Engineering Structures 128 (2016) 139–148

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Engineering Structures
journal homepage: www.elsevier.com/locate/engstruct

Full scale flexural test of jointed concrete members strengthened with
post-tension tendons with internal anchorage
Tatsuhiko Mimoto a,b, Isamu Yoshitake a,⇑, Takuya Sakaki a, Takafumi Mihara bab

Department of Civil and Environmental Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan
Kyokuto Kowa Corporation, Hikarimachi 2-6-31, Higashi-ku, Hiroshima, Hiroshima 732-0052, Japana r t i c l e

i n f oArticle history:
Received 22 July 2016
Revised 15 September 2016
Accepted 19 September 2016

Keywords:
Internal anchorage
Strengthening
Prestressing tendon
Flexural test
Water permeability
Jointa b s t r a c t
A new strengthening system, which embeds a post-tensioned PC bar tendon into the wedge-shaped
anchorage of an existing concrete member, was developed. Previously, the adequate load-bearing capacity of the prestressing tendon anchorage was confirmed on simple element specimens. In the present
study, the developed system is applied to the addition of new concrete members to old concrete structures. The strengthening effect of the system was examined in a loading test on jointed full-scale concrete
members. The saltwater permeability at the joint was also examined. The flexural properties of thejointed members were compared to those of concrete beams jointed with conventional post-installed
adhesive anchors. The concrete beams jointed by the proposed system exhibited superior crackresistance and load-carrying capacity, and their joints were strongly water-impermeable.
Ó 2016 Elsevier Ltd. All rights reserved.

1. Introduction
As is well known, concrete materials are vulnerable to tensile
forces and frequently crack under internal and external forces.
Therefore, concrete structures are usually reinforced by posttensioned prestressing systems. Owing to their effectiveness andreliability, prestressed concrete (PC) structures have become popularized around the world. In addition, technical papers andreports on post-tensioning techniques have been widely published.
In recent years, conventional prestressed tendons have been supplemented by advanced materials such as fiber reinforced polymers (FRPs) [3,11,27,24,15,16,4,28,14,22]. Flexural tests onprestressed concrete using various prestressing-materials are often
conducted for assessing the fundamental structural performance ofreinforced concrete structures.
Ng and Tan [18] developed a simple ‘‘pseudo-section analysis”
method for externally prestressed concrete beams subjected to
flexure. In addition, Ng and Tan [19] examined the flexural behavior of the prestressed beams and confirmed applicability of the
proposed analytical model. Park et al. [21] conducted flexural testsof post-tensioned girders using high-strength strands. The flexural
behaviors of their girders well agreed with the predictions of current design codes, although the concrete crack widths and stresses
in the reinforcements slightly exceeded the specified limits.
⇑ Corresponding author.
E-mail address: yositake@yamaguchi-u.ac.jp (I. Yoshitake).
http://dx.doi.org/10.1016/j.engstruct.2016.09.040
0141-0296/Ó 2016 Elsevier Ltd. All rights reserved.

Akiyama et al. [1] examined the flexural behaviors of cylindricalconcrete pile prestressed with unbonded bars. They found thatthe load capacity of prestressed concrete pile was greatly increased
by confining the pile between carbon fiber (CF) sheets. Kim et al.
[12] developed a post-tensioning method for near-surface
mounted (NSM) carbon fiber reinforced polymer (CFRP) strips,
and estimated the anchorage capacity in comparative finite element simulations. Vu et al. [25] proposed a structural model ofpost-tensioned prestressed beams with unbonded tendons. Their
model accurately predicted the deformations observed in experimental flexural tests. The structural responses of post-tensioned
concrete slab/wall structures have also been extensively reported[29,7,6,5,26,2,13,8].
The existing concrete members in civil infrastructures become
deteriorated by aging, and require regular strengthening and/or
upgrading. Prestressing tendons and cables are generally arranged
outside of the existing concrete members, demanding adequate
workspace for the strengthening work. Recently, the present
authors developed a new strengthening system using a conventional post-tensioning PC tendon [17]. The prestressing system
uses an internal anchorage within existing concrete members.
The tendon can be firmly anchored in a wedge-shaped hole filledwith high strength mortar. This post-tensioning system alsoenables the addition of new concrete members to existing
concrete structures. Whereas conventional RC jointed members
are vulnerable to steel corrosion at the joints of the new and old

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T. Mimoto et al. / Engineering Structures 128 (2016) 139–148

concrete, the developed prestressing system may increase thedurability of the jointed structure. To assess the applicability of
the new system, the present studies examine concrete members
joined by the developed post-tensioning method.
Previous investigations on jointed concrete members have evaluated the structural performance and durability of segmented element systems. Turmo et al. [20] predicted the structural behaviorof segmental concrete elements jointed by external pre-stressing
in numerical simulations. The applicability of their model was confirmed in comparisons between their predictions and experimental
observations. Pillai et al. [23] studied the service reliability of segmental PC bridges in corrosive environments. They proposed amethod that predicts the time-variant service reliability index,
accounting for damage to PC tendons and other uncertainties.
The present study examines the workability of the posttensioning system in full-size concrete members, and confirms
the improved structural performance and durability of structures
reinforced by the system. Full-scale reinforced concrete (RC) beams
were connected by the developed method, and subjected to flexural
tests. The results were compared against those of RC beam specimen jointed with conventional post-installed adhesive anchors.
To examine their water permeability and steel corrosion resistance,
jointed concrete beams were also exposed to saltwater for 5 weeks.
This paper reports the cracking resistance, load-bearing capacity
and saltwater permeability of the strengthened beams.
2. Strengthening method using post-tension tendons withinternal anchorages
The developed strengthening system requires conventional prestressing bars, high strength mortar and a wedge-shaped hole(Fig. 1) formed by a special drilling device (see Fig. 2(a)). The drilling process of the hole is described in Fig. 2(b). Fig. 3 schematizes
the strengthening process of the developed system. The prestressing tendon is firmly anchored in the internal wedge hole filled withhigh-strength mortar. Further details of the post-installed anchorage system are described in Mimoto et al. [17].
As shown in Fig. 3, the developed system can add new concrete
members to existing concrete structures. A typical application is
widening the slab width of concrete bridges (see Fig. 4). Concrete
joints formed by the post-installed prestressing method may bemuch more durable than conventional jointed RC structures.
3. Methodology
3.1. Materials and mixture proportion
Table 1 lists the materials used in the experimental investigation. The conventional reinforcing materials were those used in

Existing concrete
Ring nut
High strength mortar (Filler)

Prestressing tendon

Internal anchorage(Wedge-shaped hole)Fig. 1. Schematic of the internal anchorage system [17].

Segment for enlarging
Head

Shaft

(a) Special drilling device
Special drilling device
A

A
I. Insertion of the special drilling device

A-A cross section
Segment for enlarging

B

II. Enlargement of the holeC

B

B-B cross section

Wedge-shaped holeC

C-C cross section

III. Removal of the device after drilling(b) Drilling process
Fig. 2. Drilling of the wedge-shaped hole in concrete [17]: (a) Special drillingdevice; (b) Drilling process.

previous studies. The mixture proportions of the concrete and mortar are summarized in Table 2. The mixture of concrete (A) complies with that of general RC structures in Japan. The water-tocement ratio was reduced in concrete (B) (relative to concrete(A)) to improve its strength and durability. The specified compressive strengths of concrete mixtures (A) and (B) are 24 MPa and
30 MPa, respectively. To ensure sufficient strength and the appropriate fresh properties, the wedge-shaped anchorage was filledwith commercial mortar (premix type). According to the manufacture sheet, the minimum compressive strength of mortar is
100 MPa at the age of 28 days. Detailed information about the filling material cannot be described here because of a commercial
contract with the manufacturer.
This study reports the mechanical properties (compressive
strength, Young’s modulus and Poisson’s ratio) of the concretes
and mortar. Consistent with the Japanese standard and theauthors’ previous study [17], each test was conducted on threecylindrical concrete specimens (100 mm diameter  200 mm
height) and three cylindrical mortar specimens (50 mm diameter  100 mm height). The mechanical properties of the concretes
and the high-strength mortar are summarized in Table 3.

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T. Mimoto et al. / Engineering Structures 128 (2016) 139–148[Step 1] Concrete core drilling for internal anchorage (wedge-shaped hole)
Wedge-shaped hole

Table 1
Materials used in the experimental study.

Existing concrete[Step 2] Install of a prestressing tendon
Fill high strength mortar into the wedge-shaped holePrestressing tendon

Concrete materials

Type

Density

Water (W)
Cement (C)Fine aggregate (S)Coarse aggregate (G)Admixture (AD)Ordinary Portland cement
Crashed sand
Crashed stone
Superplasticizer

1.00 g/cm3
3.16 g/cm3
2.64 g/cm3
2.68 g/cm3
1.04 g/cm3

Materials

Properties

Reinforcing bar

JIS G-3112; Nominal diameter: 13 mm (D13)
Yield strength: 345 MPa; Young’s modulus:
206 GPaJIS G-3112; Nominal diameter: 16 mm (D16)
Yield strength: 345 MPa; Young’s modulus:
206 GPaJIS G-3109; Nominal diameter: 23 mm; Type
B-1
Tensile strength: 1080 MPa; Young’s
modulus: 202 GPa
JIS G-3101; 38 mm diameter  30 mm
heightYield strength: 235 MPa; Young’s modulus:
206 GPaJIS G-3101; Dimensions:
120  120  25 mm
Yield strength: 235 MPa; Young’s modulus:
206 GPa
High-strength mortar (see Tables 2 and 3)
Compressive strength: 104.2 MPa; Tensile
strength: 20.7 MPa

FillerPost-installed bar[Step 3] Placing of new concrete (option)
Provide tensile force (pull) to the prestressing tendon
Coupler

Prestressing tendon

TensionNew concrete[Step 4] Grouting

Ring nut

Grout
Bearing plate with a hole

Filling material
Epoxy resin

Fig. 3. Strengthening system process using a prestressing tendon fixed in theinternal anchorage [17].

Table 2
Mixture proportions of the concrete specimens.

Wheel guard
WideningaPost-installed anchor

w/
cma

W

C

Conc. A

0.53

Conc. B

0.50

b

0.12

175 kg/m3
169 kg/m3
1.2 kg/mix

330 kg/
887 kg/m3
m3
338 kg/874 kg/m3
m3
10 kg/mix

Mortar

New Concrete
Existing RC slab

Type

b

S

G

AD

Air

978 kg/m31000 kg/
m3
N/A

1.16 kg/m3
2.37 kg/
m3
N/A

4.5%
4.5%
N/A

Water–cementitious material ratio.
Premix mortar (filler).

Fig. 4. Typical application of the proposed system (increasing the slab width of aconcrete bridge).
Table 3
Properties of the materials used in the study.
Concrete A

Concrete B

MortarSpecified strength (MPa)
Production date24
July-3, 2015

Conc. slump/mortar flow (cm)Compressive strength (MPa)Young’s modulus (GPa)Poisson’s ratio

12.0
39.9
27.2
0.17

30
Aug.-10,
2015
12.0
49.1
34.8
0.18

120
July-13,
2015
12.8a
140.1
45.0
0.22

3.2. Test specimens
The applicability of the developed post-tensioning system was
examined on full-scale jointed concrete members. Fig. 5(a)–(d)shows schematics of the jointed beam specimens and the arrangement of the reinforcing bars. Each beam was 400 mm high,
800 mm deep and 3000 mm long. Specimen PC-0 is a control beam
embedding tendons that are not post-tensioned. Specimen PC-1 isa jointed beam strengthened by the developed post-tensioning
system. Both specimens were embedded with two prestressing
tendons (each of 23 mm diameter). Two wedge-shaped holes were
drilled in 10-day-old concrete (A) by a special device (Fig. 2a). Following Mimoto et al. [17], the diameter and length of the wedgeshaped hole was 66–42 mm and 100 mm, respectively. The waterrequired for drilling was removed by a vacuum (340 W), and thehole size was confirmed by microscopy and a special measurement
tool. The drilled hole was filled with high-strength mortar andinserted with the tip of the tendon. At age 38 days, the concrete(A) member embedding the tendon was conjoined with cast-inplace concrete (B). Fig. 6(a) presents the jointed concrete substratea

Cylinder test (50 mm dia.  100 mm height).

roughened by chipping with an impact hammer. After anchoringfor 3 days, the tendon installed in specimen PC-1 was subjected
to a tensile force of 320.8 kN. The axial force applied to each tendon(allowable load for design) was approximately 70% of the loadbearing capacity (448.7 kN) of the prestressing bar, as specified
in Japanese industrial standards [10,17].
Specimen RC is a conventional jointed structure using postinstalled adhesive anchors. In this specimen, eight reinforcing bars
(each of 16 mm nominal diameter) were installed and bonded withepoxy resin (Table 1). Cast-in-place concrete (B) was added to the142

T. Mimoto et al. / Engineering Structures 128 (2016) 139–148<Side-view>

3000
1550

1450

Concrete A

Concrete B

Internal anchorage system

ConventionalanchorPrestressing tendon
23mm dia. Type B-1

400

200 200<Cross sectional view at joint >800
200 400 200
Prestressing tendon
23mm dia.

Unit: mm(a) Schematics of PC-0 and PC-1
Prestressing tendon
23mm dia. Type B-1

4213mm dia. (5 bars)

13mm dia. (5 bars)
Steel-plate
25mm thick

66

100

Screwedbar-end
Internal anchorage
66-42 dia.

13mm dia.
(5 bars)

13mm dia. (5 bars)

2500

13mm dia. (22 bars)

300

200 Unit: mm(b) Rebars arrangement of PC-0 and PC-1
<Side-view>
1550
Concrete A

1450
Concrete B

Post-installed anchor 16mm dia.

400

100 200 100<Cross sectional view at joint >800
152 3x165 153
Post-installed anchor=495
16mm dia.

Unit: mm(c) Schematic of RC
13mm dia. (5 bars)

13mm dia.
(5 bars)240

13mm dia.
(22 bars)

500

13mm dia. (5 bars)

13mm dia. (5 bars)
Post-installed anchor 16mm dia.

(d) Rebars arrangement of RC
Fig. 5. Test specimens: (a) Schematics of PC-0 and PC-1; (b) Rebars arrangement of PC-0 and PC-1; (c) Schematic of RC; (d) Rebars arrangement of RC.

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T. Mimoto et al. / Engineering Structures 128 (2016) 139–148

Load cell

PC tendons

LVDT

Concrete B
Joint
SupportConcrete A(a) PC-0 and PC-1

RebarsData acquisition

LVDT

Fig. 8. Flexural test of full-scale jointed concrete beams.

3.3. Test procedure(b) RC
Fig. 6. Cross-sections of the concrete specimens at their joints: (a) PC-0 and PC-1;(b) RC.

Fig. 7 presents the test procedure of the experimental investigation. To ensure joint opening, the flexural test was first conducted
on 28-day-old concrete (B). Hereafter, openings are referred to as
joint-cracks for convenience. The load on specimen RC was
increased until the crack width at the joint reached 0.2 mm, as
specified in a Japanese guideline [9]. The observed maximum loadin the first phase was then applied to specimens PC-0 and PC-1. In
the second phase, the cracked beams were reversed and the concrete joints were exposed to saltwater (3%) for 35 days. In the third
phase, the concrete joints were removed from the saltwater, andtheir load-carrying capacity was again determined in a flexural
test. Finally, in the fourth phase, the chloride penetration depth
was examined in concrete cores obtained from the joints of eachspecimen. The flexural and the salt-water permeability tests aredescribed below.
3.3.1. Flexural test
Fig. 8 presents the flexural test conducted on the full-scale
jointed concrete beams. The jointed beams were monotonicallyloaded in a four-point bending apparatus, and subjected to a flexural load applied by a hydraulic jack system. The beam span andloading span lengths were 2500 mm and 500 mm, respectively.
Fig. 9 illustrates the arrangement of the strain gages and related
sensors. The concrete surfaces and reinforcing bars of the three
specimens were affixed with wire strain gages of lengths 60 mm
and 3 mm, respectively. The internal stress was observed byembedded-strain-gages (EmSGs) set into concrete (B), and theforce on the prestressing bars of PC-1 was monitored by centerhole load cells. The deflection was monitored by linear variable displacement transducers (LVDTs) placed on the top and bottom surfaces of the beams. In addition, the joint crack width was observedby PI-shaped displacement transducers (PiDTs) placed on the bottoms of the joints. Table 4 lists the capacities and accuracies of thesensors used in the flexural test.

Fig. 7. Schematic of the test procedure.

concrete (A) of this specimen (see Fig. 6(b)) at the same time as
specimens PC-0 and PC-1.
It should be noted that the reinforcement arrangements forthese specimens were designed to achieve almost equal yielding
load. The designed yielding loads are 188 kN for PC-1 and 186 kN
for RC, respectively.

3.3.2. Saltwater permeability test
Fig. 10 outlines the saltwater permeability test. The concrete
joints of the concrete beams tested in the first phase were subjected to 3% salt water for 35 days (5 weeks). After the third phase,
cylindrical specimens (diameter = 100 mm) were extracted fromthe concrete joints by a dry coring method. To check the improved
durability of concrete strengthened with the post-tensioning system, the chloride penetration depths in the core specimens were
examined by a silver nitrate spraying method.

144

T. Mimoto et al. / Engineering Structures 128 (2016) 139–148<Side-view>

3000
1550

1450

1000
LVDT

500
Load cell

Load P/2

1000

Load P/2
Concrete strain gage

Load cell

66

Concrete strain gage
Steel strain gage

EmSG
LVDT

PiDT
300

250 250
2500

200<Top-view>

Unit: mm

1 2 3 4 5 67Concrete strain gage

C.L.

Concrete A

Concrete B

120 5x100=500(a) PC-0 and PC-1
<Side-view>

3000
1550

1450

1000

500

1000
Load cell

LDVT

Load P/2

Load P/2

Steel strain gage

EmSG
LVDT

PiDT
300

250 250
25 0 0<Top-view>200
Unit: mmConcrete strain gage
C.L.
Concrete A

Concrete B(b) RC
Fig. 9. Arrangement of strain gages, EmST, LVDTs and PiDTs: (a) PC-0 and PC-1; (b) RC.

4. Results and discussion
Table 4
Sensors used in the experimental tests.

4.1. Crack resistance at the joint

Gages
For concrete
For rebars
EmST

Gage length
60 mm
3 mm
60 mm

Resistance
120 X
120 X
120 X

Minimum measurement
1.0  10 6
1.0  10 6
1.0  10 6

Sensors
LVDT
PiDT

Capacity
0–100 mm
2 mm – +2 mm

Rated output
2.5 mV/V
2.0 mV/V

Minimum measurement
0.1 mm0.001 mm

Load cells

Capacity
0–500 kN

Rated output
1.5 mV/V

Minimum measurement
0.1 kNThe RC specimen developed its first joint crack under a load of
68.5 kN. After the cracking, the applied load was increased until
the crack width reached 0.2 mm (at approximately 73 kN). The
same load (73 kN) was then applied to specimens PC-0 and PC-1.
After measuring the crack widths by the PiDTs, the 73 kN load
was immediately removed. Residual cracks were also observed.
The maximum loads and crack widths are summarized in Table 5,
and the crack widths and upper surface strains on the concrete areT. Mimoto et al. / Engineering Structures 128 (2016) 139–148

145

Saltwater (3%)(b) Test condition (35 days)(a) Concrete joint subjected to saltwater<Top-view>

300 200 300

Unit: mmConcrete A

80
Test piece
Joint
Concrete B(c) Dimensions of the test specimens(e) Core specimens(d) Dry coring

Fig. 10. Saltwater permeability test: (a) Concrete joint subjected to saltwater; (b) Test condition (35 days); (c) Dimensions of the test specimens; (d) Dry coring; (e) Core
specimens.

Table 5
Load and cracks observed in the first phase of the experimental procedure.
RC
Load (kN)Max. crack width (mm)Residual crack width (mm)
a

a

72.7
0.216
0.085

PC-0

PC-1

a

73.4a
0.008
0.001

73.0
0.013
0.003

Load at the crack width of approximately 0.2 mm in the specimen RC.

presented in panels (a) and (b) of Fig. 11, respectively. The initialstrain of specimen PC-1 is the prestress strain measured by the
EmSG (Fig. 11(b)). The maximum and residual crack widths andstrains were significantly smaller in specimen PC-1 than in specimen RC. Interestingly, specimen PC-0 (like the prestressed specimen PC-1) responded almost linearly to the load.
4.2. Load bearing capacity and deformation
The load–midspan deflection responses and the maximum loadand deflections are presented in Fig. 12(a) and Table 6, respec-tively. During this flexural test, the load was increased until thedeflection reached 5 mm. This deflection limit ensures the safetyof the loading test on the prestressed concrete member (PC-1).
Thereafter, the load was gradually removed to monitor the residual
properties.
In the RC specimen, the sudden load decrease at approximately
200 kN is attributed to the yielding of the reinforcements. Specimen PC-0 embedding tendons which are not post-tensioned broke
under a 78.6 kN load. At this time, the crack width at the joint waslarger than 2 mm, and quite visible. The load–deflection responseof PC-1 was linear in the range 0–170 kN, but nonlinear outsideof this range.
Fig. 12(b) plots the strains on the upper surfaces of the concretes. The residual compressive strain on the PC-0 surface
exceeded 500 micro-strain, but was negligible on the RC and PC1 surfaces. Notably, the load–strain response of PC-1 was nonlinear, consistent with the load–deflection response.
Fig. 12(c) presents the force variation in the prestressing tendons, measured by the load cells. The prestressing tendon forces
scarcely changed in the range 0–170 kN, but gradually increased
at higher loads. The increased prestressing force may result from

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T. Mimoto et al. / Engineering Structures 128 (2016) 139–148

250
200

60

Load (kN)

Load (kN)

80

40

RC
PC-0
PC-1

20

0
0.00

150

RC
100

PC-0
PC-1

50
0

0.05

0.10

0.15

0.20

0.25

0

Crack width (mm)

1

2

3

4

5

6

Deflection (mm)(a) Load–deflection responses(a) Load versus crack width
300

80

Load (kN)

Load (kN)

250

60

40

RC
PC-0
PC-1

20

200
150

RC

100

PC-0
PC-1

50
0

0
0

-50

-100

-150

0

-200

-500

Fig. 11. First-phase test results: Load responses of (a) Load versus crack width; (b)Load–strain responses.

300

To compare the saltwater permeability at the joints of the concrete specimens, the chloride penetration depths in core extracts
were examined by the silver nitrate spraying method. Fig. 13 presents the test results. The average penetration depths of PC-0 andPC-1 were 12.9 mm and 4.2 mm respectively, versus 185.3 mm in
the RC specimen. In other words, the penetration depths of PC-0
and PC-1 were 7.0% and 2.3% that of RC, respectively. This observation confirms that the jointed concrete members embedding thetendons are highly impermeable to saltwater. The developed
strengthening system with its internal anchorage improves the
durability of joints between the existing and new concretes, which
are generally vulnerable to steel corrosion.

5. Conclusions
This study examined the workability of the developed posttensioning system in full-size concrete members, and confirmed
its improvements to the structural performance and durability of

Load (kN)250

4.3. Saltwater permeability at the joint-1500(b) Load–strain responses(b) Load–strain responses

the significantly widened cracks in the joints as the load increases.
Note that the increase in the prestressing force (336.0 kN) associated with crack-opening was approximately 13% lower than theyielding force of the tendons (386.4 kN), and is also considerably
lower than the pull-out load bearing capacity of 490 kN [17]. This
reconfirms that the prestressing tendon is firmly anchored, evenunder flexural deformation.

-1000

Strain (10 -6)

Concrete strain (10 -6)

336.0

Average200

0.90 Py Yielding force: Py(347.8 kN)(386.4 kN)

150
100
50
0
300 310.8

325

350

375

400

Force of PC tendon (kN)(c) Forces in the prestressing tendons of PC-1
Fig. 12. Third-phase test results: (a) Load–deflection responses; (b) Load–strain
responses; (c) Forces in the prestressing tendons of PC-1.

those members in a series of tests. The conclusions of the investigation are summarized below:
 The developed strengthening system significantly reduced thecrack widths at the joints between old and new concretes,
and improved the load-bearing capacity of the jointed concretebeams.
Table 6
Load bearing capacities and deflections observed in the third phase.

Max. deflection Dmax (mm)Load at Dmax (kN)
Load bearing capacity (kN)

RC

PC-0

PC-1

5.10
187.8
203.8

5.16
44.4
78.6

5.06
241.0
241.0

T. Mimoto et al. / Engineering Structures 128 (2016) 139–148

149.0 mm221.5 mm147

the structural performance are highly desired, and the effects ofthe environmental conditions must also be determined.
Acknowledgments
The authors thank to Dr. Era (Kyokuto Kowa, Co.), Dr. Kawakane(Kyokuto Kowa, Co.), and a graduate student Mr. Mizushima (Yamaguchi University) for their assistance.
References(a) RC

15.5 mm10.3 mm(b) PC-0

8.3 mm

0.0 mm(c) PC-1
Fig. 13. Fourth-phase test results, showing the saltwater permeabilities in thesample cores (a) RC; (b) PC-0; (c) PC-1.

 The force increase in the joints under high load was sufficiently
lower than the pull-out capacity in the previous investigation,
confirming that the prestressing tendons were firmly anchoredeven under flexural deformation.
 The jointed concrete member strengthened by the internal prestressing system was significantly less permeable to saltwater
than the conventional adhesive anchor system.
This study focused on the applicability and performances ofjointed concrete members strengthened by the developed system.
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