13th World Conference on Earthquake Engineering
Vancouver, B.C., Canada
August 1-6, 2004
Paper No. 704

SHEAR BEHAVIOR OF STEEL REINFORCED PVA-ECC BEAMS
Katsuyuki SHIMIZU1, Toshiyuki KANAKUBO2, Tetsushi KANDA3, Satoru NAGAI4SUMMARY
ECC (Engineered Cementitious Composites), which is grouped in one of the fiber reinforced cementitious
composites, shows pseudostrain hardening behavior with several percent tensile strain. In this research,bending shear test of steel reinforced PVA-ECC (ECC with Polyvinyl alcohol fiber) beam is conducted tograsp fundamental properties of reinforced PVA-ECC. From the results of beam test, shear strength
increases as volume percentage of PVA fiber increases. Average shear strain in shear crack surface atmaximum strength is influenced by differences of volume percentage of PVA fiber. Predicting method forshear strength of beams is proposed based on the tensile strength obtained from uniaxial tensile test ofPVA-ECC.
INTRODUCTION
ECC (Engineered Cementitious Composites) [1], which is grouped in one of the fiber reinforced
cementitious composites, shows pseudostrain hardening behavior with several percent tensile strain. To
use fiber reinforced cementitious composites such as ECC as structural elements, steel reinforced ECC
members have been experimented by several research institutes. Most of those specimens are flexural
yielding type, because of utilizing as energy absorbing elements for structural control, upgrading materials
for flexural members, and so on. It is important that shear behavior is comprehended for the purpose ofstructural performance design as same as flexural behavior. Additionally, it is significantly important thattensile behavior of ECC is appropriately evaluated, and structural performance of ECC members can bepredicted and designed from tensile behavior evaluation.
In this research, uniaxial tensile test for PVA-ECC (ECC with Polyvinyl alcohol fiber) and bending shear
test of steel reinforced PVA-ECC beam is conducted to obtain fundamental properties of reinforced PVAECC. Specimens for reinforced PVA-ECC beam test are designed to show shear failure. Parameters areratio of lateral reinforcement and volume percentage of PVA fiber. Predicting method for shear strength ofbeams is considered based on the tensile stress - strain model obtained by uniaxial tensile test of PVAECC.

1M.Eng., Doctor program student, University of Tsukuba, JapanDr.E., Assist. Prof., IEMS, University of Tsukuba, Japan
3Ph.D., Chief Research Engineer, Kajima Technical Research Institute, Japan
4M.Eng., Senior Research Engineer, Kajima Technical Research Institute, Japan
2

MATERIAL PROPERTIES
Fiber of ECC is polyvinyl alcohol (PVA) fiber. Volume percentage (Vf) of PVA fiber is set to 1.0, 1.5, and
2.0%. Mechanical properties of PVA fiber are shown in Table 1. These values are given by manufacturer.
Table 2 shows the mixture proportion. Results of compression test using 100φ - 200mm cylinder test
pieces are summarized in Table 3. Normal concrete (NC) beams are designed for comparison to PVAECC one. Compressive strength of normal concrete is similar level to compressive strength of PVA-ECC.
Mixture proportion and compression test results of normal concrete are shown in same table. Specimensof reinforced beam are made with D13 main bar and D4 stirrup. Tensile test results of reinforcing steel areshown in Table 4.

Fiber type
PVAMatrix type
PVA10PVA15PVA20NC

Matrix type
PVA10
PVA15
PVA20NC

Table 1 Properties of PVA fiber
TensileLength ofDiameter
strengthfiber
(mm)
(MPa)
(mm)
120.041600
Table 2 Mixture proportion
Fiber
Water bySand byvolumebinder ratio
binder ratio
percentage
(%)
(%)
1.0
42.7
0.74
1.5
42.7
0.73
2.0
42.7
0.71
48.5
5.11
Table 3 Compression test results
CompressiveCompressive
strain atstrengthmaximum
(MPa)
(%)
37.3
0.35
35.7
0.35
39.1
0.36
39.0
0.23

Elasticmodulus(GPa)
40Air content(%)
1010105.0

1/3 Secantmodulus
(GPa)
17.8
16.3
19.5
26.2

Table 4 Tensile test results of reinforcing steel
Elongation
Elastic
Yield strain
Yield stressafter fracture
modulus
Name(MPa)
(µ)
(GPa)
(%)
D13*1
719.7
190.5
3779
9.8
*2
D13719.0
193.2
3721
14.5
D4*3
294.5
192.7
1528
27.4
*1 Main bar of PVA-ECC beams *2 Main bar of NC beams *3 Stirrup

BENDING SHEAR TEST OF PVA-ECC BEAMS
Specimens and Test Methods
The dimensions and bar arrangements of the beam specimens are shown in Fig. 1. Specimens have the180 x 280mm size rectangular section, and shear span ratio is 1.5. Main bar of yield stress 719MPa isused so that flexural yielding may not occur first. Parameters are ratio of stirrup and volume percentage ofPVA fiber. Normal concrete (NC) beams are planned for the comparison. List of specimens are shown in
Table 5.
Beam specimens are loaded under anti-symmetrical moment monotorically by Ohno Method. LVDTs areset to measure relative displacement between the stubs, partial deformations of each zone (A-C) shown inFig. 1. Strain guages are set to measure main bar and stirrup strain.

Location of LVDTs
p w=0.15%zone A zone B zone C520

1040
D4@93520

300

D4@93480

30 35 35 30
150280180Concrete

PVA-ECC

190

Casting direction

8-D13820

Strain gauge
840
2480

820

Fig. 1 Dimension and bar arrangement of beam specimen
Table 5 List of beam specimens
Fibervolumepercentage(%)

Section
bxD
(mm)

Shear
spanratio

Main bar

NC-00（Normal concrete）
NC-15
NC-30
PVA10-00
1.0
PVA10-15
PVA10-30
PVA15-00
1.5
PVA15-15 PVA
PVA15-30
PVA20-00
2.0
PVA20-15
PVA20-30

180 x280

1.5

8-D13
SD685
pt=2.43%

Specimen

Fiber

Stirrup
Reinforcement
Arrangement
ratio(%)
0.00
2-D4@93
0.15
2-D4@47
0.30
0.00
2-D4@93
0.15
2-D4@47
0.30
0.00
2-D4@93
0.15
2-D4@47
0.30
0.00
2-D4@93
0.15
2-D4@470.30

Test Results
The crack patterns at translational angle (R) of 0.01rad. are shown in the Fig. 2. Bending and shear crack
are observed at 0.0025rad.. In PVA-ECC beams, multiple cracks and effect of crack opening repression
can be observed in comparison with NC beams. When load becomes around the maximum value,deformation is concentrated on a certain one shear crack as for PVA-ECC beams as well. Another crack
width is decreased due to localize deformation. Main bar does not show yielding in all specimens.

NC-30

PVA10-30

PVA15-30

PVA20-30
Fig. 2 Crack patterns at 0.01rad.

Results of beam tests are shown in Table 6. Angle of main shear crack is measured values of main shear
crack of zone B with a ruler. Maximum stirrup strain is the biggest value in all strain guages at maximumstrength. The average angle of main shear crack of PVA-ECC beams is 28.6deg., nearly cotφcr = 2.0 (φcr =26.6deg.). Comparison of maximum strength is shown in the Fig. 3. Maximum strength increases asvolume percentage of PVA fiber increases and reinforcement ratio increases. The increase rate ofmaximum strength due to the increase in fiber volume percentage almost shows constant value. Since
stirrup strains show larger strain than yield strain at maximum strength, stirrup is assumed to be yielded.
Shear load - translational angle curve is shown in Fig. 4. It is observed in PVA-ECC beams that loaddecreases at opening shear crack and concentration of deformation.
Table 6 Results of beam tests
At maximum load

Load at first crack (kN)Specimen

NC-00
NC-15
NC-30
PVA10-00
PVA10-15
PVA10-30
PVA15-00
PVA15-15
PVA15-30
PVA20-00
PVA20-15
PVA20-30

Bendingcrack
43.6
36.9
41.9
26.1
20.4
18.8
31.1
42.4
27.9
17.0
20.8
19.8

Angle of main
shear crack(deg.)
Shear crack
97.5
69.4
74.3
66.7
55.3
60.5
66.6
63.7
123.7
36.3
33.0
90.6

26.6
21.8
29.7
31.0
23.2
29.2
34.5
23.2
32.4
33.4
26.2
24.2

Load(kN)

Translationa
l angle(x10-3rad)Maximum
stirrup strain
(µ)

116.4
104.8
132.3
123.9
144.8
171.5
142.8
169.7
182.9
182.7
205.8
208.6

5.05
6.93
12.01
6.44
8.07
11.75
9.11
11.01
11.64
10.90
13.82
12.62

2082
1330
3278
981
5267
8695
985
3825

250

200
150pw

100

0 .0 0 %500 .1 5 %0

Shear load (kN)Maximum load (kN)

250

0 .3 0 %

NC

200
150
100

P VA2 0 -3 0
P VA1 5 -3 0
P VA1 0 -3 0
NC-3 05000

PVA10 PVA15 PVA2010203040Translation angle (x10-3rad.)Sp ecimen

Fig. 3 Comparison of maximum strength

50Fig. 4 Relationship between shear load andtranslational angle

UNIAXIAL TENSILE TESTS OF PVA-ECC

Joint

60

Test Results
Tensile stress - strain curves are shown in Fig. 6. PVA15 and
PVA20 test results clearly indicated the pseudostrain hardening
characteristics, where stress increased after first crack. Test results
are summarized in Table 7. The ultimate strain is defined as thepoint at whith stress bocomes smaller than half of maximum stressafter maximum stress. It can be recognized that difference of fiber
volume percentage influences maximum stress and ultimate strain.

160

LVDT

400Specimens and Test Methods
Fig. 5 shows the outline of uniaxial tensile test method. This tensile
specimen is used to minimize the influence of fiber orientation andwas expected to reproduce a more precise tensile performance ofECC in a structure [2]. Sectional dimension in test region of thisspecimen is 100 x 60mm. The head speed of loading machine is set
to 0.5mm/min. Two LVDTs are set to measure axial deformation
with gauge length of 160mm. Each number of specimens withPVA10, PVA15, and PVA20 are six.

100R350

SteelplateFig. 5 Uniaxial tensile test

Tensile stress (MPa)5PVA10

PVA15

PVA20

432

At first crack
At maximum stressAt ultimate strain

1001

2
3Tensile strain (%)

012
3T ensile strain (%)

0Fig. 6 Tensile stress - tensile strain relationship

123Tensile strain (%)

4Specimen

Table 7 Uniaxial tensile test results
At first crack
At maximum stressTensile stress Tensile strain Tensile stressTensile strain
(MPa)
(%)
(MPa)
(%)

Ultimate strain
(%)

PVA10

2.54

0.017

2.52

0.10

0.33

PVA15

2.41

0.018

2.50

1.16

1.74

PVA20

3.41

0.018

4.06

1.67

2.37

EVALUATION OF SHEAR STRENGTH PVA-ECC BEAM
Strain Behavior of Beam
Principal strain (ε1, ε2) and principal shear strain (γ12) are calculated by using Mohr’s strain circle fromaverage strain (εx, εy, and εxy) which is calculated from partial deformation shown in the Fig. 1. Normalstrain (εcr) and shear strain (γcr) on the shear crack (φcr = 26.6deg.) is calculated, too. Method ofcalculating these strains is shown in Fig. 7.

γ /2
γ12/2

ε2(ε cr , γ cr/2)
2αεx

2φ cr

ε xy

ε xy ε y ε 1 ε

ε cr

2θ

φ cr

γ cr

Shear crackεyεxαyx (Axial direction)tanα = 190/280

Fig. 7 Method of calculating principal strain
Transitions of principal strain in zone B is shown in Fig. 8. X axis shows load step. Compressive principal
strain remained almost zero. On the other hand, tensile principal strain of PVA10, PVA15, and PVA20
beams at maximum strength are 0.5 to 0.9%, around 0.9%, and 1.0 to 1.3%, respectively. It is consideredthat fiber volume percentage influences tensile performance of PVA-ECC in beam test. In uniaxial tensile
test results of PVA-ECC, however, tensile stress of PVA10 is zero when tensile strain is 0.5 to 0.9%, andtensile stress of PVA15 and PVA20 does not reach the limit value of tensile performance when tensile
strain is around 1.0%. Therefore, it is considered that principal strain is not the cause to occur shear failureof PVA-ECC beams.

0.50
Load step

PVA 15-00
PVA 15-15
PVA 15-30
1○ : A t maximum
load

0.5
0

Principal strain (%)

Principal strain (%)

Principal strain (%)

PVA 10-00
PVA 10-15
PVA 10-30
1○ : A t maximum
load

PVA 20-00
PVA 20-15
PVA 20-30
1○ : A t maximum
load

0.50

Load step
Fig. 8 Transitions of principal strain in zone B

Load step

Transitions of nomal strain and shear strain on the shear crack in zone B is shown in Fig. 9. Influences offiber volume percentage and reinforcement ratio are not clear about normal strain, which is around 0.3%
at maximum strength. On the other hand, the differences are comparatively clear about shear strain. Shearstrain at maximum strength of PVA10, PVA15, and PVA20 are 0.4 to 0.7%, around 0.6%, and 0.7 to0.8%, respectively. The possibility is recognized that shear failure of PVA-ECC beams is influenced byshear transmittance capacity of PVA-ECC.

0.20

PVA 15-00
PVA 15-15
0.8
PVA 15-30
Thin lin es : εcr
0.6 Heavy lines :γcr
● : A t maximum
0.4
load0.2

1Strain (%)

1

PVA 10-00
PVA 10-15
0.8
PVA 10-30
Thin lines :εcr
0.6 Heavy lines :γcr
● : A t maximum
0.4
lo ad

Strain (%)

Strain (%)

1

PVA 20-00
PVA 20-15
0.8
PVA 20-30
Th in lines : εcr
0.6 Heavy lin es :γcr
● : A t maximum
0.4
lo ad

0.20
Load step

0Load step
Fig. 9 Trasitional normal and shear strain

Load stepProposal of Shear Strength Evaluation
At present, the research of shear transmittance capacity of ECC on cracks has been conducted [3]. There
have been many unclear points in relationship between stress and strain at ultimate state (i.e., failure
completing curve concerning stress and strain under multi-axial stress). In literature [3], for example, it
was reported that shear strength is almost equal to uniaxial tensile strength, even this depends on stress
path of normal and shear stress.
In order to design simply, predicting method for shear strength of beams is proposed using truss - arch
method. Assuming that stress of PVA-ECC is influenced by shear stress on crack, shear strength which issame value as uniaxial tensile strength is added to truss mechanism. From Method A of AIJ [4], Eq.(1) canbe obtained.
ECC)+ tan θ (1− β )b ⋅ D ⋅ν ⋅σ B / 2Vu = b ⋅ jt ( p w ⋅σ wy ⋅ cot φ + σ max(1)tan θ = ( L / D ) 2 + 1 − L / D(2)

(1 + cot φ )( p ⋅σ + σ2β=wwyECCmaxν ⋅σ B/ cot φ )≤1cot φ = min{2, j t /( D tan θ )}where,b: width of member
D: depth of member
L: clear span lengthjt: distance between tensile and compressive main bars
pw : reinforcement ratio
σ wy : yield strength of stirrup

(3)

(4)

ECC
σ max
: tensile strength of PVA-ECC
σ B : compressive strengthν: effective coefficient of concrete compressive strength

It is necessary that stirrups are yielded at maximum load of PVA-ECC beams, because stress of PVA-ECC
is superposition to stirrup strength in truss mechanism. Fig. 10 shows comparison between calculated
results and beam test results. Since average strain at tensile strength is 0.10% not more than yield strain ofstirrup in PVA10, 2.23MPa is used for calculation as tensile stress at yeild strain of stirrup. Following
Eq.(5) is used for calculating effective coefficient of concrete compressive strength. Average ratio of test
results to calculus is 1.03. Shear strength of PVA-ECC beans can be evaluated well by this calculation
method.

ν = 3.68σ B −0.333 (unit of σ is kgf/cm2)

Experimental strength (kN)B(5)

250200

PVA 10PVA 15PVA 20150100100150200250
Calculated strength (kN)
Fig. 10 Comparison between calculated strength and experimental strength

CONCLUSIONS

1.
2.

In the beam test, maximum strength increases as volume percentage of PVA fiber increases andreinforcement ratio increases.
In the uniaxial tensile test of PVA-ECC, it can be recognized that difference of fiber volume
percentage influences maximum stress and ultimate strain.

3.
4.

Influences by fiber volume percentage and reinforcement ratio are not clear about normal strain atmaximum strength. On the other hand, the differences are comparatively clear about shear strain.
Predicting method for shear strength of beams is proposed based on the tensile strength obtained
from uniaxial tensile test of PVA-ECC. Shear strength of PVA-ECC beans can be evaluated well by
this calculation method.
REFERENCES

[1]

[2]

[3]
[4]

Li, V.C. : From Micromechanics to Structural Engineering - The Design of Cementitious
Composites for Civil Engineering Applications, Journal of Structural Mechanics and Earthquake
Engineering, JSCE, Vol.10, No.2, pp.37-48, 1993
Shimizu, K., Kanakubo, T., Kanda, T., & Nagai, S. : Influence of Casting Direction on Uniaxial
Tensile and Bending Behavior of HPFRCC, Proceeding of the Annual Meeting of JCI, Vol.25,
No.1, pp.281-286, 2003.7 (in Japanese)
Kabele, P. : New Developments in Analytical Modeling of Mechanical Behavior of ECC, Journal ofAdvanced Concrete Technology, Vol.1, No.3, pp.253-264, 2003
Architectural Institute of Japan : Design Guidelines for Earthquake Resistant Reinforced Concrete
Buildings Based on Ultimate Strength Concept, pp.106 - 116, 1990