No. 48 August 2016

STEEL CONSTRUCTIONTODAY & TOMORROW

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

Special Features:

30-year Offshore Exposure
Tests for Steel Structures
Lifecycle Design for Port andHarbor Steel Structures
1 30-year Offshore Exposure Tests and Symposium on Research on
Civil Engineering Steel Structures

2 Long-term Exposure Tests in

Suruga Bay (1): Outline of Marine
Engineering Research Facility

5 Long-term Exposure Tests in

Suruga Bay (2): Steel Structures
and Corrosion-protection Methods

7 Long-term Offshore Exposure

Test for Steel Pipe Piles at HORS

10 Port and Harbor Administrationin Japan: Maintenance andManagement of Port and Harbor
Facilities

13 Structure Design System under the Concept of Life-Cycle
Management

15 Structural Integrity Assessment Method forJacket-type Steel Pier with Corrosion Damages

17 Inspection and Repair Technologies forCorrosion-Damaged Port Steel Structures

Back cover JISF Operations

Published Jointly by

The Japan Iron and Steel Federation
Japanese Society of Steel Construction

Special Issue: Maintenance of Port and Harbor Steel Structures

Report on Research Attainments of
30-year Offshore Exposure Tests
Steel products are the main construction
materials for port and harbor facilities,
but they have one shortcoming-corrosion. The marine environment is a severesite for steel product applications, wheresteel products are likely to corrode. Accordingly, in order to maintain offshore
steel structures in sound condition overa long period, it is necessary to provide
them with appropriate corrosion-protection measures.
The Japan Iron and Steel Federation
jointly with the Public Works ResearchInstitute has carried out long-term offshore exposure tests starting in 1982 at
the Marine Engineering Research Facility located in Suruga Bay, off the coastof Shizuoka Prefecture. The main aim ofthese tests is to discern how to improvethe durability of offshore steel structures,or how to prevent the corrosion of steel
products from occurring when applied
offshore.
In addition, another set of long-term
offshore exposure tests have been carriedout from 1984 at the Hazaki Oceanographical Research Station located in the
open sea of Kashima-nada, off the coastof Ibaraki Prefecture. These tests havejointly been promoted by the Port andAirport Research Institute, the Coastal Development Institute of Technology
and the Japanese Technical Associationfor Steel Pipe Piles and Sheet Piles withthe aim of developing corrosion-protection technologies for steel pipe piles applied offshore.
Taking the opportunity presented bythese two sets of exposure tests having
passed 30 years since their start, a joint
report meeting on the research attainments obtained in the exposure tests washeld on February 16, 2016 in Tokyo.
An outline of these two tests is intro￭
duced on pages 2 to 9.

Hazaki
Suruga Bay

Marine Engineering
Research Facility

Hazaki Oceanographical Research
Station

Joint report meeting on the research attainments obtained in the exposure tests

20th Symposium on Research on Civil
Engineering Steel Structures
The Japan Iron and Steel Federation heldits 20th Symposium on Research on Civil Engineering Steel Structures on February 26, 2016 in Tokyo. In 1995, JISF
established a “subsidy system for steelstructure research and training” andsince then has provided subsidies to researchers working in steel construction.
The symposium has been held every yearwith the aim of publicizing the results ofresearch, supported by the subsidy system, in the field of civil engineering steel
structures while at the same time promoting the wider application of steel
structures in the civil engineering field.
In the field of civil engineering structures, concerns are growing about deterioration in and the prolongation of theservice life of existing and new port andharbor steel structures. To cope with thissituation, a symposium titled “Initiatives
for Establishing the Lifecycle Design of
1 Steel Construction Today & Tomorrow August 2016

Port and Harbor Steel Structures” wasorganized and held, with the delivery ofvarious lectures centered on the researchattainments regarding long-term man-agement technologies for port and harbor steel structures and their durability
assessment. The symposium was successfully finished with the attendance ofabout 300 researchers and engineers.
The outlines of several of the lecturesdelivered at the symposium are intro￭
duced on pages 10 to 18.

20th Symposium on Research on Civil Engineering Steel Structures

Exposure Tests in Suruga Bay (1)Outline of Long-term Exposure Tests at
Marine Engineering Research Facility in
Suruga Bay

Iwao Sasaki: He has been studying application and durability of construction materials since fledgling researcher of PWRI Chemistry Division in 1989. B.Eng.: Tokyo
University of Agriculture and Technology, Ms. International development studies: National Graduate Institutefor Policy Studies, Dr.Eng.: Hokkaido University

by Iwao Sasaki
Public Works Research Institute
In Japan, diverse kinds of national land
improvement plans have been worked
out from the 1960s-such as straightscrossing highway projects and coastal preservation facilities. Most of theseprojects are located in severe corrosion
environments in offshore and coastal areas, which requires the establishment ofcorrosion protection technologies in order to secure structural durability. The
Public Works Research Institute (PWRI)
has promoted from the 1960s atmospheric exposure tests for improving coating
technologies for long-span bridges, andresearch on the corrosion characteristics
of steel structures in splash, tidal, submerged and mud zones. Corrosion-protection methods for these structures were
tested at a site within Tokyo Bay and at
the Ajigaura and other sites in marine environments facing the Pacific Ocean.
Given this situation, comprehensive
exposure tests for construction materials
in Suruga Bay was planned. In 1983, “research on the effective utilization of offshore space employing offshore structures” was started and supported bySpecial Coordination Funds for Promoting Science and Technology of the Science and Technology Agency. Of the re-lated research projects, the Chemistry
Division of the Ministry of Construction(currently the Materials and Resources
Research Group of PWRI) undertook “research on durability improvement technology for offshore structures by meansof corrosion protection.” The current exposure tests originated from this research
project. PWRI has installed the Marine
Engineering Research Facility (MERF)
as an exposure test facility on the coast of
Suruga Bay of Shizuoka Prefecture.
Fig. 1 Outline of Marine Engineering
Research Facility
Anemoscope/anemometer
Main light
Observation
tower

Coatedspecimen
Ultrasonic wave
height meter

Exposure tests employing MERF havebeen promoted as a cooperative project
between PWRI and private organizations.
The exposure tests for corrosion-protection technologies for steel structures installed in the splash, tidal and submergedzones have been promoted jointly with
the Kozai Club (currently the Japan Iron
and Steel Federation); that for concrete
structures in the splash and tidal zones
with the Japan Prestressed Concrete Contractors Association; and that for longterm protective coatings in an offshore
atmospheric zone and cathodic protection
design technology with the Public Works
Research Center.
In 2014, the exposure tests in Suruga
Bay reached their 30th year. In this article, an outline of the long-term exposure
tests over a 30-year period is introduced1).
Outline of Test Facility
For the exposure tests, MERF has been

Observationbuilding

Recorder,power source
Auxiliarylight(No. 1 deck)(No. 2 deck)
Corrosion-protection
specimen(splash and tidal zones)(No. 3 deck)

Flow direction/
velocity meter

Cathodic
protection
specimen

Cathodic protection
specimen (large size)
Sea bottom
surface

Corrosionprotection
methodLong-term
protective
coating/
painting

Corrosionprotection
liningCathodic
protection

Photo 1 Full view of Marine Engineering Research Facility

August 2016 Steel Construction Today & Tomorrow 2

Corrosive Environments in
Exposure Tests
Because MERF has been installed withthe primary aim of conducting durability tests on construction materials, a corrosive environment has been selected thatfaces the open sea and is exposed to alarge amount of airborne salts.
In ISO/TC156/WG4, internationally cooperative exposure tests were conducted in 49 areas of 13 countries over aspan of 5 years starting in 1986. The main
aim of the tests was to prepare a databasethat substantiates the standards. In Japan,
a specialized research/survey committee
was established to conduct the exposure
tests at four locations in Suruga, Choshi,
Okinawa and Tokyo.
3 Steel Construction Today & Tomorrow August 2016

In the surveys at MERF in Suruga
Bay, various affecting factors were measured employing various measuring devices (ISO Wet Candle Method, JIS
Gauze Method, PWRI-type Tank Method, etc.)-temperature, humidity, wetness
duration (estimated from temperature andhumidity), sulfur dioxide and airborne
salt2). The environment surveys and survey results on the corrosion loss of steel
products have made clear the relation between the corrosion factors and the distance from the sea surface and the weather conditions.
These survey results indicate that thecurrent exposure test facility is designatedas category C (High) in terms of environ-mental corrosivity in ISO’s corrosion environment classification standard (ISO129442). Accordingly, it is accepted that the
MERF can be utilized as a standard exposure site that is positioned as a corrosive environment from a global perspective.
Fig. 2 shows the survey results in
FY1986~1989 and Fig. 3 shows those in
FY2013~2015, both of which were obtained by means of the PWRI-type airborne
salt collector (tank method). The amount of
airborne salt falls in the range of 0.1 to several mg/dm2/d, excluding abnormal numerical values, which shows values consistent
with the range of results in surveys in the
Tokai area (covering Suruga Bay) among
the nationwide surveys made by the PublicFig. 2 Secular Change of Airborne Salt Amount by Means of PWRI-type Tank Method(Secular Changes of Past Survey Results: East and West Sides of No. 1 Deck)
100
1988
1989
1987
1986

Airborne salt (mdd)

10

1

0.1

East side of No. 1 deck

WinterAutumnSummerSpring

WinterAutumnSummerSpring

WinterAutumnSummerSpring

WinterAutumnSpring0.01

SummerWest side of No. 1 deck

Fig. 3 Secular Change of Airborne Salt Amount by Means of PWRI-type Tank Method
100

Irregular value due to effect of typhoon

East side of No. 2 deck
West side of No.2 deck
East side of No. 1 deck

10
Airborne salt (mdd)adopted that is located in Suruga Bay facing the open sea of the Pacific Ocean. The
testing site was selected as a representative coastal zone in Japan.
At MERF, exposure tests for corrosionprotective materials were conducted. Further, research relating to the prevention ofcoastal erosion was simultaneously conducted-offshore wind, wave and othermarine conditions, phenomenon regarding the supply of sand to the coast, clarification of coastal deformation and drift
sand phenomenon, and development ofother coastal erosion preventive measures.
The location of the exposure test facility is 250 m off the Suruga coast in Suruga
Bay with its commanding view of Mt. Fuji. Photo 1 shows an entire appearance of
MERF. The facility is located outside thedetached breakwater and is subjected directly to the waves of the open sea. It is installed in a high-wave area, including thesurf zone, where the seabed sand undergoes great movement.
The MERF is built as shown in Fig. 1,
with a steel-structure jacket installed onsteel pipe piles supported by a sandy seabottom. The entire facility is targeted forcorrosion-protection testing. The structure above the sea surface is composedof three decks, where large- to small-size
test specimens are arranged. In its submerged area, steel pipe and sheet piles
and cathodic protection test specimens
can be installed. Its depth to the sea bottom is about 7.5 m, and its height to the
top about 30 m. At the facility, material
tests can be applied in wide corrosive environments ranging from the offshore atmospheric zone through splash and tidal
zones to the submerged zone.

1
115 days

0.1

227 days

91 days

102 days

55 days

138 days
21 days

0.01
July ’13

Jan. ’14

July ’14
Survey period

Jan. ’15

July ’15

Works Research Institute in the past3).
In marine environments, the corrosive environment greatly differs depending on thevertical height from the sea surface. In past
surveys made at MERF, it has been observedthat the progress of deterioration differs depending on the deck used for the survey. The
MERF has multiple decks in the vertical direction and thus comparative surveys of airborne salt environments are available.
Fig. 4 shows the effect of deck heightfrom the sea surface on salt penetration
obtained by means of the mortar thinplate method4). The level of salt penetration was highest in the No. 3 deck locatedabout 2 m from the sea surface, fell as thedeck height increases, and then showeda trend toward converging to nearly an
identical level.
Research Fields and Main Test
Materials
In the current research, exposure tests
were applied mainly to steel and concrete
structures, and various corrosion-protection methods for these structures were
tested that employ highly corrosion-resistant metals, coating/painting and cathodic protection. Research fields and specificthemes were settled by the corrosion-protection method, and the exposure tests andsurveys were promoted as cooperative research projects among related organizations. (See Table 1)
Knowledge Obtained in the
Exposure Tests and Future
Prospects
In the long-term exposure tests thus conducted in Suruga Bay over 30 years, arich store of knowledge has been obtained
about corrosion-induced deterioration

Height from sea surface (m)Fig. 4 Effect of Height from Sea Surface on Airborne Salt Amountby Means of Mortar Thin Plate
Method2105 spring/2015 summer

mechanisms and rates pertaining to not
only conventional materials but also newmaterials.
In exposure tests for steel productswith no corrosion-protection measures, it
has been clarified that the corrosion rate
differs depending on the exposure position and how the macro cell is formed,
and at the same time it has been confirmed that the corrosion rate gradually reaches a constant level with the lapseof exposure time. As regards high corrosion-resistant metal protection, the effectof scratch damage in the tidal zone wasclarified, and the combined applicationof corrosion-resistant metal and cathodic protection was indicated. In the corrosion protection by means of coatings, it
has been confirmed that the improvementof the durability employing the zinc-rich
paint-type primer coating was significant.
Continued exposure tests in the future
will allow longer-term assessment of the
durability of offshore structures, and theattainments obtained in the tests can beused for reference in assessing the expected durable years. Similar tests have been
carried out in Okinotorishima and othersites where corrosion environments differ.
It is considered that durability at diverse
sites including those in the Asian block
can be forecasted by comprehensively examining the exposure test results not onlyin Suruga Bay but at the other sites mentioned above.
We intend to promote continued exam-

References
1) Public Works Research Institute and theJapan Iron and Steel Federation: Cooperative Research Report on Durability
Improvement Technologies for Offshore
Structures “Research on Corrosion-protection Technologies for Steel Structuresin Splash and Tidal Zones”-Research
Attainments over 30-year Exposure Period by First Working Group, Cooperative Research Report of Public Works
Research Institute, No. 480, March 20162) Public Works Research Institute and Other: Cooperative Research Report on Durability Improvement Technologies for
Offshore Structures-Summary Reporton 20-year Offshore Exposure Tests, No.
345, pp. 55~58, 2007
3) Public Works Research Institute: Report
on development of durability improvement technology of concrete (Part 1), Integrated technology development project,
Ministry of Construction, pp. 76-78, 1988
4) T. Saeki, Y. Nose and M. Kikuchi: Basic
Examinations on Environmental Assessment Approach for Micro Salt Damages
Employing Mortar Thin Plates, Proceedings of Japan Concrete Institute, Vol. 33,
pp. 803~805, 2011

Table 1 Research Fields and Themes, and Research Allotment
Research allotment

Research ﬁeld

Speciﬁc research theme

Research on corrosionprotection technology forsteel structures in splash
and tidal zones

1) Application test for corrosion-protection
coating/painting materials (MERF structure)2) Durability test for corrosion-protection
coating/painting materials (test specimen)

Research on
corrosion-protection
technology for concrete
structures in splash zone

1) Corrosion-protection technology for steel
product used in concrete2) Development of design technology forseawater-resistant concrete member

Research on cathodic
protection design
technology in submergedzone1) Development of cathodic protection design
method according to structure shape2) Development of combined coating-cathodic
protection design technology

AD

Research on long-term
protective coatings inmarine atmospheric zone

1) Application test for long-term protective
coating system
2) Durability test for long-term protective
coating system

AD

Arrangement of researchattainments

Salt penetrated into mortar thin plate (mdd)

ination aimed at the establishment of performance assessment approaches requiredfor corrosion-protection methods for offshore steel and concrete structures and theperformance forecasting approaches for￭the future.

1st WG 2nd WG 3rd WG

AB
B
AC
AC

AD

AD
ABCD

Research allotment:
A: Public Works Research Institute
B: The Japan Iron and Steel Federation
C: Japan Prestressed Concrete Contractors Association D: Public Works Research Center

August 2016 Steel Construction Today & Tomorrow 4

Exposure Tests in Suruga Bay (2)Long-term Exposure Tests for Steel
Structures and Corrosion-protection
Methods in Suruga Bay

Kenichiro Imafuku: After graduating from Department of Civil Engineering of Tohoku University in
1993, he entered Nippon Steel Corporation (currently
Nippon Steel & Sumitomo Metal Corporation) andthen was assigned to the company’s Steel ResearchLaboratories. He assumed his current position as Senior Researcher, Materials Reliability Research Lab.
Steel Research Laboratories in 2013.

by Kenichiro Imafuku
Steel Research Laboratories
Nippon Steel & Sumitomo Metal Corporation

Outline of Exposure Test Results
The exposure test conditions are shownin Photo 1, and the exposure test results
are outlined in the following:• Steel Products with No Corrosion-protection Measures
As a result of 19.5-year exposure tests forsteel products with no corrosion-protection measures (140×140×18×3,800 mm),the following facts were confirmed:-The corrosion rate becomes high in
5 Steel Construction Today & Tomorrow August 2016

Photo 1 Exposure test conditions

Fig. 1 Distribution of Depth-direction Corrosion (Ordinary Steel)
2.5 years
14.5 years

15.5 years

5.5 years
19.5 years

9.5 years

Splash zone

Depth(mm.VS.TP)

Kind of Exposure Test Specimens
In the current research, diverse kinds ofsteel product test specimens have been
subjected to exposure tests in the marine
environment extending from the splash
zone to the submerged zone: steel products with no corrosion-protection measures, steel products covered with diverse kinds of highly corrosion-resistantmetals, painted steel products, organic
coated steel products and others.

(main cause: in the tidal zone a large
macro cell is formed in steel structures).
-The corrosion rate is low in the submerged zone (main cause: the supply of oxygen is less in the submergedzone than in the splash and tidal zones).
-The corrosion rate decreases with thepassage of time, and gradually approaches a constant corrosion rate
similar to that specified in the Technical Standards and Commentaries forPort and Harbor Facilities in Japan.
(Refer to Figs. 1 and 2)

marine environment, particularly inthe splash zone.
-The corrosion rate becomes somewhat
low in the upper area of the tidal zone

Reduction of corrosion
due to macro cell

Tidal zone

Reduction of oxygen inunderwater area

Submerged zone

Loss of plate thickness (mm)Fig. 2 Secular Change in Corrosion Rate by Marine Environment
0.8
Corrosion rate (mm/year)

In order to improve the durability of marine steel structures, the Japan Iron andSteel Federation and the Public Works
Research Institute have jointly promoted
long-term exposure tests for these structures. The main objective of the tests was
to develop advanced corrosion-protection technologies for marine steel structures and to assess the long-term durability of these technologies. The tests wereconducted employing Marine Engineering Research Facility located in Suruga
Bay-250 m off the coast of Shizuoka
Prefecture.
This article reports on the corrosion
behavior of and the corrosion-protection
technologies for marine steel structures,and the corrosion protection performanceof these technologies and the care to betaken in their application, based on the
results of long-term exposure tests over a
maximum period of 30 years.

Upper area ofsplash zone

0.7
0.6

Lower area ofsplash zone

0.5

Upper area oftidal zone

0.4
0.3

Lower area oftidal zone

0.2

Submerged zone

0.1
0
0

5

10
Exposure period (years)

15

20

• Coated Steel Products (Common

Painting, Thick-film Painting)
In common painted steel products (inorganic zinc 25 μm+epoxy resin 600 μm),
the corroded area increased in and after
the 5th year in the tidal and submergedzones (Fig. 3). On the other hand, in the
thick film-painted steel products (organic zinc-rich paint 15 μm+ultra-thick filmtype epoxy resin 2,000 μm+fluorine 25μm), it was confirmed that some corrosion
occurred in damaged sections forecasted to be caused by driftwood, but painting film loss, cracking and other painting
deteriorations were not observed, and thepainting remained sound. (See Fig. 4)• Organic Coated Steel Products(Polyurethane, Polyethylene)
No damage was observed in polyurethane coatings even after 23 years of
exposure, and the coating remained insound condition (Fig. 5). The normalpart of polyethylene coatings also remained in sound condition even after
10 years of exposure, but in the scratchdamaged part (width: 1 mm, length 100mm) that was artificially provided in advance, it was observed that corrosion occurred with a maximum plate thickness
loss of 1.2 mm. As regards the section inwhich the damaged part was exposed for
one year and then repaired by means of
on-site deposition, sound conditions remained even after 9 years of exposure.
• Highly Corrosion-resistant Stainless Steel Covering
Observations were made of the corrosion conditions in highly corrosion-resistant stainless steel (Cr+3Mo+10N≥38(mass%))-covered pipe to which cathodic protection was also applied. As a result, in the stainless steel-covered surfaces including the weld and weld-repaired
sections, no corrosion was observed evenafter 10 years of exposure.
In the case where scratch-penetrated
damage existed in the tidal zone, corrosion of the base metal of the steel pipe
was not observed due to the effect of cathodic protection. On the other hand, inthe case where scratch-penetrated damage existed in the splash zone, because
the effect of cathodic protection did notextend to the splash zone, corrosion wasobserved in the base metal of the steel
pipe (about 0.05 mm/y).
Further, when cathodic protection
was not applied, corrosion (crevice corrosion) was observed in the gaps (specimen-fixed section) produced during in-tection methods, the cupronickel, corrosion-protection cover method and the
combined method by use of stainlesssteel, titanium or other materials were
subjected to exposure testing, and it was
confirmed that they offer long-term durability.

stallation of the specimen in the splash
and submerged zones.
Based on the knowledge thus far obtained, a list was created of concerns regarding the marine environment when applying highly corrosion-resistant stainless steel
covering protection, as shown in Table 1.
• Titanium Covering
In titanium-covered steel pipe after 29
years of exposure, while discoloration
was observed in the splash zone, corrosion was not observed (Fig. 6). Even in
the section below adhered organisms andgaps artificially produced by piling a titanium sheet on another titanium sheet,corrosion was not observed.
• Other Corrosion-protection
Methods
In addition to the above corrosion-pro-

Exposure Tests Will Continue
Diverse kinds of corrosion-protection
methods were subjected to long-term exposure tests, which led to the confirmation of their application effectiveness in apractical marine environment. Plans callfor continued exposure tests for highly
corrosion-resistant metal-type protection
methods that are expected to offer long￭term durability.

Fig. 3 Appearance of Common
Painted Steel Products after Rust Removal (top:5-year exposure; bottom:
19.5-year exposure)Splash zone

Fig. 4 Appearance of Thick Filmtype Painted Steel Products(19.5-year Exposure)Splash zone

Fig. 5 Appearance of Polyurethane
Coating after Rust Removal(23-year Exposure)Tidal zone

Submerged zone

Rust section

Tidal zone

Upper end sectionof test specimen

Submerged
zone

Lower end sectionof test specimen

Rust stains

Splash zone

Tidal zone

Submerged
zone

Table 1 Cares in Application of Highly Corrosion-resistant
Stainless Steel Covering Protection Method
Corrosion-protection
methodEnvironment

SectionSplash zone
Tidal zone
Submerged zone

Highly corrosion-resistant stainless steel cover (Cr+3Mo+10N≥38 (mass%))
Combined use of cathodic protection (about −770~−1000 mV (vs. SCE))
Damagepenetrated
Weld-repaired section section

Weld

Selection of
appropriate
welding material andimplementation of
appropriate welding

Gap section

Repair is necessary

No production of gap
in specimen installation

Cathodic protection
is effective

Cathodic protection iseffective

Fig. 6 Appearance of Titanium-covered
Steel Pipe after Shell Removal(29-year Exposure)Gap (between titanium and titanium)

August 2016 Steel Construction Today & Tomorrow 6

Exposure Tests at HORS

Long-term Offshore Exposure Tests forCorrosion-protection Methods for SteelPipe Piles at HORS

Toru Yamaji: After graduating from the University of Kyushu in 1997, he entered the Ministryof Transport and was assigned to Researcher,Port and Harbour Research Institute in 1998. He
became Head of Materials Group, Port and Airport
Research Institute in 2010, and assumed his current position as Director of Structural Engineering
Field, Port and Airport Research Institute in 2012.

by Toru Yamaji, Materials GroupPort and Airport Research Institute
Steel products are an important construction material used in improving infrastructure facilities, and are extensively
used for port/harbor facilities and offshore structures. Meanwhile, when steel
products are left without corrosion-protection measures for long periods, cases arise in which the durability of thesesteel-structure facilities is impaired due
to corrosion of the steel, which causes a
deterioration of their safety and function.
Accordingly, in order to maintain soundness over long periods in steel structures,
particularly those in an offshore environment, it is necessary to take appropriate
corrosion-protection measures.
Given such conditions, the Port andAirport Research Institute, the Coastal Development Institute of Technology
and the Japanese Technical Associationfor Steel Pipe Piles and Sheet Piles jointly started in 1984 field tests in which
various corrosion-protection methods
have been applied to the steel pipe pilesof a practical steel structure located offshore. The main aim of this test is to examine corrosion-protection methods thatcan be expected to offer long-term corrosion-protection performance. In 2014,
the field test reached its 30th year.
This article introduces an outline of
the results of this 30-year, long-term offshore exposure testing1).

Outline of the Exposure Test Site
For these field tests, the Hazaki Oceanographical Research Station (HORS),
which is located in the open sea at Kashima-nada in Ibaraki Prefecture, has beenused (Photo 1). The Kashima-nada open
sea area is a high-wave area, including
the surf zone, where the seabed sand undergoes great movement. Because highwaves and rapid tidal currents work directly on the pier of HORS, the site is exposed to an extremely severe environment and serves as an excellent test field
for corrosion-protection methods.
In HORS, a concrete superstructuresits upon steel pipe piles that are 600~800
mm in diameter and upon which prestressed concrete girders are placed (Fig.
1). The total length of the pier is 427 m
and 47 steel pipe piles have been driven. The field tests have been conductedby applying various corrosion-protection
methods to these pipe piles.
Corrosion-protection Methods
Applied in the Field Tests
The corrosion-protection methods applied for the field tests are roughly classified into the following five types: organic coatings, inorganic coatings,
petrolatum coating, painting and cathodic protection. The main features of eachmethod are as follows.

• Organic Coating Method

The organic coating method is a corrosion-protection method in which the surfaces of steel products are coated with
polyethylene, an underwater cured-typematerial or other organic materials. The
common coating thickness is 2~10 mm,
which is heavier than the thickness applied in painting.
The polyethylene coating method has
excellent durability, seawater corrosion
resistance and atmospheric corrosion resistance. It is applied for newly-installed
structures. (See Photo 2)
In underwater cured-type coatings, anunderwater cured-type paint is applied
to the surface of steel products to form a
Fig. 1 Example of Sections of Hazaki Oceanographical Research
StationCorrosion-protection
coatingWear-resistant coverSteel pipe pile

Photo 1 Full view of Hazaki Oceanographical Research Station

7 Steel Construction Today & Tomorrow August 2016

thick coating. This application is effective
even as a repair method. (See Photo 3)• Inorganic Coating Method
The inorganic coating method is a corrosion-protection method in which the surfaces of steel products are coated withcement mortar, reinforced concrete orother inorganic materials, including metals. The steel product surfaces are pro-tected from corrosion by the dense, passive film formed on the steel surfaces
due to the alkalinity possessed by the cement mortar or concrete.
• Petrolatum Coating Method
The petrolatum coating method is a corrosion-protection method that combines
the use of a corrosion-protection material
that is composed of petrolatum (a kind of
petroleum-based wax) and the cover that
protects the corrosion-protection material. It is a highly reliable corrosion-protection method having a rich application
record.
• Painting Method
The painting method is a corrosion-protection method in which the steel surface
substrate is coated first with a zinc-richprimer (zinc powder-containing paint) andthen with a liquid or semi-liquid paint. It
has an extensive application record.
Among the paints adopted in typical
Photo 2 Polyethylene coating (black section:polyethylene)
painting methods in the field tests are extra heavy, thick film-type epoxy resin
paint, glass flake epoxy resin paint andtar-epoxy resin paint.
• Cathodic Protection Method
The cathodic protection systems areroughly classified into galvanic anodesystem and impressed current system.
The mainstream method currently adopted for port and harbor steel structures is
the galvanic anode system.
In the galvanic anode system, a metPhoto 3 Underwater cured-type coating (coating
al that is less noble than the steel prodof putty-state coat)uct is electrically connected to the steel
product, and a corFig. 2 FT-IR Analysis Results of Polyethylene-coated Surface
rosion-protection
FT-IR analysis section
CH2 1450cm-1
current is supplied
to the steel product by means ofEmbedded resin
cell action that utiPolyethylene-coated surface
lizes the electrical potential difference between
the metal and the
Polyethylene
coatingsteel product. In
terms of practical application, ca-1
-1-1thodic protection
2
CH 1450cm / C=O 1740cm
C=O 1740cm
becomes feasible
when the electric
potential of a steel
product surface islower than −780mV with the reference to silver-silver chloride-seawater electrode.

Survey Results after 30-year
Exposure Tests• Organic Coating Methods-Polyethylene coating
It was confirmed that the polyethylene
coating method has been effective over 30
years of the corrosion-protection testing.
In the FT-IR (Fourier transform infrared
spectrometer) test, nearly no ultraviolet
ray-induced deterioration was observed(Fig. 2). Further, the insulation resistanceshows no problems pertaining to the corrosion-protection performance, and it isassumed that the polyethylene coating
will provide durability over the long term
well into the future.
It was also confirmed that volume resistivity (calculated from the insulation resistance) is useful as an indicator in assessing the corrosion-protection performance ofpolyethylene coating.
-Underwater cured-type coating
When 20 years had passed since the startof the test, the underwater cured-type
coating showed favorable corrosion-protection performance. However, after 30
years, some degradation was becoming
outwardly apparent in the coating. Further, it was confirmed that the coating
performance had clearly fallen in termsof insulation performance and the penetration depth of chloride ions.
It was confirmed that the insulation
resistance and the penetration depth ofchloride ions are useful as an indicator inassessing the performance of underwater-cured type coatings.
• Inorganic Coating Method
It was confirmed that after 30 years theconcrete coating method not only showedno degradation in its outward appearance
but maintained favorable corrosion-protection performance (Photo 4). MeanStud dowel

Reinforcing bar

Concrete

Photo 4 Internal structure of concrete coating

August 2016 Steel Construction Today & Tomorrow 8

while, in the concrete coating exposedin the submerged and tidal zones, there
was no remarkable corrosion even whenchloride ions accumulated in high densities at the surface of the steel productor, further, when penetration of chloride
ions from the interface of steel products
was found. These two survey results suggest that it is difficult to forecast whencorrosion of steel products due to thepenetration of chloride ions will occur.
As far as an approach to forecasting
the deterioration of concrete coatings isconcerned, it will be necessary to conduct further examinations in the future.
• Petrolatum Coating Method
The corrosion-protection condition of
the petrolatum coating method after alapse of 30 years showed that, while theprotective cover was in a nearly soundstate, deterioration was confirmed of thebolts and other accessary members used
to affix the protective cover (Photo 5).
The oil residual ratio is commonly
applied as an indicator in assessing theperformance of the petrolatum coating
method. However, the accuracy of measurements employing the oil residual ratio is not so high, and it was reconfirmedthat there are deterioration factors other than those found by use of the oil residual ratio, and many tasks remain pertaining to the appropriate performanceassessment of the petrolatum coating
method. In the future, it will be necessary to conduct further examinations of
the deterioration mechanism of the petrolatum coating method to establish an
appropriate approach to assess the performance of the method.

• Painting Method

Examinations were made mainly on extra heavy, thick film-type epoxy resin
paints. While the outward appearanceof the painting method was sound aftera lapse of 30 years, it was confirmed thatsalt gradually penetrated into the paintfilm to cause a gradual lowering of thefilm’s corrosion-protection performance.
It was confirmed that impedance isuseful as an indicator in assessing theperformance of various painting methods (Photo 6).
• Cathodic Protection Method
In surveying the common galvanic anodesystem of the cathodic protection method, it was shown that the period of anode consumption can more quickly beforecasted by subdividing the deterioration judgement criteria from the current
2 levels to more levels. However, as regards the threshold value, it is necessary
to cautiously settle it.
Further, examinations were made on
the method to affix galvanic anodes tosteel products employing magnets, andthis showed that no anodes had fallen
off after a lapse of 5 years since affixing them and that a favorable corrosionprotection condition was kept (Photo 7). However, because there are cases
in which the electric potential fluctuates
due to the effect of waves, it will be nec-

Photo 6 Impedance measurement for painting
methodPhoto 5 Appearance of protective cover of petrolatum coating method

9 Steel Construction Today & Tomorrow August 2016

Photo 7 Magnet at anode-affixed section in cathodic protection method

essary to implement longer-term observation of the progress condition.
Useful Results from Long-term
Exposure Tests
Our survey of long-term offshore exposure tests for steel pipe piles shows that
there exist many corrosion-protection
methods that have demonstrated surecorrosion-protection performance overa 30-year period. It will become possible by continuing the exposure tests inthe future to assess the longer-term durability of corrosion-protection methods applied offshore. At the same time,
the attainments thus obtained will serve
as reference points in assessing the expected durability of corrosion-protection
methods.
The approach to assessing the performance of the different corrosion-protection methods are classified into two: approaches by which parameters could be
extracted that can serve as indicators of
performance assessment; and other approaches where there currently remain
many tasks. Towards the establishmentof approaches to assess the performancerequired for coating corrosion-protection methods and the establishment ofmethods to forecast the future corrosionprotection performance of the different
methods, we will promote continuing ex￭
aminations in the future.
References
1) Toru Yamaji et al: Research on Durability Assessment of Corrosion-control
Methods for Steel Pipe Piles Based on
Long-term Marine Exposure Test (Report of 30-year Tests), Reference Material of Port and Airport Research Institute, June 2016
2) Coastal Development Center of Technology: Manual for Corrosion Control and Repair of Port Steel Structures(2009), 2009

Maintenance of Port/Harbor Facilities

Port and Harbor Administration in Japan:

Maintenance and Management of Portand Harbor Facilities

Isao Sakai: After finishing the master’s course of
School of Engineering, The University of Tokyo, he
entered the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) in 1992. In 2010, he served
as Director, Port and Airport Research Institute. He
assumed his current position as Director, Engineering Administration Office, Engineering Planning
Division, Ports and Harbors Bureau, MLIT in 2016.

by Isao Sakai, Ports and Harbors Bureau
Ministry of Land, Infrastructure, Transport
and Tourism
For Japan, a country surrounded on all
sides by the sea and where the population and properties are accumulated incoastal areas, it is the ports and harbors
that support the distribution of goods
and the flow of people as nodal points
for both marine and land transport. Also, ports and harbors provide the international infrastructure that are indispensable in handling the export and import ofmost of the goods and materials that are
required for the daily life of the people
and are demanded by the manufacturingindustry, the basis of the Japanese economy.
For these ports and harbors, new demands are arising. One is to structure
efficient and stable transport networks,
in the global market, that are connected to foreign ports and harbors in order
to secure the competitiveness of enterprises operating in Japan. Another is tostrengthen the competitiveness of all industries operating in Japan by enhancing
their international logistics efficiency inorder to create new jobs and incomes.
In such situations, there is a rapidly
increasing number of port and harbor facilities in Japan that have seen 50 years

pass since their construction, and thus it
is important now to put into effect appropriate facility maintenance and management that take into account the entire
port/harbor stock management in Japan.
In the following, diverse measures
are introduced that are being promoted
for the maintenance and management ofport/harbor facilities in Japan.
Management Entities for Ports andHarbors and Their Facilities in Japan• Role and Kind of Ports
The ports and harbors of Japan are classified into the following four kinds: “International Container Hub Port” that places
priority importance on the strengthening of international competitiveness as
the hub of international marine containertransport; “International Hub Port” thatserves as the hub of international marine
cargo transport networks; “Major Port”
that serves as the hub of marine transport
networks and that have important relations with national interests; and local
ports other than those mentioned above.
The number of these ports and harbors inJapan totals 933. (See Table 1)

Table 1 Kind and Number ofPorts in Japan
Kind

NumberInternational Container Hub Port

5

International Hub Port

18

Major Port

102

Local ports

808

Total

933

• Improvement and Management

Entities for Port and Harbor
Facilities
The core facilities of ports and harbors
are classified into two types: public facilities that are improved and managed for
public use by the central government andport/harbor administrators (local public
entities); and private facilities that are
improved and managed for the exclusive
use of private enterprises. In basic practice, the management of port and harbor
facilities to be improved by the central
government is commissioned to the port
and harbor administrator, who manages the public facilities in a bulk system.
(Refer to Fig. 1)

Fig. 1 Improvement and Management Entities of Ports and Harbor Facilities
Improvement entity

Central government

Port/harbor administrator(Local public entity)

Private enterprise

Facility provider(Owner)Central government(Government-owned
port/harbor facility)

Port/harbor administrator

Private enterprise

Port/harbor administrator
Commissioning ofmanagement operation to
port/harbor administrator

Port/harbor administrator

Private enterpriseCommissioning ofmanagement operation
Facility administrator

August 2016 Steel Construction Today & Tomorrow 10

Superannuating Port and Harbor
Facilities and Their Preventive
Maintenance• Increase of Superannuating
Facilities
Port and harbor facilities in Japan were
improved along with the growth of theJapanese economy. Most of these facilities were constructed during the period
from the 1970s to the 1980s, and haveplayed an important role as basic infrastructure for economic growth and physical distribution in Japan.
On the other hand, these facilities are
becoming superannuated. To illustrateusing wharfs that play a basic role in port
and harbor facilities: of about 5,000 public wharfs nationwide with water depths
of 4.5 m or less, those that have seen 50

years or more pass since their construction will rapidly increase from about
10% of the total in March 2014 to about
60% in March 2034, as shown in Fig. 2.
• Preventive MaintenanceFor these rapidly superannuating port
and harbor facilities, it will be necessary
in planning appropriate maintenanceto attempt to reduce the lifecycle costs
while simultaneously securing stable facility functions. To attain this goal, it will
be necessary to further promote preventive maintenance and renewal that willaccount for the prolongation of service
life and the reduction of lifecycle costs,
rather than corrective maintenance inwhich response measures are not taken
until the renewal period. (Refer to Fig. 3)

Mechanism of Maintenance of Portand Harbor Facilities• Maintenance Cycle for Port andHarbor Facilities
The objective of maintaining port andharbor facilities is that the required performances be satisfied over a specificin-service period. For that purpose, it isnecessary to systematically conduct inspections, diagnoses and repairs, whileat the same time closely monitoring thein-service period.
Specifically, port and harbor facility
maintenance is carried out in the maintenance cycle shown in Fig. 4. In order toappropriately proceed with this maintenance cycle, related laws have been prepared and various guidelines have also
been prepared that are useful in working

Fig. 2 Ratio of Public Wharfs with Water Depth of 4.5 m or Deeper and Pass of 50 Years since Start of Service toTotal Wharfs

No. of wharfs

No. of wharfs
newly constructed
March 2014
About
10%

No. of wharfs with pass of 50 years since construction(estimate in terms of accumulated numbers)
March 2024

10 years
later

About
35%

March 2034
10 years
later

About
60%

Fig. 3 Image of Preventive Maintenance
Conversion to preventive maintenance

Effectiveness, performance

Prolongation of service life of facility
Improvement
work(cost: small)
Radicalrenewalwork(cost: large)

Limit for standard serviceability
Initial lifecycle (design service period)
In-service period

11 Steel Construction Today & Tomorrow August 2016

out maintenance/management plans andconducting inspections and diagnoses.
• Maintenance Plans by Facility
and Stock Management by Portand Harbor
The maintenance of port and harbor facilities consists of two wheels: maintenance plans required to appropriately conduct maintenance by facility, andpreventive maintenance plans required
to strategically manage the facility stockby port and harbor (Fig. 5).
In preventive maintenance plans
worked out by port and harbor, the priorities in the maintenance and renewal of each facility are determined basedon the maintenance plans worked out by
facility, and the expense required for the
maintenance of each facility is leveled.
Another role of preventive maintenanceplans is to strategically promote stock
management by port and harbor, such as
facility integration, application changes and qualitative improvements, in conformity with emerging changes in social￭and economic situations.

Fig. 4 Maintenance Cycle for Port/harbor Facilities
Working out of maintenance plan
“Guidelines for Working out of Maintenance and Management Plan for Port and Harbor Facilities”

Inspection and diagnosis“Guidelines for Working out of Maintenance and Management Plans for Port and Harbor Facilities”
Kind of inspection and diagnosis

Periodical
inspection
anddiagnosis

Facility subjected to regularinspection and diagnosis

Common periodical• Once at least withininspection and5 years
diagnosis
Detailed periodical
inspection anddiagnosis

Facility subjected to priority
inspection and diagnosis• Once at least within
3 years• Once at least in
appropriate time duringservice period• Whenever service
period is prolonged• Once at least within
10~15 years• Once at least within 10 years
for the facility that faces
main navigation route andis subjected to speciﬁed
technical standard

Comprehensive assessment“Guidelines for Working out of Maintenance and Management Plans for Port and Harbor Facilities”• Assessment based on engineering knowledge and judgement

Maintenance and repair plan

Reexamination of
inspection anddiagnosis plan

• Planning of maintenance/repair method and implementation period

Implementation of maintenance work

Reexamination of maintenance and management plan

Fig. 5 Maintenance/Management Plan and Preventive Maintenance Plan
Maintenance and management plan

Wharf

Breakwater

Harborroad

Preventive maintenance plan

XX Port
Wharf
Breakwater
Harbor road

Navigation
route(By facility)(By port)

Plan

Maintenance and management plan

Preventive maintenance plan

Plan unit

By each facility

By each port and harbor

Objective

To contribute towards promotion of appropriate
maintenance and management (inspection, maintenance,etc.) by each facility

To contribute towards planned implementation ofcountermeasure against superannuation by eachport and harbor

Plancontent

Working out of basic concept for facility maintenance andmanagement, planned and appropriate inspection anddiagnosis of relevant facility and their implementation period,
maintenance content and its implementation period

Working out of countermeasure against superannuation andprioritizing of implementation of countermeasure dependingon importance level of facility by taking superannuation andapplication condition for respective facility into consideration

August 2016 Steel Construction Today & Tomorrow 12

Life-cycle Management Design

Structure Design System under theConcept of Life-Cycle Management
Hiroshi Yokota: After finishing the M. Eng course at
Graduate School of Engineering, Tokyo Institute ofTechnology, he entered Port and Harbour ResearchInstitute, Ministry of Transport (currently Port andAirport Research Institute) in 1980. He assumed his
current position as Professor, Faculty of Engineering,
Hokkaido University in 2009. His specialized field covers concrete structure and maintenance engineering.

by Hiroshi Yokota
Professor, Hokkaido University
Introduction
A structure has been adequately plannedand designed to keep its structural performance over respective requirements
throughout its life-cycle. However, serious deterioration of structural members
may be caused due to various reasons.
To meet these facts, it is extremely important to pursue coordination between
design and maintenance. The life-cycle
management is an organized system tosupport engineering-based decision making for ensuring sufficient structural performance and long life of a structure at
the design, maintenance, and all related
work during its life-cycle1). This article
deals with structural design system under
the concept of life-cycle management.

ciated performance requirements definedat the time of design or as may be subsequently modified. Figure 22) shows the
PDCA cycle that is a key procedure of thelife-cycle management. The PDCA cycle
is implemented based on the data collected at the maintenance stage. For maintenance procedure, it is important to identify the mismatch or difference of design
assumption and real situation (Check),
which may be applied for improvements
on future maintenance, design and/or execution methods (Action). During thatprocess, the output from the system canbe fed back to planning, design, and/or
execution stage(s) if necessary. Therefore, it can be said that mainte-nance data
should be of very importance.

Life-Cycle Management
The service life of a structure is made up
of all the activities, which includes planning, basic (conceptual) and detailed designs, execution, maintenance and repair,and decommissioning. The life-cycle
management is an integrated concept
to assist in activities managing the total
life-cycle of structures based on managements of each stage to ensure structuralfunctions and performance and to realize
sustainability as shown in Fig. 1. In other words, the life-cycle management can
provide an overall strategy to be used inensuring that a structure meets the asso-

Service Life Design
The fundamental concept on how thestructural performance should be ensured must be well considered based on
conditions, design service life, structural characteristics, material properties, difficulties in assessment and remedial action, social and economic importance,
etc. During the initial design stage, theservice life (durability) design will beapplied to predict the performance degradation. Specific methodologies on
the service life design for structures are

Fig. 2 P-D-C-A Cycle in LCM2)

Fig. 1 Life-Cycle of Structure and Its Management
Planning
Management
S tandards
C odesDesignExecution

Management

Use

Life-end

Longer utilization
Meet people’s expectation

Management
S tandards
S peciﬁcations
S tandards
Management
Guidelines
Performance
S ustainability

13 Steel Construction Today & Tomorrow August 2016

based on the concept of a fully probabilistic approach, a partial safety factor approach, a deemed-to-satisfy approach,and an avoidance deterioration approach.
For steel structures, corrosion of steel
is a principal cause of performance degradation to be considered at the initial design. Accordingly, corrosion of steel itself and/or deterioration of a corrosion
protection system should be fully taken into account. Prediction at the design
stage is done based on theoretical models
or specific values determined by investigating existing structures or experimental findings. When the fully probabilistic
approach is taken, all the design parameters should be modelled with probability
functions. An example showing changes
in failure probability over time due to corrosion of steel has been provided in somereferences1)3). Otherwise, corrosion protection has been generally applied as an
avoidance of deterioration approach suchas surface covering and cathodic protection. Under that approach, deterioration
models for corrosion protection should beconsidered for the service life design.
Serious deterioration may be caused
by insufficient durability design with optimistic assumptions against materials
deterioration and by lack of proper maintenance after construction of the structure.

PLAN
Optimum LCM scenario
Feedback
Maintenance (DO)Inspection
Evaluation

RecordCountermeasure

Feedback

ACTION
Improvements(maintenance,
design, and/or
execution
methods)

CHECK
Reason of the mismatch
Transferring and utilizing the information

Planning

Feedback (life extension,
maintainability, etc.)

DesignFeedback(construction
quality, etc.)
Execution

Based on the performance-based designconcept, it is necessary to provide the methods to ensure the structural performance requirements over the minimum limits during
the design and maintenance stages.
Performance Assessment in
Maintenance
Maintenance is the major strategy tocounter the degradation, which is carried out to assess the present conditionsof structure and to quantify the level ofstructural performance. In addition, it isnecessary to predict the future progress ofstructural performance degradation. During the maintenance stage, maintenanceengineers will initially follow the scenario (life-cycle management scenario;
LCM scenario) that had been assumed at
the design stage. The output of the design
has to be verified with the maintenancework because progress of deterioration
would not follow the design assumptions.
The progress of corrosion differs widely by its location because of inhomogeneous characteristics of materials and diversity of environmental conditions. By
using the real corrosion data, the LCM
scenario has to be updated.
The level of inspection and investigation has an influence on the method of
structural performance assessment. Assessment can be made by the conditionbased concept and the performancebased concept4). Visual inspection is only
able to provide the change in appearanceof structural member, but structural performance has to be evaluated as precisely as possible. If the relationship between
structural performance and the grade of
deterioration could be found even tolerate margins of errors, the intervention
could be discussed using the deterioration grade.
Feedback from Maintenance
Results
As shown in Fig. 3, prediction at the design stage is generally done based ontheoretical models, but that at the main-

tenance stage may be done with stochastic mathematical model such as survival
analysis and Markov model. Some theoretical rules, simulation models, verification formulae, etc. are used for the prediction of deterioration progress. However,
the trend that is observed through regular
maintenance work, for example the measured corrosion rate, may have potentials
for use in the future progress of deterioration and/or degradation during the maintenance stage. Based on the data and assessment results, the rule and process ofdeterioration and/or performance degradation have to be modified and the scenario be updated for further prediction.
If member failures might cause hazards to safety, possible failures should be
categorized by their consequences. To reduce the risk of failure occurring within the design life when the consequences of failure are judged to be critical, it
may be necessary to require particularly
long design lives for specific members or
to strengthen the requirements for inspection and maintenance.
Sustainability Indicators
The life-cycle management takes into account the sustainability indicators suchas life-cycle cost, environmental impact,etc. as shown in Fig. 4. To determine the
LCM scenario including one or more sustainability indicators will be of great use.
To evaluate the LCM scenario, costs orlife-cycle costs have been generally used
as an indicator, where the scenario having the lowest cost/life-cycle cost should
be selected as the most appropriate scenario. However, from the viewpoint ofsustainability, not only indicators of economic aspects but also indicators of social and environmental aspects should beconsidered hopefully in the future. These
indicators, as examples5), should be determined in consideration of the following items:• Use of energy and material resources;• Emissions to air, water, and soil;

InitialRequirement

Prediction
at present -2

Repairstrategy

Present
Design service life

Time

Concluding Remarks
The life-cycle management concept
should be installed in the structural design of steel structure and performanceassessment system should be establishedsoon. This can lead to realize life-cycle
design of structure. To highly develop thesystem, research is necessary on the following subjects:• Performance verification at the design
and maintenance stages which includes
prediction on future performance degradation;
Probability
approach;•Risk
management;
and•Appropriate
sustainability
indicator(s)•References
1) Yokota, H. (2013). Life-cycle management of port and harbour steel structures. Steel Construction Today & Tomorrow, 39, 4-6.
2) Nagai, K., Matsumoto, K. and Yokota,
H. Discussion materials for the SIP research program. Unpublished. (slightly modified by the author).
3) Ozaki, R., Yokota, H., Hashimoto, K.
and Furuya, K. (2013). Evaluation oflife cycle scenarios for open-type wharfbased on change in failure probability
by corrosion of steel pipe piles, Journalof Japan Society of Civil Engineers, B3,
69(2), I_179-I_184.
4) Yokota, H. (2016). Practical application of life-cycle management system
for shore protection facilities, Journal of
Structure and Infrastructure Engineering, (in press).
5) International Organization for Standardization. (2015). ISO/TS 21929-2, Sustainability in building construction − Sustainability indicators − Part 2: Framework
for the development of indicators forcivil engineering works.

Fig. 4 Sustainability Indicators
Sustainability

Fig. 3 Assessment and Prediction
Assessment• Production and management of wastes;• Species and ecosystem;• Landscape;• Community and territorial system; etc.

Environmental
aspectSocialaspectEconomic
aspect・Climate change
・Resources consumption
・Pollution
・Biodiversity
・Ecological system
etc.

・Safety・Health・Satisfaction
・Cultural property
・Community
etc.

・Economic value
・Cost
・Productivity
・Beneﬁtetc.

August 2016 Steel Construction Today & Tomorrow 14

Structural Integrity Assessment of Corrosion-damaged Steel Pier

Structural Integrity Assessment Method forJacket-type Steel Pier with Corrosion Damages
Kunitomo Sugiura: After finishing the doctor’scourse at State University of New York at Buffalo, he became Assistant Professor at Kyoto
University in 1988. He assumed his current
position as Professor, Department of Civil andEarth Resources Engineering, Graduate Schoolof Engineering, Kyoto University in 2006.

by Kunitomo Sugiura
Professor, Kyoto University
Toward Longer Service Life of Portand Harbor Facilities
After the Sasago Tunnel Ceiling Collapse
on the Chuo Expressway in 20121), theMinistry of Infrastructure, Land, Transport and Tourism of Japan (MILT) has
notified the regulation to periodically inspect all the infrastructures, e.g. for every
5~10 years in order to assess their healthcondition. Particularly, developments inthe technology of damage detection andhealth condition assessment are urgent inorder to implement “preventive maintenance” to prolong the service life of large
stocks of such facilities2).
Because of the applicability of steel
sheet piles in rapid construction, thesesteel products have been extensively used
for port and harbor facilities. However,steel port facilities are exposed to seawater and its severe corrosive environments,
so that developments have been made inunderstanding corrosion mechanisms, diverse corrosion-protection methods, inspection methods and improving repair
and strengthening methods3). Meanwhile,
it is well known that corrosion reduces the steel plate thickness of structuralmembers applied in steel structures andcauses a deterioration in the load-carrying capacity. Then, various parameters
have been assessed by means of analytical and experimental approaches to evaluate the load-carrying capacity of steel
members with various cross sectional
shapes subjected to combined sectional
forces4). However, most of these experimental and analytical approaches werebased on precise corrosion profiles ofthe structural members, and thus evaluations are not very frequently made in-situ
condition and a performance assessmentof an entire structure composing of steel
pipe piles and RC slabs with corrosion
damages was very limited5).
Then, in the following, an assessment by means of vibration characteristics is conducted targeting a jacket-typepier composed of steel pipe piles and RC
decks (the existing Shiomi No.3 Wharf ofSakai-Senboku Port referred to Photo 1).
The frequency characteristics are summarized based on FE analysis as well as
the loading test on this existing steel pierand its feasibility to assess structural integrity based on vibration characteristics
is discussed.
FE Analysis of a Spatial Jackettype Steel Pier with Pipe Piles and
Its Assessment by Loading Test
A spatial frame structure (pile length:26.0 m; pile intervals: 4.0 in the direction parallel to the shoreline and 4.5 m
in its perpendicular direction (land-sea)),
in which 20 pipe piles (outside diameter:
812.8 mm; wall thickness: 14 mm) are arranged regularly to lengthwise and crosswise at identical intervals, is adopted as amodel of an entire jacket-type pier having
steel pipe piles and RC deck in width of
20 m, in depth of 17.5 m and with thickness of 1.2 m referred to the structuraldetails of Shiomi Wharf No.3 of SakaiSenboku Port of Osaka Prefecture. Dueto the corrosion damages in steel pipe
piles as well as the deterioration of RC
decks, this wharf is under reconstruction

Photo 1 Overview of Shiomi Wharf No.3 of Sakai-Senboku Port
(Osaka Prefecture, Port Authority)

http://www.pref.osaka.lg.jp/kowan/kankatsu/sakasen-all.html
15 Steel Construction Today & Tomorrow August 2016

works. Therefore, the effect of a spatial
frame with certain damages on the horizontal load-carrying capacity is assessedby the vibration test using shaker in conjunction with the frequency analysis bychanging the corrosion deterioration patterns in steel pipe piles and varying other conditions. In the analysis, the finite
element analysis code ABAQUS (Ver.
6.12)6) is used. Fig. 1 shows the spatial
frame model that is structured as a piermodel by shell elements and beam elements in the FEM analysis.
Steel pipe piles are embedded in seabed with depth of 15, 15, 13, and 11 (m)in every row from the shoreline. The
pipe piles are modeled by shell elements
for the upper 6 m length and by pipe elements for the lower 20 m length. Meanwhile, the shell elements and the pipe elements are to be rigidly joined at the nodes.
On the other hand, the RC deck is modeled by solid elements, and to be rigidly joined with the shelled area of the pipe
pile tops. The base edges of the pipe piles
are completely fixed on soil-pile springsin the vertical direction and the pipe piles
embedded in the seabed are also connected to soil-pile spring in the horizontal direction. The ground spring constants usedin the FE analysis are based on the groundprofile investigated by Osaka Prefecture
and calculated according to the specifications for highway bridges as given in
Fig. 1 Finite Element Model of Shiomi
Wharf No.3

Table 17). As for the steel pipe piles, thedensity of 7.85 (ton/m3), the elastic modulus of 210 (kN/mm2), and Poisson’s ratio of 0.3 are assumed. Furthermore, thedensity of 2.4 (ton/m3), the elastic modulus of 23.1 (kN/mm2), and Poisson’s ratioof 0.2 for RC deck are also used. As forthe eigen-frequency analysis, the consistent mass matrix is used and the RayleighDamping is employed, where the damping factor of 0.03 is assumed. The natural frequency is summarized in Table 2. It
is understood that the natural frequency is
influenced significantly by the subgrade
reaction from the seabed. It is also reminded that the riprap at seabed surface could
cause a change in the natural frequency.
On the other hand, the stiffness of RC deck
is found to be less influential. This is because the bending moment becomes largenear the seabed as well as close to RC
deck for the 1st horizontal vibration mode.
The shaker with loading capacity of
19.6 kN is set at the center of RC deck. In
Fig. 2, the maximum acceleration responsein the numerical simulation is plotted varying the frequency of excitation. It is obviously understood that the peak acceleration is obtained at the natural frequency of
0.7-1.5 Hz as obtained by eigen-frequency
analysis, and that the peak is significantly affected by subgrade reaction from theseabed and riprap. Furthermore, the good
agreement is also obtained in acceleration
response as shown in Fig. 3.
According to Renewal Works of Shiomi No.3 Wharf, the pipe piles are inspected by measuring their thickness at thedepth of 0.75 and 1.75 m below the L.W.
level and it is reported that the average
thickness loss ratio of 5.0% and 4.25% ateach location made the Osaka Prefectural Government to decide the reuse of existing steel pipe piles in reconstruction.
In the FE analysis of a pier with corrosion damages in steel pipe piles, according to thickness measurement, the fictitious thickness loss in pipe piles by 2, 12
and 39% is assumed and the dynamic response analysis is made subjected to sinusoidal excitation given at RC deck.
Table 3 summarizes the reduction in the
maximum acceleration response for all
the cases. It is understood that the peakacceleration is reduced by 58% at most,and it is indicated that the structural integrity could be assessed by the changes
in vibration characteristics.
Concluding Remarks andAcknowledgements
As a result of a spatial frame analysis ona jacket-type steel pier with vertical steel
pipe piles and RC deck, it was learned
that the natural frequency of a steel pieris affected by mainly the stiffness of pipe
piles, and that the less effect by the stiffness of RC slab is observed. Therefore, acorrosion-damaged steel pipe piles could
be assessed by the change of vibration
characteristics such as a first horizontal
vibration mode because the stiffness ofa section expected to have severe corrosion may contribute the natural frequenFig. 2 Acceleration Response of RC
Deck in the Horizontal Direction

Table 1 Ground Spring Constants
Assumed in FE Analysis
Ground spring
constants

Height from groundreference in seabed (m)0-11Vertical (kN/m)

11-13 13-15
49,247

Horizontal (kN/m)

5,294

Rotation (kN･m/m)

29,136 20,863 15,647

3,208

2,088

Table 2 Natural Frequency Obtained by
FE Model (1st order horizontal
vibration mode)

Fig. 3 Comparison of Acceleration
Response

cy of lower vibration modes. It is also
found that since the shaker with capacity of even several tons could be utilized
to evaluate the natural frequency, the dynamic interaction of fully loaded trucks
running over RC deck with steel piercould be practical use for the structural
integrity assessment.
At the end, acknowledgements should
be given to Port Authority of Osaka Prefectural Government for the loading teston the existing steel pier and providing
the information of structural design andground conditions. The author also would
like to thank Toyo Construction Co. Ltd.
￭for their technical assistance.
References
1) i.e., http://www.mlit.go.jp/road/road_tk1_000033.html
2) Ministry of Infrastructure, Land, Transport and Tourism: MILT White Paper
20123) Coastal Development Institute of Technology, “Corrosion Prevention of Portand Harbor Steel Structures: Improvement Manual (Revised in 2009), CDIT
Library No. 35, 2009.
4) Task Committee on Evaluation of Corrosion Protection and Durability for
Steel and Composite Structures under
Offshore Environment (ed. by Watanabe, E.) “Guidelines for Evaluation of
Durability and Load-Carrying Capacity
for Steel Structures under Marine Environment” Committee of Structural Engineering JSCE, 2009.
5) Suzuki K., Hashimoto K., Kitahara T.
and Sugiura K.: “Assessment of Remaining Seismic Performance of Pier structure with Corroded Steel”, Proceedingsof Constructional Steel, JSSC, Vol.22,
pp.102-109, 2014.11.
6) Dassault Systemes Simulia: “ABAQUS
Analysis User’s Manual, Version 6.14”,
2012.
7) Japan Road Association: “Specificationsfor Highway Bridges, Part 4 Substructures”, 2012.4.

Table 3 Reduction in Acceleration
Response by Corrosion Damages

Condition

Perpendicular
Parallel tothe shoreline to the shoreline

Fixed at seabed(top surface)

1.037 (Hz)1.091 (Hz)Fixed at seabed(bottom surface)

0.393 (Hz)0.389 (Hz)Intact0.158-

Ground spring
considered

2

0.157

0.62

0.688 (Hz)0.718 (Hz)

12

0.125

20.8

Note: Torsional vibration mode with 0.843 Hz

39

0.090

57.5

Reduction in
Maximumcross sectional acceleration
area (%)
response (m/s2)

Reduction(%)

August 2016 Steel Construction Today & Tomorrow 16

Repair of Corrosion-Damaged Port Steel Structures

Inspection and Repair Technologies forCorrosion-Damaged Port Steel Structures
by Yoshito Itoh, President, National Institute ofTechnology, Gifu College; Yasuo Kitane, Associate
Professor, Dept. of Civil Engineering, Nagoya
University; Kazuo Furunishi, Senior Manager, ToyoGiken Consulting Civil Engineers Inc.; and Mikihito
Hirohata, Associate Professor, Dept. of Civil
Engineering, Nagoya University

Introduction
To keep port/harbor steel structures ina satisfactory condition with less maintenance cost, a maintenance cycle ofinspection, condition evaluation, repair/strengthening, and record keeping
should be repeated during the design service life of a structure. In this article, anefficient inspection method to measure
thickness of steel members and a repair
design for corrosion-damaged steel pilepiles to recover seismic performance are
discussed.
Inspection and Condition
Evaluation
Corrosion reduces a cross-sectional area of steel members, leading to a decrease in load carrying capacity. Therefore, to evaluate a current condition ofsteel structure, a thickness measurementof steel members should be conductedduring an inspection. The most popular thickness measurement method is theultrasonic testing method (UT), whichyields an accurate measurement, but requires a surface preparation to remove
marine growth, coating and rust prior tomeasurement. Since the surface preparation needs time and resources, more efficient thickness measurement methods
are desired.
One of such efficient thickness measurement methods is the pulsed eddy current testing method1) (PEC), which does
not require the surface preparation since
PEC uses a pulsed magnetic field to produce eddy currents in the surface layerof steel plate. PEC has been used to detect corrosion in pipelines, risers, and insulated pipes. It is said to give an average
thickness of a certain area called footprint, and therefore, it is usually used ina screening process of inspection. After
detecting corrosion by PEC, a more ac-

17 Steel Construction Today & Tomorrow August 2016

Yoshito Itoh: After graduating from Graduate
School of Engineering, Nagoya University in 1977,
he served as a research associate, Nagoya University. He became Associate Professor, Nagoya University in 1988 and Professor in 1995. He assumed his
current position as Invited Professor and Emeritus
Professor, Nagoya University, and President, National Institute of Technology of Gifu College in 2016.

curate measurement is usually conducted by removing surface coating and rust.
PEC Thickness Measurement
To examine a feasibility of PEC thickness measurement for underwater inspection work of port steel structures,the field thickness measurement2) ofsteel pipe piles by PEC was conducted
at a quay in the Port of Nagoya, and theresults were compared with values from
Fig. 1 Measured Pipe Piles

Fig. 2 Measured Thickness

UT. Fig. 1 shows the measured pipe
piles. The quay was 41.5 years old at thetime of measurement. Since the subsea
zone of piles has been cathodically protected, and the atmospheric, splash, andtidal zones of piles have had coating protection, severe corrosion damage was notobserved for these piles.
Measurement was done by PEC first.
Then the surface of piles was cleaned
to remove marine growth and rust, andthickness was measured by UT. Finally,
PEC measurement was conducted again
to examine the effect of surface preparation. Fig. 2 summarizes the measurement
results at L.W.L−2.5 m of Pile A and at
L.W.L.−1.25 m of Pile B. The horizontal
axis of Fig. 2 shows circumferential locations in the cross-section of pile, and
12 h and 6 h correspond to the sea sideand the land side, respectively.
The results show that the difference
between PEC and UT measurements
ranges from 1 to 8% of the thickness
with an average of 5.5%, and that the effect of surface preparation on the PEC
measurement is insignificant. Furthermore, the time required for the measurement was 15 to 20 min. per location for
UT while it was only 15 to 30 sec. per
location for PEC. These results indicatethat thickness measurement by PEC has
a potential to be used for the inspectionof port steel structures.
Patch Plate Repair Design
One of the popular repair methods for corroded pipe piles is to weld a patch plateon the corrosion-damaged area, and in the
typical design practice, a patch plate witha thickness equivalent to a thickness reduction is used. However, to recover seismic performance of the pipe pile to theinitial level, a larger thickness may be required to recover the energy absorption
capacity. In this study, finite element modeling for a steel pipe pile repaired by patch
plates was developed, and pushover analyses of pipe piles with different structural parameters were carried out to examine
the patch plate thickness required to provide the same energy absorption capacity
based on the load-displacement curve asthat of an intact pipe pile3).
A pipe pile was modelled as a cantilever which is the top 60% of the wholepile. Fig. 3 shows the cantilever mod-el extracted from the upper part of steel
pipe pile. In the model, a thickness reduction was assumed to be uniform forthe length of 3000 mm. The axial force,N, was applied first at the loading end,
and the pushover analysis was carriedout by gradually increasing horizontal
displacement.
Pipe diameters used in the analysis are
600 mm, 700 mm, 800 mm, and 900 mm.
Original thickness of steel pipe is either
12 mm or 16 mm. Thickness reductions
are assumed to be 6 mm, 8 mm, and 10
mm. Cantilever lengths considered are
6000 mm, 7500 mm, and 8000 mm. Steelpiles of both SKK490 and SKK400 are
used. A ratio of the axial force to yielding axial force of an intact steel pipe, N/
Ny, was considered in the analysis ranges from 0% to 20%. A total of 106 cases
were analyzed.
Required thicknesses of patch platefrom 106 cases are plotted in Fig. 4. In
Fig. 4, the parameter of the horizontal
axis was selected by referring to Ref. 4),
where λp is a slenderness ratio parameterof thickness-reduced steel pipe pile, and
Rtp is a radius thickness ratio parameterof the pile. The vertical axis is a parameter that represents a ratio of the patch
plate thickness to the intact pipe thickness, where ts, tp0, σys, σy0 are patch plate
thickness, intact pipe thickness, yieldstress of patch plate, and yield stress of
SKK490, respectively. A ratio of the required patch plate thickness to the thickness reduction was found to range from
1.0 to 1.4.
In Fig. 4, a trend curve of average values obtained by a nonlinear least square
method is shown as a dashed line, and asolid line is an upper limit curve of therequired patch plate thickness which isan average plus twice the standard deviation. The equation of the upper limit curve is also shown in Fig. 4. By using

this empirical formula, a required patch
plate thickness can be determined.
Summary
In order to achieve true life cycle management of port steel structures, the life
cycle performance should be understoodfor the whole structure. Efficient inspection methods and effective repair methods discussed in this article will be able
to contribute to better life cycle manage￭
ment techniques.
References
1) Crouzen, P. and Munns, I (2006),“Pulsed eddy current corrosion monitoring in refineries and oil production
facilities – experience at Shell,” Proceedings of the 9th European Conference on Nondestructive Testing, Berlin, Germany.
2) Kitane, Y., Nishijima, Y., Itoh, Y.,
and Nakano, Y. (2014), “Feasibility
study of thickness measurement using pulsed eddy current for port steel
structures,” Proceedings of Constructional Steel, Vol. 22, pp. 944-949 (inJapanese).
3) Furunishi, K., Kitane, Y., and Itoh, Y.
(2015), “Required patch plate thickness based on seismic behavior ofsteel piled jetty repaired by steel patch
plate,” Journal of Structural Engineering, JSCE, Vol. 61A, pp. 463-472(in Japanese).
4) Ge, H., Gao, S., Usami, T. and Matsumura, T. (1997), “Numerical study on
cyclic elasto-plastic behavior of steel
bridge piers of pipe-sections without
stiffeners,” Journal of Civil Engineering, JSCE, Vol. 577(I-41), pp.181-190(in Japanese).
Fig. 4 Required Patch Plate Thicknesses from 106 Analytical
Cases

Fig. 3 A Cantilever Model of Thickness-reduced Pipe Repaired by Patch Plate

August 2016 Steel Construction Today & Tomorrow 18

JISF Operations

Two Seminars for the Steel Industry Cooperation Program ofJapan-Thailand EPA
The Japan Iron and Steel Federation (JISF) in collaboration
with the Iron and Steel Institute of Thailand (ISIT) held twosteel seminars in Japan. These two seminars were planned aspart of government-initiated cooperative projects pursuant to
the Japan-Thailand Economic Partnership Agreement.
• Steel Construction Seminar
A one-week Steel Construction Seminar was held in December
2015 in Tokyo, in which 18 Thai engineers participated. The
seminar has been held every year since the start of the JapanThailand EPA, and the 2015 seminar marked its eighth year.
The seminar programs, selected for their interest to Thailand, covered a wide range of fields in steel constructionbridges, welding, concrete-filled steel tubular structures, seismic design and wind-resistant design. In parallel with thelectures, a tour of program-related construction sites and production plants was held. Further, the current state of concrete
bridge construction in Thailand was introduced by Thai
participants. In the seminarfor an exchange of views, various measures being promoted for the wider applicationof steel bridges in Japan were
presented.
• Newly Recruited and Young Engineer Training
Program
As a new program of the Steel Industry Cooperation Program,
two Training Programs were held, one in September 2015 andthe other in March 2016 (each for one week), in Osaka. They
were attended by a total of approximately 50 young engineersfrom the Thai government, steelmakers and trading companies.
The training program in the first program covered basic metallurgy and flat steel products for automobiles, and those in thesecond program, steel for machinery and construction and civil engineering which were added by the request of Thai side. A
tour of steelworks and other sites was also held.

♦♦♦

In the Japan-Thailand Economic Partnership Agreement: Steel
Industry Cooperation Program, diverse kinds of programs in addition to those mentioned above were held both in Japan and
Thailand.

Steel Structure Conference in Cambodia
The Japan Iron and Steel Federation held a conference titled “Recent Technologies for Steel Structures 2015” in Phnom-Penh,
Cambodia on December 3, 2015. It was jointly held by the Ministry of Public Works and Transport of Cambodia and the Instituteof Technology of Cambodia, and was supported by the Embassyof Japan in Cambodia, JICA Cambodia Office, JETRO PHNOMPENH and the Japanese Business Association of Cambodia.
In the conference, five lectures covering such topics as ports
and harbors, bridges and building construction were delivered byexperts from both Cambodia and Japan, and about 120 engineers
and university students from Cambodia attended. Key persons
from both nations participated in the subsequent Small Group
Session of the conference, where views were exchanged on the

STEEL CONSTRUCTION TODAY & TOMORROW
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Phone: 81-3-5919-1535 Fax: 81-3-5919-1536
URL http://www.jssc.or.jp/english/index.html

current situation of standardization and legislation in Cambodia
and the future diffusion of steel structures in Cambodia.
This conference is the third in the series, following those heldin 2012 and 2014. A fourth conference is planned to be held in
Cambodia in 2016.

© 2016 The Japan Iron and Steel Federation
Edited byCommittee on Overseas Market Promotion, The Japan Iron and Steel Federation
Chairman (Editor): Eiji Katayama
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