The 7th International Conference of Asian Concrete Federation“SUSTAINABLE CONCRETE FOR NOW AND THE FUTURE”
30 Oct – 02 Nov, 2016, Hanoi, Vietnam
www.acf2016.vn

EFFECT OF FIBER TYPES ON SHEAR PERFORMANCE OF PRECAST
CONCRETE BEAM-COLUMN JOINTS USING DFRCC
H. Yamada1, M. Ando1, A. Yasojima2, and T. Kanakubo3
12

Master Program, Dept. of Engineering Mechanics and Energy, University of Tsukuba, Japan
Associate Professor, Dept. of Engineering Mechanics and Energy, University of Tsukuba, Japan
3Professor, Dept. of Engineering Mechanics and Energy, University of Tsukuba, JapanABSTRACT: In this study, the loading test of PCa beam-column joints using DFRCC in panel zone wasconducted to evaluate the effect of shear performance of joint panel. The main parameters are the fiber
type (PVA and steel) and fiber volume fraction (1.0% and 2.0%) in mortal matrix. From the experimentresults, it can be recognized that the maximum load of beam-column joint increased by mixing fiber, andthe fiber bridging effect of PVA fiber and steel fiber were different. According to the image analysis ofobserved cracks in panel zone, shear force that is carried by fibers can be calculated from the bridging
law of PVA fiber and results of uniaxial tension test of DFRCC with steel fiber. In the case of PVA fiber,
the calculated shear force showed a good agreement with the test results. On the other hand, thecalculated shear force disagreed with the experimental results in the case of steel fiber.

1INTRODUCTION

Construction method using precast (PCa) members has been more common for the skyscraper buildings
to rationalize workmanship. Up to now, new PCa system, in which the panel zone of the beam-column
joint is also manufactured as a PCa member in factory, has been proposed. On the other hand, many
researches on ductile fiber-reinforced cementitious composites (DFRCC), which has a high ductility, havebeen carried out in recent years (Japan concrete institute, 2012). Previous study reported that DFRCC
used in panel zone can inhibit the damage of joint panel and increase the maximum load (Sano et al.,2015). It is also considered that the shear force carried by fiber can be calculated by evaluating thebehavior of cracks in panel zone and using briding law.
In this study, the loading test of PCa beam-column joints using DFRCC in panel zone, which are designed
to fail by shear failure in panel zone before flexural yielding, was conducted to evaluate the effect offiber types on shear performance and crack behavior of joint panel.

2

EXPERIMENTAL PROGRAM

2.1

Test specimens

Table 1 shows the specimens list. The dimension of the specimens is shown in Figure 1. Specimens
No.26, 27, 28 and 29 are tested in this study and specimens No.24 and No.25, of which results havebeen reported in the previous study (Sano et al., 2015), are also included to discuss. The internal beamcolumn joint in skyscraper RC buildings is scaled with the beam section of set up 380 mm × 420 mm andthe column section of 500 mm × 500 mm. The specimens are designed to fail by shear in joint panel
before flexural yielding in order to evaluate the shear capacity of panel zone. Therefore, the safetymargin of shear capacity of joint panel is set at approximately 0.6 by using high strength bars in beamand column. The main parameters are the fiber type (PVA and steel) and fiber volume fraction (1.0% and2.0%) in mortal matrix of panel zone. For specimens No.26 and No.27, PVA fiber with 1% and 2% ofvolume fraction was used. Specimens No.28 and No.29 were manufactured using steel fiber with 1% and2%. Specimen No.26 was designed as the specimen with hoops in panel zone area. Mechanicalproperties of PVA fiber and steel fiber are shown in Table 2. The results of material tests for concrete,DFRCC and reinforcing bars are summarized in Table 3 and Table 4.

Table 1. Specimen list

ID

No.24
No.25

Panel Zone

BeamColumn

TargetFiber
Fiberstrength
volumeHooptype(MPa)
fraction (%)

Longitudinal
Stirrupreinforcing bar

Longitudinal
Hoop
reinforcing bar

40

No.26
No.27 48
No.28
No.29

-0.0

PVA 1.0
fiber

6-D10@60(SD785)2.0
Steel 1.0
fiber 2.0-

18-D22(USD685)

616-D22
D10@60(USD685)(SD785)

6D10@60(SD785)

55 50420
210

100 5050 55

75

100 12550500

Beam Section

50 70 7070 7050380500

42057050 100 100 50
100 100570

1880

Column Section

DFRCC(PVA fiber or steel fiber)

1100

500

1100

3500
Figure 1. Specimen dimensions.
Table 2. Mechanical properties of fiber

Fiber Length (mm) Diameter (mm) Tensile strength (MPa) Elastic modulus (GPa)PVA 120.10

1200

28

Steel 130.162830

210

Table 3. Mechanical properties of concrete and DFRCC

TypeConcrete
DFRCC

SpecimenPlace
No

Compressivestrength (MPa)

Splitting tensile strength(MPa)Elastic modulus(GPa)No.26

Beam and

54.6

3.71

29.5

No.27

Column

57.1

3.03

30.5

52.9

-

15.6

50.0-

15.7

No.26

(PVA fiber) No.27
ConcreteDFRCC

Panel zone

No.28

Beam and89.4

5.57

38.4

No.29

Column

88.6

4.42

39.0

56.8

-

18.7

59.2-

19.6

No.28

(steel fiber) No.29

Panel zone

Table 4. Mechanical reinforcing of bar

Specimen
TypeNoDiameter

No.26

D22 (22 mm)

USD685Note

Yield
strength(MPa)Tensilestrength(MPa)Elasticmodulus(GPa)

Longitudinal
reinforcing bar

717

899

192

No.27

No.26

No.28
No.29

2.2

SD785

D10 (10 mm)

Stirrup and hoop in
833
Column and Beam991

216

SD295

D10 (10 mm)

Hoop in PanelZone

346

468

192

USD685

D22 (22 mm)

Longitudinal
reinforcing bar712

898

189

SD785

D10 (10 mm)

Stirrup and hoop in
833
Column and Beam

1047

209

Loading method and measurement

The inflection points of the columns were supported by oil jacks and the story drift angle was controlled
by the actuators attached to the inflection points of the beams. The reversed cyclic loading was appliedwith the target story drift angles of R=±1/400, ±1/200, ±1/100, ±1/67, ±1/50, ±1/33, ±1/25 and ±1/20. In
this study, to observe shear cracks behavior in panel zone, photos were taken using two cameras during
the loading (details are explained in Chapter 4).
3

EXPERIMENTAL RESULT

3.1

Load-story drift angle curve and failure mode

Figure 2 shows the relationship between the applied load to beam and the story drift angle, and shows
the failure mode of the panel zone at the maximum load. Shear cracks in panel zone and those in beams
occurred in all specimens. After that, the shear crack width in panel zone increased. The maximum loadof No.26 and No.27 was observed at 1/50 rad, and that of No.28 and No.29 was observed at 1/33 rad.
After the maximum load, although the shear cracks opened in panel zone of all specimens, damage ofjoint panel was inhibited comparing with specimen No.24, which is without fiber in panel zone. It can berecognized that the maximum load of beam-column joint increased by mixing fiber. The maximum loadof specimens with steel fiber are higher than that of specimens with PVA fiber. It can be also recognizedthat the fiber bridging effect of PVA fiber differs from that of steel fiber. From the comparison betweenspecimens No.25 and No.26, of which maximum load is 459kN and 447kN respectively, hoops
arrangements do not affect the maximum load. This leads that hoops in panel zone do not affectsignificantly shear capacity of joint panel using DFRCC.
Q(kN)

No.24

No.25

500

R(rad)-0.05

0Q(kN)

Q(kN) Q(kN)

500

0.05
Qmax=385(kN)
Qmin=-389(kN)

-500

No.26
R(rad)

-0.05

00.05
Qmax=443(kN)
Qmin=-459(kN)

R(rad)-0.05

00.05
Qmax=397(kN)
Qmin=-447(kN)

-500

-500

No.24

500

No.25No.26

Q(kN)

No.27

Q(kN)

500

No.28

00.05

No.29

500

R(rad)

R(rad)

R(rad)
-0.05

Q(kN)

500-0.05

Qmax=465(kN)
Qmin=-467(kN)
-500

0-500

No.27

0.05

-0.05

Qmax=577(kN)
Qmin=-560(kN)

No.28

0-500

0.05
Qmax=644(kN)
Qmin=-629(kN)

No.29

Figure 2. Load – story drift angle curve and crack pattern (R=1/33rad.).

4CRACK BEHAVIOR IN PANEL ZONE

4.1

Method of observation

To evaluate the crack behavior in panel zone, photos of panel zone with the mesh of 10 mm x 10 mm
intervals on the surface were taken by two cameras as shown in Figure 3. The target photographing
regions were top left and bottom right area (120 mm x 80 mm). 1 pixel corresponds to 0.02 mm square.

80mm

Mesh：10mm×10mm

Target region

120mm

Figure 3. Target region.

4.2

Crack behavior

The calculation method of crack width is shown in Figure 4. It is considered that the panel zone has abiaxial stress field in which tensile stress and shear stress are distributed along shear crack. The crack
width is defined as the relative displacement between two points printed in same mesh line. Crack
opening and crack sliding is severally defined as the normal movement and the parallel displacementwith crack plane between two points.

(Ｘ₁’，Ｙ₁’)：Principal strain angle(Ｘ₁，Ｙ₁)Crack
slidingCrack
opening
Crack
width

Figure 4. Calculation method of crack.

Observed cracks of each specimen are indicated in Figure 5. Figure 6 shows the development of crack
width, crack opening, crack sliding and principal strain angle. The plotted marks are the peak values ofeach first loading cycle. The crack width spread with an increase in the story drift angle. The crack widthof specimen No.26 and No.27 with PVA fiber attains approximately 0.8mm at maximum load that thestory drift angle reaches 1/50 rad. After the maximum load, the crack width increase furthermore andreaches around 4-6mm at most. On the other hand, although the crack width of specimen No.28 andNo.29 with steel fiber is small until 1/50 rad. of story drift angle, the width increases remarkably atmaximum load in 1/33 rad. At the maximum load, the crack width reaches approximately 2-4mm whichis considerable larger than that of No.26 and No.27 and the width increases furthermore after that. Boththe crack opening and the crack sliding of all specimens increase as the target story drift angle also
increases. However, the values of crack sliding are smaller than crack opening until the maximum load.
The principal strain angle is around 40 degrees when cracks appear on the surface of panel. Although
the angle increases as the story drift increases, the angle decreases after maximum load. The differenceof principal strain angle between No.28 and No.29 was not clearly confirmed. From those results, it isconsidered that fiber volume fraction does not affect the principal strain angle. The principal strain angleof No.26 which has hoops in panel zone is smaller than that of No.27 without hoops. It is consideredthat is due to horizontal restraint effect of hoops.

B

No.26

A

Target region

No.27

BAA

Target region

No.28

BNo.29AB

Target region

Target region

108610No.26 A
No.26 B
No.27 ANo.27 B

86442

200.01

0.02

0.03

0.04

Story drift angle (rad)0.05 0

Crack opening (mm)Crack width (mm)Figure 5. Observed cracks

No.28 A
No.28 B
No.29 A
No.29 B

0.01

0.02

0.03

0.04

Story drift angle (rad)

0.05

1086

No.26 A
No.26 B
No.27 A
No.27 B

1086442

20

0.01

0.02

0.03

0.04

Story drift angle (rad)0.05 0No.28 A
No.28 B
No.29 A
No.29 B

0.01

0.02

0.03

0.04

Story drift angle (rad)0.05

86410No.26 A
No.26 BNo.27 A
No.27 B864

No.28 A
No.28 B
No.29 A
No.29 B

2200-20-2
0.05 0

0.01

0.02

0.03

0.04

0.01

0.02

0.03

0.04

0.05

Story drift angle (rad)Story drift angle (rad)Principal strain angle (degree)

Crack sliding (mm)10No.26 A
No.26 B

No.28 A
No.28 B

No.27 A
No.27 B

80

80

60

60

4040

20

200

0.01

0.02

0.03

0.04

0.05 00.01

0.02

No.29 A
No.29 B

0.03

0.04

0.05

Story drift angle (rad)Story drift angle (rad)Figure 6. Crack behavior

5SHEAR FORCE CARRIED BY FIBER

5.1

Calculation method

The calculation process of shear force carried by fiber is shown in Figure 7. The shear force carried byfiber is derived from the crack width and the principal strain angle explained before. The tensile stressand tensile force are calculated using these values, which are defined as the averages of those ofneighbor two points for target crack. The sectional area generating these stresses is assumed as the area
between the two points. The tensile stress carried by fibers across cracks can be calculated from thebridging law of PVA fiber (Asano et al., 2014) and the results of uniaxial tension test of DFRCC with steelfiber (the upper right figure in Figure 7). Uniaxial tension test was carried out using the specimen withthe same shape as previous report (Tsukizaki et al., 2014.). The bridging law of PVA fiber is calculatedusing same method with the previous study (Kanakubo et al. 2016) based on the assumption that fiber
orientation distribution is given as same with uniaxial tension test.

Crackwidth6
Vf=2.0%Vf=1.0%420123Crack width (mm)Bridging low ofPVA fiber
Shear forcedQTensileforce

Tension stress (MPa)Tensile stressis calculated
from crack
width

Tension stress (MPa)The tensile force is estimated from tensile stress multiplied by the sectional area. The sectional area
generating tensile stress is assumed to be crack surface between mesh lines with the principal strain
angle. The fiber shear force is obtained as the horizontal component of tensile force. Panel shear force
carried by fiber is summed for all of the forces in each mesh. It is assumed that the cracks out of thephoto areas show the same behavior with those in the photo area.

Shear force iscalculated as thecomponent oftensile force
All shear forces ineach mesh aresummed

46
Vf=2.0%Vf=1.0%420123Crack width (mm)4Results of uniaxial tension
test of DFRCC with steel fiber
Shear force carriedby fiber Q j=SdQ
dQ
dQ
dQ
dQ
dQ

Figure 7. Derivation process of shear force by fiber

5.2

Comparison of shear force carried by fiber

Figure 8 shows the transitions of the shear force differences between specimens No.25 and No.27 forPVA fiber, and specimens No.28 and No.29 for steel fiber. The straight lines show the difference incalculated shear force given by the method explained before, and the dotted lines show the shear force
difference from the test results. Calculation results are defined as the average shear force from twocracks shown in Figure 5. The calculated ones between specimens No.28 and No.29 from 1/67 rad. to
1/33 rad. of story drift angle are only shown in the figure, because cracks could not be observed up to1/67 rad. and the calculated tensile stress is zero over 1/33 rad. due to rapid expansion of crack width inNo.29.
Comparison of specimens No.25 and No.27 with PVA fiber shows that the calculated shear force had agood agreement with the test results. On the other hand, in comparison of specimens No.28 and No.29,
although the calculated shear force show a good agreement with the test results until story drift angleof 1/50 rad., the calculated value disagreed with the experimental results after that angle. It isconsidered that steel fiber has larger effect of fiber bridging across cracks than PVA fiber due to norupture behavior of steel fiber. It is assumed that shear resistance caused by crack sliding does not giveconsiderable effect because crack sliding is small until story drift of 1/50 rad. After increasing of cracksliding, shear resistance caused by crack sliding assumed to increase. Therefore, it is considered that
calculated shear force underestimates test results after 1/50 rad. of story drift angle.
Difference of calculated shear force
Difference of tested shear force
between No.25 and No.27

Difference of calculated shear force
Difference of tested shear force
between No.28 and No.29
400

Shear force (kN)Shear force (kN)

400
300
200
10000.01
0.02
0.03
Story drift angle (rad)

300
200
100

0.04

00.01
0.02
0.03
Story drift angle (rad)0.04

Figure 8. Comparison of shear force carried by fibers

6CONCLUSION

In this study, the loading test of specimens using DFRCC in panel zone was conducted to evaluate theeffect of fiber types on shear performance. The maximum load of specimens with steel fiber are higher
than specimens with PVA fiber. According to the image analysis of observed cracks in panel zone, shear
force carried by fibers is calculated from the bridging law of PVA fiber and results of uniaxial tension testof DFRCC with steel fiber. In the case of PVA fiber, the calculated shear force showed a good agreementwith the test results. On the other hand, the calculated shear force disagreed with the experimental
results in the case of steel fiber. It is considered that the fiber bridging effect of PVA fiber differs fromthat of steel fiber.
7ACKNOWLEDGEMENT

The authors wish to express their gratitude and sincere appreciation to the Tokyoutekkou Co., Ltd. forproviding the experiment materials. This study was supported by the JSPS KAKENHI Grant Number
26289188.

8REFERENCES

Asano, K. and Kanakubo, T. (2014) “Study on Fiber Bridging Constitutive Law in Consideration of Fiber Orientationin High Performance Fiber Reinforced Cementitious Composites”, Summaries of technical papers of annual
meeting Architectural Institute of Japan, Materials and Construction, pp. 185-186. (in Japanese)
Japan Concrete Institute (2012) “Technical Committee Report on Innovation Application of Fiber ReinforcedCementitious Composites”, Committee Report JCI-TC-104A, (in Japanese)
Kanakubo, T., Miyaguchi, M. and Asano, K. (2016) “Influence of Fiber Orientation on Bridging Performance of
Polyvinyl Alcohol Fiber - Reinforced Cementitious Composite”, ACI Materials Journal, Vol.133, No.2, pp.131141.
Sano, N., Yamada H., Miyaguchi, M., Yasojima, A. and Kanakubo, T. (2015) “Structural Performance of Beamth
Column Joint using DFRCC” The 11 Canadian Conference on Earthquake Engineering-Facing Seismic Risk-,
PaperID:94163
Tsukizaki, R., Miyaguchi, M., Wan, Z., Asano, K. and Kanakubo, T. (2014) “Study on Fiber Orientation of HPFRCC:
Part1: Experimental results of tension and bending tests”, Summaries of technical papers of annual meeting
Architectural Institute of Japan, Materials and Construction, pp. 179-184. (in Japanese)