is
positioned as an expressway that serves
as a trunk line for the Kansai Region, oneof the representative economic zones ofJapan, particularly as a trunk line in the
coastal area covering international ports
in the Kansai Region. (Fig. 1)
Construction of the Osaka Wangan
Expressway started in July 1970 with astarting point at the Minato Bridge andthe route was put into service in July
1974. Then, the route in service was extended one after another, and prior to the
opening of the Kansai International Airport in September 1994, the Osaka Wangan Expressway that connects the airport with Rokko Island opened to trafficin April 1994. Because the expressway
was constructed by Hanshin Expressway
Company Limited, it is called the Hanshin Expressway Wangan Route.
The route of the Osaka Wangan Expressway Western Extension Project covers a 14.5 km-long section from Rokko
Island to Nagata-ku in Kobe City. Whilethe implementation of the extension
project had been delayed due to the influence of the Great Hanshin Earthquakeof 1995, the extension project was designated as a national public works project1 Steel Construction Today & Tomorrow August 2022

Hidesada Kanaji (Dr. Eng.): After graduating fromthe Graduate School of Engineering, Kobe University, he entered Hanshin Expressway Company
Limited in 1988. He successively held various technology-related posts in this company and assumed
his current position as Corporate Executive Officer
in 2022.

Fig. 1 Hanshin Expressway and Osaka Wangan Expressway
Hyogo Pref.

Rokko Island Hanshin Expressway
Wangan Route Hokko JCT
Minatogawa JCT
Port Island
Tempozan
Port of Kobe
JCT
Myodani JCT Minamikomae JCT
Kobe Airport(tentative)
Port of Osaka
Tarumi JCT

Decision incity planning(September 1994)
Extension:
6.4 kmSection of Osaka
Wangan Expressway
Western Extension Project(Rokko Island Kita to Komae)
Extension: 14.5 km

Osaka Pref.

Decision in city planning(March 2009)
Extension: 14.5 km

Section of Osaka Wangan Expressway
Extension Project Extension: 20.9 km
Osaka Wangan Expressway Extension: About 80 km(Section in service Extension: About 59 km)
High-spec. trunk and other toll roads
High-spec. trunk and other toll roads under construction
Hanshin Expressway
Hanshin Expressway under construction
Osaka Wangan Expressway Western
Extension Project (decision in city planning)
Osaka Wangan Expressway Western Extension
Project (Rokko Island Kita to Komae)

Location of Long-span Bridges on
Hanshin Expressway

Rinku JCT
Nishinomiyako Bridge

Amagasakiko Bridge
Shorenjigawa
BridgeRokko Island Bridge

Centerspan (m) Bridge type

Rokko Island
Higashi-Kobe
Nishinomiyako

217
485
252

Amagasakiko

223

Shorenjigawa

235

Umemachi215

Tempozan
MinatoYamatogawa
Shinhamadera

350
510
355
254

Kishiwada

255

Sukematsu JCT

Kansai International Airport

Higashi-Kobe Bridge

Bridge name

Sambo
JCT

International
strategic port:
Port of Hanshin

Umemachi Bridge

Tempozan Bridge

Reference (m)Steel slab 2-layer Lohse arch217
3-span continuous cable-stayed 200+485+200
Steel slab Nielsen (network) arch 252
3-span continuous steel slab
130+223+102
2-box girder
3-span continuous steel slab
119.5+235+180
2-box girder
5-span continuous steel slab
90+215+85
2-box girder V-footing rigid-frame
3-span continuous cable-stayed 170+510+120
3-span continuous Gerber truss 235+510+235
3-span continuous cable-stayed 149+355+149
Steel slab Nielsen (network) arch 254
3-span continuous half-through 95+255+95
arch

Minato Bridge
Yamatogawa Bridge

Kishiwada
BridgeShinhamadera Bridge

in 2016, and then in 2017 the method of
merging public works and toll-road project was introduced to the extension project, and it was decided for this extension
project to participate in the governmentcontrolled port-harbor project in 2018.
Currently, the Osaka Wangan Expressway Western Extension Project is steadily being promoted toward the earlier
opening of the full-length route to traffic.
Bridge Technologies Applied in
the Construction of Hanshin
Expressway Wangan Route• Truss Bridges
The Minato Bridge is a representative
long-span bridge on the Hanshin Expressway. It is a Gerber truss bridge having a center span length (L) of 510 m, theworld’s third longest, and a total lengthof 980 m (Photo 1). At the stage of project planning, many bridge types werecompared for the construction of the Minato Bridge-Gerber truss bridge, archbridge, cable-stayed bridge and suspension bridge, but the bridge types otherthan the Gerber truss type were shelved
by taking into account the support of thebridge on the soft ground of reclaimed
land or by worrying about the occurrenceof uneven sinking between supports on
the soft ground.
A specific feature in the constructionof the Minato Bridge lies in that a greatamount of 80 kgf/mm2-grade high-strength
steel (HT80) was applied as a means to reduce the steel weight of the bridge.

pressway Wangan Route (see Photo 2).
In its construction, rationalized structureand structural aesthetics were thoroughly pursued, which thus led to the adoption of an H-shaped tower with long columns installed on the horizontal member
and harp-type multi-cables. In terms ofseismic design, extensive attempts weremade to apply a long-period structure
called the all-free system in which all
supports are movable, and a vane-typeoil damper was adopted as a safety device for the long-span bridge, the first of
its kind in Japan.

• Arch Bridges

Diverse kinds of arch bridges were constructed one after another, including
a spandrel half-through arch bridgeKishiwada Bridge (L=255 m), four bas-ket-handle type Nielsen Lohse (networkarch) bridges-Shinhamadera Bridge(L=254 m), Nakajimagawa Bridge(L=157 m), Kanzakigawa Bridge (L=148m) and Nishinomiyako Bridge (L=252m) and a double-deck Lohse bridgeRokko Island Bridge (L=217 m).

• Seismic Retrofitting

The type of bridge that has been extremely difficult to retrofit since the Great Hanshin Earthquake (1995) was the long-spanbridge. For the Minato Bridge in particular, because of its huge steel weight peculiar to a truss bridge, conventional seismic retrofitting such as additional steel
plate reinforcement and concrete filling
could not be applied. Given this situation,
new seismic retrofitting measures were
worked out-the base-isolation structure• Cable-stayed Bridges

The Yamatogawa Bridge (L=355 m) is acable-stayed bridge, the first of its typein Japan with a center span surpassing
300 m. It is a three-span continuous cable-stayed bridge composed of one column tower and employing one fixed support from the aspect of seismic design, arare seismic design not found in current
bridge construction. The bridge clearanceof the cable-stayed Tempozan Bridge(L=350 m) is very high, about 50 m, andthe bridge adopts a long-period structureby the use of a flexible tower with two
fixed supports in the tower section. In theconstruction of these two bridges, extensive R&D was promoted on wind-resistant design to pursue high wind-resistantstability by the use of a flap structure anda flat hexagonal-section structure withsplitter plates and fairings.
It is the Higashi-Kobe Bridge (L=485m) that is cited as the compilation of cable-stayed bridges of the Hanshin Ex-

Photo 1 Minato Bridge

Photo 2 Higashi-Kobe Bridge
August 2022 Steel Construction Today & Tomorrow 2

and response-control structure, which
thus led to the adoption of base-isolation
floor framing and response-control braces. The fundamental factor that facilitatedthe adoption of such measures is a damage-control design worked out based on
past seismic damage experience.
These seismic retrofitting concepts
have since been applied effectively in theshear panel of the main tower at the Tempozan Bridge that treats displacement in
the direction perpendicular to the bridge
axis and the cable damper at the HigashiKobe Bridge that controls the bridge axis-direction movement of the main girder.
Structural Plans for Osaka Wangan Expressway Western Extension Project• Concept of Structural Plans
The highway section of the Osaka Wangan Expressway Western Extension
Project is composed mostly of bridge
structures at both the land and sea areas,among which is a long-span bridge witha main span length of about 600 m thatstraddles the route at the Port of Kobe.
In the selection of the bridge type to be
applied in the extension project, a basic
policy was formulated in which the selection be made by working out the concept of structural plans based not only on
the design/construction and maintenanceof the bridges in service mentioned
above but also past seismic experience,
and at the same time comprehensively
taking into account the performance andeconomic advantage that conform to thisconcept (refer to Fig. 2).

• Shinko-Nadahamakoro Bridge(tentative name)For the bridge type that conforms to the
proposed concept of the structural plan,
three plans for the bridge type weredrafted for the Shinko-Nadahamakoro
Bridge: single cable-stayed bridge, continuous cable-stayed bridge and continuous suspension bridge. While the span
length of the planned Shinko-Nadahamakoro Bridge will reach 650 m, it was
judged that the possibility is high for theconstruction of a multi-span continuous
long-span bridge when taking into account the recent trend in bridge technologies. Meanwhile, it was considered thata center span of 600-m class will exceed
the common span range applicable by
the use of truss, arch and other bridges
and that the adaptability of these bridges
to the proposed structural plan concept is
low from the aspect of seismic resistance

3 Steel Construction Today & Tomorrow August 2022

Fig. 2 Concept of Structural Plans
Concept item forstructural plans

Design consideration

Network in
the event ofdisasters

Considerations
to unexpected
design conditions

Inspection
applicability

Repairapplicability

Effective useof new
technologies

Creation oflandscaping

Urban
landscaping

Continuityof routes

Innovativeness/
Developability

Harmonization
with society
and nature

Long-term
maintenance

Securementof durability

Reliablemaintenance

Mitigationof traffic
obstruction

Construction
qualityand maintenance.
Finally, the continuous cable-stayed
type was selected for the Shinko-Nadahamakoro Bridge (Fig. 3). Specifically,
while its cost (initial and lifecycle costs)
is high, the cable-stayed bridge was evaluated comprehensively as an excellent
bridge type from such aspects as highmaintenance/landscaping performance,
sufficient redundancy to resist seismic
motion and ground displacement andhigh inspection/restoration performance.

• Kobe-Nishikoro Bridge

As a bridge type that conforms to the
proposed concept of the structural plan,
two plans were drafted for the Kobe-Nishikoro Bridge-1-main tower cablestayed bridge and 2-main tower cablestayed bridge. In the case of constructing
the 1-main tower cable-stayed bridge,
while its span length will reach 480 m,a world-class length for cable-stayed
bridges, it was judged that the construction of 1-main tower cable-stayed bridge
would be highly feasible when taking
into account the recent trend in bridge
technologies.

Regarding the truss, arch and otherbridge types, the span length of 480 m is
not cost effective for these types and it was
judged that their adaptability to the proposed concept of structural plans is low
in terms of seismic resistance and maintenance. Further in the case of adopting thesuspension bridge, it would be required to
install anchorages in the sea area, which
would bring about great influence due
to circumjacent land changes, and it was
further judged that the adaptability of thesuspension bridge to the proposed concept of the structural plan is low.
To these ends, because the bridge construction site is not located in the center
portion of sea space, the 1-main tower
cable-stayed bridge was evaluated as thebridge type for Kobe-Nishikoro Bridgefrom the perspective of excellent landscaping performance in terms of asymmetrical space and high adaptability tothe proposed concept of the structuralplan (Fig. 4). Meanwhile, the position of
installing the tower of the 1-main tower
cable-stayed bridge will be located on asite where the risk of uncertain fault canbe mitigated.

Fig. 3 Shinko-Nadahama Koro Bridge (continuous cable-stayed bridge)
160

2730
390

650

650

207
650

Shinko route

Nadahama routeFig. 4 Kobe-Nishikoro Bridge (1-main tower cable-stayed bridge)
Port Island

Wadamisaki

Kobe-Nishi route390

Feature Article: Towards Highly Resilient and Longer-lasting Steel Bridges (2)Activities of the Research Committee
on Steel Bridges with Higher Resilienceand Longer Service Life (2nd Term)by Kazuo Tateishi
Chairman of the Research Committee on Steel
Bridges with Higher Resilience and Longer Service
Life (Professor, Nagoya University)

Kazuo Tateishi: After finishing the master course
at the Tokyo Institute of Technology, he entered
East Japan Railway Company in 1988. Then,he served as associate professor at the Tokyo
Institute of Technology and The University of Tokyo in 1997. He assumed his current position as
professor of the Graduate School of Engineering,
Nagoya University in 2003.

Towards Social Infrastructurewith Higher Resilience andLonger Service Life
Recently, phenomena such as large-scale
earthquakes, wind and flood damage andother natural disasters have occurred almost every year, jeopardizing human lives
and lifestyles. The importance of providing measures against disasters is now being emphasized more than ever before.
Social infrastructure is required to be resilient and continue to deliver flexible performance sufficient to resist a massive earthquake deemed likely to occur in the near
future and wind and flood damage expected to become more and more devastating.
Meanwhile, how to cope with the aging ofmany structures that form lifelines is an
imminent issue and how to extend the service life of those structures, new and old,
is now a matter of growing concern.
In the field of steel bridges, there isalso a rising need for the provision ofcountermeasures against large-scale
damage and for the recovery of function of obsolete structures, with two key
points-higher resilience and longer service life. Bridge engineers are required
to make contributions toward the protection of human lives and the maintenanceof the national economic vitality by solving these emerging tasks.
In order to solve these tasks, it is important to prepare more resilient and longer-life structures than ever before and at
the same time to appropriately maintainthese structures. The technologies that accurately meet these needs are wide-ranging. For example, it is necessary to establish technology that can surely guarantee
the diverse performances required for steel
bridges. In addition, these technologies areimportant: design technology that takes into account ease of renewal, technology thatallows sure and effective maintenance, andin research on steel bridges for more than
20 years since 1997 based on the assignment of research from The Japan Iron
and Steel Federation (see Table 1). JSSC
has made contributions toward solving
diverse tasks that meet the needs of thetimes by tackling many problems facing
steel bridges, accumulating research attainments and reflecting them in various
kinds of standards and specifications.

technology that is conducive to recoveringand improving bridge functions by meansof repair and function reinforcement.
Research Committee on Steel
Bridges with Higher Resilienceand Longer Service Life (1st Term)
The Japanese Society of Steel Construction (JSSC) has promoted the activities
of various research committees involved

Table 1 Chronology of Research Committees on Steel Bridges
FY

Research Committee

Working Group

1997- Research Committee
1999 on Next-generation
Civil Engineering
Steel Structures• Working Group on Design of Rationalized Steel Bridge Girders• Working Group on Seismic Design Method for Steel Bridges• Working Group on Application of High-performance Steel
Products for Steel Bridges

2000- Research Committee
2002 on the Performancebased Design ofSteel Bridges• Working Group on Safety and Applicability of Steel Bridges• Working Group on Corrosion Protection and LCC for Steel
Bridges• Working Group on Seismic Resistance of Steel Bridges• Working Group on Higher Performance of Steel Bridges

2003- Research Committee
2005 to Improve Steel
Bridge Performance• Working Group on Rationalized Design Methods• Working Group on Improvement of Steel Bridge Durability• Working Group on Seismic Design Guidelines for Steel Bridges• Working Group on Weathering Steel Bridges

2006- Research Committee
2008 to Improve
Performance andReliability of Steel
Bridges• Working Group on Rationalized Structure and Design for Steel
Bridges• Working Group on Fatigue Strength of Steel Bridges• Working Group on Seismic Design Guidelines for Steel Bridges• Working Group on Weathering Steel Bridges

2009- Research Committee
2012 on Improvement ofStructures andDesign Method for
Steel Bridges• Working Group on Rationalized Structure and Design for Steel
Bridges• Working Group on Fatigue Strength of Steel Bridges• Working Group on Seismic Design Method for Steel Bridges• Working Group on Weathering Steel Bridges

2013- Research Committee
2014 on Improvement ofStructures andDurability of Steel
Bridges• Working Group on Rationalized Structure and Design for Steel
Bridges• Working Group on Fatigue Strength of Steel Bridges• Working Group on Maintenance for Weathering Steel Bridges

2015- Research Committee • Working Group on Rationalized Design2017 on Steel Bridges with • Working Group on Fatigue Strength
Higher Resilience and • Working Group on Corrosion and Durability
Longer Service Life
(1st Term)2018- Research Committee • Working Group on Rationalized Design
2019 on Steel Bridges with • Working Group on Fatigue Strength
Higher Resilience and • Working Group on Corrosion and Durability
Longer Service Life
(2nd Term)

August 2022 Steel Construction Today & Tomorrow 4

Fig. 1 Road Map to Attain Respective Research Tasks of the Committee on
Steel Bridges with Higher Resilience and Longer Service Life
Tasks

① Subtask 1
Working Group on
Rationalized Design② Subtask 2
Working Group on Fatigue
Strength③ Subtask 3
Working Group on
Corrosion and Durability

Interdisciplinary tasks inabove-mentioned threesubtasks
Steering Conference〜 FY2014
Verification ofload-carrying
capacity ofcolumn andun-stiffened plate

FY2015FY2016FY2017FY2018FY2019
Revision of Specifications for Highway
Bridges: Introduction of load andresistance factor design method
Presentation of load and resistance factor for
Presentation of example ofcolumn and stiffened plate and presentation of
application of SBHS (steel for
constitutive law for seismic analysis that canbridge high-performance structure)deal with cyclic loading
member in seismic design

Preparation of
Structuring of design, inspection andload rating manual rating systems; Organization of(draft)manual for bridge assessment
Effect on fatigue life improvement including that by theuse of high-strength steel (experiment, analysis andStandardization of effect on fatigue
design method)life improvement
Collection of load rating data andits trial analysis

Expansion ofdesign fatigue
class
Trial for andarrangement of
fatigue life
improvement
Surveys of task
submitted by
Ministry of Land,
Infrastructure,
Transport andTourism

Collection of information on detective method for fatigue
crack, proving of repairing and reinforcing methods forfatigue crack

Preparation of guideline for crack
repair and service life prolongation
methods

Guideline for maintenance andcorrosion diagnosis data
Assessment of practical bridge dataand examination of reliability
improvement measure

Maintenance andcorrosion
diagnosis

Preparation of handbook on design
and maintenance and its reflection
in standards

Survey andTechnical data on steel bridge
Preparation of
Examination about steel bridge
assessment ofcorrosion diagnosis technology
corrosion map and having high corrosion resistancepractical example
corrosionof corrosion ofprotection manualbridge① Interdisciplinary assessment of attainments of each working group→Proposal of
attainments to society ② Tackling with the research task that supplements the niche between
fields (between subtasks and different fields) ③ Creation of research theme for future

The Research Committee on Steel
Bridges with Higher Resilience and Longer Service Life was established in 2015as a research organ that took over these research activities and in light of the need forthe higher resilience of steel bridges as acountermeasure against natural disasters
and for the longer service life for aging
bridge structures. In the three-year research
activities (1st term) aimed at the greater resilience and longer service life of steel
bridges, the Research Committee achieved
definite achievements such as the rationalized assessment of load-bearing capacityof steel bridges and steel product members,
long-lasting technology as a means to treat
the fatigue and corrosion of steel bridges,
and assessment and repair technologies
useful for appropriate maintenance.
Research Committee on Steel
Bridges with Higher Resilience andLonger Service Life (2nd Term)
During the period of activities by the
Research Committee, the Kumamoto
Earthquake occurred in 2016 and the periodic inspection of bridges was legally required to be carried out. Triggeredby these events, steel bridges have faced
emerging tasks such as the damage control, and easy and reliable maintenance.
Given such a situation, the ResearchCommittee on Steel Bridges with Higher Resilience and Longer Service Life
(2nd Term) was established with the pur5 Steel Construction Today & Tomorrow August 2022

pose of putting into practice the higher resilience and longer service life ofsteel bridges by contributing to the revision of technical standards and specifications through accumulation of researchachievements (Fig. 1). The Committee
is composed of three working groups asshown in Fig. 2. The committee members cover those from wider fields-not
only research organizations but also highway/railway companies, The Japan Iron
and Steel Federation, Japan Bridge Association and The Japan Civil Engineering
Consultants Association. Its specific feature lies in that the committee takes a pro-active approach to reflect research results
in practical bridge construction works.

♦♦♦

The Research Committee on Steel Bridges with Higher Resilience and Longer
Service Life promoted its 2nd-term research activities mainly in the period
from 2018 to 2019 while at the sametime reexamining its 1st-term research
activities. In the following pages, the research achievements of each of the threeworking groups-Working Group on
Rationalized Design, Working Group on
Fatigue Strength and Working Group on
Corrosion and Durability-are outlined.

Fig. 2 Outline of Research Committee on Steel Bridges with Higher Resilienceand Longer Service Life and Its Working Groups
Research Committee on Steel Bridges with Higher Resilience and Longer Service Life
Chairman: Kazuo Tateishi (Nagoya University); Vice Chairman: Yoshiaki Okui (Saitama University);
Jun Murakoshi (Tokyo Metropolitan University); 27 managers and committee members
Working Group on Rationalized Design
Chief: Yoshiaki Okui (Saitama University);
Deputy Chief: Takao Irube (FaB-Tec Japan Corporation);
Secretary-general: Takeshi Miyashita (Nagaoka Institute of Technology);
21 committee members and observers
Working Group on Fatigue Strength
Chief: Kengo Anami (Shibaura Institute of Technology);
Secretary-general: Takeshi Hanji (Nagoya University);
22 committee members and observers
Working Group on Corrosion and Durability
Chief: Eiji Iwasaki (Nagaoka University of Technology);
Secretary-general: Tetsuhiro Shimozato (Ryukyu University);
40 committee members and observers

Feature Article: Towards Highly Resilient and Longer-lasting Steel Bridges (3)Report of the Working Group on
Rationalized Design-Experiments towards Rationalized Design and Load Rating in Maintenanceby Yoshiaki Okui
Chief of the Working Group on Rationalized
Design, Research Committee on Steel Bridges
with Higher Resilience and Longer Service Life
(Professor, Saitama University)

In the 2nd-term research, the Working
Group on Rationalized Design of the Research Committee on Steel Bridges with
Higher Resilience and Longer Service
Life promoted research focusing on thefollowing themes:• Ultimate and serviceability limit strengthsof single-rib compressive stiffened plates• System redundancy in load rating• Examination towards the wider application of composite girders• Local-global coupling buckling of columns• Examination of elastoplastic parameters of steel products applicable to seismic analysis
Outlines of the achievements from research on three themes-the first, secondand fourth-are introduced in the following article.
Ultimate and Serviceability Limit
Strengths of Single-rib
Compressive Stiffened Plates
Both ultimate limit strength (ULS) andserviceability limit strength (SLS) of single-rib stiffened plates were investigat-

ed using numerical analyses. The singlerib stiffened plates with large aspect ratios
are a structural element that is showing increasing application in narrow-width box
girder bridges. While it is well known that
ULS of single-rib stiffened plates is higher than that of standard stiffened plates
specified in the Specifications for Highway Bridges of Japan Road Association(JSHB)1), its predominance is not taken into account in the current version of JSHB.
Furthermore, the property of recently developed “Steels for Bridge High Performance Structure” (SBHS) is not properly assessed in the specifications in current
use. In this research, we aimed at clarifying probabilistic information about theload-bearing capacity of single-rib stiffened plates considering these aspects.
The deterministic elastoplastic finite
element analysis (FEA) and finite difference approximation (FDA) were employed to estimate probability parametersof ULS and SLS. The residual stress andinitial out-of-plane displacement wereconsidered as initial imperfection, andthey were treated as random variables.

Fig. 1 Ultimate Limit Strength (5% Fractile)of Compressive Stiffened Plates

The peak compressive stress was adopted as ULS, while the compressive stressobtained when the out-of-place displacement reached the limit value of manufacturing tolerance was assigned to SLS.
As examples of numerical results,
Figs. 1 and 2 show the 5% fractile values of ULS and SLS, respectively. In
both figures, the vertical axis is ULS andSLS normalized using the yield stress
σy, and the horizontal axis stands for thewidth-to-thickness ratio parameter Rr of
sub-panels in a stiffened plate. They also
show the numerical results of stiffened
plates with 2-3 longitudinal stiffeners obtained in the 1st-term research. In addition, experimental results for bridge highperformance steel SBHS500 and normal
steel SM490Y are plotted in Fig.1.
In 2021, the wide stiffened plate withmore than 4 longitudinal stiffeners wasstudied. In 2022, it is scheduled to propose a design method by incorporating all
results (ULS, SLS, narrow stiffened platewith a single rib, intermediate stiffened
plate with 2-3 ribs, wide stiffened plate)
and a design code for JSHB as well.

Fig. 2 Serviceability Limit Strength (5% Fractile)of Compressive Stiffened Plates

ULS 5% fractile value

SLS 5% fractile value

1.0

1.0

0.8

0.8

0.6

0.6

FEA 2-3 ribs
FEA 1-rib
JSHB
Exp 1-rib SBHS500
Exp 1-rib SM490Y

0.4
0.2
0.0

0.0

0.2

0.4

γl /γl,req = 1.0

σcr /σyσcr /σyYoshiaki Okui: After graduating from the Graduate Schoolof Science and Engineering, Saitama University, he joined
Kawasaki Heavy Industries, Ltd. in 1985. Then he served
as associate professor at Saitama University in 1993 andvisiting researcher at Delft University of Technology in Netherlands in 1996. He assumed his current position as professor at Saitama University in 2009. His areas of expertisecover structural engineering and bridge engineering.

0.4

FEA 2-3 ribs
FEA 1-rib
JSHB

0.2

0.6

0.8
Rr

1.0

1.2

1.4

0.0

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Rr
August 2022 Steel Construction Today & Tomorrow 6

System Redundancy in Load Rating
A system factor of load rating for existing bridges was investigated. In thisstudy, the system factor ϕs is multiplied
to member capacity C to reflect the system redundancy when calculating a rating factor RF. The following general expression is assumed to estimate the rating
factor:where
γD and γL: Dead load factor and live
load factor
D, L, I: Dead load effect, live load effect, dynamic load allowance
C: Member capacity
ϕc: Condition factor
In bridge design practices, the ultimate state of a member is regarded as theultimate state of the whole bridge system,
but in most bridges, the bridge system
possesses a load-carrying capacity higher than that of the single bridge member.
The system factor is used to maintain an
adequate level of system safety.
In order to evaluate the system factor,
both linear elastic and nonlinear finite element analyses (FEA) were carried out,
and the system factor ϕs was calculated from the difference between the ultimate-state live load factors using:

where
λ,λ*: Ultimate-state live load factors
obtained from nonlinear FEA
and linear elastic FEA, respectively
Because system redundancy resultsfrom changes in stiffness due to plastic
behavior cannot be considered, λ* obtained from linear elastic FEA does not
involve the system redundancy. On theother hand, λ from nonlinear FEA reflects the system redundancy. Hence,
when the rating factor RF is calculated
based on Equation (1) and using the system factor in Equation (2), it has become
possible to calculate a rating factor RFthat takes into account the effect of system redundancy.
As a case study, the system factor was
calculated for the three bridges shown in
Table 1. While these three bridges were
designed in accordance with the former
design standard that adopted the allowable stress design method, the system
factor was calculated based on the current version of JSHB. As an example of
7 Steel Construction Today & Tomorrow August 2022

FEA, Fig. 3 depicts the strain distribution of the concrete deck and the effective stress distribution of steel girders at
the ultimate state in A Br. shown in Table 1.
Fig. 4 shows the system factor obtained from Equation (2) and the live loadfactor at the limit state obtained from thenonlinear FEA. G1 stands for the outer girder, and G2 for the inner girder.
As the number of main girders increases, the system factor becomes larger. In
the 3-span continuous plate girder N Br.,the ultimate live load factor for negative
bending moment case “Mmin” becomes
lower than that for positive bending moment case “Mmax”, and the system factors became nearly 1.0. The standard approach for load rating is arranged as the“Bridge Evaluation Manual” by incorporating these results and the achievements

attained in the 1st-term research.
Local-global Coupling Buckling ofColumns
In the 1st-term research, two compressive loading tests were conducted for longcolumns with non-stiffened box-section.
The dimensions of both test specimens
reflected the cross section of actual truss
bridges. Furthermore, the dimensions of
two test specimens were settled in accordance with JSHB so that global buckling
occurred in the one specimen and localglobal coupling buckling took place in theother one. In the 2nd-term research, first
nonlinear FEM analysis was conducted toreproduce the loading tests.
Fig. 5 shows the comparison between
the test and analytical results for the specimen using bridge high-performance steel
SBHS500. The peak load-carrying capac-

Fig. 3 Nonlinear FE Analysis of A Br. at the Ultimate State3)(a) Strain distribution of concrete decks(b) Effective stress distribution of steel girders

Table 1 Outline of Model Bridges for Case Study
Model name

A Br.

B Br.

N Br.

Type

Composite simple-spanplate girder

Composite simple-spanplate girder

Non-composite 3-spancontinuous plate girder

Span length (m)

34.4

39.3

3@28.0No. of girders

5

3

4

1983

1975

Construction year 1971

ity could be obtained within a margin of
6% compared to the experimental results
obtained by introducing the measured initial displacement and residual stress of
specimens into the FEM analysis.
Since it was found that the bucklingstrength can be predicted by using the developed FE models, the design equation
for the local-global coupling strength forcolumns was examined by means of FE
analysis. Fig. 6 shows examples of theparametric study results, in which thecircles stand for the FEA results and theblue and violet curves indicate the design strengths of the current version of
JSHB. It can be seen from the study results that the buckling strength decreases
owing to the local-global coupling effectas the width-thickness ratio parameter Rof the plate that composes the non-stiff-

ened box-section increases. Meanwhile,
JSHB underestimates the coupling buckling strength especially for R=1.5.
We proposed Equation (3) as a design
equation for local-global coupling buckling strength σcr :where ρcrg is the reduction rate for column buckling strength specified in JSHB,
and χ stands for the coupling effect, andis given in the following expression:

Fig. 7 illustrates a comparison between the proposed equation and theanalytical results. Although the slightly safety-side assessment was made, theproposed equation and the analytical re-Fig. 4 System Factor ϕs and Ultimate Live Load
Factor λ Obtained from Nonlinear Finite
Element Analysis

sult showed a favorable correspondence.
References
1) Japan Road Association: Specificationsfor Highway Bridges-I Common, II
Steel Bridges and Steel Product Members, Maruzen, 2017 (in Japanese)
2) Research Committee on Steel Bridges
with Higher Resilience and Longer Service Life (II): Advanced Design and Verification Technologies for Steel Bridges,
JSSC Technical Report No. 119, 2020
(in Japanese)3) Okui, Y., Denda, D., Kumaki, K., Sakuma, S: A proposal for evaluation methodof system redundancy and system factors in load rating of steel bridges, J. of
Struct. Eng., JSCE, Vol.68A, pp.1-10,2022 (in Japanese)

Fig. 5 Comparison between Experiment and
FE Analysis of Box Column Buckling Test
for Bridge High Performance Steel (SBHS500, R=0.9, λ=0.6)

8

G1

G1

6
5

G2

G2

4
A Br.
B Br.
N Br. M max
N Br. M min

G2

2
1

G1

G2

3

G1
0.8

0.9

1.0

1.1

1.2

1.3

1.4

FEA
Exp

3000

Axial force (kN)

Ultimate live load factor

7

1.5

2000

1000

0
1.6

0

2

4

System factor

10

Fig. 7 Comparison between Proposed Design
Equation and FEA Results

1.6

1.2
1.0
0.8
0.6
0.4

1.0
Proposed eq. σcr /σyEuler curve
R=0.5
R=0.7
R=0.9
R=1.1
R=1.3
R=1.5
JSHB R=0.5
JSHB R=1.5

1.4

σcr /σy

8

Axial disp. (mm)Fig. 6 Design Buckling Strength (Solid Curve) andNonlinear FEA Results (Circle Mark) with
Various Width-to-Thickness Ratio Parameters R
and Column Slenderness Parameters λ

0.8

R=0.5
R=0.7
R=0.9
R=1.1
R=1.3
R=1.5

0.6
0.4
0.2

0.2
0.0
0.0

6

0.4

0.8

1.2

Column slenderness ratio λ

1.6

2.0

0.2

0.4

0.6

0.8

1.0

FEA σcr /σyAugust 2022 Steel Construction Today & Tomorrow 8

Feature Article: Towards Highly Resilient and Longer-lasting Steel Bridges (4)Report of the Working Group on Fatigue
Strength-Improvement of Fatigue Strength and Verification of Detection and Repair
Technologiesby Kengo Anami
Chief of the Working Group on Fatigue
Strength, Research Committee on Steel
Bridges with Higher Resilience and Longer
Service Life (Professor, Shibaura Institute ofTechnology)

Quantitative Evaluation Method
for the Effect of Peening
Treatment on Fatigue Strength
Improvement
Diverse approaches have been proposed as the method to improve thefatigue strength of welded joints bymeans of weld toe treatment. As forthe peening treatment that improves fatigue strength by introducing compressive residual stress, an object of thisresearch, many approaches have been
proposed and extensive research has
been promoted. As a result, this peening treatment has been put into practicaluse in bridges, centering on the existingbridges, but fatigue strength classes after peening treatment have not yet been
established in Japan.
Noticing the application of peening treatment in newly-built or existingbridges, the Working Group promoted
the examination of fatigue strength classafter peening treatment, part of which is
introduced below:

Fig.1 Fatigue Design Curve of Peened Welded Joints

Stress range (N/mm2)

Yield stress
235≦σγ≦550 N/mm2 +3 classσγ > 550 N/mm2 +4 class

1

Δσf

m=3

Stress ratio
R≦0.2
0.2<R≦0.5
0.5<R≦0.7
0.7<R

Δσf

m=7

Δσce Peening

Δσce AW
2×106
Fatigue life
9 Steel Construction Today & Tomorrow August 2022

Classes of Welded Joints after
Peening Treatment
In steel bridges, out-of-plane gusset andcruciform welded joints are joint forms
that frequently pose fatigue-induced problems. Targeting these joints after threekinds of peening treatments-ultrasonic impact treatment (UIT), hammer peening on base metal (HP) and air-type needle
peening (PPP), the Working Group experimentally examined the effect of peening
treatment on fatigue strength improvement
and evaluated the dependency of the effectof peening treatment on steel strength andstress ratio. At the same time, the Working
Group analyzed the existing fatigue test
data available in Japan and abroad.
As a result, it was confirmed that steel
strength (yield strength) and stress ratio
strongly affect the fatigue strength improvement by peening treatment, andthen the Working Group proposed the fatigue design curve after peening treatment shown in Fig. 1. Fig. 2 shows ex-

400

Stress ratio increase
1

Yield stressincrease-0 class-1 class-2 class-3 class• Settlement of Fatigue Strength

Fig.2 Comparison between Proposed Design Curveand Fatigue Test Results(Out-of-plane Gusset Welded Joints)

Stress range (N/mm2)

In order to tackle two major propositions imposed on steel bridgeshigher resilience and longer service
life, the Working Group on Fatigue
Strength of the Research Committee on Steel Bridges with Higher Resilience and Longer Service Life promoted research and surveys with theaim of contributing to two propositions from the perspective of welded
joint fatigue. Specific activities were
promoted in view of the following twotasks:• Quantitative evaluation method for theeffect of weld toe treatment on the improvement of fatigue strength from theperspective of improving the fatigue
strength of welded joints
Effective
and rational maintenance (ef•fect of inspection and repair/reinforcement) from the perspective of the maintenance of steel bridges
An outline of the achievements of theWorking Group on Fatigue Strength is asfollows:

Kengo Anami: After graduating from the School of Engineering, Tokyo Institute of Technology in 1993, he served
as research associate at Lehigh University in the US in
2001 and as associate professor at Shibaura Institute ofTechnology in 2008. He assumed his current position as
professor at the Department of Civil Engineering, Shibaura
Institute of Technology in 2014. His areas of expertise coversteel structures and their maintenance.

r : Root crack
JSSC
A(190)
B(155)

200

C(125)

100
80
60
40

20 4
10

D(100)
235≦σY≦550 N/mm2
R≦0.2

Yield stress:+3 classStress ratio: +0 class
Total:+3 class

AW
Peening
105

106
Fatigue life (cycles)

H(40)
107

108

Effective and Rational Maintenance
Aiming at the effective and rational
maintenance of steel bridges, the Working Group promoted the following examinations: (1) applicability of non-destructive method to detect fatigue crack
without removing steel paint was examined; (2) focusing on the 2 typical countermeasures for the fatigue crack in steel
bridge, namely (stop hole+splice plate)and (stope hole applied to weld bead),the rational repair/retrofit design method and quantitative evaluation method ofeffects of the countermeasure were discussed. In this section, examination of(stop hole+splice plate) is introduced.
In the activities of the Working Groupon Fatigue Strength introduced in Steel
Construction Today & Tomorrow No. 54(August 2018), two methods to forecast
the stop hole periphery stress that governs
the reinforcement effect were explained:a method employing the cracking lengthand the splice plate structure as a param-

Fig. 3 Compressive Loading prior to Fatigue Test

Out-of-plane gusset joint specimen

eter and another method employing thestress occurring at the upper surface of the
splice plate. Aiming at establishing a rational splice plate design method, the Working Group examined the estimation of thefatigue strength of stop holes under the
Fig. 4 Reduction of Residual Stressdue to Pre-compressive Loading
150
Nominal stress (N/mm2)• Examination of Precautions
That Take into Account New
Bridge Design
Regarding precautions for peening treatment at the stage of new bridge construction, the Working Group examined thestress ratio, blast treatment after peening treatment and working of compressive force occurring during bridge construction. In this connection, the result of
examination of the influence of the precompressive loading on the peening effectis introduced in the following:
The plate-bending fatigue test (R=0.5)
was implemented employing an out-ofplane gusset joint specimen as shown in
Fig. 3 to which pre-compressive loading
was applied. Fig. 4 shows the change inresidual stress at the position 2 mm fromthe weld toe of the air-type needle peened
specimen. As seen in the figure, the levelof reduction of residual stress introducedby means of peening increased due to theincreased pre-compression loading. In
this examination, setting the level of precompression loading as a parameter, thefatigue test (R=0.5) was implemented af-

ter introducing pre-loading to examine
the effect of pre-loading on the fatigue
strength improvement by peening (thecase of pre-compressive loading at 5.8
kN is shown in Fig. 5). The examination
results showed that, as the level of precompressive loading increases, the effect of all 3 peening methods on fatigue
strength improvement decreases.
Future plans call for further examination (including additional fatigue testing under R=0) of the relationship between the reduction of the rate of fatigue
strength improvement and the pre-loading level, and incorporation of the effectof pre-compressive loading in the proposed design curves introduced above.

100
50
0
-50
-100

0

0

0 0

0

22
44

66

89

200
100
0
-100
Residualstress after
pre-loading

-200
-300
-400

Reduction ofresidual stress

Residual stressafter peening

Fig. 5 Fatigue Test Results(Pre-compressive Loading: 5.8 kN/-230 N/mm2)
400

Stress range (N/mm2)

245 mmLoad cell

JSSC
A(190)
B(155)

200

C(125)
100
80
60

D(100)
Bending test (R=0.5)

40

20 4
10
Pre-loading

Fatigue test
(R=0.5)112
Pre-compressive loading

Residual stress (N/mm2)

amples of fatigue design curves obtainedby improving fatigue strength at 2 million
cycles by 3 class, which is the sum of theinfluence of steel strength (yield stress: +3
class) and stress ratio (±0 class). The slopeof design curve is proposed to be 7. Meanwhile, when the stress range is extensive,the effect on fatigue strength improvement becomes unavailable, and accordingly in the stress range that surpasses thepoint where the as-welded design curve
and the peening curve intersect, a fatigue
design curve similar to the as-welded fatigue design curve is applied in the figure.

AW
UIT
HP
PPP

CL‑5.8

E(80)
F(65)
G(50)
H(40)

105
106
107
Fatigue life to N10 (cycles)

108

Hydraulic jackAugust 2022 Steel Construction Today & Tomorrow 10

splice plate and a simple structural analytical approach for the stress at the stop holeperiphery applicable in practical design,
which are introduced in the following:that can forecast the stress at the periphery of the stop hole under the splice plate
within an elastic range, it is consideredthat this simple model will expand thepossibility to design rational splice plates
even for practical applications.
Currently, targeting the fatigue test specimen shown in Fig. 6, examinations are underway of several modelling approaches,
which has led to the proposal of a simple
model employing the solid element (Fig. 7).

• Fatigue Strength of Stop Holeunder Splice Plate
In accordance with the results of estimated stresses at the stop hole periphery, thetension fatigue test was conducted employing fatigue test specimens in which
the splice plate thickness was changed sothat the crack initiates from the stop holeperiphery and from the area near bolt holedue to fletching (refer to Fig. 6). The fatigue test results are shown in Fig. 6. In
the test, most specimens caused fracturing due to fletching in the neighborhoodof the first bolt, and the fatigue strengthof the specimen was equivalent to thatof a high-strength bolt friction joint thatcaused similar fractures. Currently, thetension fatigue test is underway employing a specimen that can take into accountthe tensile residual stress due to welding.
Capitalizing on the results of both tests,
it is planned to confirm the fatigue strengthclass of the stop hole under the splice plate
and to make proposals towards the establishment of a rational design method for
splice plate reinforcement.

The proposed model is a linear model thatshares the nodes of the splice plate and thebase plate within a rectangular range with abolt center of 2.5D (D: bolt diameter). Whileslight differences are found in the load-displacement relationship between high-precision and proposed simple models, the stressat the stop hole periphery in both the highprecision and proposed simple models wellcoincide each other and is also well correlated with the experiment results.

Fig. 7 Proposed Simple Analytical Model

Proposed simple modelHigh precision model

Bolt
Washer• Geometrical &material nonlinear
analysis• Contact elem.
between plates,
bolt and washer• Linear analysis• Base and splice plates are combinedat the certain area centered on bolt center(a) Analytical models

600
500

2000

400

1500

Strain at SH (με)

Load P (kN)

• Simple Model to Forecast theStress at Stop Hole Periphery
In the activities of the Working Groupon Fatigue Strength introduced in Steel
Construction Today & Tomorrow No.
54 (August 2018), it was explained thatthe stress at the stop hole periphery andthe behavior of the splice plate structure
can precisely be shown by structuring
the advanced high-precision FEM model shown in Fig. 7 (a). In this connection,
if a simple FEM model were structured

300

Simple

100
0

1000

Experiment200

High precision
0

0.1

0.2
0.3
0.4
0.5
Displacement δ (mm)0.6(b) Relationship between load and displacement

Experiment
Simple5000High precision
0

400

800

1200

Nominal strain (με)1600(c) Relationship between nominal strain
and strain at stop holeFig. 6 Fatigue Tests for Stop Hole under Splice Plate
Loading

18

40 55 55 55 55 40

473

30 55 30High strength bolt M16/F10T

Stop hole(a) Fatigue test specimen

Base plate
thickness:12 mm
Splice plate
thickness Ts
12 mm (Expect
fletching fatigue)
6 mm
3.2 mm（Expect
fatigue from SH）

Crack from SH and hole on splice
400 plate for gage instrumentation
Nominal stress range (N/mm2)tS
tM

Splice plate

115
17.5

150

17.5

Loading
Base plate

JSSC C
100
80
60
40

11 Steel Construction Today & Tomorrow August 2022

JSSC A Ts=12mm:
fletching
JSSC B200

Ts=3.2 mm
Ts=6 mm
Ts=12 mmExisting data
Existing data (bolted joint)
105

106
107
Fatigue life (cycles)(b) Fatigue test results

JSSC D

Ts=3.2 mm:
fletchingFeature Article: Towards Highly Resilient and Longer-lasting Steel Bridges (5)Report of the Working Group on
Corrosion and Durability-Tasks of Applying Weathering Steel Bridges and Corrosion
Repair Method for Steel Bridgesby Eiji Iwasaki
Chief of the Working Group on Corrosion and
Durability, Research Committee on Steel Bridges
with Higher Resilience and Longer Service Life
(Professor, Nagaoka University of Technology)

Eiji Iwasaki: After finishing the doctoral course at
the Graduate School, Nagaoka University of Technology in 1990, he served as associate professorof Nagaoka University of Technology. He assumed
his current position as professor, Graduate Schoolof Nagaoka University of Technology in 2012. His
areas of expertise cover structural engineering,steel structure engineering and structural analysis.

Noticing the technology conducive to
reducing corrosion-protection costs andpreventing corrosion-induced deterioration and damage to steel bridges, theWorking Group on Corrosion and Durability of the Research Committee on
Steel Bridges with Higher Resilience andLonger Service Life promoted examinations focusing on the following themes:• Application of weathering steel in bridge
construction that allows the minimizationof lifecycle cost (LCC) in an appropriate
corrosion environment and maintenancetechnology for weathering steel bridges• Structural improvement and corrosionprotection material application technology as a means to improve the corrosion
resistance and durability of steel bridges• Measures to maintain and recover the
corrosion resistance of steel bridges
In the survey of and research on theapplication of weathering steel bridges,
the Working Group tackled the judgement on applicability or inapplicabilityof weathering steel bridges and the improvement of weathering steel bridge
maintenance technology. Specifically,
the Working Group promoted the following research and surveys-analysis
of soundness levels based on periodic
inspection data, the proposal of implementing periodical inspections, the effect of anti-freezing agent (deicing salt)
spraying on weathering steel bridges,
and the judgement of corrosion conditions of weathering steel bridges and of
measures to cope with the occurrence of
unusual corrosion.
As for measures to improve the corrosion resistance and durability of steel
bridges, the Working Group tackled thejudgement of the strength to resist thecorrosion damage and measure to repair damaged bridges, structural improvement and methods to apply corro-ing of anti-freezing agents has occurredin weathering steel bridges constructedin cold snow-fall areas, quantitative examinations of corrosion occurrence havescarcely been made. Then, we made surveys of the sprayed amount of antifreezing agent on the road (refer to Photo 1), the amount of air-borne salt on thebridge girder and the amount of the reduction of the thickness of exposed steel
members.
Survey results made clear that regarding the sprayed amount of antifreezing agent on the road S (kg/m/day/lane) and the airborne salt on the girder C (mdd=mg/dm2/day), a certain relationship of S=kC can be obtained1). In
this relationship, k shows the contribution ratio of flying of the anti-freezing
agent sprayed on the road to the girder
section. Fig. 1 shows the contribution ratio of flying of the anti-freezing agent toa parallel bridge with no difference in el-sion-prevention materials, and measures
to maintain/recover corrosion resistanceand its inspection method. Specifically,
the Working Group promoted the following research and examinations: strength
diagnosis for girder end and highstrength bolt friction joints, the method
to repair corrosion-induced thickness reduction and the effect of repair methods
on strength improvement, and methods
to improve corrosion resistance. Developmental research on a steel bridge inspection simulator employing the corrosion map was also promoted.
Part of the specific activities of theWorking Group on Corrosion and Durability are introduced in the following:
Evaluation of Applicability of
Weathering Steel Bridges in
Anti-freezing Agent Spraying Areas
While a few examples have been reported in which corrosion due to the scatter-

Photo 1 Road surface on the Kochi Expressway in WinterAugust 2022 Steel Construction Today & Tomorrow 12evation. The spraying amount S on theroad (4 lanes, each 2 for inbound andoutbound) where 53 kg of anti-freezing
agent is annually sprayed is 53 kg/m/365
days/4 lanes or 0.036 kg/m/day/lane. Because the contribution ratio of flying to
the upper surface of flanges k is withina range of 2~5 as shown in the figure,it can be obtained that the flying amountto the upper surface of lower flange C is
0.072~0.18 mdd.
The practically-measured flying
amount of anti-freezing agent on thebridge installed on this 4-lane roadamounted to 0.113 mdd on the outside
area of the inbound lane and 0.248 mdd
on the outside area of the outbound lane,
and thus it can be considered that the approximate flying amount on the girder
can be calculated by the use of this flying contribution ratio. In addition, theabove-mentioned examination showedthat there is a correlation between the airborne salt amount and the corrosion-induced reduction in the thickness of steel
test pieces. (Refer to Fig. 2)
Improvement in the Objective
Evaluation of Rust Appearance ofWeathering Steel Bridges
Weathering steel bridges suppress the development of rusting by forming an adhesive rust layer on their surface. However,there are cases in which the adhesive rustis not formed depending on the bridge
installation environment and the specificproperty peculiar to the weathering steel
cannot be demonstrated. To this end, it isnecessary to evaluate the soundness levelof rust conditions. Then, based on transparent-adhesive-tape tests, we structured
a binary classification AI that is applied
to determine whether or not the rust that
occurred requires special care to be paidin maintenance. (Refer to Photo 2)
In order to confirm the classification
accuracy of the AI, 8 kinds of data sets
were prepared that are composed of the
training data and the data used for evaluation (Table 1). In the table, the datameans the transparent-adhesive-tape test
data, C means the rust that requires carein maintenance and S means the rust that
does not require care in maintenance.
While the amount of data and the ratioof C to S are changed for every data set,
AI was structured for which the classification accuracy surpassed 90% for every
data set. AI that showed the highest classification accuracy of 95.6% was that fordata set 2-7, with which the correct evaluation result for rust appearance was obtained.
Meanwhile, there were cases of incorrect evaluation such as the case in which
C was judged as C. How to reduce theFig. 1 Contribution Ratio of Flying of Anti-freezing Agents k

1~2
2~5

Height
2~3 m

Space
1m

1~2
2~5

Position of measuring instrument(bottom of web, top on lower flange)

Fig. 2 Amount of Flying Deicing Salts
and Corrosion Loss of Plate
Thickness
Corrosion loss of plate thickness
by one year exposure A (μm)

300

1~2
2~5

30

Central of Honshu
Shikoku Island
Hokuriku and Niigata
Previous research (protective rust)Previous research (detached rust)

1
0.001

0.01

0.05 0.1

1Annual flying amount of deicing salt C (mdd)
13 Steel Construction Today & Tomorrow August 2022

case of undesirable evaluation is a futuretask in terms of practical applications.
Diagnosis of Strength at Corroded Bolted Joints
High-strength bolted joints are the typical structural section where corrosion isliable to occur, and various countermeasures are applied according to the levelof corrosion-induced deterioration-repainting, replacement of bolt and reinforcement and replacement of splicing
plates. Therefore, in order to appropriately and rationally maintain high-strength
bolted joints, it is required to understandand evaluate the sliding strength thatmeets the corrosion condition of eachstructural member (base plate, splicing

Table 1 Binary Classification Data Sets and Classification Accuracy
Number of training data

Number of data forevaluation

Classification
accuracy (%)

140

160

91.9

60

420

160

93.1

2-3

100

700

160

94.4

2-4

140

980

160

94.4

2-5

220

1540

160

92.5

2-6

220

220

160

93.8

2-7

1540

1540

160

95.6

2-8

1540

3080

160

93.8

Data set

100

10

1~2
2~5

Photo 2 Sample of transparent adhesive tape test

C

S

2-1

20

2-2

plate, high-strength bolt).
Taking into account these situations
and notifying the high-strength bolt andsplicing plate, examinations were madeof the method to evaluate the tightening axial force and the sliding strengththat conform with the thickness reduction form of the high-strength bolt andthe splicing plate in which corrosion-induced thickness reduction occurs2). Examination results showed that the residual tightening axial force of corrodedbolts can be evaluated with an accuracyof ±15% based on the corrosion form andthe thickness reduction amount, which
led to the proposal of the flow to evaluate the retained sliding strength of corroded splicing plates. (Refer to Fig. 3)
Development of Steel Bridge
Inspection Simulator Employing
Corrosion Map
One of the specific advantages brought
about by the use of steel bridges lies inthat their corrosion can be recognized
immediately and visually, but corrosion
characteristics (corrosion condition, corrosion factor, corrosion form, etc.) arediverse. Accordingly, high-level corrosion inspection skills are required suchas continued accumulation of knowledge, on-site visual approach based on
experience, capability to effectively implement inspections, and understandingof not only the serious corrosion that involves traffic regulation but also the specific features of the structure that is likely to cause corrosion.
Given such situations, we developed asteel bridge inspection learning software
employing 3D corrosion maps preparedby means of the collection and analysis
of corrosion examples3). In order to verify the validity of this software system,
hands-on learning and questionnaire surveys with the participation of engineers
were carried out and the results thus obtained were examined. (Refer to Fig. 4)

Fig. 3 Diagnosis of Strength at Corroded Joint Section

Corrosion of bolt

Corrosion of splicing plate

Diagnosis of bolt

Diagnosis of splicing plate

In the conventional learning method,a corrosion map was used that was prepared by arranging the corrosion recordsof bridges with different construction
environments and lapse of application
years to a record. In the newly-developed
learning method, a 3D-CG corrosion
map is used that was prepared based on
respective bridge inspection data. Compared to the conventional method, thislearning system employing the 3D-CG
corrosion map was successfully evaluated as a system that is valid in effectively
learning knowledge about corrosion inspections.
References
1) Eiji IWASAKI, Ryuichirou NAKASHIMA, Hiroshi TAWADA and Ikki ISHII:EVALUATION OF APPLICABILITY
OF WEATHERING STEEL BRIDGEIN DEICING SALT SPRAYING DISTRICTS, Doboku-Gakkai-Ronbunsyuu
A1, Vol.74，No.3, 440-457, 2018 (inJapanese)2) Shuhei YAMASHITA, Tetsuhiro SHIMOZATO, Masayuki TAI, Tasunori
ARIZUMI and Tetsuya TABUKI: CORROSION BEHAVIOR OF SPLICED
PLATE AND SLIP RESISTANCE IN
HIGH STENGTH BOLTED CONNECTIONS, Doboku-Gakkai-Ronbunsyuu
A1, Vol.74, No.3, 359-375, 2018 (inJapanese)
3) Yasushi NAGASWA, Tetsuhiro SHIMOZATO, Masayuki TAI, Yoshiaki TAMAKI and Yusuke HIWA: DEVELOPMENT OF LEARNING SYSTEM FOR
CORROSION INSPECTION OF STEELBRIDGE USING 3DCG, Doboku-Gakkai-Ronbunsyuu H, Vol.75, No.1, 3547, 2019 (in Japanese)

Evaluation of bolted joint

Fig. 4 Corrosion Inspection Simulator
Corrosion near the gusset

Lower surface of gusset

Upper surface of gusset

Gusset plate

Coloring

Situation

Primary color

Healthy

No corrosive rust

Pink

Thickness
reduction

Reduction of plate thickness
due to corrosion

Red

Cross section
lack

Lack of cross section or breakageof member due to corrosion

August 2022 Steel Construction Today & Tomorrow 14

Special Topic

SBHS-High-performance Steel for Bridges Originated in Japanby Masahide Takagi
Chief Manager, Research Group on Steel Products for Bridges
The Japan Iron and Steel Federation
Masahide Takagi (Dr. Eng.): After receiving his Master’s degree at the Graduate School of Engineering,Osaka University, he entered Nippon Steel Corporationin 1994 and has since been engaged in technical development and promoting the application of steel products for bridges. He concurrently serves as a memberof the Research Group on Steel Products for Bridges at
The Japan Iron and Steel Federation.

Outline of SBHS
It is said that the origin of iron bridges in Japan is the Kurogane Bridge constructed in 1868 in Nagasaki Prefecture(the Japanese term Kurogane meansiron). Since then, iron and steel materials applied in bridge construction have
evolved from cast iron and wrought ironto steel and at the same time incessantly followed the path towards higher performance in conformity with the needsof the times.
Two motivating forces behind thesteady development of steel products
for bridges are cited: the progress ofsteel product manufacturing technology and the growing need for higher-performance steel products. SBHS (Steels
for Bridge High Performance Structure)
is a high-performance steel product destined for bridge construction and originating in Japan. Triggered by the project
to develop high-performance steel products in the U.S., SBHS has been developed capitalizing on joint efforts among
universities (incl. research institutions),

Table 1 Digest of SBHS Standard (JIS G 3140)
Designation

Plate
thickness
(mm)

Yield
strength(N/mm2)Tensilestrength(N/mm2)Charpyabsorbed
energy*Cracking
parameter
PCM(%)

SBHS400
6≦t≦100 ≧400
490〜640≧100J@0℃≦0.22
SBHS400W**
SBHS500≧500
570〜720≧100J＠-5℃≦0.20
SBHS500W**6≦t≦50≦0.30
SBHS700≧700
780〜930≧100J＠-40℃
SBHS700W**
50<t≦75≦0.32*Sampling direction: Perpendicular to rolling direction**W: Specifications of weathering steel (Prescription of composition range: Cu, Cr and Ni)

steelmakers and bridge fabricators1).
Currently, it is accepted that SBHS is
the steel product positioned as the forefront in the advancement of steel products destined for common application tosteel bridge construction.
Table 1 shows an outline of SBHS specified in JIS (JIS G 3140), andTable 2 shows the comparison of theproperties of SBHS and conventional structural steel for bridge use. SBHS
is produced by reflecting the advanced
steel product manufacturing technology available in Japan, applied with theaim of improving the diverse performance offered by steel bridges as infrastructure. Further it guarantees tensile
strength, fracture toughness, weldability, workability, weather resistance performance and other properties higher
than those of conventional steel products.
A specific feature in the productionof SBHS is the standard use of the ther-

Table 2 Comparison of Characteristic Properties between SBHS and Conventional Steel (SM, SMA) (Example in 50 mm-thick steel plate)Strength

Workability
Weldability

Corrosion
resistance

Yield point(N/mm2)
Constant
yield point
Excellent
toughness
Reduction ofpreheating
temperature
Weathering
steel spec.

490 N/mm2-grade steel
SBHS400
Conventional steel
SBHS400W(SM490Y/SMA490W)
≧400
≧335

570 N/mm2-grade steel
SBHS500
Conventional steel
SBHS500W(SM570/SMA570W)
≧500
≧430

780 N/mm2-grade steel
SBHS700
Conventional steel
SBHS700W(HT780*)
≧700
≧685

〇
△
(6-100 mm)（≧ 40 mm)〇△(≧100J@0℃)I(≧47J@ 0℃)II〇△(No preheating) (Preheating
temperature:
80℃ or more)〇△(6-100 mm)（≧ 40 mm)〇△(≧100J@ 5℃)I (≧47J@-5℃)II〇△(No preheating) (Preheating
temperature:
80℃ or more)〇△(6-75 mm)（≧ 40 mm)〇△(≧100J@-40℃)I (≧47J@-40℃) II〇△(Preheating(Preheating
temperature:temperature:
50℃ or more)
100℃ or more)〇(SBHS400W)〇(SMA490W)〇(SBHS500W)〇(SMA570W)〇: Response with common specifications △: No response with common specifications
I: Sampling direction: Perpendicular to rolling direction II: Sampling direction: Rolling direction *: HBS G 3102
15 Steel Construction Today & Tomorrow August 2022〇
(SBHS700W)‒

Application Advantages of SBHS
In conventional steel products, as thestrength required increases, the workability such as weldability lowers,
thereby causing the difficulty in fabrication of steel structures. In contrast, in
SBHS, because the addition of the alloying elements that adversely affectweldability can be reduced due to theapplication of TMCP, the weldability isimproved by a great margin comparedto that of conventional steel plates with
an identical level of tensile strength.
Furthermore, welding materials havebeen developed that can conform withvarious welding methods and fully secure the specific performance required
for welded joints, and steel member
fabrication techniques have been prepared that allow for the application ofhigh-strength steel plates in various
structures.
Diverse advantages are expected to
be brought by the use of SBHS-not
only an economic advantage available
by means of the lightweight construction of bridge structures but an im-

mo-mechanical control process (TMCP), an original steel plate manufacturing technology from Japan. TMCP
is a technology that appropriately controls the rolling temperature and cooling speed of steel plates and makes
the microstructure of steel fine (Photo1), which allows for the improvementof the mechanical properties of steel
plates such as high tensile strength andimproved fracture toughness. In addition, TMCP brings about further advantages-for example, higher tensile
strength is attained by the addition ofsmall amounts of alloying elements,
and thus weldability is improved (seeFig.1).
In the development of SBHS application technology for bridge construction, an important task has been how
to maximize steel bridge performancewith the effective use of improved
properties of steel products mentioned
above.

provement in safety, reliability and durability required as the infrastructure.
For example, not only can heavy-thicksteel members be used by changing onsite joint from bolt joint to weld joint
by the optimized use of favorable weldability peculiar to SBHS but the thickness of the plates to be applied can also
be reduced due to no bolt hole-related
reduction of cross-sectional area, andfurther the durability can be widely improved by eliminating the bolt jointinduced uneven member surface thatmight serve as a defect in terms of corrosion protection. To this end, expectations are high for the effective use of
specific properties of SBHS to makea steady contribution towards the improvement of the overall performanceover the life cycle of bridges.
Practical Application of SBHS in
Bridge Construction
The bridge to which SBHS was first applied is the Tokyo Gate Bridge (Photo 2) with the main span composedof a truss-box hybrid structure. It was

Photo 1 Microstructure of SBHS

Fig.1 Relationship between PCM and Yield Strength
650

Yield strength (N/mm2)

600

550

TMCP

Photo 2 Tokyo Gate Bridge

SBHS500
Conventional rolling+
Heat treatment

500
Conventional steel
SM570
450

400
0.15

Favorable weldability(Elimination or reductionof preheating)

0.20

0.25

Weld-crack sensitivity composition PCM (%)

0.30
Photo 3 Ground assembly of large blocks by means of on-site welding
August 2022 Steel Construction Today & Tomorrow 16

opened to traffic in 2012 in the mouthof the Port of Tokyo. In the bridge, diverse technologies were introduced
to promote rationalized construction.
Specifically, large-block truss structures were assembled by means of onsite welding at an on-site yard, and thebridge was constructed employing alarge-block erection method (see Photo3). It is reported that the specific property of not only high strength but alsoease of application of on-site welding
peculiar to SBHS greatly contributed
towards labor saving in construction
and the reduction of construction cost.
Table 3 shows the main application
record for SBHS. Since the first application with the Tokyo Gate Bridge, SBHS is showing increasing adoption in
ways that are conducive to realizing rationalized bridge structures and larger-scale bridges in diverse bridge types
such as space-truss (see Photo 4), arch,rigid-frame and box-girder bridges,
which has thus led to the contributionof economical construction of bridges
and the enhancement of their reliability.

tive, including those not specified in
the technical standard.
In the development of SBHS, withthe cooperation of the university andother related organizations, the Research Group on Steel Products for
Bridges accumulated useful data pertaining to strength characteristics suchas material property, load-bearing capacity and fatigue strength as the structural member and further the workability through the systematic welding
tests, and at the same time compiled
a track record of application to practical construction, such as the Tokyo
Gate Bridge. The goal of the ResearchGroup was to demonstrate the reliability of SBHS.
Specifically, in the experiment ofbuckling strength, in order to prove nolowering of the strength attributable tothe difference of material properties
and the dispersion of strength not onlyin the plate elements such as outstanding plates and simply supported plates
that compose the structural member
but in the structural members such ascolumns and girders that compose theIncorporation of SBHS in
Technical Standards for Bridges
It was in 2008 that SBHS and its welding materials were standardized in Japanese Industrial Standards (JIS G 3140
and others), so it was standardized at a
relatively early stage of SBHS development. However, it took a long time
until SBHS was incorporated in thetechnical standard for bridges (Specifications for Highway Bridges). This is
attributable to the fact that it was notallowed for bridges to see the deterioration of safety from the application of
new materials, and thus it was required
to verify whether or not bridges constructed using new materials possessedsufficient safety from a wider perspec-

Photo 4 Nagata Bridge (space-truss)

bridge, some research institutions conducted systematic material tests and diverse kinds of full-scale fracture tests
that take into account the initial imperfections at the stage of member manufacture over several years. These endeavors successfully verified that
SBHS offers sufficient safety in bridge
construction.
The steady accumulation of this data was highly assessed, which led to theincorporation of SBHS400 and 500 in
the 2017 version of the Specificationsfor Highway Bridges3). The preparationof the technical standards showed that
SBHS, which until now was imagined
as a steel material destined for special-purpose bridges, could be appliedin the construction of general-purpose
bridges.
Future Prospects
A trial calculation was made for thecase of applying SBHS400 and 500 in
the construction of a 3-span continuouscomposite twin I-girder bridge with anaverage span of 60 m and a 3-span continuous composite narrow box-girder

Table 3 Record of Applications of SBHS
Year

Bridge name

Structure type

Steel grade (t MAX)2006

Rinkai Chuo Bridge, Tokyo Port Seaside Road

Box girder

BHS500 (59 mm)

2006–
2009

Tokyo Gate Bridge
Tokyo Port Seaside Road

Truss-box hybrid
Box girder

BHS500 (50 mm)

2009

Nagata Bridge

Space truss

SBHS500 (67 mm)

2009

Inba-shosuiro Bridge

Box girder

SBHS500 (59 mm)

2011

Shin-Miyagawa Bridge

Truss

SBHS 400W (22 mm)

2012

Otagawa-ohashi BridgeArch

SBHS500 (67 mm)

2012

Takatsuki JCT Bridge, Shin-Meishin Expressway

Bridge pier

SBHS500 (57 mm)

2012

Asakegawa Bridge, Shin-Meishin Expressway

Arch

SBHS500 (86 mm)

2014

Nutanohara Bridge

Rigid frame

SBHS500W (27 mm)

17 Steel Construction Today & Tomorrow August 2022

bridge with an average span of 80 m,
the common bridge types in Japan. It
was reported from the calculation results that the steel weight could be reduced by about 5~6% and the construction cost by about 2% in the case of
applying SBHS400 and 500 comparedto the case of applying conventional
steel products (refer to Figs. 2-4)4).
The application of high-performance steel products such as SBHS allows for the reduction of the amountof steel products to be applied and it
will be feasible to rationalize bridge
construction and reduce the construction cost due to the effective use of
improved weldability and lightweight
bridge construction. In addition, thereduced steel weight and labor saving in construction will serve as an effective means for reducing CO2 emissions, which has become as important

as ever.
SBHS is an advanced steel productthat meets the Japanese steel industry’s
initiative toward solving environmental issues through the supply of ecofriendly steel products. In light of this,the Research Group on Steel Products
for Bridges is exerting every effort toward promoting the application of SBHS.
References
1) Chitoshi Miki, Atsushi Ichikawa, Takashi Kusunoki and Fumimaru Kawabata: Proposal of New High Performance
Steels for Bridges (BHS500, BHS700),
Journal of the JSCE, No.738, I-64,
pp.1-10, July 2003 (In Japanese)2) (e.g.) Katsuyoshi Nozaka, Yoshiaki Okui,
Masato Komuro, Takeshi Miyashita,
Kuniei Nogami, Masatsugu Nagai:
Experimental Study on the Strength

Fig. 2 Bridges subjected to
Trial Calculation

Fig. 3 Calculation Results for I-girder

10,7009,500
Asphalt pavement 80 mm
Composite slab 240 mm

Girderheighth(unit: mm)
2,350

6,000

2,350

500

500

Asphalt pavement 80 mm
Composite slab 240 mm

1,950

5,200
6,400

1,200

Composite narrow-box girder(average span: 80 m)

Steel weight
Construction cost (all incl.)
Fabrication cost
Erection cost

1
0.98
0.96
0.94
0.92
0.9
Case 1Case 2 Case 3-1 Case 3-2 Case 3-3 Case 3-4

2,900Steel gradeSM

Min. webthickness

14 mm

2,700

2,600

2,550

2,500

SM+SBHS
15 mm

14 mm

13 mm

Fig. 4 Calculation Results for Narrow-box Girder

Girderheight
h
1,200

1.02

Girder height(mm)

Composite twin I-girder(average span: 60 m)
11,50010,500

Steel weight ratio/Cost ratio

600(unit: mm)
1,950

Steel weight ratio/Cost ratio

600

of SBHS I-girder, Journal of Structural Engineering, Vol. 59A, pp. 70-79,
March 2013 (In Japanese)
3) Japan Road Association: Specificationsfor Highway Bridges, II Steel Bridges
and Steel Members, November 2017
(In Japanese)
4) Masahide Takagi, Masashi Kato, Masahiro Matsushita, Hiroshi Iki: A study
on Effective Utilization of SBHS for
Steel Highway Bridge based on a Trial Design，Bridge & Foundation Engineering, pp. 35-40, January 2020 (InJapanese)

1.02

Steel weight
Construction cost (all incl.)
Fabrication cost
Erection cost

1
0.98
0.96
0.94
0.92
0.9

Girder height(mm)Case 1Case 2

2,900

Steel gradeSM

Min. webthickness

14 mm

Case 3-1

Case 3-2

Case 3-3

2,700

2,600

2,550

SM+SBHS
15 mm

14 mm

13 mm

August 2022 Steel Construction Today & Tomorrow 18

JISF Operations

FY 2021 AJSI Webinar: Energy-Efficient andEnvironmental Transition towards Sustainable
Steel Industry

The Japan Iron and Steel Federation(JISF) concluded a memorandum with theASEAN Iron and Steel Council (AISC) in
fostering interaction concerning the environment, standardization and trade in May
2014. In the field of the environment, withthe cooperation of the Ministry of Economy, Trade and Industry, the JISF has
started up a public-private collaborative
scheme called the ASEAN-Japan Steel
Initiative (AJSI). The purpose of this initiative provides the platform for exchanging knowledge and experiences to contribute to energy saving and environmental
protection in the ASEAN countries. In addition, the AJSI aims to encourage technology transfer from Japan to the ASEAN
steel industry. To make them realize, theJISF focuses on three main activities of
Steel Plant Diagnosis, Technologies customized List and Public and Private Collaborative Workshop.
On February 24, 2022, as a part of AJSI, the JISF held the online seminar “FY
2021 AJSI Webinar: Energy-Efficient andEnvironmental Transition towards Sustainable Steel Industry” targeting Indonesia, Singapore, Thailand, the Philippines, Vietnam, Malaysia and Myanmar,
to which a total of more than 200 persons
from the government, steelmakers andothers in those nations participated.
For the ASEAN steel industry, which
has been impacted by the COVID-19 aswith other nations, the webinar covered
examples of short-term energy efficientand environmental protection measuresthat are currently in high need and simple
in practical use. Moreover, the JISF introduced the outline of the online Steel Plant
Diagnosis conducted for the first time.
In addition, the webinar provided information about medium to long-term energy efficient, and environmental initiatives
and measures. The AISC expressed gratitude for the contribution of the past AJSI activities in the ASEAN steel industry,
and also showed the view that it would bemeaningful to discuss the solutions to thestagnation of energy saving and environ-mental protection initiatives by the Corona disaster with Japan.
The JISF, jointly with the Japanese
government, is determined to continue tosupply support for energy efficiency andenvironmental protection to the ASEAN
steel industry through the activities of AJSI in the future.

Presentation at the SEAISI Online Event
At the South East Asia Iron and Steel Institute (SEAISI) Sustainability & Construction Fortnight e-Event held on November 26, 2021, Takehiko Tagami, amember of JISF’s Committee on Overseas Market Promotion, gave a presentation titled “Market Development of
Steel Structures in Japan: Standardization, Building Codes and Steel Products.” The presentation was deliveredat the request of the Sub-Committee on
Steel Application in Construction Sectorof SEAISI to which JISF participates as
an observer.
This SEAISI’s event is annually heldat the year-end. The online event in 2021
was held in two parts: ASEAN iron andsteel sustainability topics at 1st week
(15-19 Nov.) and sustainable construction including related presentation fromJapan at 2nd week (22-26 Nov.).
In the Japan’s presentation, Takehiko Tagami addressed the background of growth and trends ofsteel construction markets in Japan, the relationship among government, academia and industry
for application of steel structures, and Japan’s building codes
and its management system. In

STEEL CONSTRUCTION TODAY & TOMORROW
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19

addition, he introduced the effort for thedevelopment of advanced steel products
for construction such as steel productfor earthquake-resistant buildings andtheir applications.

© 2022 The Japan Iron and Steel Federation/Japanese Society of Steel Construction
Edited byCommittee on Overseas Market Promotion, The Japan Iron and Steel Federation
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