thｃThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China

STUDY ON STRUCTURAL PERFORMANCE OF PRECAST CONCRETE
BALCONY WITH HPFRCC
12Yuka ONIZUKA , Norimichi SAKO and Toshiyuki KANAKUBO

31

Graduate student, Graduate School of Systems & Information Engineering,
University of Tsukuba, Ibaraki, Japan
2Production Control Dept., Daisue Corporation, Tokyo, Japan
3Associate Prof., GSSIE, University of Tsukuba, Ibaraki, Japan, Dr.E.
Email:onizuka@rcs.kz.tsukuba.ac.jp, n-sako@daisue.co.jp, kanakubo@kz.tsukuba.ac.jp
ABSTRACTIn this study, the construction method of precast concrete balconies with High Performance Fiber- Reinforced
Cementitious Composite (HPFRCC), in which only the head of the cantilever slab is replaced by the precast
members, is introduced. The test parameters are type of concrete and thickness of lateral groove part. The static
cyclic loading for test specimens is carried out. The specimen with HPFRCC failed at the lateral groove part
avoiding reinforcing bars. The test result shows that thickness of lateral groove part affects ultimate load. Theresults of section analysis suppose the reduction of tensile strength of HPFRCC due to cyclic loading. All
specimens show enough load capacity to the horizontal force by structural design.
KEYWORDS:

HPFRCC, precast, balcony, structural performance

1.INTRODUCTION
Recently, in reinforced concrete apartment housing construction, an industrialization method of construction has
been required to reduce the cost and to be improved of process control and the quality control. The construction
method of precast concrete balconies, in which only the head of the cantilever slab is replaced by the precast
members, has been adopted. By using this method, it is possible to work without heavy industrial machine suchas a big drane. In this study, High Performance Fiber-Reinforced Cementitious Composites, called HPFRCC, isused in the precast part. HPFRCC is made by mixing with organic fibers of the polyvinyl alcohol (PVA) in
cement materials and make performance as high ductility in tension. Due to the tensile capacity of HPFRCC,reinforcing bars are not arranged in the precast part. That causes the reduction of manufacturing process ofmembers and cover thickness. In addition, the reduction of cover thickness at the precast part make possible toreduce the whole floor slab thickness and total weight of balcony. If the weight of slab is lighter, the weight ofwhole building can be lighter as leading the improvement of earthquake resistance.
In order to investigate structural performance of specimens manufactured by this method, the static cyclicloading test which is assumed as an earthquake response to the balcony had been carried out by authors [1]. The
results of this experiment show the proper method of connecting between the precast concrete member in caseof ordinary concrete and floor slab. Based on the results of the experiment, the un-reinforced precast member
with HPFRCC is manufactured and static loading test is carried out in this study. The purposes of this study are
to investigate the possibility of employing HPFRCC for the un-reinforced precast member and to develop theconstruction knowledge.
2.OUTOLINE OF LOADING TEST
2.1. Specimen
An example of specimen and arrangement of reinforcement is shown in Figure 1, details of the precast member

thｃThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China
are shown in Figure 2 and list of specimen is shown in Table 1. Each specimen has a different thickness of floorslab part and lateral groove part. The shape of specimen and arrangement of reinforcement are same. The
construction of specimen is same as actual construction of buildings. The precast concrete member of the headof the cantilever slab is manufactured then floor slab part and guardrail part of the balcony is cast in-situ. The
test part of specimen is from the connection between the precast member and guardrail to the anchored floorslab part. In the loading test, the floor slab is fixed to loading bed with channels-using steel bars. The width ofspecimen is 1,500mm. The main parameters are type of concrete of the precast member (ordinary concrete orHPFRCC) and thickness of lateral groove part. The connection method between the precast member andguardrail are same in all specimens. Y-insert is set up in the precast member and is connected by joint
reinforcing bars, D13. Shear cotters which size is 80x40mm and depth is about 20mm are set at the Y-insertpart.
For PCD-2and PCD-3, the precast member is connected to floor slab by anchors, and has no ordinary
reinforcing bars inside. The anchoring bar is D10. To keep cover depth of lateral groove part, the anchor has
cross shape and shear cotters are set at the slab connection in order to have better connection between the
precast member and the part of concrete casted in-situ. For PCS-4, the arrangement of reinforcing bars of theprecast member is the same as a ordinary RC balcony and reinforcing bar also has a role of anchors at slabconnection. All specimens are same arrangement of reinforcing bars at guardrail part and floor slab. In addition,
the precast members are casted from the downside.
Because the guardrail connections of each specimen would be yield first as expected, the loading process isdivided into two parts for the specimen PCD-3 and PCS-4. As the first part, the basic performance of theguardrail connection is investigated. After that, carbon fiber sheets are attached on the guardrail connection toprevent the failure of that part so that the performance of precast part and the slab connection is investigated as
the second part of the loading test. The specimens to investigate the guardrail connection are called PCD-3P andPCS-4P.

Figure 1 Specimen and layout of reinforcement

Figure 2 Detail of the precast members

thｃThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China
Table 1 List of specimen
the precast member
Guardrail
connection
Floor slab
Y-insert
Jointanchorreinforcing
barSpecimen
nameInsidereinforcing
bar

PCD-2

nothing

D10@200

100

PCD-3(PCD-3P)

nothing

D10@200120

PCS-4(PCS-4P)

6-D101-D13

D10@150

D13@250

Thicknessat groove

M12

Reinforcementof floor slab

Main bar
D13@150
D10@150

Reinforcementof guardrail

D10@200

130

2.2.Material properties
Deformed reinforcing bar, HPFRCC with PVA fiber, ordinary concrete and carbon fiber sheet are used for thespecimens. The sizes of deformed reinforcing bars are D10 and D13 (SD295). Mix property of HPFRCC isshown in Table 2. Mechanical properties of HPFRCC and concrete are shown in Table3. Fiber volume fractionof PVA in HPFRCC is 1.5% and PVA fiber properties are shown in Table 4. Carbon fiber sheets are attachedwith epoxy resin after grinding surface of concrete and flattening with putty type resin.
Table 2 Mix Property of HPFRCC

Unit quantity (kg/m3)

Water
Fiber volume/fraction
cement ratio
60%
1.5%

Type
HPFRCC

CementWater

Fine aggregate

Fly ash

576

380

484

291

Table 3 Mechanical properties of HPFRCC and natural concrete
TypeConcrete

HPFRCC
Precast partIn-situ casting part

*1 JCI-S-003-2007

Compressive
strength(MPa)
40.5
47.1
29.0

1/3 secant
modulus(GPa)
15.1
33.3
26.6

Tensile strength(MPa)3.93*1
3.74*2
2.52*2Tensile ultimatestrain(%)
0.959*1-*2 Splitting tensile test
Table 4 PVA fiber properties

Material
PVA fiver

Fiber length(mm)
12Diameter(mm)0.04

Tensile strength
(MPa)
1600

Elastic modulus
(GPa)
40

2.3. Method of loading and measurement
The position of loading and LVDTs are shown in Figure 3. The horizontal displacement of the top of theguardrail part (δtop: the guardrail-top displacement, average of D1 and D2) is monitored and the static loading
tests are performed by the monitoring displacement control using actuator which is fixed at the guardrail part.
The actuator is kept holding by chains to prevent own weight acting to specimens. The loading direction that thespecimen is pushed by actuator is defined as plus loading. And opposite direction is defined as minus loading.
Slips and opening width at the guardrail connection and the slab connection are measured. The displacement intest result of each measured item is the average value of displacements on both sides.

thｃThe 14 World Conference on Earthquake EngineeringOctober 12-17, 2008, Beijing, ChinaThe loading history is shown in Figure 4. The loading has 15cycles. The loading cycles for 1mm and 2mm aretwice and from 3mm to 90mm, every one cycle loading is carried out. In PCD-3P and PCS-4P, loading history
has 8 cycles that are from 0.5mm to 10mm as peak displacement in order to avoid much failure at the guardrail
connection.

Figure 3 Position of loading and LVDTs
guardrail-top
100 displacement(mm)50151413121011
89cycle number12 3 4 5 6 70-50-100

Figure 4 Loading history
3.TEST RESULT AND ANALYSIS
3.1. Failure Process
The final crack patterns of the precast part of each specimen in a side view are shown in Figure 5.
For PCD-3P, the guardrail connection is opened and the slab connection showed slip. The guardrail connection
showed slip and lateral groove part was cracked later. Finally, the loading finished without more cracking.
PCS-4P had similar behavior as PCD-3P. The guardrail connection showed slip and opened. The slab
connection opened more keeping constant load and the loading finished. Only the connection part had cracks.
For PCD-2 reinforced with carbon fiber sheet at guardrail connection, the slab connection opened and showed
slip firstly. Opening at the slab connection became clearly and multiple cracks were observed at the undersurface of the lateral groove part in minus loading. Then, a crack between downside groove and bottom ofguardrail part became clearly and collapsed avoiding inside reinforcing bars of the precast member at this crack.
For PCD-3, similar behavior was observed as PCD-2. The slab connection opened and showed slip. The lateralgroove part had multiple cracks. After that, cracks were observed from the part of shear cotter to the slab
connection. These cracks were almost perpendicular to the slab connection. PCD-3 failed due to a crack
between downside groove and bottom of guardrail part. Final collapse section in PCD-3 is shown in Figure 6
For PCS-4, opening at the slab connection, which had already opened in the loading for PCS-4P, became wideat the early loading stage. After that the lateral groove part and bottom of guardrail part were cracked and thesethｃThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, Chinacracks grew to the guardrail part. Vertical cracks along the Y-insert of the guardrail connection were observed.
In addition, it is confirmed that the opening of the slab connection became smaller with increases of crack width
at bottom of guardrail part. Finally, vertical cracks opened and loading finished with increase of the openingaround guardrail part.
Relationship between the load and the guardrail-top displacement is shown in Figure 7 and its envelope curve isshown in Figure 8. For PCD-3P, load becomes small due to slippage at the slab connection. The relationship ofPCD-4P is similar to PCS-3P. For PCS-4P, load decrement is observed due to cracks at guardrail connection. As
shown in Figure 8, the envelope curves of load-guardrail top displacement relationships of PCD-2 and PCD-3
are almost same shape although the load is difference. Both of these specimens show the slip type curve. And
the load becomes small when a crack of a final collapse opens at the lateral groove part. It is assumed thatthickness of the lateral groove part affect the load capacity. For PCS-4, the load becomes smaller because cracks
at bottom of the guardrail part are opened in minus loading. It is considered that the load in plus loading isbigger than in minus loading because a crack occurs along the Y-insert of the joint reinforcing bar at theguardrail connection in minus loading.

Figure 5 Final crack patternFigure 6 Final collapse section in PCD-3
PCD-3P-10-550 Q(kN)

05PCS-4P

10

δtop (mm)-10-50

PCD-2-50

500-500510

δtop (mm)-50Q(kN)

PCD-350-50

δtop (mm)-550 Q(kN)

50 Q(kN)

0-5050δtop(mm)

PCS-4-5050 Q(kN)050δtop (mm)-50

Figure 7 Relationship between load and the guardrail-top displacement

thｃThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China

PCD-3P
PCS-4P-1030 Q(kN)

PCD-2
PCD-3PCS-40-5010
δtop (mm)500Q(kN)50
δtop (mm)

-50

-30

Figure 8 Envelope curve
3.2. Analysis of maximum load
The maximum load of the loading test is compared with the calculated value of bending ultimate strength bysection analysis. The section analysis is conducted in three focused sections, which are the guardrail connection(section A), the lateral groove part (section B) and the slab connection (section C). For PCD-3P and PCS-4P,section A is dangerous section. For PCD-2, PCD-3 and PCS-4, section B and C are dangerous sections. The
bending moment calculated for dangerous sections is converted to the force at loading point of the guardrail part.
Concrete strength for connection part is to be same as that of the concrete in-situ part. The concrete strength ofthe precast member is used for section B. The stress-strain model of HPFRCC is shown in Figure 9. The tensilestress of HPFRCC is assumed to be uniformly distributed all over tensile side of section. The maximum loads ofexperiment and analytical values are shown in Table 5.
stress (MPa)
-0.35

-0.5

0-100.5 strain (%)-20-30-40

Figure 9 Stress –strain model of HPFRCC
Table 5 Comparing maximum load and calculation value
Specimen name

PCD-3P
PCS-4P

Loading
direction

Maximum loadof experiment
(kN)

Plus
Minus
Plus
Minus

23.6
16.3
28.4
19.0

Plus

21.1

Minus

17.6

Plus

37.6

Minus

28.7

Plus

49.9

Minus

24.6

PCD-2

PCD-3

PCS-4

Calculated
sectionMaximum loadof analysis(kN)

Experiment/Analysis

A
A
A
A
B
C
B
C
B
C
B
C
B
C
B
C

19.1
20.5
19.1
20.5
41.7
54.1
23.2
51.4
47.6
71.6
27.5
71.667.7
36.8
32.0
39.0

1.24
0.80
1.49
0.93
0.51
0.39
0.76
0.34
0.79
0.53
1.04
0.40
0.74
1.36
0.77
0.63

thｃThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China
In addition, the operating load acts as axial force on the calculated section B and C. The convergence calculation
is carried out to have same value between the load and axial force. Calculation for section B of PCD-2 andPCD-3 is done for the section where the reinforcing bars are crossed as the weak section.
Calculated strength is determined as the smallest value of each section. For PCD-2 and PCD-3, in which
HPFRCC is used, failed at the lateral groove part in experiment. However as shown in Table 5, calculation
result shows that the weakest point of these specimen is the slab connection. Therefore, because collapse surfaceof these specimens avoided reinforcing bars, the existing of reinforcing bar is omitted. In addition, the tensile
strength is reduced to be half value in the precast member. Calculation result is shown in Table 6.
In this result, the maximum loads of experiment and analysis become closer. Therefore, it is assumed that theactual tensile strength of HPFRCC is the half value of tensile strength evaluated by material test. It is consideredthat tensile strength of HPFRCC becomes smaller because PVA fibers pullout from matrix or rupture at collapse
section. However it is necessary to investigate the effects of cyclic loading on HPFRCC.
For PCS-4, the maximum load of experiment and analysis dose not fit in minus loading because of cracks along
Y-insert of the joint bars. The average ratio of experimental load to analytical one is 1.36 in plus loading. So, it
is confirmed that section analysis can be adopted to evaluate experimental maximum load in safe side in case ofPCS-4.
Table 6 Calculation result
Specimen name
PCD-2
PCD-3

Loading direction
Plus
Minus
Plus
Minus

Maximum load ofexperiment
(kN)
21.1
17.6
37.6
28.7

Maximum load ofanalysis
(kN)
18.7
16.8
27.3
23.9

Experiment/
Analysis
1.13
1.05
1.38
1.20

3.3.Design force for earthquake and wind
The design force is calculated as the 15-story buildings (the height of buildings is 45 meters) at three dangerous
sections which are same as the case of section analysis. The design seismic force is calculated using Eq. (3.1)
and the design wind force is calculated using Eq. (3.2). Calculation result of the design force is shown in Table
7. By comparing calculated and experiment load, it is confirmed that all specimens have enough strength against
the design force.

Pe = k × W
Pw = C × q × A
Pe : designing seismic force
Pw : designing wind force
where,k : horizontal seismic coefficient (=1.5)
W : weightC : wind factor (=1.2)
q : velocity pressure (N/m2) (= 1204 h × 9.81 )A : area receiving wind pressure (m2)h : height (m)

(3.1)
(3.2)

thｃThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China
Table 7 Calculation result of design force
SectionAB
C

Design seismic force
(kN)
8.9
10.9
12.3

Design wind force
(kN)
6.0
7.4
7.4

4. CONCLUSIONSIn this study, the balcony specimen using the precast concrete member is manufactured and static loading iscarried out. The parameters are type of concrete and thickness of lateral groove part. From the test results, thefollowings are summarized.
1.

The specimen with HPFRCC showed multiple cracks at lateral groove part and collapse took place at thesurface avoiding reinforcing bars. Thickness of lateral groove part affects the maximum load.

2.

The maximum load of experiment is compared with that of calculation by section analysis. The resultshows that for PCD-2 and PCD-3 with HPFRCC, the tensile strength of HPFRCC is considered as about
half value of the strength examined by material test. It is assumed that the cyclic loading influences thestrength of HPFRCC.

3.

All specimens show enough load capacity to the earthquake and wind design.

REFERENCES
1.

T. Yagi, N. Sako, T. kanakubo. (2007). Study on PCa Members used in Balcony. Summaries of TechnicalPapers of Annual Meeting, C-2 Structure 4, No.23077, Architectural Institute of Japan, 2007, pp.171-172(in Japanese)

2.

Method of test for bending moment–curvature curve of fiber-reinforced cementitious composites,JCI-S-003-2007, Japan Concrete Institute Standard, 2007