No. 71 August 2024

STEEL CONSTRUCTIONTODAY & TOMORROW

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

Feature Article

Technologies to Reinforce
and Make ResilientFoundation Structures
1 Development of Method to Reinforce Gravity-type Breakwaters
Employing Steel Piles

5 Secondary Design Method for Building Foundations Capitalizingon the Deformation Capacity of Steel Pipe Piles

7 New Development in Construction Management in the Hammer
Driving of Steel Pipe Piles

9 Research on Additional Piling Method for Pile Foundationsof Road Bridges

11 Model Experiments on Piping Failure of River Levees
13 Low-carbon Measures in the Life Cycle of Concrete Structures

19 JISF Operations
AJSI Webinar 2024
Japan-Thailand Steel Cooperation Program

Published Jointly by

The Japan Iron and Steel Federation
Japanese Society of Steel Construction

Feature Article: Technologies to Reinforce and Make Resilient Foundation Structures (1)Development of Method to Reinforce
Gravity-type Breakwaters Employing
Steel Piles

Yoshiaki Kikuchi
Coastal Development Institute of Technology
Need for Highly Resilient
Breakwaters
The coastal area of the Tohoku district
has been frequently attacked by tsunamis
for a long time. Consequently, as a tsunami countermeasure in the district, tsunami breakwaters have been constructed at
the mouth of bays where ports are located.
As a typical example of tsunami breakwaters, a breakwater constructed in the Kamaishi Bay is introduced. As shown in Fig.
1, as much as 95% of the bay mouth wasshut with mounds and caissons of the breakwater so as to suppress the intrusion of seawater into the bay. Further, the dimensionsof stone materials and the caisson used
there were designed with reference to the
maximum-scale tsunamis that have landedin the past. Notwithstanding, the tsunamisthat landed in March 2011 surpassed thosein the past in terms of scale, and as a result
more than 80% of this breakwater suffereddamage from these tsunamis (Fig. 2).
In a gravity-type breakwater in whichlarge caissons are mounted on the mound,the caisson is structured in ways that secure its stability to the wave force-induced
horizontal forces with the friction resistance demonstrated in the lower surfaceof the caisson (see Fig. 3). As can be understood from this, because it is required
for the caisson to be designed usually tosatisfy the balance of horizontal forces,
if a horizontal force surpassing that as-Dr. Yoshiaki Kikuchi: After graduating from the
Graduate School of the University of Tokyo, he
entered the Ministry of Transport and was assigned to Port and Harbour Research Institutein 1983. Then he moved to Tokyo University of
Science as a professor in 2012. He assumed his
current position as councilor of Coastal Development Institute of Technology in 2024.

Fig. 1 Sectional Profile of the Breakwater at the Mouth of Kamaishi Bay
Kobune Av.50

North breakwater 990 m +6 m Opening 300 South breakwater 670 m Kobune Av.50
Deep section 654.7
Deep section 578.2
Shallow

Shallow section 335.3

Sec.1 Sec.2-1 Sec.2-2 Sec.3 Sec.1 Sec.2

Sec.3 451.7

Sec.4 365.1

Sec.3 Sec.2 Sec.1 Sec.3 Sec.3 Sec.3

section
91.8

-19 m

-27 m

Foundation stone-63 m

RectangularcaissonTrapezoid caisson

HybridRectangular caisson
caisson Trapezoid caisson

Source of data: Kamaishi Port Office, Tohoku Regional Development Bureau, Ministry of Land,
Infrastructure, Transport and Tourism

sumed in the design stage works on the
caisson, its stability cannot be ensured.
As can be seen from the tsunami disasterin March 2011, a structure that is damaged atonce when an external force surpassing assumed levels works is insufficient as a countermeasure against natural disasters. In lightof this situation, it was proposed to constructa breakwater that is resilient or that will noteasily suffer damage, even when an external force surpassing assumed levels strikes.
Tsunami-induced Suffering
Mechanism and Countermeasures
Another reason attributable to the suffer-Fig. 2 Movement of Caissons and Deformation of Mounds
Offshore side

ing of damage at bay mouth breakwaters
is that tsunamis overflowed the caisson
to cause scouring of the mound behindthe caisson. It was shown in a hydraulic experiment conducted by the Portand Airport Research Institute (PARI)1)
that, when the mound was scoured due
to overflowing, the caisson became unstable at once in a certain timing, thereby
leading to collapse. It was desired fromthis experiment that, in order to improvetsunami resistance, not only should horizontal resistance be enhanced but scouring of the mound behind the caisson
should also be prevented from occurring.

Fig. 3 Stability of Caissons Applied for Breakwaters Is
Determined by Sliding Resistance
Offshore side

Port sideP
F

Port side
Source of data: Ministry of Land, Infrastructure, Transport and Tourism

1 Steel Construction Today & Tomorrow August 2024

Safety factor Fs =Friction force occurring between caisson bottom
surface and rubble based on deadweight F
Horizontal force occurring due to wave force P

Fig. 4 shows an image of a breakwater
reinforced by the use of steel pipe piles,
which was proposed to meet the abovementioned need. The premise of this proposal was that a certain level of horizontal movements should be allowed for thecaisson. When a horizontal force works
on the breakwater and the mound behind the caisson is scoured, it is forecast
that the entire tsunami breakwater structure will show the displacement behavior
shown in Fig. 5. But, as can be understoodfrom the figure, the passive resistance ofthe ground behind the pile can be expected due to the deflection of the pile, and theincrement of the horizontal force from theuse of the pile cannot be expected when
the pile is not deflected.
In other words, this reinforcing method can be applied only to structures having large allowable displacement, such asa breakwater. Further, in this reinforced
Fig. 4 Image of Breakwater Reinforcedby the Use of Steel Pipe Pile
Coating Port
material side

Offshore side

Steel
pipe
pile

Infilling material

Fig. 5 Behavior of Entire Breakwater Systemin the Event of Tsunami Attack
Offshore side
Tsunamiload

Mound
GroundCaissonInfilling earth

Port side
Occurrenceof eddy
due tooverflowing

structure, the pipe pile is not driven justbehind the caisson but driven with a certain separation to provide infilling between the caisson and the pile. The aimof this pile driving system is to reducethe maximum bending moment working
on the pile by dispersing the load working on the pile.
Incidentally, regarding the scouring of
the rear ground, while the ground further
behind the pile is scoured as seen in Fig.
5, it is expected that scouring is less likely
to occur between the pile and the caisson.
Photo 1 shows scouring of the rear groundin the hydraulic experiment conducted at
PARI, from which it is understood thatscouring did not occur at the range sandwiched between the pile and the caisson.
Effects of New Reinforcing Method
In order to examine the effect and impact when the caisson is reinforced withpiles, at first it is necessary to confirm
the following seven factors2) 3): effect ofpile application, separation between pileand caisson, height of infilling, rigidityof piles, embedding length of piles, interval between piles, and scouring behindthe piles.
A horizontal loading experiment was
conducted on two of the above-mentioned seven factors: the effect of pile application and the rigidity of pile, the results of which are reported below.
Fig. 6 shows an image of the loading
experiment that was conducted. The sandbox used in the experiment measured 40
cm in width and 158 cm in length, and asteel box, mass of which was adjusted to
70 kg by sand, was adopted as the caisson. The length of the caisson (width direction of the earth tank) was set at 38 cm.
The width of the caisson (length directionof the earth tank) was set at 30 cm with an

Souring ofrear ground
Steel pipe pileFig. 6 Image of Horizontal Loading Experiment
Caisson-type breakwater (W300 H300 D380)

image prepared at a scale of 1/60 of thepractical structure. Dry silica sand No. 5
was used for the model ground, and therelative density of the ground was set at80%. Gravel was used as the infilling material. In the experiment, two steel plates
3.2 and 1.2 mm in thickness (embedded
length: 28 cm) were used in place of asteel pile.
Fig. 7 shows the experimental results.
In the case of reinforcement by meansof backfilling, backfilling was provided with a crest width of 3 cm behind thecaisson, a height of 15 cm and a slopeof 1:1.5 and by the use of gravels. In thecase of reinforcement by steel plate, theseparation from the caisson at the stage ofreinforcement with steel piles was set at
5 cm. As can be understood from the figure, the horizontal resistance in the backfilling reinforcement method becameslightly larger than that in the non-reinforced method, but its effect was limited.
On the other hand, in the case of reinforcement by the use of steel piles, it isforecast that the horizontal resistance farlarger than that in the backfilling reinforcement method can be obtained, and further
the effect in which the resistance increases
along with the displacement of the caisson
is significant. Photo 2 shows the deformation of the caisson within the ground in thecase of reinforcement with the steel piles.
In the case of non-reinforcement or reinforcement by means of backfilling, while
the caisson showed displacement only inthe form of sliding on the ground under
the current loading experimental conditions, the caisson also showed the behavior of sinking into the ground due to reinforcement with steel piles, and thus it wasunderstood that the collapse mode of thecaisson also changed.
By the way, the lifeline in the case of
Photo: Port and Airport Research Institute(unit : mm)

Displacementtransducer
Jack

Ground and mound450

Infilling material
1580

Steel plate(W380 H300 t3.2)

400
Photo1 Scouring of the ground behind the breakwater reinforced by theuse of steel pile
August 2024 Steel Construction Today & Tomorrow 2

reinforcing a structure is whether or not
the reinforcing member collapses, andthus in the case of reinforcement with steel
piles, it is important for the pile to cause nobuckling or falling down. That is, it is important how the embedding length and thecross section of the pile are designed.
Specifically, while the weight and dimension of the caisson are decided by
the wave force and other conditions, itis necessary to change the cross sectionof the pile according to the ground condition in addition to the wave force. In
order to simplify the experimental conditions, because of the simplicity of theexperiment conducted on sandy ground,

section. The earth tank applied was thesame as that in Fig. 6, and the groundmaterial applied was the same as that inFig. 6 (silica sand No. 5, gravel). The relative density of the ground (layer thickness: 55 cm) applied was 10% and 80%.
The steel box applied as the caisson was
the same, but its weight was adjusted to
115 kg and 24 kg. The separation between the pile and the caisson was 5 cm.
For this experiment, a total of 12 rectangular piles (steel, 3 cm in width, 2.3
mm in thickness) were applied, and theembedding length was set at 55 cm. The
reason why the embedding length wasincreased in this experiment was to reproduce conditions in which the embedding length is long so that the experimental results could easily be assessed.
In the examination of experimental
results, the bending moment distribution
observed in steel piles was first obtained.
Based on this, the deflection distribution
was found by means of calculation via
second integration and division by flexural rigidity, while the ground reaction
force distribution was found by a second
derivative. The ground reaction force
distribution that was found in this analysis referred to the differences in loads
working on both sides of the piles. Actually, however, the aim of this examination was to learn how much load wasworking on the piles from the caisson.
Therefore, the degree of external force
working from the caisson was estimatedby subtracting the ground reaction force
based on the deflection of the steel piles
from the load distribution found by thederivative, as imaged in Fig. 9.
This external force distribution took
complex forms depending on the conditions. This examination focused on thecase of the shape approximating a trian-

it was decided to also conduct the experiment on sandy ground, but in order
to work out the condition in which theground is relatively weak, it was decided
to work out the effect of the weak groundby changing the weight of the caisson.
In other words, the experiment was
conducted with the collapse pattern ofthe caisson changed to several patterns bychanging not only the ground density but
also the caisson weight, and examinations
were made of how the distribution of theload working on the pile changed depending on the fracture mode of the caisson4).
Fig. 8 shows an image of the experiment used for the design of the pile crossFig. 7 Effect of Reinforcement by the Use of Steel Plate
1600
1400

Reinforcement by the use of steel plate (plate thickness: 3.2 mm)

Horizontal load (N)

1200
1000

Reinforcement by the use ofsteel plate (plate thickness: 1.2 mm)

800

Backfilling method

600
400

Non-reinforcement

200
0

0

20
40
Horizontal displacement in the center of caisson (mm)① Non-reinforcement② Backfilling method

Rotation60

Reinforcement by the use of③ steel plate

Fig. 8 Image of Experiment Used for Examining Design of Pile Cross Section(30 mm-width, 12 piles)
Steel sheet pile

Sinking
CaissonDeformation within groundPhoto 2 Behaviors of the caisson and theground in the case of reinforcement by
the use of steel plate

Laser
displacement 12.5-mm
transducer
pitch

Displacement transducer
Infilling material (gravel)◎ Model groundTohoku silica sand No. 5 (air-dried state)
ps = 2.651 Mg/m3
D50 = 0.548 mm

25-mm
pitch

(unit: mm)
3 Steel Construction Today & Tomorrow August 2024

Center pile
Positions ofstrain gaugesgle; how this would affect the bending
moment distribution and the deflection
distribution as obtained by calculation.
The result of this comparison is as shownin Fig. 10. The conditions applied in thisloading experiment were: a caisson massof 115 kg; the ground relative density of80%; and the horizontal loads used towork on the caisson being 600N, 800N
and 1,000N, respectively.
In order to approximate the shape ofthe external force distribution to a triangle, a decision was made to adopt the top
position of infilling soil as the upper endof a triangle and the first 0 point depth ofpile deflection as the lower end of a triangle, where the area of the triangle coincided with the load applied to work on
the caisson. As is clear from Fig. 10, it
was revealed that the experimental results
were also largely reproducible throughapproximating the shape to a triangle.

References
1) Taro Arikawa, Masaharu Sato, Kenichiro Shimosako, Takashi Tomita, GyeongSeon Yeom, Tatsuya Niwa: Failure Mechanism and Resiliency of Breakwaters
under Tsunami, Technical Note of The
Port and Airport Research InstituteNo.1269, 37p., 2013.
2) Motohiro Suguro, Yoshiaki Kikuchi,
Taichi Hyodo, Masatsugu Kiko, Soichiro Nagasawa, Shunsuke Moriyasu,
Shin Oikawa: Horizontal Loading Experiment on Breakwater Reinforced by
Steel Pipe Piles, Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean
Engineering), Vol. 71 Issue 2, pp. I_617I_622, 2015. DOI https://doi.org/10.2208/
jscejoe.71.I_617
3) Motohiro Suguro, Yoshiaki Kikuchi,
Taichi Hyodo, Yutaro Yamazaki, Sayako Tamaki, Shunsuke Moriyasu, Shin
Oikawa: Effect of Flexural Rigidity of
Piles on Horizontal Resistance of Reinfoced Gravity Type Breakewater with
Steel Pipe Piles, Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean
Engineering), Vol. 72 Issue 2, pp. I_241I_246, 2016. DOI https://doi.org/10.2208/
jscejoe.72.I_241
4) Kentaro Ichinose, Yoshiaki Kikuchi, Yusuke Mochida, Shin Oikawa: Distribution of External Forces Acting on the
Piles of a Gravity Type Breakwater Reinforced with Steel Pipe Piles, Japanese
Journal of JSCE, Vol. 79 Issue 18, Article ID: 23-18142, 2023. DOI https://doi.org/10.2208/jscejj.23-18142
5) Shunsuke Moriyasu, Ryuta Tanaka, Shin
Oikawa, Masato Tsujii, Shinji Taenaka,Kazuo Kubota, Noriyoshi, Harata: Development of New Type of Breakwater
Reinforced with Steel Piles against a
Huge Tsunami, Nippon Steel and Sumitomo Metal Technical Report, No.403,
pp.63-69, 2015.

Tasks in Application
Several tasks involved in applying the
newly-developed breakwater reinforcing
method with steel piles are cited below.
Because this breakwater reinforcement
method involves the horizontal resistance ofthe ground being expected to work, if a certain level of horizontal force cannot be expected for the ground, it is difficult for the
method to demonstrate its effect. In lightof this, it is considered that this reinforcement method is rather unsuitable for clayey ground. In addition, when this method isapplied to a newly constructed breakwater,
care needs to be given to bending of the pileunder construction. Further, in the case of
applying to an existing breakwater, it is required to drive the pile into the mound.
As to the task of whether the pile canbe driven into rubble ground like a mound,
this possibility has definitely been examined, and it has been confirmed that thepile can be driven into the rubble groundby using a special pile driving method5).

Fig. 9 Concept of External Force Working on Pile from Offshore Side
Distribution of load
working on both sidesof pile=Second derivative value ofbending moment(experimental value)
CaissonDistribution of subgrade
reaction force

Infillingmaterial

Caisson

Pile

External force from
offshore side
Difference between loadand subgrade reaction
force working on pile

S-type model of
PARI systemp = ks・x・y 0.5

Infillingmaterial+

CaissonInfillingmaterial

Pile

Pile

Fig. 10 Confirmation of Validity of Approximated External Force Distribution
0

0

0

-100

-100

-100

-200
-300
-400
-500

-200

Horizontal load
600N
800N
1000N
1000N (measure value)-600-0.8 -0.6 -0.4 -0.2 0.0 0.2
Assumed external force (kN/m)

-300
-400
-500

Depth (mm)100

Depth (mm)100

Depth (mm)

100

-200

Calculated value
Measured value
600N
800N
1000N

-600
-0.5 0.0 0.5 1.0 1.5 2.0 2.5
Bending moment (Nm)-300

Calculated value
Measured value

-400

600N
800N
1000N

-500
-600

-2

0

2 4 6 8 10 12
Deflection (mm)August 2024 Steel Construction Today & Tomorrow 4

Feature Article: Technologies to Reinforce and Make Resilient Foundation Structures (2)Secondary Design Method for Building
Foundations Capitalizing on the
Deformation Capacity of Steel Pipe Piles

Katsuichiro Hijikata
Former Professor, Shibaura Institute of Technology

Need for Examination ofSecondary Design
In the Building Standard Law of Japan,
while the secondary design of building
foundations structures is not prescribed, atrend towards the adoption of secondary design is growing in both public and private
sectors from the perspectives of business
continuity plans and asset protection. In the
Recommendations for Design of Building
Foundations of the Architectural Instituteof Japan (AIJ Recommendations) revisedin 2019, the secondary design method forbuilding foundations was shown.
Given this situation, a research projectcommissioned by the Japan Iron and SteelFederation was started at the Japanese Society of Steel Construction (JSSC). Specifically, the Research Group on Structuring Secondary Design Methods for Steel Pipe Piles
for Building Foundations was establishedwithin JSSC, which promoted the examination of secondary design methods employing steel pipe piles and concrete-filled steel
tube (CFT) piles in the two years from 2019.
Course of Examinations
The Research Group directed its research

efforts towards establishing a secondary
design method that capitalizes on thecharacteristic property of steel pipe piles
and CFT piles of being high in toughness, and promoted examinations in accordance with the following course:• For level 2 seismic loads, it was confirmed
how much the strength of foundations is
improved in the case of setting limit values for steel pipe piles and CFT piles as“limit deformation” compared to the caseof setting limit values for steel pipe piles
and CFT piles as “limit strength.” Fig.
1 shows the definition of limit strengthand limit deformation of steel pipe piles
and CFT piles. In this examination, “limit
strength” was defined as a state in which
one of group piles reaches the limit strength,and “limit deformation” was defined as astate in which one of group piles reaches the limit deformation (limit curvature)or two-point hinges occurred in one pile.
For• the relationship between the moment
and the curvature of steel pipe piles (Mϕrelationship) used in this examination,
the assessment formulae shown in the AIJ
Recommendations was adopted. For the
relationship between the moment and theFig. 1 Definition of Two Limit States③②

curvature of CFT piles (M-ϕrelationship),an assessment formulae was adopted thatwas revised by the JSSC’s Research Group
based on the Recommendations for Design and Construction of Concrete Filled
Steel Tube Structures of AIJ.
• In the calculation of the stress occurringin the pile, the “Group Pile Frame Model”
shown in the AIJ Recommendations was applied. In this calculation method, one rowof group piles and foundation beams wasmodeled, on which the building inertia force
and the ground displacement are simultaneously worked (refer to Fig. 2), and it isFig. 2 Outline of Group Pile Frame

Overturning moment

G.L.

Building inertia
Foundation beam

Soil springaround pile

Pile

Ground displacement

Limit deformation(limit curvature)

Limit strength (hinge)④

Katsuichiro Hijikata: After finishing the Schoolof Engineering, The University of Tokyo, he
entered Tokyo Electric Power Co., Inc. in 1981.
He obtained a doctor’s degree in engineeringfrom The University of Tokyo in 1991. Then hebecame professor at the Shibaura Institute ofTechnology in 2013. He is currently part-time instructor of the Shibaura Institute of Technology.

④

①

③

②

RollerLimit strength not reached
①

④

③

②

Limit strength
not reached
M

①

②

③

④

M

①ʼ

Limit strength not reached①

Limit strength(hinge)φ
5 Steel Construction Today & Tomorrow August 2024

①

②

③

Limit deformation(limit curvature)

④

M

①
①ʼ
φ

②

③

④

2 point hingeφto the rational design of steel pipe piles
and CFT piles.
A full version of the examination results was published in the “Technical
Explanations pertaining to Secondary
Design Methods for Steel Pipe Piles for
Building Foundations” in JSSC Technical Report (No. 127, August 2022).

Fig. 3 Soil Condition (N-Value)

Fig. 4 Pile Placement
G.L.
-3.0 m5

CFT pile10-7.7 m
-9.7 mSteel pile

15

26 m

0

N-value
0 10 20 30 40 50 60 70

Steel pile20

-24.0 m

25

36 m

30

Fig. 5 Q-δ Relationship of Group Pile Frame
7000
Design load

6000

Limit strength
Limit deformation

5000
Q (kN)

Examination Results
Fig. 5 shows the relationship between
the horizontal load working on the grouppile frame model Q (building’s inertia
force) pertaining to the group pile in row
X2 as shown in Fig. 4 and the displacement δ. The horizontal load at which thepile reaches the state of limit deformation showed an increase of 1.69 times thehorizontal load at which the pile reaches the state of limit strength (1.77/1.05),
where the figure shown in parenthesis is
the ratio to the level 2 seismic load.
Fig. 6 shows the formation of hinges at each pile. It was confirmed that, at
first the hinge occurred in the head of theY1 pile, where its limit value reached thelimit strength, then the hinge occurredin each pile head one after another, andfinally the hinge occurred in the underground section of the Y3 pile, where its
limit value reached the limit deformation.

Useful Results
In the above examination, it was confirmed that the horizontal load borne by
the group pile frame sharply increased
by setting the criteria on the “limit deformation,” compared to the case of setting the criteria on the “limit strength.”
This is a useful knowledge that will leadDepthpossible to take into account the nonlinearity of the pile structure and the ground.
• The target subjected to examination wasa steel-structure hospital building with
5 floors and a total floor area of about
5,000 m2. Fig. 3 shows the soil condition, and Fig. 4 the pile placement. The
ground was assumed to be located in the
coastal area of Japan. The pile lengthwas 21 m, and the upper part was structured with CFT piles, and the lower partwith steel pipe piles. The cross sectionof piles was set based on an appropriate
level 2 seismic load and in conformity
with currently prevailing practice. The
diameter of the piles ranged from 900
mm to 1,200 mm.
• Analysis was made in ways that proportionally increase the building’s inertia force and the ground displacement
and work them on the group pile frame
model to find the load at which the pilereaches the limit strength and limit deformation.

Q

4000

δ

3000
2000
1000
0

0

100

200

300

400

500

600
δ (mm)

Fig. 6 Hinge Formation Process<Limit strength><Limit deformation>

1.05

Y1

Y2

1.09

Y3

Y1

Y2

1.25

Y3

Y1

Y2

1.77

Y3

Y1

Y2

Y3

August 2024 Steel Construction Today & Tomorrow 6

Feature Article: Technologies to Reinforce and Make Resilient Foundation Structures (3)New Development in Construction
Management in the Hammer Driving ofSteel Pipe Piles

Takaaki Mizutani
Port and Airport Research Institute
Need for Automated Measurement
and Streamlined Construction
Management
In the construction of port and harbor facilities in Japan, long, large-diameter steel
pipe piles have been used extensively.
High marine construction efficiency andhigh bearing capacity can be obtained fromthe use of steel pipe piles, and thus thesepiles are commonly driven by the use of
hydraulic hammers. Execution control inpile driving is undertaken based on the Rd
obtained from the following formulae thathas been simplified from Hiley’s Formula.

Rd

0.5 F
S K
2

where
F: Blow energy
S: Amount of penetration per blow
K: Amount of rebound per blow
S and K are measured by operating
the hydraulic hammer under conditions
where paper is pasted on the pile and theworker fixes by pencil (Photo 1).
However, this measurement method
offers some problems: dangerous workin which the worker enters under thehammer, and the risk that the recording
paper may be stained or lost. Further, thereading of recorded data and the inputof this data into computers take a lot oftime. In light of this, there is a strong callto further promote not only automatedTakaaki Mizutani: He obtained a doctor’s degree in engineering from The University of Tokyo in 2000. Thenhe has worked at the Port and Airport Research Institute. He currently serves as researcher of the Institute’s
Geotechnical Engineering Department. (In 2006-2007, he worked at Kansai International Airport Co., Ltd.)measurement but streamlined construction management method.

help automate the measurement and streamline construction management.

Two Main Purposes in Piling
Construction Management
Two main purposes are cited for construction management in steel pipe pile driving.
One is to confirm that the pile tip hasreached the bearing stratum. For that purpose, it is necessary to select a value corresponding to the change in the soil layer (for example, the change in the SPT-N
value) as the value to be used for construction control and then to obtain these values continuously in the depth direction.
Another is to detect the defective piles.
When multiple steel pipe piles are driven
at an identical construction site, the bearing capacity of the respective piles willshow variation due to the depth of the
bearing layers and local changes in soil
properties, and thus there may arise cases in which a defective pile occurs. In order to securely detect the defective pile, it
is important that the variation in the values for construction control itself is low.
As a mechanism to obtain a construction
control value that appropriately satisfies thetwo purposes mentioned above, it has been
examined to use an insertion pipe with sensors to measure the amount of blow energy and penetration between the pile and thehammer (Fig. 1). This method is expected to

Unification of Pile Driving Procedure
In order to perform highly reliable construction control, it is also important thatthe method and procedure applied for piledriving be unified. Even when the pilingsites and soil properties are identical andpiles with identical dimensions are applied, if a unified driving procedure is not
adopted, the relative comparison of construction control values becomes difficult, which thus makes it difficult to detect the occurrence of defective piles. In
particular, it is empirically known that theeffect of blow energy on execution control is large. Given this, during pier-supporting pile driving at Nagoya Port, hammering was performed by controlling theblow energy of hydraulic hammer.
The horizontal axis in Fig. 2 shows the pilenumber, and the vertical axis the blow energy. In the figure, the data are divided into four depth sections just before 1 meter from the pile embedded depth, and theaverage blow energy in each section isshown. It can be confirmed from this figure that all piles within an identical depth
section could be driven with an identicalFig. 1 Conceptual Drawingof Measurement
Employing Insertion
Pipe with Sensors

HydraulichammerSensorInsertionpipe withsensors
Pipe pile

Photo 1 Measurement of penetration and rebound
7 Steel Construction Today & Tomorrow August 2024

blow energy, excluding partial piles.
Fig. 3 shows the penetration condition of each pile, where the horizontal ax-

is shows the pile number, and the verticalaxis the penetration per blow. As with Fig.
2, the data are divided into four depth sec-

tions just before 1 meter from the pile embedded depth, and the average penetration
per blow in each section is shown. A clear
tendency can be seen from the figure thatthe penetration per blow of each pile decreases from the left side toward the rightside in the figure, even though the piles
are driven with an identical blow energy.
Regarding the composition of the soil
layers in this area, while there is a slightdifference in the surface layer between
the right and left sides of the figure, thebearing layer is composed of an identicalsoil layer (Fig. 4). It is supposed that thepile penetration resistance near the pileembedded depth may have changed due
to a gradual change of the soil propertiesof the bearing layer itself from the left
side toward the right side in the figure.
When looking again at Fig. 3, there arepiles, such as pile No. 39 in the B2 site,that has a penetration amount larger thanthat of its neighboring piles. In performing
appropriate construction control for piledriving, it is considered necessary to pay
attention to such piles. It should be notedthat at this site, all piles were confirmed
to have sufficient bearing capacity throughpile loading tests and other means.

Fig. 2 Results of Measurement of Blow Energy
250

Blow energy E0 (kNm)

200
150
100
50

0
Pile 1
number

21
26
31
36
41 42
6
11
16
21 24 16
11 13 16
Construction 12
Construction site B2
Construction site A
site B1
Pile embedded length -56.8 m
Pile embedded length -56.9 m

Pile embedded
length -56.4 m
Before pile
A-1〜24 B1-1〜12 B2-13〜15
B2-16〜42
driving-stop 1.00 ~ 0.60 m
Before pile driving-stop 1.00 ~0.70 m
0.60 ~ 0.30 m
0.70 ~0.45 m
0.30 ~ 0.15 m
0.45 ~ 0.15 m
0.15 m ~ Pile embedded length0.15 m ~ Pile embedded length
Pile for in-situ loading test : A-3
B1-1
A-2
B1-2
Piles driven under the procedure differing from that of other piles : A-1

Penetration per blow S (mm)Fig. 3 Results of Measurement of Amount of Penetration per Blow
30
25

Toward a New Pile Driving Method
We have a plan to perform on-site tests forthe measurement of blow energy and theamount of penetration employing an insertion pipe with sensors. At the same time,
we will continue to promote discussions on
the unification of pile driving proceduresand further examine whether certain standards for construction management in steel
pipe pile driving can be established.

20
15
10
5

0
Pile 1
number

21
26
31
36
4142
6
11
16
21 24 16
11 13 16
Construction site A
Construction 12
Construction site B2
Pile embedded length -56.9 m
site B1
Pile embedded length -56.8 m
Pile embedded
length -56.4 m

Altitude

As2

Ac2

-4

2

-2 6
As1

D3Uc

B2

25

B2

A-3 A-425

B
B2 1-12-13

A-1(unit: m)
1.5

A
B1 -2 4
-1

Fig. 4 Profile of Soil Layers on Construction Site (Pile Bearing Layer: Dms Layer)0Seabottomsurface
-10

Bc

As1
-20
As2

Name ofsoil layer

D3Uc
D3Us

Ac2

D3Lc
-40

STP-N
value
(average)
1~22(8)

Description

As1

Medium soil
Silt-mixed fine sandSilty fine sand

Ac2

Sandy silt
Silty clay

1~4
(2)

Mostly homogenous clayey soil
Shell piece, thin fine-sand layer, containing plant piece

As2

Silty sand
Clayey sand
Sand

4~25
(11)

Mainly sand containing a slightly higher amount of fine grain
Rarely thin sandy silt layer,containing sub-pebble gravel withgrain diameter of 7 mm or lessPartial mixing of shell piece

D3Uc Silt
Tuffaceous silt

6~19
(11)

Mainly tuffaceous clay soil
Partially consolidated into gravel state
Mostly uniform but partially sandwiching gravel and thin sandy
layer with thickness of about 1 cm

D3Us Silty fine sandSilt-mixed fine sandFine sand
D3Lc Silt
Clay
Silty clay

19~50
(41)

Composed of sand containing a slightly higher amount of finegrain and sand containing no fine grain
Partially containing gravel with grain diameter of 7 mm or less

4~20
(10)

Homogeneous clayey soil, containing a slightly higher amount ofsand and sandy silty state in upper layer
Entirely shell piece, containing organic substanceSlightly containing sand in block stateDms

Silt-mixed sandSilty sandFine sand andmedium sand

11~50
(38)

Sand containing a slightly higher amount of fine grain in upper
layer and sandwiching thin silty layer
Sand containing a slightly higher amount of fine grain in lower
layer and mostly homogenous
Gravel in part of lower layer, sandwiching thin silty layer

Dmc

Sandy silt

13~22
(16)

Soil layer confirmed at partial survey sites
Mostly homogenous sandy silt and increasing fine grain downward
Partially sandwiching volcanic ash layer

-30

Dms

-50

Dmc
-60

Type of soil

4.44.44.44.44.4

Construction site A
Pile embedded length -56.9 m

Construction
site B1
Pile embedded
length -56.4 m

Construction site B2
Pile embedded length -56.8 m

Sand containing fine grain, mixed sandy soil containing nearly nofine grain
Silt thin layer, mixing of shell pieceAugust 2024 Steel Construction Today & Tomorrow 8

Feature Article: Technologies to Reinforce and Make Resilient Foundation Structures (4)Research on Additional Piling Method
for Pile Foundations of Road Bridges

Kodai Takimoto
Public Works Research InstituteKodai Takimoto: After finishing the master’s course at the Graduate School ofEngineering, Tohoku University, he entered the Ministry of Land, Infrastructure,
Transport and Tourism (MLIT) in 2016. He worked at the Kumamoto Earthquake Recovery Div. of National Institute for Land and Infrastructure Management, MLIT in 2018 and he assumed his current position as senior researcher,
Center for Advanced Engineering Structural Assessment and Research, Public
Works Research Institute. His specialized field is structural engineering.

It is required for highway administrators
to examine the need or no need for reinforcing highway bridge foundations
taking into account the structural safety demonstrated by the existing highway
bridges and the traffic function required
for the road in the event of an earthquakeand other disasters.
In light of this, the following article
introduces the tasks in the case of applying additional piling methods used to reinforce the pile foundations of existing
highway bridges and examples of related
research promoted at the Public Works
Research Institute.

Given such issues, the Public Works
Research Institute is promoting the examination of a new footing widening method by which existing and newly-installedfootings are rigidly-joined by the use of
post-installed anchors. In order to verify
the level of footing integration attainedby the use of this new footing widening
method, a bending test was conductedusing an RC specimen as shown in Fig.
1. As a result, it was confirmed that thecalculation results based on the assumption of full-section RC members nearlycoincided with the load required for the
post-installed anchor and the axial-direc-

Widening of Footings
In most cases of the applying additional piling method, it is necessary to widen the existing footing. In general practice adopted in conventional widening
methods, reinforcing bars arranged in
the footing are cut, which are then weldjoined with the reinforcing bars in the
additionally-installed footing. However, when applying this method, the loading mechanism causes temporary changes due to the cutting of reinforcing bars
in the existing footing, which may leadto the occurrence of some tasks to secure
structural safety. In addition, because thespace required for welding is narrow,
there arises the issue of whether welding
reliability can be secured.

Fig. 2 Load-Displacement Relationship(Displacement: Measured atSpecimen Center)tion reinforcing bar of the specimen toyield (Fig. 2). On the other hand, there remained the task that brittle fracturing finally occurred in integrated footing due tobond splitting fracture occurring after theyielding of reinforcing bars (Photo 1).

Development of splitting fracturefrom both sides to the center
Photo 1 Condition of specimen at the stage ofmaximum loading

Left side Joint(additionally-installed surface
footing side) position
Center400

Maximum load
(extreme lowering just after yielding)

300
Load P (kN)

Right side
(existingfooting side)

Initial yield strength (271 kN)*
* Calculated value in the case of
Yielding of post-installed applying full-section RC member
anchor (left side) and axial-direction reinforcing bar (right side)
Occurrence of crack due tobond splitting (left side)
Occurrence of crack due tobond splitting (right side)
Occurrence of flexural crack (right side)

200

100

Occurrence of crack on joint surface
0

0

20

40
60
Displacement δ (mm)

80

100

Fig. 1 Dimensions of Specimens (unit: mm) and Detailed Reinforcing Bar Arrangement
Joint section(joint surface: rough surface)

1,819

Additionally-installed Loading point A
footing side

Loading point

Axial-direction reinforcing bar on upper-surface side (D19)*Full section, continuous
Axial-direction
Existing footing
250
reinforcing bar (D19)
side

1,031

738

700

12@80=960
A’

1,000

2,900
Supporting point
Axial-direction reinforcing bar on lower-surface side (D19)*Only on the existing footing side

9 Steel Construction Today & Tomorrow August 2024

700

150

12@80=960
250

500

Reinforcing
hoop (D10)

50

1,081

300

Post-installed anchor (D22)250

Supporting point

A-A section

Post-installed anchor• Drill pit diameter: 33 mm• Filling agent (epoxy resin)
Axial-direction
reinforcing bar (D19)Plans call for further examination pertaining to the relation between the placement positions of existing reinforcing
bars and post-installed anchors and thepromotion of the research toward thepractical application of this new footing
widening method.

tirely identical diameter and grade (caseA) to a foundation with a combination ofpiles having different diameter and grade(case B), the level of the ground reaction
force of the back-row pile at a depth close
to the pile head differed between cases A
and B, and further the ground reaction
force in case B with different pile diameter and grade was larger than that in caseA with identical pile diameter and grade.
In the future, we will further promote
the verification of the factors affecting
the group pile effect such as not only
the pile diameter and grade but the interval between piles and ground conditions. The final aim is to establish a general-purpose method to verify the grouppile effect.

Effects of Group Piles on
Foundations Reinforced withAdditional Piling
In the currently prevailing technical standard (Specifications for Highway Bridges)1), the effect on horizontal displacement
due to interference between piles is considered as a group pile effect, assumingthat all the piles that make up the pile foundation have identical dimensions. However, in the additional piling method, there isa case in which the adoption of piles witha dimension different from that of existing piles becomes more rational becauseof the difference between the construction
method adopted at the initial stage and the
additional piling method and also restrictions imposed on the construction site.
Then, in order to make a basic assessment of the group pile effect on a foundation structured with the combined useof piles of different diameters and grades,
the Public Works Research Institute carried out a 3D FEM pushover analysis targeting two piles shown in Fig. 3.
As shown in Fig. 4, this analysis showeduseful results: Specifically, when comparing a foundation with piles having en-

Future Tasks
In this additional piling method applied
to pile foundation, there remain someFig. 3 Analytical Model

Acknowledgements
Part of the research introduced above
was promoted capitalizing on a subsidy
from the Japan Iron and Steel Federation,
for which we would like to express our
sincere gratitude.
Reference1) Specifications for Highway Bridges (November 2017), Japan Road Association

Rigid beam: Fixing of XYZ axial rotation
Horizontal force
Rigid beam
Enlargement
Pile in front row
Cast-in-place pile (1.0 m in diameter)
Pile in back row Interval between pile centers: 2.83 m
Cast-in-place pile (1.0 m in diameter)
Case A (identical diameters and grades)
27.7 m52 mtasks to be solved such as load bearing
by new and existing piles and a method
to establish the critical state in addition
to the tasks explained above. At the Public Works Research Institute, research tosolve these tasks is being promoted so
as to contribute towards the building of
highways that are high in safety and reliability.

Rigid beam: Fixing of XYZ axial rotation
Horizontal force
Rigid beam
Pile in front row
Steel pipe pile (0.6 m in diameter)
Pile in back row Interval between pile centers: 2.83 m

52 m

Cast-in-place pile (1.0 m in diameter)
Case B (different diameters and grades)

Fig. 4 Ground Reaction Force of Piles for Each Pile Head Displacement

4
6
8

10
-200
0

Case B(different diameters and grades)

Depth (m)

2
4
6
8
10

Ground reaction force (kN/m)
200
400
600
800

Pile in back row
Cast-in-place pile
Pile diameter(1.0 m)δ =10 mm
δ =35 mm
δ =60 mm
δ =100 mm
δ =10 mm (Single pile)δ =35 mm (Single pile)δ =60 mm (Single pile)δ =100 mm (Single pile)
Ground reaction force (kN/m)
0
200
400
600
800

-200
0

1000

2
Depth (m)Case A(identical diameters and grades)

Depth (m)20

δ =10 mm
δ =35 mm
δ =60 mm
δ =100 mm
δ =10 mm (Single pile)δ =35 mm (Single pile)δ =60 mm (Single pile)δ =100 mm (Single pile)

6

10
-200
0

1000

Pile in back row
Cast-in-place pile
Pile diameter(1.0 m)4

82Depth (m)

-200
0

4
6
8

10

Ground reaction force (kN/m)
0
200
400
600
800

1000

Pile in back row
Cast-in-place pile
Pile diameter(1.0 m)δ =10 mm
δ =35 mm
δ =60 mm
δ =100 mm
δ =10 mm (Single pile)δ =35 mm (Single pile)δ =60 mm (Single pile)δ =100 mm (Single pile)
Ground reaction force (kN/m)
0
200
400
600
800

1000

Pile in front row
Steel pipe pile
Pile diameter (0.6 m)
δ =10 mm
δ =35 mm
δ =60 mm
δ =100 mm
δ =10 mm (Single pile)δ =35 mm (Single pile)δ =60 mm (Single pile)δ =100 mm (Single pile)

August 2024 Steel Construction Today & Tomorrow 10

Feature Article: Technologies to Reinforce and Make Resilient Foundation Structures (5)Model Experiments on Piping Failure ofRiver Levees

Kiyonobu Kasama
Professor, Kyushu University

Kiyonobu Kasama: He is currently professor at the Divisionof Civil and Structural Engineering, Faculty of Engineering,
Kyushu University. He received Ph D. in Civil and StructuralEngineering from Kyushu University in 2004. Among his
main area of research are experimental and numerical characterization for cement-mixed ground, reliability theory approach to ground improvement and earth reinforcement, andrecycling geomaterial to concrete material.

Aim of Experiment
In recent years, damages arising fromriver levee failures have occurred due tothe continuous rise of river water levelcaused by heavy rain rainfall. The following three are accepted as the levee
collapse mechanisms:• Piping failure which grows in the foundation ground just beneath a levee structure
Sliding
failure of the levee structure due•to the rise of river water levels causedby heavy rainfall
Erosionand scouring failures due to the•overflowing of river water
Because of the intensified heavy rains
and continuous rise of river water level,
it is anticipated that the multiple failure
mechanism will occur.
From these backgrounds, an experimentdevice was developed that can simulate
the three failure mechanisms mentioned
above, and a model experiment was conducted by reproducing the piping failure
occurring in the foundation ground. In addition, the effectiveness of reinforcementwith steel sheet piles on piping failure wasverified, and a risk assessment for piping
failure was conducted based on the ratioof total weight of covered layer G to water pressure W at the piping failure points.

Experiment Method
An experiment device was composed ofa water-level control device, pump, tank,drainage channel, levee and earth tank to
produce the foundation ground (Fig. 1). The
left side of the device was settled as the riverside and the right side as the land inside. The
water was supplied using the pump, and theriver water level was adjusted using the water level control device. The water flown toland side was returned for circulation via thedrainage channel installed at a height similar
to that of the foundation ground.
The levee structure was a trapezoid
shape having an upper bottom of 200
mm, a lower bottom of 1,400 mm and aheight of 300 mm. The dimensions of thefoundation ground measured 2,100 mm
in length and 200 mm in height. In order to reproduce piping failure, the foundation ground was composed of two layers-a covered layer in the surface layer
section and a permeable layer in the lower section with a layer thicknesses of 50
mm and 150 mm respectively. Referring to research by Igami et al1), part ofthe permeable layer was exposed by 80
mm, and a non-permeable boundary wasprovided in a position 350 mm from theslope toe of the levee.

The foundation ground was preparedin the following manner: silica sands No.
2 and No. 7 were mixed so that the watercontent became 5% for each sand, andthe sand layer was compacted for every
50 mm using a compaction device. For
the levee structure, silica sand No. 7 andkaolinitic clay were mixed so that thewater content became 10%, and the soil
mixture of silica sand No. 7 and kaolinitic clay was compacted for every 30 mm.
In order to verify the effectiveness ofreinforcement by means of the installationof steel sheet piles against piping failure,
an experiment was conducted by installingsteel sheet piles, whose installation lengthis 90% of the foundation ground thickness,at the slope toe on land side of the leveeand at the center of the levee structure.
As for the experiment procedure, water
was passed through the foundation groundand it was confirmed with a moisture sensor that the foundation ground caused sufficient saturation, then the water level was
raised by 6 mm/min using the water level control device as shown in Fig. 2. After the water level reached 300 mm, it was
confirmed whether or not piping failure occurred, while maintaining the water levelfor 10 minutes. In addition, the ratio of theFig. 1 Experiment Device
Water pressure meter
Water level control device

200 mmMoisture sensor
600 mmDepth: 150 mm

350 mmNon-permeable boundary

Water level
Steel sheet pile
50 mm
Pump

150 mmLevee structure:
Silica sand No. 7 and kaolinitic clay
Steel sheet pile

Covered layer(silica sand No. 7)

Permeable layer(silica sand No. 2)

Tank
11 Steel Construction Today & Tomorrow August 2024

300 mm

100 mm
80 mm

DrainagechannelWater level fromfoundation ground (mm)Fig. 2 Relationship between Lapse of Timeand Water Level
No installation of steel sheet pile
Water levelOccurrence of piping

Slope toe reinforcementwith steel sheet pile

Levee center reinforcementwith steel sheet pile
Lapse of time (min.)Pore water pressure (kN/m2)

Fig. 3 Water Pressure of Permeable Layer justbeneath Slope Toe inside Levee
No installation of steel
sheet pile

Levee center reinforcementwith steel sheet pile
Slope toe reinforcement with steel sheet pile
Lapse of time (min.)Fig. 4 Comparison of G/W Values

G/W

total weight of covered layer G to waterpressure W at the bottom of covered layer was calculated employing the pore waterpressure measured during the experiment.
Fig. 2 shows the relationship between
the lapse of time and the water level. It also shows the time of occurrence of piping
failure confirmed through visual observation. Piping failure occurred after a lapseof 42 minutes in the case of no installationof steel sheet piles, 43 minutes in the caseof slope toe reinforcement with steel sheet
piles and 41 minutes in the case of levee
center reinforcement with steel sheet piles,
and thus it was impossible to prevent piping failure from occurring even by installing steel sheet piles. However, the size ofthe piping hole was reduced to about 30%.
Fig. 3 shows the water pressure of thepermeable layer observed in the case of no
installation of steel sheet piles, slope toe reinforcement with piles and levee center reinforcement with piles. In the case of slope
toe reinforcement with steel sheet piles, thewater pressure decreased by about 75%
from the case of no installation of piles, andalso in the case of levee center reinforcement with piles, the water pressure decreased by about 50% from the case of no
installation of piles. These large decreases
are considered attributable to the narrowed
sectional area for water flow and reduced
amount of the seepage flow attained by the
installation of steel sheet piles.
In addition, the water pressure in thecase of slope toe reinforcement with piles
reached about 70% of that in the case of levee center reinforcement with piles. This isconsidered attributable to levee center reinforcement with piles being closer to the location of piping failure, where the effect ofsteel sheet pile installation on the reductionof seepage flow was more pronounced.
Fig. 4 shows G/W, a risk level for theoccurrence of piping failure calculatedusing the measured water pressure. The
value G was calculated by setting theunit saturated volume weight at 19.29
kN/m3 and the covered layer thickness at
0.05 m, which led to a value of 0.96 kN/
m2. The value W was calculated by theuse of the water pressure measured at theposition of the covered layer bottom surface. It is understood from the figure thatthe value G/W decreased with the lapseof time. The value G/W at the stage of theoccurrence of sand blasting in the caseof no installation of steel sheet piles was
1.11, and in the case of levee center reinforcement was 1.31, and further, G/W in
the case of the covered layer bottom surface showed a value close to 1.

Levee center reinforcementwith steel sheet pile
No installation ofsteel sheet pile

Occurrence of piping

Lapse of time (min.)

It was shown from these values thatthe condition of the occurrence of piping
failure and its timing can quantitively beverified by the use of the value G/W. As
a cause attributable to the value G/W not
falling short of 1, it is considered that thewater pressure W dispersed widely. To
that end, it is necessary to improve themeasurement accuracy.
Useful Experiment Results
The following results were obtained
from the model experiments.
• An experiment device was developedthat could reproduce three major collapse mechanisms for river levees: piping
failure at the foundation ground, sliding
failure of the levee structure and erosion/scouring failure due to overflowing.
• In reinforcement with steel sheet piles
that cut off the foundation ground by
90%, as applied in this experiment, it

was impossible to prevent piping failure from occurring regardless of the steel
sheet pile installation position. However, the size and scale of the piping hole
could be reduced to 30%.
The
• risk level of the occurrence of piping failure was judged using the G/W obtained based on the total weight of thecovered layer G and the measured waterpressure W. The measurement variationof water pressure W was large, and it isnecessary to improve measurement accuracy in the future, but there is a possibility that risk assessment involved in piping failure can be carried out using G/W.
Reference
1) T. Igami, K. Maeda, Y. Maki and R. Okada: Suppression effect of piping progressin river levee by sheet-pile installation,
The 33rd JGS Chubu Ground Engineering Symposium, 2021
August 2024 Steel Construction Today & Tomorrow 12

Feature Article: Technologies to Reinforce and Make Resilient Foundation Structures (6)Low-carbon Measures in the Life Cycleof Concrete Structures

Akio Kasuga
Executive Fellow, Sumitomo
Mitsui Construction

Introduction
According to European data, 60% of cement is used in structural concrete[1].
Concrete emits 2.8 billion tons of CO2
per year worldwide, so if the ratio were
the same as in Europe, cement in structural concrete would emit 5.2% of theamount of CO2 emitted by mankind in ayear. We cannot just wait for these materials to go zero carbon. The countdown
to carbon neutrality has already begun.
The author explained how carbon neutrality will affect concrete structures[2].
This paper will present low-carbon
and decarbonisation technologies in the
supply chain of concrete structures thatcan be applied today and those that need
to be developed in the future to achievecarbon neutrality by 2050 and will pres-

Dr. Akio Kasuga is an Executive Fellow of Sumitomo Mitsui
Construction and also a Senior Principal Researcher of the
University of Tokyo. He has been designing and building many
bridges and has developed many new bridge technologies. He
received Trophy Eugene Freyssinet 2013 and Albert Caquot
Prize 2021 of AFGC from France. He was the President of fib(Fédération internationale du béton) from 2021 to 2022. He
was awarded as the Honorary President of fib in 2023.

ent possible concrete measures that could
be taken.
Economic Implications of Carbon
Neutrality
To begin with, consider how much it
would cost to go carbon neutral in 2050.
This is not a particularly difficult calculation. If emissions of 32.5 billion tCO2 peryear were to be reduced at a constant rate
for 30 years, it would amount to about
500 billion tCO2. Multiply this by an assumed average carbon pricing of 12,000
yen/tCO2, and the result is 6,000 trillion
yen[3]. This is a tremendous amount ofmoney, but the IPCC subsequently announced that a maximum of $30 trillion
would be required to halve carbon emissions[4]. This is equivalent to the author’s

Fig. 1 CO2 Emissions/GDP of Each Country (2021)

13 Steel Construction Today & Tomorrow August 2024

estimate. Bill Gates defined a green premium of $5.1 trillion/year by multiplying 51 billion tons of annual greenhousegas emissions by $100[5].
Fig. 1 shows the CO2 emissions[6]of each country in 2021 divided by its
GDP[7]. The global average is 426 tCO2/
million $ (red dotted line), which meansthat China, India, Russia, Iran, Indonesia, Saudi Arabia and South Africa havehigh CO2 emissions relative to their economic size. The CO2 emissions divided
by the money index is a key factor in theargument of this paper. There is still a lotof data to be developed on the CO2 footprint of structural concrete. And when
considering strategies to decarbonise andreduce the carbon footprint of structuralconcrete, the answer that it cannot be do-ne because of a lack of data is a missed
opportunity. Such a comprehensive indicator will help us make decisions towards carbon neutrality.
CO2 Emissions of Structural
Concrete
Fig. 2 shows the EN15978 construction
supply chain in Europe. And the CDP(Carbon Disclosure Project) classification of each area of the construction supply chain is shown below. Scope 1 and
2 CO2 emissions need to be reduced un-

der the responsibility of the key players.
However, as long as they are integrated
into the supply chain, Scope 3 must also
be addressed in some way in each area.
In particular, designers will be involved
throughout the LCA and therefore proposals for low-carbonisation and decarbonisation will be required from operators in the LCA.
According to the construction companies’ data disclosed by the CDP, the indicator of annual CO2 emissions divided bytheir turnover is 98% Scope 3 with 1000

tCO2/100 million yen (Table 1). The construction stage of A4 and A5, Scope 1
and 2 for construction companies, is only
2% in the case of Japan. Most of the CO2
in the construction supply chain is emitted during the material production stage
from A1 to A3 and the use stage from B1
to B5. The former is Scope 1, 2 of thematerial supplier and the latter is Scope
1, 2 of the operator. According to a construction company to which the author
belongs, 400 tCO2/100 million yen from
A1 to A3 emits about 40% of CO2, andFig. 2 Scope of CO2 Reductions to Be Addressed in Construction and Areas of the Construction Supply Chain

Table 1 CO2 Emissions by Japanese Industry(calculated by author from CDP data)
Industry(tCO2/100million JP yen)
Scope 1 and 2

Scope 3

Construction

25

1,080

Real estate

90

270

Internet service

12

110

Finance

5

13

Fund

300

260

Chemical materials

470

830

Transportation (railroads)

290

200

Transportation (vehicles)

50

90

Transportation (ships)

1,220

160

Transportation (aviation)

1,720

460

Retail30

1,070

General trading

80

350

Manufacturing (electrical equipment)

70

3,370

Manufacturing (industrial equipment)

50

920
August 2024 Steel Construction Today & Tomorrow 14

600 tCO2/100 million yen from B1 to B5emits about 60% of CO2. Therefore, A1
to A3 and B1 to B5 CO2 emission reduction is an important key.
Here is an interesting database. Fig.
3 shows the relationship between CO2emissions and construction costs forbridge construction in the UK[8]. Although there are some differences amongroad bridges, railroad bridges, and pedestrian bridges with different loads, agood correlation is shown, and the gradient is approximately 400 tCO2/million€. Despite the influence of prices and exchange rates, it can be said to be at thesame level as the 400 tCO2/million € of
A1 to A3 shown earlier. We believe thatthese facts indicate that CO2 emissions
are closely related to economic activities. The indicator of 400 tCO2/million €or 400 tCO2/100 million yen is a usefulindicator to consider now for future strategies for reduction, as the CO2 emissions
database in the LCA for structural concrete is currently insufficient.
Low-carbon Technologies at theMaterial Manufacturing Stage
The relationship between the durability of structural concrete and CO2 emissions is shown conceptually in Fig. 4(a). As shown in Fig. 4 (b), we must aim
to reduce CO2 emissions at all stages.
The first step is to deal with the material

Fig. 3 CO2 Emissions in Bridge Construction (processed based on Reference 8)

manufacturing stage. Until steel and cement achieve zero-carbon status, the A1
to A3 stages must be low-carbon. There
are already many studies and achievements in concrete where cement is replaced by by-products. Of course, it is
not possible to substitute all of the current cement with by-products, but it isa transitional measure until zero-carbon
cement is achieved. In addition, since
low-carbon concrete is slow to develop strength, steam curing is required forprecast products due to restrictions on
the use of formwork diversion. However, steam curing using boilers emits thesame amount of CO2 in exhaust gas asthat reduced by the concrete itself, so
it is necessary to consider the reuse of
CO2 through CCUS or other means.
Furthermore, since low-carbon concrete has a lower alkalinity than normal concrete, it can be said to be a neutralized concrete from the beginning.
Therefore, some measures that do not
deteriorate the reinforcing steel are necessary to prevent the durability of theconcrete. And when low-carbon concrete is used in structures, the issue isstrength. There are examples of concrete without cement that has achieveda strength of over 100 MPa[9], and thistechnology can reduce CO2 emissions
by about 70% (Photo 1).
Low-carbon Technologies in the
Use Stage
In order to reduce CO2 emissions during
the use stage shown in Fig. 4 (b), data on
the relationship between durability and
LCA, as well as data on conservation by
operators, are indispensable. However,this type of data is currently very scarceand must be accumulated in the future.
The biggest issue in maintenance is how
to prevent the deterioration of reinforcing steel. The high durability of structural concrete is important to reduce CO2
emissions during the use stage. Currently
available technologies such as stainlesssteel, aluminum reinforcement, or steel
bars with anti-corrosion coating can beused for this purpose. However, the useof reinforcing steel in low-carbon concrete is still a subject of limited knowledge and must be studied further. Importantly, even if steel and cement achievezero-carbon status, durability and CO2
emissions at the use stage will remain anissue.
Increasingly, FRPs such as carbon, aramid, and basalt are being used for reinforcement. The world’s first non-metal-

15 Steel Construction Today & Tomorrow August 2024

Fig. 4 Concept of Durability and CO2 Emissions(a) Conventional Technology(b) Low-carbon Technology

Photo 1 Zero cement concrete
August 2024 Steel Construction Today & Tomorrow 16

Low-carbon Technologies That
Contribute to the Circular Economy
The life cycle of concrete structures islong and involves social and environmental changes during the use stage. In
other words, changes in population, climate, and technological paradigm shifts
are expected to force changes in thefunction of the structure. It is important
to design the first cycle with the expectation of minimizing CO2 emissions at thattime.
Concrete structures that are easy todismantle and reuse the dismantled
components can reduce CO2 emissions
from A1 to A3 to as close to zero as possible[2]. Various technologies related tomulti-cycle concrete structures are issues to be addressed in the future, including standards. They include newchallenges such as in-service monitoring, evaluation of components after dismantling, technologies to remanufacture
them equivalent to new ones, and standardization of structures. In the Netherlands, the “Bridge Bank”[13], a governmental bridge reuse program, is alreadyin place as a multi-cycle attempt, and it
is very interesting.
17 Steel Construction Today & Tomorrow August 2024

Photo 2 World’s first non-metallic bridge (Bessodani Bridge)

Photo 3 Non-metallic deck (Tadenodaini Bridge)

Photo 4 Fusion of zero-cement concrete and non-metallic technology

Fig. 5 Comparison of CO2 Emissions[12]250.0CO2 emissions (tCO2)

lic bridge with aramid FRP prestressing
tendons was built as a motorway in 2020
(Photo 2)[10], and non-metallic decks
were built using the same technology in
2021 (Photo 3). These materials can remove deterioration factors from structural concrete and are compatible with lowcarbon concrete with low alkalinity. FRP
can be used as a tendon to provide prestressing forces as well as reinforcement.
Estimates using American Association ofState Highway and Transportation Officials (AASHTO) girders show that the
combination of zero cement concrete, aramid FRP tendons, and nonmetallic technology of GFRP reinforcements can reduce CO2 emissions by 82% in LCA
compared to conventional technology (Table 2)[2], [11]. In addition, a pretensioned girder combining high-strength
zero-cement concrete and aramid tendons was constructed in 2019 (Photo 4).
This girder has reduced CO2 emissions
by about 75% compared to conventional technologies in LCA (Fig. 5)[12]. These
low-carbon technologies will be valued
at a carbon price for the reduced CO2
emissions if a carbon tax is introduced inJapan in the future. And the carbon credit market becomes as large as in Europe.
This will be a great motivation for technology development.

200.0
150.0
100.0
50.0
0

Conventional

Non-metallic

Concrete (main girder)
PC strand + Re-bar

Non-metallic
Non-metallic+ STC-ZERO-FR + STC-ZERO-FR+ Ad
Concrete (parapet)
AFRP + GFRPTable 2 Probabilistic Estimation of Whole Life tCO2 of the BT-72 Girder Bridge
Superstructure[11]tCO2Whole life tCO2
Stage Aemission reduction
Stage B and(A+B+C)
A1-A3
A4-A5
rate
(%)
Stage C
(80% of A) (20% of A)(tCO2/m3)
Conventional
Repair and
326
174
43
543
2.2
NA
bridgereplacement(1.5 times of A)
4.5
Next-generation No repair and
70
18
100
0.4
82
(12% of wholebridgereplacement
life emission)
Lifecycle
factorToughening in the Use Stage
Disasters such as earthquakes and floods
not only cause significant economic losses, but also emit large amounts of CO2
due to debris disposal and reconstruction. In 2018, the Japan Society of Civil
Engineers (JSCE) published a forecast of
economic, property, and financial damage from a possible major disaster[14]. For
example, for an earthquake directly under the Tokyo metropolitan area, whichis said to have a 70% probability of occurring within the next 30 years, they
forecast economic damage of 731 trillion yen, asset damage of 47 trillion yen,and financial damage of 77 trillion yen.
Based on this data, CO2 emissions estimate due to an earthquake directly under
the Tokyo metropolitan area was thenmade. Assuming that the cost of reconstruction is equivalent to the asset damage, the reconstruction cost of 47 trillion
yen is multiplied by 400 tCO2/100 million yen, the index shown above, to derive 1.9 billion tCO2. This is equivalent
to 16% of Japan’s annual CO2 emissions,or 3% extra CO2 emissions every year if
reconstruction is completed in five years.
At the same time, JSCE has also
shown that a 34% reduction in disaster mitigation is possible if more than
10 trillion yen of seismic retrofitting of
infrastructure is implemented against
an earthquake directly under the Tokyo
metropolitan area. In other words, CO2
emissions could also be reduced. Disasters are events in the use stage. In other words, reducing CO2 emissions here
is Scope 1 and 2 for operators. The hugecost can be financed by private funds.
It is known that a pay for success typefund can be established as a SIB (Social Impact Bond)[15], [16]. The amount of
CO2 emissions from the disposal of disaster debris can also be roughly calculated, but it is only a few percent of thatof reconstruction. Private-sector funds
invested in the strengthening of thisuse stage will significantly reduce CO2
emissions, making it the feasible ESG
investment.

Conclusions
For concrete structures, which alone
account for 6% of global CO2 emissions from major materials, the cost ofachieving carbon neutrality by 2050
will be significant. However, depending on whether this is seen as a cost ora value, the actions will be very different. The technologies that will contribute to carbon neutrality in structural concrete are largely the result of ourinnovation. In other words, it is not arisk but an opportunity[2]. The value attached to CO2 reduction means that low
carbon and decarbonisation technologies will be properly paid for and will
attract investment in these new technologies. However, these new technologies need to be fairly verified by athird party. The ESG investments thatare now making headlines will increasingly be in valuable technologies thatare not greenwashed.
As part of the move towards carbon
neutrality, fib (Fédération internationaledu béton) has initiated a special activity group to build a useful platform for its
members by filling in the missing dataon the use stage and combining it witha materials footprint database. This is amajor move that spans the entire organisation, and the main players are the next
generation of young people. Although
the movement in Japan is still slow, I
hope that what I have described above
will help you in the future.
References[1] Favier A., De Wolf C., Scrivener K.
and Habert G., A sustainable future for
the European cement and concrete industry, ETH, EPFL, 2018[2] Kasuga, A., Impact of carbon neutrality on structural concrete – Not a risk
but an opportunity, fib Structural Concrete, 2012, pp1725-1736[3] Kasuga, A., The “Anthropocene” billas indicated by CO2, Nikkei, 24 June
2021 (In Japanese)[4] Climate Change 2022: Impacts, Adaptation and Vulnerability, IPCC, Au-

gust 2022[5] Gates B., How to avoid a climate Disaster, Knopf, 2021 Feb[6] Ritchie H., Roser M., CO2 emissions, Our
World in Data, 2017 May (last revised2020 Aug.), Available from: https://ourworldindata.org/co2-emissions#globalco2-emissions-from-fossil-fuels-andland-use-change[7] The World Bank open data. GDP (current US$), https://data.worldbank.org/
indicator/NY.GDP.MKTP.CD[8] Collings D., The carbon footprint ofbridges. Structural engineering international, 2021 May[9] Matsuda T., Mine R., Geddes D., Walkley B. and Provis J., Development of
ultra-low shrinkage and high strength
concrete without Portland cement withexperimental study on its fabrication,
fib Oslo Congress, 2022 Jun[10] Matsuo Y., Wada Y., Fujioka T and
Nagamoto N., Construction of nonmetal bridge, fib Symposium in Lisbon, 2021 June[11] Zerin A. and Kasuga A., LCA of achallenging low carbon ultra-high durability non-metallic bridge, fib Congress 2022 in Oslo, 2022 June[12] Shinozaki H., Matsuda T. and Kasuga A., Construction of non-metallic
bridge using zero-cement concrete,
fib Congress 2022 in Oslo, 2022 June[13] https://www.nationalebruggenbank.
nl/en/[14] Report on Technical Study on Countermeasures for Mega Disasters Causing “National Disaster”, Japan Societyof Cicil Engineers, 2018 (in Japanese)[15] Kamatani, T., et al., A study on PFS(Pay for Success) investment in development of infrastructure for disaster prevention, Policy and PracticeStudies, Volume 7, Number 1, 2021
(in Japanese)[16] Recommendations on Social Implementation of Disaster Mitigation SIB
for Private Sector Financing of Disaster Mitigation Investments, Disaster
Mitigation Infrastructure PFS Study
Group, Resilience Japan Promotion
Council, April 2022 (in Japanese)

August 2024 Steel Construction Today & Tomorrow 18

JISF Operations

AJSI Webinar 2024: Achieving Carbon Neutrality
in the Steel Sector

The Japan Iron and Steel Federation(JISF) concluded a memorandum with
the ASEAN Iron and Steel Council(AISC) in fostering interaction concerning the environment, standardization andtrade in May 2014.
In the field of environment, JISF haslaunched a public-private collaborative
scheme called the ASEAN-Japan Steel Initiative (AJSI) with the cooperation of the
Ministry of Economy, Trade and Industry. The purpose of this initiative is to provide a platform to exchange knowledge
and experiences, thereby contributing toenergy saving & environmental protection in ASEAN countries. In addition, AJSI aims to encourage technology transferfrom Japan to the ASEAN steel industry.
To achieve this goal, JISF has establishedthree main activities: Steel Plant Diagno-

sis, Technologies customized List and Public and Private Collaborative Workshop.
On February 6, 2024, as Public andPrivate Collaborative Workshop, JISF
held an online seminar “AJSI Webinar
2024: Achieving Carbon Neutrality in
the Steel Sector” targeting ASEAN countries, to which a total around 180 participants from the government, steelmakers
and others in those nations participated.
Reflecting the growing pressure fordecarbonization, this webinar focusedon Carbon Neutrality, introducing policies and initiatives of both the public andprivate sector.
JISF also incorporated items such as
programs for overseas human resource
development by ECCJ and best practiceof an EAF company, in response to the
feedback survey from last year. The we-binar also provided information on Japan’s Policies towards Green Transformation. Not only did we welcome thesteel companies of Japan, but we also had
Thailand and Indonesia steel makers tohave an informative presentation on theirinitiatives towards Carbon Neutrality.
South East Asia Iron and Steel Institute (SEAISI) expressed gratitude for thecontribution of the past AJSI activities,
and also shared the view that the continuous cooperation between Japan and ASEAN countries, which shares the same goalof carbon neutrality, is truly meaningful.
JISF, together with the Japanese government, will continue to support energy
efficiency and environmental protection in
the ASEAN steel industry and cherish thelong-term relationship between Japan and
ASEAN countries fostered through AJSI.

Courtesy Visit to TISI and the FY2023 JapanThailand Steel Cooperation Program
Since 2008, the Japan Iron and SteelFederation (JISF) has initiated technical cooperation programs in Thailand’s
steel sector under the Japan-Thailand
Economic Partnership Agreement (JTEPA). Since 2017, JISF has been providing the technical cooperation program to
the Thai steel industry between JISF andthe Iron and Steel Institute of Thailand(ISIT) on an annual basis. The program
mainly involves the standardisation ofsteel product in Thailand, including
formulation of steel product standards
in Thailand and technical guidance tostrengthen a quality inspection system of
the testing laboratory owned by ISIT.
In July 2022, a Memorandum of Understanding (MoU) was signed between JISF,
the Thai Industrial Standards Institute (TI-

SI) and ISIT. Under this agreement, TISI
gained permission to use the copyright ofJapanese Industrial Standards (JIS) held by
the JISF Standardisation Centre. The MoU
also established a contact point on bothsides for exchanging operational information regarding TIS’s mandatory standards.
Approximately a year later, on 29 May,
JISF paid a courtesy visit to TISI to discuss the MoU’s implementation and mutual trade concerns. The update and formulation of new TIS mandatory standards
were also discussed. The meeting concluded with confirmation of ongoing friendly
relations and future technical cooperation
between JISF, TISI and ISIT.
Under the steel technical cooperation
program in FY2023, JISF conducted atechnical guidance by the Japanese experts

STEEL CONSTRUCTION TODAY & TOMORROW
Published jointly by

The Japan Iron and Steel Federation
3-2-10, Nihonbashi Kayabacho, Chuo-ku, Tokyo 103-0025, Japan
Phone: 81-3-3669-4815 Fax: 81-3-3667-0245
URL https://www.jisf.or.jp/en/index.html
Japanese Society of Steel Construction
3F Aminosan Kaikan Building, 3-15-8 Nihonbashi, Chuo-ku, Tokyo 103-0027, Japan
Phone: 81-3-3516-2151 Fax: 81-3-3516-2152
URL http://www.jssc.or.jp/english/index.html

19

to the ISIT Testing Laboratory which covered analysis of coating layer, appropriate
use of the testing equipment and management system in Bangkok in May 2024 together with a seminar on JIS steel standards
such as Plated Steel Sheets and Strip, Prepainted Sheet and Strip and Steel Tubes forgeneral/mechanical structure for TISI officials and ISIT member companies by theexperts of JISF’s Standardisation Centre.

© 2024 The Japan Iron and Steel Federation/Japanese Society of Steel Construction
Edited byCommittee on Overseas Market Promotion, The Japan Iron and Steel Federation
Chairman (Editor): Shunsuke Usami
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