The 2019 World Congress on
Advances in Structural Engineering and Mechanics (ASEM19)
Jeju Island, Korea, September 17 - 21, 2019

Shear behavior of DFRCC coupling beams using PVA and steel fiber*Toshiyuki Kanakubo1), Yuriko Ozu2) and Keisuke Namiki3)
1)2)

Dept. of Eng. Mechanics and Energy, Univ. of Tsukuba, Ibaraki, 305-8573, Japan
Technical Research Inst., Sumitomo Mitsui Const. Co., Ltd., Chiba, 270-0132, Japan
3)
GSSIE, Univ. of Tsukuba, Ibaraki, 305-8573, Japan
1)
kanakubo@kz.tsukuba.ac.jp

ABSTRACT
Ductile fiber-reinforced cementitious composite (DFRCC) is expected to provide
sufficient shear performance of coupling beams in high-rise buildings under severe
seismic loads and decrease the deterioration of energy absorption performance. This
study focuses on shear behavior of coupling beams through anti-symmetrical loading
test of beam specimens using PVA and steel fiber-reinforced cementitious composite.
The test parameters are fiber types and the volume fraction of fiber. The shear capacity
is evaluated by using tensile strength of DFRCC obtained by four-point bending test of
test pieces. The shear capacities of DFRCC beams with higher volume fraction can beevaluated by adding the effect of fiber-carrying capacity to calculated shear capacity inthe case of no-fiber.

1. INTRODUCTION
Ductile Fiber-Reinforced Cementitious Composite (DFRCC), which shows adeflection hardening branch and multiple cracking under bending stress, have been
focused by lots of researchers because of its unique mechanical performance. In otherhand, Engineered Cementitious Composite (ECC), which has been introduced by Li (Li1993), exhibit a maximum tensile strain of several percent owing to the synergetic
effect of high-performance fiber under pure tension. Unprecedented high-performance
structural members by ECC have already been applied to seismic components such as
coupling beams (Kanda et al. 2006).
The authors have studied the structural performance of beam-column joints inhigh-rise RC buildings using DFRCC in the panel zone (Sano et al. 2015, Yamada et al.
2016). These studies have reported that beam-column joints using DFRCC shows lessdamages and small crack opening compared with conventional concrete members.
1)

Professor
Research Engineer
3)
Graduate Student2)

The 2019 World Congress on
Advances in Structural Engineering and Mechanics (ASEM19)
Jeju Island, Korea, September 17 - 21, 2019

DFRCC can also make it possible to improve durability and sustainable use ofstructures. However, it is difficult to evaluate tensile characteristic of DFRCC andstructural performance of seismic components.
In the case of ECC, it is not so difficult to evaluate its tensile characteristic
because of strain hardening behavior. Tensile stress increases after first cracking, andtensile stress carrying capacity does not start failing until cracks saturating. For
example, bi-linear model with hardening branch or perfectly elastic-plastic model canbe applied to express the tensile stress-tensile strain relationship for ECC (Rokugo andKanda 2012). In fact, the authors have proposed the evaluation method of tensile
strength of ECC by four-point bending test results as the material test of ECC(Kanakubo et al. 2007). In the case of DFRCC, however, its tensile stress generally
starts decreasing after peak load in pure tension stress field. So, it is difficult to confirm
the carrying tensile stress by DFRCC on its softening branch in seismic components.
The objective of this study is to confirm the structural performance of coupling
beams as seismic components using DFRCC by various types of fibers and fiber
volume fraction. The same methodology with tensile strength evaluation of ECC iscarried out, i.e., four-point bending test as the material test of DFRCC is conducted.
The specimens modeling coupling beams used in high-rise RC buildings are loaded byanti-symmetrical bending moment manner to simulate stress field in earthquake force.

2. OUTLINE OF LOADING TEST FOR BEAM SPECIMENS
2.1 Specimen
Fig. 1 shows the dimensions of beam specimen and Table 1 shows thespecimens list. The total length of the specimen is 1,960mm. The central portion of660mm length is the test region which is subjected to the anti-symmetrical bending
moment. The depth (D) and width (b) of cross-section is 220mm and 160mm,respectively. Three steel deformed rebars D16 (SD490) were arranged as tension
longitudinal reinforcements. Steel deformed rebars D4 (SD295) was arranged as
stirrups at 120mm interval in the test region. Total of five specimens were tested.
The test parameters are types of fiber for DFRCC and volume fraction of fiber.
PVA fiber with 0.10mm diameter and steel fiber with 0.16mm diameter were used. Fiber
450

860
2-D6@100

2-D4@120 3-D16 l=2000

450

100

2-D6@10045 35
35 45

35

150 35

Castingdirection
打設方向20650(Test region)
660 (試験区間)

160
650

1960

Fig. 1 Specimen dimensions

20220100

The 2019 World Congress on
Advances in Structural Engineering and Mechanics (ASEM19)
Jeju Island, Korea, September 17 - 21, 2019

volume fraction was set to 1.0% and 2.0% for PVA fiber, 0.5% and 1.0% for steel fiber.
Table 2 shows the dimensions and mechanical properties of fibers. To investigate theeffect of fibers, mortar without fiber was used for specimen No.1. Table 3 lists themechanical properties of steel rebars.
Table 1 Specimen list
ID

Common factor

Fiber type

No.1
No.2
No.3
No.4
No.5

Cross-section: 160x220mm
Shear span: 330mm (M/QD=1.5)
Tension bar: 3-D16 (SD490)
Stirrup: 2-D4@120 (SD295)

―PVA
PVA
Steel
Steel

Fiber
volume fraction
―1.0%
2.0%
0.5%
1.0%

Table 2 Mechanical properties of fiber
FibertypeDiameter(mm)Length(mm)Tensilestrength(MPa)Elasticmodulus(GPa)

PVA

0.10

121200

28

Steel

0.16

132825210

Appearance

Table 3 Mechanical properties of steel rebar
Tensilestrength(MPa)
D16 (SD490) 714
D4 (SD295) 548
Type

Yield
strength(MPa)513
391

Elasticmodulus
(GPa)
196
180

Remarks
Longitudinal bar
Stirrup

2.2 Loading and measurement
The monotonic loading following anti-symmetric bending moment manner(Ohno-type shear test method) was carried out. The bending moment diagram is shownin Fig. 2. Applied shear force (Q) can be obtained by 0.344 times applied force (P).
To avoid shear failure outside the test region, both ends of beam specimen
were jacketed by steel plates with 22mm thickness as shown in Fig. 3. Steel round bars
were subjected through the steel plates at both loading points and supports.

The 2019 World Congress on
Advances in Structural Engineering and Mechanics (ASEM19)
Jeju Island, Korea, September 17 - 21, 2019Fig. 2 Bending moment diagram

430880100450860
1960

450100Fig. 3 Steel plate jackets for beam specimen
Two LVDTs were set to measure loading point displacements via holding jig
fixing at the supporting points of the beam specimen as shown in Fig. 4. Assuming therotation of rigid bodies of the specimen ends jacketed by the steel plates, translational
angle (R) is obtained from relative displacement at the center of the specimen (δ)
divided by clear span length.
The strains of stirrups and longitudinal bars at the both ends of clear span weremeasured by strain gauges.

Fig. 4 Steel plate jackets for beam specimen

The 2019 World Congress on
Advances in Structural Engineering and Mechanics (ASEM19)
Jeju Island, Korea, September 17 - 21, 2019

3. TENSILE CHARACTERISTICS OF DFRCC BY FOUR-POINT BENDING TEST
3.1 Specimen and loading method
Table 4 shows the mixture proportion of DFRCC and compression test resultsby φ100mm x 200mm cylinder test pieces at the age of loading of beam specimens.
Used cement was high-early-strength Portland cement, fly ash was Type II of JapaneseIndustrial Standard (JIS A 6202), and sand was size under 0.2 mm. The high-range
water-reducing admixture and thickening agent were added.
The specimen dimensions for four-point bending test are 100mm x 100mm incross-section, and 400mm in length, these follows JCI-S-003-2007 “Method of test forbending moment–curvature curve of fiber-reinforced cementitious composites” (JCI2007). Axial deformations at upper and lower side in constant moment region weremeasured by pi-type LVDTs as shown in Fig. 5. Three specimens were tested for onetype of DFRCC.
Table 4 Mixture proportion of DFRCC
Unit weight (kg/m3)
TypeWater

PVA 1.0%
PVA 2.0%
380
Steel 0.5%
Steel 1.0%

Cement Sand

678484

Fly ashFiber291

1326
3978

Comp.
strength(MPa)
45.3
43.1
44.5
42.2

Elasticmodulus(GPa)
16.8
15.7
16.6
17.2

Fig. 5 Four-point bending test for DFRCC
3.2 Test results
Table 5 lists test results of four-point bending test of DFRCC. Some ofspecimens finally failed by the opening of crack which took place outside of LVDT.
Curvature at maximum load could not be obtained in these specimens. All specimens
showed deflection hardening behavior as that the load increased after first cracking.
Tensile strength and ultimate strain are calculated following Appendix of JCI-S003-2007 “Evaluation method for tensile strength and ultimate tensile strain of fiber-

The 2019 World Congress on
Advances in Structural Engineering and Mechanics (ASEM19)
Jeju Island, Korea, September 17 - 21, 2019

reinforced cementitious composites” (JCI 2007). In this evaluation method, tensile
strength can be calculated under the assumption that the tensile stress distributes as aconstant manner in tension zone of the section. Though this assumption is mostly
accepted in the case of ECC, it is considered that the actual stress distribution in thecase without strain hardening DFRCC is different from the assumed distribution.
The curvature at maximum load could not be measured by LVDT for specimensof steel 1.0%, these values are assumed to have same one with the average ofspecimens of steel 0.5%. As the calculation results, averages of tensile strength of thespecimen of PVA 1.0% and PVA 2.0% are 1.25MPa and 1.90MPa, respectively. Thoseof steel 0.5% and steel 1.0% are 2.08MPa and 1.76MPa.
Table 5 Test results of four-point bending test of DFRCC

TypeAt maximum load

Calculation resultBending
moment(kN･m)

Tensilestrength(MPa)Curvature(1/m)

Ultimatestrain(%)

Average oftensile
strength(MPa)

0.562
0.172
1.18
1.58
PVA 1.0% 0.528
0.093
1.16
0.82
1.25
0.424
0.004
1.41
0.02
0.869
0.162
1.88
1.44
PVA 2.0% 0.866
0.088
1.93
0.74
1.90
10.737
―*――
0.945
0.056
2.21
0.45
Steel 0.5% 0.872
0.067
1.95
0.56
2.080.686―*1――0.891―*11.76
Steel 1.0% 0.923―*11.83(0.61)*2
1.76
10.839―*
1.69*1: Specimen failed by crack out of LVDTs.
*2: Curvature at maximum load is assumed to be same with steel 0.5% specimen.

4. TEST RESULTS OF BEAM SPECIMENS AND DISCUSSIONS
4.1 Failure progress
Beam specimens after loading are shown in Fig. 6. Cracks are traced by a pen
after loading. At first, small bending cracks took place at the ends of clear span intension zone. After that, diagonal shear cracks were observed in the central part of thespecimens. In specimen No.1, the shear crack widely opened at the same time ofyielding of stirrups, and cover mortar fell from the specimen. In other specimens, small
shear cracks took place in sequence, and maximum load was observed at the sametime of localizing of crack opening. Falling of covers were not observed in specimens

The 2019 World Congress on
Advances in Structural Engineering and Mechanics (ASEM19)
Jeju Island, Korea, September 17 - 21, 2019from No.2 to No.5. In all specimens, yielding of stirrups was observed at the maximumload.

No.1 (w/o fiber)

No.3 (PVA 2.0%)

No.2 (PVA 1.0%)

No.4 (Steel 0.5%)
No.5 (Steel 1.0%)
Fig. 6 Specimens after loading
4.2 Shear force-translational angle curve
Fig. 7 shows shear force (Q)-translational angle (R) curves of all specimens.
Except for specimen No.2 (PVA 1.0%), the maximum shear force of the specimens withfibers are larger than that of specimen No.1 (w/o fiber). It is considered that shear force
is carried also by fiber bridging.
No.1(w/o fiber)
No.2(PVA 1.0%)
No.3(PVA 2.0%)
No.4(Steel 0.5%)
No.5(Steel 1.0%)
Max. load

Shear force (kN)1201008060
40
2000123456-2
Translational angle (x10 rad.)Fig. 7 Shear force-translational angle curve

7

The 2019 World Congress on
Advances in Structural Engineering and Mechanics (ASEM19)
Jeju Island, Korea, September 17 - 21, 2019

Comparing the curves of specimens No.1 and No.2, though the maximum shear
force is almost same, shear force until maximum load in specimen No.2 is larger thanspecimen No.1. It is assumed that the effect of fiber bridging in specimen No.2
vanished before reaching maximum load. Comparing the curves of specimens No.4(Steel 0.5%) and No.5 (Steel 1.0%), the curves show almost similar tendency until
R=0.6 x10-2 rad. After that, an increment of shear force in specimen No.4 becomes
smaller than specimen No.5. It is also assumed that the effect of fiber bridging inspecimen No.4 starts decreasing before reaching maximum load. The reducing ofshear force after maximum load are larger in PVA specimens (No.2 and No.3).
4.3 Shear capacity of beam specimens
In the case of ECC, the evaluation method of shear capacity of beam has been
propose by Eq.(1) (Kanakubo et al. 2007). This formula consists of shear capacity bytruss and arch mechanism, and fiber bridging. The former two items are same as thecase of the conventional RC beams. Shear capacity by fiber bridging is simply added toconsider the contribution of tensile stress of DFRCC. In this study, the same evaluation
method is adopted for evaluation of shear capacity of DFRCC beams.
Vsu  Vt  Va  V f(1)

Vt  b  jt  pw   wy  cot (2)Va  tan   1       B  b  D 2(3)

 L D  1 L D(4)

t a n 2  1  c o2t  pw w y   B(5)  1.70 B(6)

0.333j
c ot  m in 2 . 0 , t
D  t a nV f  b  jt  t   t  cot where,Vsu: shear capacity

VtVaVf  B, pw   w y 1: shear capacity by truss mechanism: shear capacity by arch mechanism: shear capacity by fiber bridging: width of member: distance between compression and tension barsbjtpw
 wy: stirrup ratio: yield strength of stirrup

B: compressive strength of DFRCC: angle of compressive strut

(7)
(8)

The 2019 World Congress on
Advances in Structural Engineering and Mechanics (ASEM19)
Jeju Island, Korea, September 17 - 21, 2019DLtt: angle of arch mechanism: effective coefficient of compressive strength of DFRCC: depth of member: clear span length: reduction factor for tensile strength of DFRCC: tensile strength of DFRCC

Table 6 lists the test results of shear capacity and calculation results by Eq.(1).
The tensile strength of DFRCC listed in Table 5 is utilized for the calculation. Fig. 8shows the comparison between the test results of shear capacity and calculation
results. Both shear capacity is standardized by calculated flexural capacity of beamspecimen considering fiber bridging in tension zone as indicated by Eq.(9) (Shimizu etal. 2007).

b  D2 V fu  0.9  at   y  d  t  /  L / 22where,: flexural capacity
V fuatyd(9): cross-sectional area of tension bars
: yield strength of tension bars
: effective depth of member

As seen in Table 6 and Fig. 8, the calculated shear capacity overestimates thetest results in the case of lower volume fraction of fiber, both in PVA and Steel. For thespecimens with higher volume fraction, the ratio of test results to calculations is 0.95
and 0.98. It is considered that the shear capacities of DFRCC beams with higher
volume fraction can be evaluated by adding the effect of fiber-carrying capacity tocalculated shear capacity in the case of no-fiber. It is assumed that the effect of fiber
bridging in specimens with lower volume fraction starts decreasing before reaching theshear capacity of beam.

Table 6 Shear capacity of beam specimen
Specimen
No.1 (w/o fiber)
No.2 (PVA 1.0%)
No.3 (PVA 2.0%)
No.4 (Steel 0.5%)
No.5 (Steel 1.0%)

Test result(kN)
76.1
75.1
110.987.7
110.8

Calculation(kN)
83.1
105.9
116.8
121.6
113.1

Test / Calc.
0.92
0.71
0.95
0.72
0.98

Maximum shear force Qmax /Vfu

The 2019 World Congress on
Advances in Structural Engineering and Mechanics (ASEM19)
Jeju Island, Korea, September 17 - 21, 2019
10.8

No.1(w/o fiber)
No.2(PVA 1.0%)
No.3(PVA 2.0%)
No.4(Steel 0.5%)
No.5(Steel 1.0%)

0.6
0.4
0.2

00.2

0.4

0.6

0.8

1

Calculated shear capacity Vsu /Vfu

Fig. 8 Comparison of shear capacity

5. CONCLUSIONSIn this study, to evaluate shear behavior of seismic components using DFRCC
with PVA and steel fibers, five beam specimens were subjected to anti-symmetricalbending moment loading. The tensile strength of DFRCC is evaluated by the four-point
bending test results. The shear capacities of DFRCC beams with higher volume
fraction can be evaluated by adding the effect of fiber-carrying capacity to calculated
shear capacity in the case of no-fiber. It is assumed that the effect of fiber bridging in
the case of lower volume fraction starts decreasing before reaching the shear capacityof beam.

6. REFERENCES
JCI (Japan Concrete Institute). (2007), “Method of test for bending moment–curvature
curve of fiber-reinforced cementitious composites”, JCI-S-003-2007, http://jcinet.or.jp/j/jci/study/jci_standard/JCI-S-003-2007-e.pdf.
Kanakubo, T., Shimizu, K., Kanda, T., Nagai, S. (2007), “Evaluation of Bending andShear Capacities of HPFRCC Members toward the Structural Application”,
Proceedings of the Hokkaido University COE Workshop on High Performance Fiber
Reinforced Composites for Sustainable Infrastructure System, pp.35-44.
Kanda, T., Tomoe, S., Nagai, S., Maruta, M., Kanakubo, T., Shimizu, K. (2006), “FullScale Processing Investigation for ECC Pre-cast Structural Element”, Journal ofAsian Architecture and Building Engineering, Vol.5, No.2, pp.333-340.
Li, V.C. (1993), “From Micromechanics to Structural Engineering -the Design of
Cementitious Composites for Civil Engineering Applications”, JSCE J. of Struc.
mechanics and Earthquake Engineering, 10(2), pp.37-48.
Rokugo, K., Kanda, T., ed. (2012), “Strain Hardening Cement Composites: Structural
Design and Performance”, State-of-the-Art Report of the RILEM TechnicalCommittee 208-HFC, RILEM State-of-the-Art Reports 6

The 2019 World Congress on
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Sano, N., Yamada, H., Miyaguchi, M., Yasojima, A., Kanakubo, T. (2015), “StructuralPerformance of Beam-Column Joint using DFRCC”, 11th Canadian Conference on
Earthquake Engineering -Facing Seismic Risk-, Paper ID 94163
Shimizu, K., Kudo, S., Kanakubo, T. (2007), “Scale Effect in Flexural and Shear
Behavior on Ductile Reinforced Cementitious Composites”, Proceedings of the Japan
Concrete Institute, Vol. 29, No.3, 1429-1434. (in Japanese)
Yamada, H., Ando, M., Yasojima, A., Kanakubo, T. (2016), “Effect of Fiber Types on
Shear Performance of Precast Concrete Beam-Column Joints Using DFRCC”, The
7th International Conference of Asian Concrete Federation, 3. Concrete structures,Paper No.46.