STRUCTURAL PERFORMANCE OF BEAM-COLUMN JOINT USING
DFRCC
Naoya SANO
Master Program, Dept. of Engineering Mechanics and Energy, University of Tsukuba, Japan
s1420894@u.tsukuba.ac.jp

Hiroshi YAMADA
Master Program, Dept. of Engineering Mechanics and Energy, University of Tsukuba, Japans1520931@u.tsukuba.ac.jp

Masaru MIYAGUCHI
Master Program, Dept. of Engineering Mechanics and Energy, University of Tsukuba, Japan
s1420932@u.tsukuba.ac.jp

Akira YASOJIMA, Ph.D.
Assistant Professor, Dept. of Engineering Mechanics and Energy, University of Tsukuba, Japanyasojima@kz.tsukuba.ac.jp
Toshiyuki KANAKUBO, Ph.D.
Associate Professor, Dept. of Engineering Mechanics and Energy, University of Tsukuba, Japankanakubo@kz.tsukuba.ac.jp
ABSTRACT: In this study, the loading test of precast beam-column joints using DFRCC in panel zone
was conducted to evaluate the effect of the shear performance of joint panel with DFRCC. Theexperiment factor is the fiber (PVA) volume fraction in mortal matrix at panel zone. From the experimentresult, it can be recognized that the fiber could inhibited the damage of panel zone. According to theimage analysis of observed cracks at panel zone, shear force which is carried by fibers can be calculated
from the bridging law of PVA fiber. The calculated shear force shows an agreement with the increment ofshear force of the specimen with fiber. This result indicates that the shear force carried by fibers can beevaluated by the behavior of cracks at panel zone.

1. Introduction
Rationalization of workmanship is demanded on precast (PCa) concrete buildings. Up to now, while PCa
members have been utilized for beams or columns, beam-column joints in PCa systems have been castin situ. Recently, developments and researches for new PCa systems, in which the panel zone of thebeam-column joint is manufactured as the PCa members together with the PCa beams (Fig. 1), havebeen carried out. The previous paper reported that the structural performance of beam-column joints
produced by the proposed PCa system showed the similar one with the conventional beam-column joints
cast-in-situ (Hosoya et al., 2012). However, when the safety margin of shear capacity of joint panel isclose to 1.0, shear failure occurs at panel zone after the flexural yielding of beams. Ductility becomesworse due to the slip behavior subjected to a large deformation.
On the other hand, many researches on ductile fiber-reinforced cementitious composites (DFRCC), which
can improve the ductility of concrete, have been carried out in recent years (Japan concrete institute,

Page 1 of 10

2012). Previous study reported that the shear capacity of the beams using DFRCC is higher than that ofordinary concrete beams (Shimizu et al., 2004). The authors also studied that using DFRCC in panelzone can improve ductility of beam-column joints after flexural yielding (Sano et al., 2014). In order tocomplete the structural design of beam-column joint using DFRCC, however, the further research on
evaluating the shear capacity of beam-column joints is necessary. In this study, the loading test for beamcolumn joints using DFRCC in panel zone, which are designed to fail by shear failure in panel zone before
flexural yielding, is conducted to evaluate the shear capacity of joint.

Hole for main
reinforcementof column

Groutfilling port

PCa jointpanel

Filling grout

PCa uppercolumn

PCa beam
PCa lowercolumnPCa beam

MechanicaljointFig. 1 – PCa system

2. Experimental Program
2.1. Test Specimens
Specimens are listed in Table 1. Fig. 2 shows the dimention of the specimens. The internal beam-column
joint in high-rise RC buildings is scaled with the beam section of 380 mm x 420 mm and the column
section of 500 mm x 500 mm. To evaluate the shear capacity of joint panel, the specimens are designed
to fail by shear in panel zone before flexural yielding. The safety margin of shear capacity of joint panel isset at approximately 0.6 using high strength longitudinal bars (USD685). The experimental factor is thefiber volume fraction in DFRCC at panel zone. No.24 is without fiber, while No.25 within the fiber volume
fraction which is set to 1.0 %. In order to obtain the effect on the shear capacity by only fibers in DFRCC,
the hoops are not arranged in panel zone. Moreover, the bar-joints and sheaths, which are ordinary
required in PCa system, are not arranged for easy making of specimens.
Mechanical properties of fibers used in DFRCC are summarized in Table 2. The results of material tests
for concrete, DFRCC and reinforcing bars are summarized in Table 3 and Table 4. The compression testand splitting test were carried out with the cylinder test pieces (100 mm x 200 mm). In case of DFRCC,
the splitting tensile strength is regarded as the peak load when the first crack initiates.

Page 2 of 10

ID

Targetstrength(MPa)No.24

Fiber volume
fraction (%)

40

No.25

Table 1 – Specimen list
BeamColumn

Longitudinal
reinforcing bar

StirrupLongitudinal
Reinforcing BarHoop

0.0

18-D22

6-D10@6016-D22

6-D10@60

1.0(USD685)(SD785)(USD685)(SD785)500
100 100 50
50 100 1004205555
50 210 50

730
570

500
100 125 50
50 75 100

380
70 70 5050 70 70

Beam Section

420

Column Section

730
570

DFRCC

1100
1500

1100
1500

500

Fig. 2 – Specimen dimensions
Table 2 – Mechanical properties of fiber
Fiber Length (mm) Diameter (mm) Tensile strength (MPa) Elastic modulus (GPa)PVA

12.00.10

1200

28

Table 3 – Mechanical properties of concrete and DFRCC
TypeConcrete
DFRCC

SpecimenNoPlace

Compressive strength(MPa)

Splitting tensilestrength (MPa)Elastic modulus(GPa)

No.24

Beam

39.9

3.55

29.6

No.25

Column

39.1

3.42

28.0

No.24

PanelZone

50.3

2.55

17.6

52.5

2.57

17.1

No.25

Page 3 of 10

Table 4 – Mechanical properties of bar
TypeDiameter

USD685
SD785

SpecimenNo

Place

D22(22 mm)

No.24

D10No.25(10 mm)

TensileElastic
Yield strength(MPa)strength (MPa) modulus (GPa)Longitudinal
reinforcing bar

717

900

195

Stirrup and hoop

832

996

218

2.2. Loading Method and Measurement
The column was supported by oil jacks and the story drift angle was controlled by the actuators attachedto the inflection point of the beams. The reversed cyclic loading was applied with the target story drift
angles of R = ±1/400, ±1/200, ±1/100, ±1/67, ±1/50, ±1/33, ±1/25, ±1/20 and +1/14 rad.
Fig. 3 and Fig. 4 show the setups of LVDT. The measuring items were the applied load to beams, storydrift (Fig. 3), deformations of columns and beams, and local deformations around the panel zone (Fig. 4)
and strains of the longitudinal bars. In addition, for specimen No.25, to observe shear cracks behavior inpanel zone, photos were taken in every 10 second using two cameras during the loading (details areexplained in Chapter 4).

Pin570

LVDT
Minus

Minus

Plus

570

420

Plus

LVDT

Roller（Linear Bush）
1100

500

1100

Fig. 3 – Measurement of story drift

PI-5-200

Minus

Plus

Jigs fixedpoints

LVDT
1190

320

PI-5-150

1190

Fig. 4 – Measurement of local deformation

Page 4 of 10

PI-5-200

PI-5-200

320

PI-5-250

PI-5-150
PI-5-150

PI-5-200

PI-5-150

645

Minus

270

Plus

PI-5-250

PI-5-150

270645

LVDT

PI-5-150

3. Experimental Result
3.1. Load-Story Drift Angle Curve and Failure Mode
Fig. 5 shows the relationship between the applied load to beam and the story drift angle, and Fig. 6shows the crack patterns of the panel zone at the maximum load. Shear cracks in panel zone, bending
cracks at the end of the beams and shear cracks in beams occurred in both two specimens. After that, theshear crack width in panel zone increased. The maximum load was observed at 1/50 rad. of story driftangle.
After the maximum load, the shear crack width in panel zone of specimen No.24 increased. And the peakload started decreasing due to shear failure in panel zone. On the other hand, although the shear cracks
in panel zone of specimen No.25 became wider, the peak load started decreasing due to compression
failure at the ends of the beams and columns. From the results, it can be observed that the damage ofjoint panel is inhibited by using DFRCC in panel zone.

No.25

400

Q (kN)No.24

Q (kN)The maximum load of specimen No.24, which is without fiber in panel zone, is 389 kN, and that ofspecimen No.25, in which the fiber is mixed in panel zone, is 459 kN. It is considered that the shear
capacity of joint panel can be improved by the effect of fiber bridging.

400

200-0.05

0-200
-400

2000.05
R (rad)

-0.05

0-200

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

-400

Fig. 5 – Load - story drift angle curve
No.24

No.25

Fig. 6 – Crack pattern at maximum load

Page 5 of 100.05
R (rad)Qmax = 443 (kN)
Qmin = -459 (kN)

3.2. Local deformations
Fig. 7 shows the transition of deformations of panel zone, columns and beams. Each deformation isexpressed by the conversions into ratio to the story drift. In both specimens, the similar tendency that theratio of panel zone increases until story drift reaches 1/50 rad. After the maximum load, the ratio of panelzone of specimen No.24 increases while that of No.25 shows reduction and the ratio of column increases.
The deformation of panel zone of specimen No.25 is smaller than that of No.24 because the fiber
prevents the panel shear cracks increasing.

No.24

PanelColumn

Beam

80
6040200100
Deformation ratio (%)

Deformation ratio (%)

100

1/400 1/200

1/100 1/67

1/50

1/33

PanelColumn

1/100 1/67

1/50

Beam

80
6040
2001/25

No.25

Story drift angle (rad)1/400 1/200

1/33

1/25

Story drift angle (rad)Fig. 7 – Deformations of panel, column and beam

4. Crack Behavior in Panel Zone
4.1. Method of Observation
To evaluate the shear cracks in panel zone of specimen No.25, the mesh with 10 mm x 10 mm intervals
was drawn on the surface in panel zone and photos were taken by two cameras as shown in Fig. 8. The
target regions for photos were center and corner area (120 mm x 80 mm) enclosed by the longitudinalbars of columns and beams in panel zone. Fig. 8 also indicates the observed cracks which are focusedfor calculating the shear force carried by fibers. The pixel number of used camera gives that 1 pixel
corresponds to 0.02 mm square. The photos were taken in every 10 second considering the datameasuring intervals and the loading speed (about 3 mm per minute).

Longitudinal
reinforcing bar

1Cracks

2 3
4

Target region(120 mm x 80 mm)
Mesh(10 mm x 10 mm)

Targetregion
1 pixel = 0.02 mm
Fig. 8 – Observation of cracks

Page 6 of 10

4.2. Crack Width and Principal Strain Angle
Fig. 9 shows the calculation methods of crack width. It is considered that the stress field in panel zone isin a biaxial stress field in which tensile stress and shear stress exist along shear crack. The crack width isdefined as the relative displacement between two points printed in same mesh line. Crack opening andcrack sliding is defined as the normal displacement and the perpendicular movement between two points,respectively. Principal strain is calculated by Mohr’s strain circle.

Crack sliding
Crack width
Crack opening(X1,Y1)
Principal
strain angle(X’1,Y’1)

Fig. 9 – Calculation method of crack width and principal strain angle
Fig. 10 - Fig. 12 show the transition of crack width, crack opening and crack sliding of crack #4 shown in
Fig. 8. The plotted marks are grouped into each loading cycle with target story drift angle shown in thefigures. The crack width increases as the story drift also increases. The width reaches approximately 0.8mm at maximum load in 1/50 rad. of story drift angle. The residual crack width, which is indicated near Yaxis, increases, as the target story drift angle rises, while increment rate shows gradual slope. After themaximum load, the crack width converges at around 0.9 mm. The crack opening and the crack sliding
also increases as the story drift increasing similarly with crack width. At the maximum load, the crack
opening and crack sliding is approximately 0.7 mm and 0.3 mm, respectively. It is considered that theincrease of crack width in panel zone is mainly affected by tensile stress acting on crack surface. After themaximum load, the crack opening does not so increase and it converges at around 0.8 mm. On the otherhand, the crack sliding increases after maximum load and reaches around 0.4 mm at 1/25 rad. of story
drift angle. It is considered that the crack width increases due to shear stress after maximum load. The
crack width, opening and sliding decrease in the second cycle of 1/25 rad. because of the increment of
deformation of columns and beams.
Fig. 13 shows the relationship between the principal strain angle and the story drift angle. At the loading
cycle of 1/100 rad. of target story drift angle, the principal strain angle varies around 60 degree. After theloading cycle of 1/67 rad., the scattering of the angle become smaller. It converges at a certain value ineach cycle. The convergent angle decreases gradually as the cycle increases. The angle is around 30degree and 20 degree at the loading cycle of 1/50 rad. and at second cycle of 1/50 rad., respectively. Theangle does not show remarkable change after those cycle.

Page 7 of 10

1

No.25

0.8
0.6

Target story drift angle
1/200
1/100
1/67
1/50
1/33
1/25
Solid : first cycle
Void : second cycle

0.4
0.2
00.01
0.02
0.03
Story drift angle (rad)Crack opening (mm)Crack width (mm)1

Crack sliding (mm)

No.25
0.8
0.6

Solid : first cycle
Target story drift angle
Void : second cycle
1/2001/100
1/67
1/50
1/33
1/25

0.4
0.2
00.01

0.02

0.03

0.6
0.4
0.2

Target story drift angle
1/200
1/100
1/67
1/50
1/33
1/25
Solid : first cycle
Void : second cycle

0.01
0.02
0.03
Story drift angle (rad)0.04

Fig. 11 – Crack opening - story drift angle
relationship0.04

Principal strain angle (degree)

Fig. 10 – Crack width - story drift angle
relationship
10.8

00.04

No.25

8060
40
200

Story drift angle (rad)Fig. 12 – Crack sliding - story drift angle
relationshipTarget story drift angle
1/200
1/100
1/67
1/50
1/33
1/25
Solid : first cycle
Void : second cycle

0.01
0.02
0.03
Story drift angle (rad)0.04

Fig. 13 – Principal strain angle - story drift angle
relationship

5. Shear Force Carried by Fiber
5.1. Calculation Method
The calculation method of shear force by fiber is presented in Fig. 14. The shear force by fiber bridging isdetermined by the crack width and the principal strain angle explained before. The tensile stress andtensile force are calculated by these values, which are obtained as the average of next points in one
crack. The sectional area acting these stresses is defined as area between the two points.
The bridging law (the upper right figure in Fig. 14) is adopted for calculating the tensile stress carried byfiber at cracks in DFRCC (Asano and Kanakubo, 2014). The bridging stress is calculated based on theassumption that the fiber randomly orients.
The tensile force is estimated from tensile stress using the principal strain angle. The sectional area
acting tensile stress is assumed using crack length between mesh lines and the principal strain angle.
Tensile stress multiplied by sectional area gives tensile force.
The shear force carried by fiber is the component of tensile force. All forces in each mesh are summed.
The extrapolated values are assumed in the out of the photo area.

Page 8 of 10210Distance between the main
reinforcement of column

Bridging law of DFRCC

Tension stress (MPa)Tensile stress iscalculated from thebridging law andcrack width

Shear force is calculated
as the component forceof tensile force12Crack width (mm)3Panel shear force
carried by fiber Q

Shearforce
Shear force is obtained
as sum of shear force inall meshes

Tensileforce

dQdQ

dQdQdQdQ

Distance between the main
reinforcement of column

Fig. 14 – Deriving Process of Fiber Shear Force

5.2. Predicted Shear Force
Fig. 15 and Fig. 16 show the relationship between the calculated shear force and the story drift angle.
The calculation results for each crack shown in Fig. 8 are shown in Fig. 15, and the average value of
those is shown in Fig. 16. The shear force difference between specimen No.25 and No.24 is also shownin the graph.

500500400

400Shear Force (kN)Shear force (kN)

The transition of the shear force carried by fiber for each crack shows similar tendency upto 1/100 rad.
After that, the shear force carried by fiber at crack #3 and #4 becomes larger due to deformation
localization. It is considered that there is the increment and decrement of shear force crack by crack. The
average of the shear force carried by fiber shows similarity with the shear force difference between No.24
and No.25 upto 1/50 rad. After 1/50 rad., difference between No.24 and No.25 becomes larger thancalculated value because of compression failure at the ends of beams and columns.

300
200
Defference of shear force
Crack #1
Crack #2
Crack #3
Crack #4

100
00.01

0.02
0.03
0.04
Story drift angle (rad)0.05

Fig. 15 – Shear force carried by fiber

300
200
1000

Average of calculated value
Defference of shear force

0.01

0.02
0.03
0.04
Story drift angle (rad)0.05

Fig. 16 – Averaged shear force carried by fiber

Page 9 of 106. Conclusion
In this study, the shear behavior of beam-column joint was examined by loading test for the specimen
using DFRCC in panel zone. The damage of joint panel was inhibited by DFRCC and the maximum loadincreased by the effect of fiber bridging. The shear force carried by fiber was estimated based on bridging
law of DFRCC and the observed crack width and the principal strain angle of shear cracks. It shows asimilar tendency with the shear force increment obtained by DFRCC specimen. It is considered that theshear force by fiber can be calculated by evaluating the behavior of cracks at panel zone.

7. Acknowledgement
The authors wish to express their gratitude and sincere appreciation to the Kuraray Co., Ltd. for providing
the PVA fiber. This study was supported by the JSPS KAKENHI Grant Number 26289188.

8. References
ASANO Kohei and KANAKUBO Toshiyuki, “Study on Fiber Bridging Constitutive Law in Consideration ofFiber Orientation in High Performance Fiber Reinforced Cementitious Composites”, Summaries oftechnical papers of annual meeting Architectural Institute of Japan, Materials and Construction,
2014, pp. 185-186. (in Japanese)
HOSOYA Hiroshi, MATSUMOTO Masashi, KANAKUBO Toshiyuki and YASOJIMA Akira, “Experimental
Study on Structural Performance of Precast RC Beam-Column Joints”, AIJ Journal of Technologyand Design, Vol. 18, No. 39, 2012, pp. 529-534. (in Japanese)JAPAN CONCRETE INSTITUTE, “Technical Committee Report on Innovation Application of Fiber
Reinforced Cementitious Composites”, Committee Report JCI-TC-104A, 2012. (in Japanese)
SANO Naoya, KIMURA Taichi, KANAKUBO Toshiyuki, YASOJIMA Akira and HOSOYA hiroshi,“Structural Performance of Precast Concrete Beam-Column Joints Using DFRCC in Joint Panel”,Summaries of technical papers of annual meeting Architectural Institute of Japan, Structures IV,
2014, pp. 419-420. (in Japanese)
SHIMIZU Katsuyuki, KANAKUBO Toshiyuki, KANDA Tetsushi and NAGAI Satoru, “Shear Behavior of
Steel Reinforced PVA-ECC Beams”, 13th World Conference on Earthquake Engineering,
Conference Proceedings DVD, Paper No. 704, 2004.

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