2c-0211

The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEESendai, Japan - September 13th to 18th 2020
Paper N° C002962
Registration Code: S-A01619

Shear behavior of DFRCC coupling beams using PVA and aramid fibers
D. Sunaga(1), K. Namiki(2), T. Kanakubo(3)(1),(2) Graduate student, Graduate School of System and Information Engineering, University of Tsukuba, Ibaraki, Japan(1) s1920914@s.tsukuba.ac.jp, (2) s1820921@s.tsukuba.ac.jp(3) Professor, Department of Engineering Mechanics and Energy, University of Tsukuba, Ibaraki, Japan, kanakubo@kz.tsukuba.ac.jp

Abstract
Ductile fiber-reinforced cementitious composite (DFRCC) is expected to provide sufficient shear performance ofcoupling beams in high-rise buildings under severe seismic loads and decrease the deterioration of energy absorptionperformance. This study focuses on shear behavior of coupling beams through anti-symmetrical loading test of beamspecimens using PVA and aramid fiber-reinforced cementitious composite. The test parameters are fiber types, volume
fraction of fibers and diameter of stirrup. According to the test results, most of the specimens with fibers showed higher
value of shear capacity than mortar specimens. The shear capacity is evaluated by using tensile strength of DFRCC
obtained by four-point bending test of test pieces. In most of the specimens, calculated shear capacities showed good
agreements with the test results.
Keywords: Shear Behavior; DFRCC; Coupling Beams; PVA fiber; Aramid fiber

1. Introduction
Ductile Fiber-Reinforced Cementitious Composite (DFRCC), which shows a deflection hardening branch andmultiple cracking under bending stress, have been focused by lots of researchers because of its uniquemechanical performance. In other hand, Engineered Cementitious Composite (ECC), which has been
introduced by Li [1], exhibit a maximum tensile strain of several percent owing to the synergetic effect of highperformance fiber under pure tension. Unprecedented high-performance structural members by ECC havealready been applied to seismic components such as coupling beams [2].
Previous study has reported that structural members using DFRCC shows less damages and small crack
opening compared with conventional concrete members [3]. DFRCC can also make it possible to improve
durability and sustainable use of structures. However, it is difficult to evaluate tensile characteristic of DFRCC
and structural 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, and tensile stress carrying capacity does not start failing
until cracks saturating. For example, bi-linear model with hardening branch or perfectly elastic-plastic model
can be applied to express the tensile stress-tensile strain relationship for ECC [4]. In fact, Kanakubo et al. haveproposed the evaluation method of tensile strength of ECC by four-point bending test results as the material
test of ECC [5]. In the case of DFRCC, however, its tensile stress generally starts decreasing after peak loadin pure tension stress field. So, it is difficult to confirm the carrying tensile stress by DFRCC on its softening
branch in seismic components.
In previous study [6], to evaluate shear behavior of DFRCC coupling beams as seismic component, antisymmetrical loading test of beam specimens using PVA and steel fiber-reinforced cementitious composite wasconducted. In this study, to accumulate more data about DFRCC coupling beams, additional loading test ofbeam specimens using DFRCC was conducted by further test parameters. 2 types of PVA fibers and aramid
fiber are used for DFRCC. In addition to that, diameter of stirrups is also changed as the test parameter to© The 17th World Conference on Earthquake Engineering- 2c-0211 -2c-0211

The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEE
Sendai, Japan - September 13th to 18th 2020

discuss the interaction between fiber bridging effect and contribution of stirrups. The shear capacity isevaluated by using tensile strength of DFRCC obtained by four-point bending test of test pieces.

2. Outline of loading test for beam specimens
2.1 Specimen
Fig. 1 shows the dimensions of beam specimen and Table 1 shows the specimens list. The total length of thespecimen is 1,960mm. The central portion of 660mm length is the test region which is subjected to the antisymmetrical bending moment. The depth (D) and width (b) of cross-section is 220mm and 160mm,
respectively. Table 2 lists the mechanical properties of steel rebars. Three steel deformed rebars D16 (SD490)
were arranged as tension longitudinal reinforcements to avoid flexural yielding before shear failure.
The test parameters are diameter of stirrup, types of fiber for DFRCC and volume fraction of fiber. Steeldeformed rebars D4 or D6 (SD295) were arranged as stirrups at 120mm interval in the test region. Table 3
shows the dimensions and mechanical properties of fibers. 2 types of PVA fiber with 100μm diameter and27μm diameter, and aramid fiber with 12μm diameter were used for DFRCC. Fiber volume fraction was set to1.0% and 2.0% for φ100 PVA fiber, 0.5% for φ27 PVA fiber and aramid fiber. NF-D4, PVA10-D4 andPVA20-D4 specimens are tested in previous study as No.1 ~ No.3 [6].
860
2-D6@100450

2-D4@120 3-D16 l=2000

100

2-D6@100

Casting
direction
打設方向2065045 3535 45220

45035 150 35

100160(Test region)
660 (試験区間)

20650

1960Fig. 1 Specimen dimensions
Table 1 Specimens list
FiberIDNF-D4 (No.1[6])NF-D6PVA10-D4 (No. 2 [6])PVA10-D6
PVA20-D4 (No. 3 [6])PVA20-D6
PVA’05-D4
PVA’05-D6
AR05-D4
AR05-D6

Common factor

Cross-section: 160x220mm
Shear span: 330mm (M/QD=1.5)
Tension bar: 3-D16 (SD490)
Stirrup: D4 or D6@120 (SD295)

2© The 17th World Conference on Earthquake Engineering- 2c-0211 -Type

Volumefraction--PVA(φ100μm)
PVA(φ27μm)Aramid(φ12μm)

1.0%
2.0%
0.5%
0.5%

Stirrup Type(pw)
D4 (0.15%)
D6 (0.33%)
D4 (0.15%)
D6 (0.33%)
D4 (0.15%)
D6 (0.33%)
D4 (0.15%)
D6 (0.33%)
D4 (0.15%)
D6 (0.33%)

2c-0211

The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEE
Sendai, Japan - September 13th to 18th 2020

Table 2 Mechanical properties of steel rebar
TypeDiameter

SD490

D16
D4
D6SD295

Yield strength(MPa)
520
380
393

Elastic modulus
(GPa)
195
183
204

Remarks
Longitudinal barStirrup

Table 3 Mechanical properties of fiber
Fiber type
PVA
AramidDiameter(μm)
10027
12Length(mm)12612PVA (φ100μ)Tensile strength(MPa)
1200
1800
3410

PVA’(φ27μ)

Elastic modulus(GPa)284541

AramidFig. 2 Visual appearance of fibers
2.2 Loading and measurement
The monotonic loading following anti-symmetric bending moment manner (Ohno-type shear test method) wasconducted. The bending moment diagram is shown in Fig. 3. 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 plateswith 22 mm thickness as shown in Fig. 4. Steel round bars were placed at both loading points and supports.
Fig. 5 shows the state of loading.

Fig. 3 Bending moment diagram

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The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEESendai, Japan - September 13th to 18th 2020

430880100450450860
1960

100

Fig. 4 Steel plate jackets for beam specimen

Fig. 5 State of loading
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. 6. Assuming the rotation of rigid bodies of the specimen ends
jacketed by the steel plates, translational angle (R) is obtained from relative displacement at the center of thespecimen (δ) divided by clear span length. The strains of stirrups and longitudinal bars at the both ends of clear
span were measured by strain gauges.
These loading and measurement method are consistent with those in previous study [6].

Fig. 6 Measurement method4© The 17th World Conference on Earthquake Engineering- 2c-0211 -2c-0211

The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEESendai, Japan - September 13th to 18th 2020

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 results by φ100mm x 200mm cylinder
test pieces at the age of loading of beam specimens. Used cement was high-early-strength Portland cement, flyash was Type Ⅱ of Japanese Industrial Standard (JIS A 6202), and sand was size under 0.2mm. The high-range
water-reducing admixture and thickening agent were added.
The specimen dimensions for four-point bending test are 100mm x 100mm in cross-section, and 400mm
in length, these follows ISO 21914, “Test methods for fibre-reinforced cementitious composites – Bending
moment - Curvature curve by four-point bending test” [7]. Axial deformation at upper and lower side inconstant moment region were measured by pi-type LVDTs as shown in Fig. 7. Three specimens were tested
for one-type of DFRCC.
Table 4 Mixture proportion of DFRCC
IDNF-D4
NF-D6PVA10-D4
PVA10-D6
PVA20-D4
PVA20-D6
PVA’05-D4
PVA’05-D6
AR05-D4
AR05-D6

Water

Unit weight (kg/mm3)
SandCement
Fly ash

Fiber
13380

678484

291

26
6.5
7.0

Comp. strength
(MPa)
47.2
43.0
45.3
49.1
43.1
50.6
48.8
51.9
47.3
48.1

Elastic modulus
(GPa)
16.3
15.1
16.8
16.6
15.7
15.7
16.7
17.1
16.3
16.6

Fig. 7 Four-point bending test for DFRCC

3.2 Test results
Table 5 lists the test results of four-point bending test of DFRCC. Some specimens finally failed by openingof crack which took place outside of LVDT. Curvature at maximum load could not be obtained in these
specimens. Most of the specimens showed deflection hardening behavior as that the load increased after first
cracking.
Tensile strength and ultimate strain are calculated following ISO 21914 Annex A “Method of estimating
tensile strength and average ultimate tensile strain” [7]. In this evaluation method, tensile strength can becalculated under the assumption that the tensile stress distributes as a constant manner in tension zone of the5© The 17th World Conference on Earthquake Engineering- 2c-0211 -2c-0211

The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEESendai, Japan - September 13th to 18th 2020section. Though this assumption is mostly accepted in the case of ECC, it is considered that the actual stress
distribution in the case without strain hardening DFRCC is different from the assumed distribution.
The average values of tensile strength in each type of specimens are used for evaluation of shear capacityof beam specimen in Section 4.3. However, tensile strength of PVA’05-D4 specimens could not obtained
because all of three specimens failed by crack outside LVDTs. Therefore, the same value as PVA’05-D6 isused for evaluation in PVA’05-D4 specimen.
Table 5 Test results of four-point bending test of DFRCC
At maximum load
Bending
Curvature
UltimateID
momentstrain(1/m)(%)(kN･m)
0.172
0.562
1.58
PVA10-D4
0.093
0.528
0.82
0.066
0.413
0.66
0.172
0.553
1.58
PVA10-D6
0.106
0.481
0.96
0.091
0.485
0.81
0.162
0.869
1.44
PVA20-D40.088
0.866
0.74
0.737
―*1―
0.882
―*1―
PVA20-D6
0.259
0.872
2.37
0.280
0.882
2.57
0.590
―*1―
PVA’05-D4
0.543
―*1―
0.470
―*1―
0.464
―*1―
PVA’05-D6
0.004
0.402
0.02
0.006
0.404
0.04
0.114
0.419
1.04
AR05-D4
0.011
0.607
0.07
0.606
―*1―
0.038
0.797
0.30
AR05-D6
0.048
0.44
―*2
0.035
0.32
―*2
*
1: Specimen failed by crack outside LVDTs.
*
2: Measurement failure due to malfunction of testing machine

Calculation resultsTensile
Averagestrengthtensile strength
(MPa)
(MPa)
1.18
1.05
1.16
0.82
1.16
1.07
1.02
1.03
1.88
1.90
1.93
―
―
1.84
1.83
1.84
―
(1.24)
―
―
―
1.24
1.32
1.15
0.91
1.31
1.70
―
1.90
1.90
―
―

4. Test results of beam specimens and discussions
4.1 Failure progress
Beam specimens after loading are shown in Fig. 8. Cracks are traced by a pen after unloading. At first, small
bending cracks took place at the ends of clear span in tension zone. After that, diagonal shear cracks wereobserved in the central part of the specimens. In NF specimens, the shear crack widely opened after yieldingof stirrups, and shear force reached maximum value. Cover mortar fell from the specimens after maximumload.
In six specimens reinforced with PVA fibers (both φ100μ and φ27μ), small shear cracks took place insequence. Except for PVA10-D4 and PVA’05-D6 specimens, shear force reached maximum value with6© The 17th World Conference on Earthquake Engineering- 2c-0211 -2c-0211

The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEE
Sendai, Japan - September 13th to 18th 2020

gradual localization of crack opening. On the other hand, in PVA10-D4 and PVA’05-D6 specimens, maximum
load was observed at the same time of rapid localization of crack opening.
In AR specimens, multiple fine cracks took place in sequence, and maximum load was observed at thesame time of rapid crack opening of some shear cracks. Until reaching maximum load, crack width was muchsmaller than the other specimens. Falling of covers were not observed in all fiber reinforced specimens. In allspecimens, yielding of stirrups was observed before reaching the maximum load.

NF-D4

NF-D6

PVA10-D4

PVA10-D6

PVA20-D4

PVA20-D6

PVA’05-D4

PVA’05-D6

AR05-D4

AR05-D6
Fig. 8 Specimens after loading

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The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEESendai, Japan - September 13th to 18th 2020

4.2 Shear force-translational angle curve
Fig. 9 shows shear force (Q) - translational angle (R) curves of all specimens. Except for PVA10-D4 andPVA’05-D6 specimens, the maximum shear forces of the fiber reinforced specimens are larger than those of
NF specimens with same type of stirrups. It is considered that shear force is carried also by fibers bridging atcracks.
On the other hand, in PVA10-D4 and PVA’05-D6 specimens, it is assumed that bridging effect of fibers
vanished before reaching maximum load due to the rapid localization of shear crack as mentioned in Section
4.1. For this reason, it is considered that fibers could not increase the shear capacity in these specimens.
150100500012
Translational angle (0.01rad)

3150
NF-D4
NF-D6
PVA'05-D4
PVA'05-D6
Max. load

100

Shear force (kN)

NF-D4
NF-D6
PVA10-D4
PVA10-D6
PVA20-D4
PVA20-D6
Max. load

Shear force (kN)Shear force (kN)

150500PVA (φ100μ) series

01
2
Translational angle (0.01rad)

NF-D4
NF-D6
AR05-D4
AR05-D6
Max. load

100503

PVA’ (φ27μ) series

001
2Translational angle (0.01rad)3AR series

Fig. 9 Shear force – translational angle curve

4.3 Evaluation of shear capacity of beam specimen
In the case of ECC, the evaluation method of shear capacity of beam has been propose by Eq.(1) [5]. This
formula consists of shear capacity by truss (Vt) and arch (Va) mechanism, and fiber bridging (Vf). Each shear
capacity is given by Eq. (2) to Eq. (8). The former two items are same as the case of the conventional RCbeams. Shear capacity by fiber bridging is simply added to consider the contribution of tensile stress of DFRCC.
In this study, the same evaluation method is adopted for evaluation of shear capacity of DFRCC beams.
(1)

𝑉 =𝑉 +𝑉 +𝑉𝑉 =𝑏⋅𝑗 ⋅𝑝 ⋅𝜎𝑉 =⋅ 𝑐𝑜𝑡 𝜙𝑡𝑎𝑛 𝜃 ⋅ (1 − 𝛽) ⋅ 𝜈 ⋅ 𝜎 ⋅ 𝑏 ⋅ 𝐷
2𝛽=

(4)

(1 + 𝑐𝑜𝑡 𝜙) ⋅ 𝑝 ⋅ 𝜎
𝜈⋅𝜎

(5)

+1−𝜈 = 1.70𝜎

8© The 17th World Conference on Earthquake Engineering(3)

𝐿𝐷𝑡𝑎𝑛 𝜃 =𝐿
𝐷

(2)

- 2c-0211 -.

(6)

2c-0211

The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEESendai, Japan - September 13th to 18th 2020𝑐𝑜𝑡 𝜙 = 𝑚𝑖𝑛 2.0,𝑗𝜈⋅𝜎,𝐷 ⋅ 𝑡𝑎𝑛 𝜃 𝑝 ⋅ 𝜎−1𝑉 = 𝑏 ⋅ 𝑗 ⋅ 𝜈 ⋅ 𝜎 ⋅ 𝑐𝑜𝑡 𝜙(7)(8)

where,𝑉: shear capacity

𝑉: shear capacity by truss mechanism𝑉: shear capacity by arch mechanism𝑉: shear capacity by fiber bridging

𝑏: width of member𝑗: distance between compression and tension bars

𝑝: stirrup ratio𝜎: yield strength of stirrup𝜎: compression strength of DFRCC

𝜙: angle of compressive strut

𝜃: angle of arch mechanism

𝜈: effective coefficient of compressive strength of DFRCC𝐷: depth of member

𝐿: clear span length𝜈: reduction factor for tensile strength of DFRCC

𝜎: tensile strength of DFRCC

Table 6 lists the test results of shear capacity and calculation results by Eq.(1). The tensile strength ofDFRCC listed in Table 5 is utilized for the calculation. Fig. 8 shows the comparison between the test resultsof shear capacity and calculation results. Both shear capacity is standardized by calculated flexural capacity ofbeam specimen considering fiber bridging in tension zone as indicated by Eq.(9) [8].

𝑉= 0.9 𝑎 ⋅ 𝜎 ⋅ 𝑑 +𝑏⋅𝐷𝜎 /(𝐿⁄2)2where,𝑉: flexural capacity

𝑎: cross-sectional area of tension bars

𝜎: yield strength of tension bars

𝑑: effective depth of member

9© The 17th World Conference on Earthquake Engineering- 2c-0211 -(9)2c-0211

The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEESendai, Japan - September 13th to 18th 2020

As seen in Table 6 and Fig. 10, the calculated shear capacity overestimates the test results in PVA10D4 and PVA’05-D6 specimens. In the loading test, these specimens show non-increasing of shear capacity byadding fibers. However, except for these two specimens, the ratios of test results to calculations exist from
0.90 to 1.05. It can be said that calculations show good agreements with the test results. Shear capacities ofDFRCC beams can be evaluated by adding the effect of fiber-carrying capacity to calculated shear capacity inthe case of no-fiber.
Table 6 Shear capacity of beam specimen
Test result(kN)
76.1
97.7
75.1
119.3
110.9
131.2
102.8
96.9
113.7134.4

ID
NF-D4
NF-D6
PVA10-D4
PVA10-D6
PVA20-D4
PVA20-D6
PVA’05-D4
PVA’05-D6
AR05-D4
AR05-D6

Calculation
(kN)
82.8
103.4
101.7
130.0
116.5
146.4
108.1
135.8
108.1
145.4

Test / Calc.
0.92
0.94
0.74
0.92
0.95
0.90
0.95
0.71
1.05
0.92

Maximum shear force Qmax / Vfu

10.8
NF
PVA10
PVA20
PVA'05
AR

0.6
0.4

D4 D6

0.2

00.2
0.4
0.6
0.8
1
Calculated shear capacity Vsu / Vfu

Fig. 10 Comparison of shear capacity

5. Conclusions
In this study, to evaluate shear behavior of seismic components using DFRCC with PVA and aramid fibers,
beam specimens were subjected to anti-symmetrical bending moment loading. The test parameters are fibertypes, volume fraction of fibers and diameter of stirrups. According to the test results, in most of the specimens
with fibers, the shear capacities increased comparing to the mortar specimens. The fiber carrying capacity iscalculated by using the tensile strength of DFRCC obtained from four-point bending test. The shear capacities
are evaluated by adding the effect of fiber-carrying capacity to calculated shear capacity in the case of no-fiber.
Calculated shear capacities of DFRCC show good agreements with the test results.

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The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEE
Sendai, Japan - September 13th to 18th 2020

6. Acknowledgements
This study was supported by the JSPS KAKENHI Grant Number 18H03802.

7. References[1] Li, V.C. (2019): Engineered Cementitious Composites (ECC): Bendable Concrete for Sustainable and ResilientInfrastructure, 1st ed., Springer[2] Kanda, T., Tomoe, S., Nagai, S., Maruta, M., Kanakubo, T., Shimizu, K. (2006): Full Scale Processing Investigation
for ECC Pre-cast Structural Element, Journal of Asian Architecture and Building Engineering, Vol.5, No.2, pp.333340.
[3] Sano, N., Yamada, H., Miyaguchi, M., Yasojima, A., Kanakubo, T. (2015): Structural Performance of Beam-Column
Joint using DFRCC, 11th Canadian Conference on Earthquake Engineering -Facing Seismic Risk-, Paper ID 94163[4] Rokugo, K., Kanda, T., ed. (2012): Strain Hardening Cement Composites: Structural Design and Performance, Stateof-the-Art Report of the RILEM Technical Committee 208-HFC, RILEM State-of-the-Art Reports 6[5] Kanakubo, T., Shimizu, K., Kanda, T., Nagai, S. (2007): Evaluation of Bending and Shear 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.
[6] Kanakubo, T., Ozu, Y., Namiki, K., (2019): Shear behavior of DFRCC coupling beams using PVA and steel fiber,
Proceedings of The 2019 World Congress on Advances in Structural Engineering and Mechanics (ASEM19)[7] ISO 21914 (2019), Test method for fibre-reinforced cementitious composites – Bending moment - Curvature

curve by four-point bending test.
[8] 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)

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