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www.springer.com/journal/13296
International Journal of Steel Structures
March 2014, Vol 14, No 1, 151-164
DOI 10.1007/s13296-014-1013-5
Structural Behaviour of Perforated Shear Connectors with Flange
Heads in Composite Girders: An Experimental Approach
Qing-Tian Su1, Guo-Tao Yang1,2,*, and Chen-Xiang Li1
1Department of Bridge Engineering, Tongji University, Shanghai, 200092, China
2Centre for Infrastructure Engineering and Safety, School of Civil and Environmental Engineering,
The University of New South Wales, UNSW Sydney, NSW 2052, Australia
Abstract
Perforated shear connector with flange head (PSCFH) as a new type of connector behaves high bearing capacity and excellentductility in steel-concrete composite girders. In this paper 15 groups, totally 45 push-out test specimens, were conducted toinvestigate the effects of plate thickness, connector height, flange length, flange number, hole diameter on the web, diameterof reinforcing bars and concrete strength on structural behaviour of PSCFH. In the push-out tests, failure mode, load versusslip curve and bearing capacity of all the specimens were obtained. Based on the results of push-out tests, bearing mechanismwas analyzed and a calculation model of the shear bearing capacity was proposed with respect to the failure modes. Calculationresults based on the proposed model agree well with the experimental values.
Keywords: composite structure, perforated shear connector with flange head, ultimate bearing capacity, push-out test,experimental research
1. Introduction
In steel-concrete composite beams, shear connectors
perform as essential members to resist the relative slip
between the steel component and the concrete component
and to ensure the efficient co-work between the two
components. Many types of devices used to function as
shear connectors in composite beams (Kim et al., 2011a;
Kwon et al., 2010; Shim and Kim, 2010) and these types
of connectors include profile steel (channels, tees, zees,
etc.), bars, spirals and headed studs. Nowadays, headed
stud shear connectors are the most common type of shear
connector used in steel-concrete composite beams of
bridge and building engineering.
The headed studs were connected to steel beam by high
pressure fusion welding, and transferring shear and
preventing uplift between the steel component and the
concrete component were by shank and enlarged end.
Headed studs were widely used in steel-concrete beams
because there is no direction limitation in transferring
shear force and it can be automatically welded in
workshop. Considerable experimental and theoretical
research has been conducted on static, dynamic and
fatigue behavior of headed stud connectors (Lam and El-
Lobody, 2005; Liu and De Roeck, 2009; Nguyen and
Kim, 2009; Xue et al., 2008), and well developed
calculation method has been successfully established and
included in the standards of Eurocode, AASHTO, GB
50017, etc (AASHTO, 2004; CEN, 2005; Ministry of
Construction of China, 2003).
However, the bearing capacity of a single stud is low
(Burnet and Oehlers, 2001; Shim et al., 2004), so in
actual engineering projects a great many studs are needed.
Besides, in the event of large stress range, application of
headed stud is restricted due to its low fatigue strength
(Civjan and Singh, 2003; Hanswille et al., 2007). Also it
use requires specific welding equipment and high generator
at the construction site.
In the past two decades, a new type of connector named
Perfobond connector as shown in Fig. 1 has been
developed in composite structures (Medberry and Shahrooz,
2002; Oguejiofor and Hosain, 1995). Perfobond connector
is a steel rib with several holes in a line welded to a girder
flange. Concrete dowel formed by concrete in the rib hole
could carry heavy forces between the steel and the
concrete, and at the same time the reinforcement bars
through the perforated holes could increase the bearing
capacity and improve the ductility significantly (Candido-
Note.-Discussion open until August 1, 2014. This manuscript for thispaper was submitted for review and possible publication on July 16,2012; approved on January 24, 2014.© KSSC and Springer 2014
*Corresponding authorTel: +61-2-93855656; Fax: +61-2-93856139E-mail: [email protected]
152 Qing-Tian Su et al. / International Journal of Steel Structures, 14(1), 151-164, 2014
Martins et al., 2010). Several researchers have recently
investigated the behavior of the Perfobond connector by
push-out tests or bending tests of composite girders, and
reference is made to the studies of Ahn et al. (2008), Kim
et al. (2011b), Valente and Cruz (2004, 2009), etc. These
researchers concluded that their structural response was
influenced by several geometrical properties such as the
number of holes, the plate height, length and thickness,
the concrete compressive strength, and the percentage of
transverse reinforcement etc, and comparing to the
headed stud connector, the Perfobond connector behaves
higher shear and fatigue strength.
The motivation of developing new products for the
shear transfer in composite structures is related to issues
involving particular technological, economical or structural
needs of specific projects. In recent years, Chung et al.
(2004) developed a new type of shear connector called
perforated shear connector with flange heads (PSCFH),
as shown in Fig. 2, which is a modified Perfobond
connector fabricated by cutting and folding the upper
edge of the perforated steel plate. The folding part forms
large heads, which could increase the contact area
between the steel and the concrete. Experimental research
by Kim et al. (2006) showed that the load bearing
capacity and ductility of PSCFH was much excellent.
As a relative new type of connector, limited tests have
been carried out. In this paper, further studies on bearing
capacity and failure mode of this connector were
conducted by 15 groups, total 45 specimens. Influence of
various parameters on structural behavior of this
connector were studied and investigated by means of
push-out tests. Calculation expressions for the ultimate
bearing capacity of this new type connector were
established, which would provide as a useful reference
for the design and application of this type of connector.
2. Experimental Program
2.1. Specimens15 groups, 3 identical specimens in each group, a total
of 45 specimens, were designed and fabricated. Push-out
tests were carried out with different parameters, i.e. plate
thickness tp, connector height hp, flange length bp, flange
number Nf, hole diameter on the web plate dh, diameter of
reinforcing bars dpr and concrete strength. The detailed
parameters of the 15 groups of specimens are described in
Table 1.
Outline dimensions of 15 groups of specimens were the
same as shown in Fig. 4(a). The details of PSCFH of
specimen in different groups were varied as shown in Fig.
4(b).
With regard to push-out specimens of stud connectors
and Perfobond connectors, concrete casting position
could affect the bearing capacity to a great extent (Ahn et
al., 2010; Akao et al., 1987; Su et al., 2009). In this
paper, to simplify the investigation and to standardize the
push-out tests, normal concrete casting position was adopted
corresponding to the common construction process of
composite girders. During the fabrication process of the
specimens, in order to guarantee the right casting position
and the same concrete age of the both concrete slabs in a
specimen, firstly I-shaped steel profile was divided into
two T-shaped parts, and then PSCFH was welded to the
flange of the T-shaped steel profile. After that, concrete
was cast on the two steel profiles. When the concrete
reached its required strength, two halves of composite
parts were connected together by high strength bolts on
the web of the steel profile. To eliminate the bonding
effect and friction force on the interface between the
concrete and the steel flange, grease was smeared on the
flange surface of I-shape steel profile.
2.2. Material properties
The cubic compressive strength of concrete was tested
by three cubic standard specimens with the dimension of
150 mm×150 mm×150 mm as shown in Table 1. Mechanical
behaviors of the reinforcement were obtained using 3
Figure 1. Perfobond connector.
Figure 2. Perforated shear connector with flange heads.
Figure 3. Dimension symbols and terminology of PSCFH.
Structural Behaviour of Perforated Shear Connectors with Flange Heads in Composite Girders: An Experimental Approach 153
coupons for each diameter, and the yield strength of
reinforcing bars embedded in the concrete with the
diameters of 19.95, 17.28, and 15.08 mm were 350, 329,
and 362 MPa respectively. The yield strength and tensile
strength of the steel of the PSCFH were 347 and 541
MPa respectively.
2.3. Test setup and Loading procedure
The specimens were tested by means of a hydraulic
jack with the loading capacity of 4000 kN in a self-
balanced frame as shown in Fig. 5. A layer of sand was
laid between the specimen and the base of frame to
absorb any imperfections present at the bottom concrete
face and ensure a relatively uniform force transferring
among the connectors in the specimen. Firstly two
specimens (labeled TPS-n-1 and TPS-n-2) in each group
were conduct mono-load respectively. In these two
specimens, the loading procedure was controlled by an
applied load less than a rate of 5 kN/s and guaranteed the
failure did not occur in less than 15 min according to
Eurocode 4. Then the third specimen (labeled TPS-n-3) in
each group was conduct cycle of loading/unloading. In
this specimen, the 0.7 times of average ultimate load of
previous two specimens were divided into 7 grades. In
each load grade the rates of loading/unloading were the
same and less than 5 kN/s. After finished the 7 cycles of
loading/unloading, the mono-load was carried out until
the specimen failure.
2.4. Measurements
Four linear variable differential transformers (LVDTs)
were installed on the middle height of the specimen to
measure the relative slips between the steel and the
concrete continuously during the testing. The specimen
failure modes of occurrence and development process
were observed.
3. Test Results
3.1. Failure modes
During the loading stage, the sign of failure is the
appearance of cracks asymmetrically in concrete slabs.
These cracks developed from the bottom of the slab
corner to the top along the height direction with the
increase of applied loading. In the ultimate limit state, a
splitting face formed in the concrete slab along the 45
degree direction, as shown in Fig. 6(a). The main reason
of the appearance of asymmetrical cracks is the flanges of
PSCFH are asymmetrically in the specimen which induces
the non-uniformity force in concrete.
After the tests, the specimens were dismantled to
investigate the failure modes of steel ribs. Plastic distortion,
due to combined bending effect and torsion force, was
observed on flange heads in a different degree, as shown
in Fig. 6(b), which indicated that the flange heads
embedded in the concrete could provide strong gripping
force. The interaction between the connector and concrete
was so powerful that obvious plastic deformation appeared
on the rib holes, as show in Fig. 6(c), and fracture of the
steel web plate was found at the bottom of the hole in
some specimens, as show in Fig. 6(d). The failure modes
shown in Fig. 6(c) and Fig. 6(d) were rarely happened in
the push-out test specimen of Perfobond shear connector,
which indicates the extra flange in PSCFH can improve
Table 1. Geometrical parameters of the tested specimens
Group Ns fc,t fc,m dpr tp dh hp bp Nf
PS-0 3 50 53.1 19.95 16 60 175 -- --
TPS-1 3 50 53.1 19.95 16 60 175 180 4
TPS-2 3 50 53.1 19.95 16 60 150 180 4
TPS-3 3 50 53.1 19.95 16 60 200 180 4
TPS-4 3 50 53.1 19.95 12 60 175 180 4
TPS-5 3 50 53.1 19.95 20 60 175 180 4
TPS-6 3 50 53.1 19.95 16 60 175 140 4
TPS-7 3 50 53.1 19.95 16 60 175 220 4
TPS-8 3 50 53.1 19.95 16 60 175 180 3
TPS-9 3 50 53.1 19.95 16 60 175 180 5
TPS-10 3 50 53.1 19.95 16 50 175 180 4
TPS-11 3 50 53.1 19.95 16 75 175 180 4
TPS-12 3 50 53.1 17.28 16 60 175 180 4
TPS-13 3 50 53.1 15.08 16 60 175 180 4
TPS-14 3 40 36.9 19.95 16 60 175 180 4
TPS-15 3 60 59.3 19.95 16 60 175 180 4
Note: Ns : Number of specimens in one group; fc,t : Compressive strength of concrete: target value (MPa); fc,m : Compressive strengthof concrete: measured value (MPa); dpr : Diameter of reinforcing bars (mm); tp : Plate thickness (mm); dh : Hole diameter of web(mm); hp : Connector height (mm); bp : Flange length (mm); Nf : Flange number
154 Qing-Tian Su et al. / International Journal of Steel Structures, 14(1), 151-164, 2014
Figure 4. Details of the test specimens (unit: mm).
Structural Behaviour of Perforated Shear Connectors with Flange Heads in Composite Girders: An Experimental Approach 155
the carrying capacity greatly. Due to different configurations
of the specimens, the failure modes of different groups
were not always the same. Fracture of the web plate
occurred in specimen TPS-4 with relative thinner web
plate and in specimen TPS-11 with large diameter of the
hole on the web, while splitting of concrete in the early
stage of loading was found in specimen TPS-14 with
lower concrete strength. As for other specimens, distortion
of flange plate, plastic deformation of web plate and splitting
of concrete slab appeared in the loading stage.
3.2. Load-slip curves
Slips between the steel and the concrete occurred when
the load was applied. Since the two halves of the specimen
are completely the same, half of the jack force can be
taken as the applied load of one connector. The relative
Figure 5. Test setup.
Figure 6. Failure modes of specimens.
156 Qing-Tian Su et al. / International Journal of Steel Structures, 14(1), 151-164, 2014
Figure 7. Load-slip curves of all the specimens.
Structural Behaviour of Perforated Shear Connectors with Flange Heads in Composite Girders: An Experimental Approach 157
slip was obtained by the average of the relative
displacements recorded by the four LVDTs in each
specimen. The measured load-slip curves (P-S curves) of
PSCFH are shown in Fig. 7. Because plastic deformation
of PSCFH was happened in the later loading stage and the
later deformation is not significant in actual composite
beam, in this paper the maximum value of slip is taken
30 mm in the P-S curves. Table 2 summarizes the shear
capacity and characteristic slip of PSCFH. Pu is the
ultimate shear capacity and Su is the slip when the load P
reaches its peak.
As shown in Fig. 7, PSCFH behaves perfect load-slip
curves and the typical P-S curves consisted of an elastic
part (P≤0.6Pu~0.7Pu, where P represents shear load of the
PSCFH and Pu represents maximum shear force) and a
plastic part (P>0.6Pu~0.7Pu). In the elastic part, the slip
was very small, the curve was a straight line, and the
PSCFH showed large shear stiffness. While, in the plastic
part, the slip increased considerably despite the slowly
increasing load, and the PSCFH shear stiffness reduced
continuously. The shear strength, initial stiffness and
durability of the PSCFH are higher greatly than those of
conventional perfobond connector.
The P-S curves of specimen with cycle of loading/
unloading was very similar to that of other two specimens
with mono-loading, which indicates the shear performance
of PSCFH under cycle load is stable considerably.
4. Discussion
Comparison between the structural behaviors of
conventional perfobond connectors and PSCFH with the
same height and the same number of holes is shown in
Fig. 8, and it can be seen that the PSCFH exhibits a
higher bearing capacity and a more excellent ductility.
The structural behavior of the shear connectors in the
composite bridges depends mainly on the P-S curves of
the shear connectors at the interface between the top flange
of the steel beam and the concrete slab. The P-S relation,
usually found in push-out tests, depends on the types and
dimensions of connectors, the amount of transverse
reinforcement, and concrete strength. Thickness of the steel
plate of the connector tp, height of the connector hp, flange
length of the connector bp, flange number of the connector
Nf, and holes diameter on the web of the connector dh are
critical parameters in the design of PSCFH. The main
parameters that affect the P-S curves of the shear
connectors are now discussed in detail.
Table 2. Results of push-out tests
Specimen Pu Su Failure mode Specimen Pu Su Failure mode
TPS-1-1 1312 22.0 A,B,C TPS-8-3 1192 16.0 A,B,C
TPS-1-2 1288 23.0 A,B,C TPS-9-1 1364 23.0 A,B,C
TPS-1-3 1442 29.8 A,B,C TPS-9-2 1343 15.3 A,B,C
TPS-2-1 1373 20.0 A,B,C TPS-9-3 1344 17.1 A,B,C
TPS-2-2 1131 16.0 A,B,C TPS-10-1 1267 20.4 A,B,C
TPS-2-3 1305 17.0 A,B,C TPS-10-2 1289 32.7 A,B,C
TPS-3-1 1341 16.7 A,B,C TPS-10-3 1310 18.2 A,B,C
TPS-3-2 1377 13.7 A,B,C TPS-11-1 1140 17.9 A,B,D
TPS-3-3 1335 16.8 A,B,C TPS-11-2 1206 16.8 A,B,D
TPS-4-1 1055 24.6 A,B,D TPS-11-3 1271 17.3 A,B,D
TPS-4-2 1099 24.1 A,B,D TPS-12-1 1309 27.4 A,B,C
TPS-4-3 1114 27.3 A,B,D TPS-12-2 1331 23.8 A,B,C
TPS-5-1 1387 16.7 A,B,C TPS-12-3 1290 15.9 A,B,C
TPS-5-2 1525 21.0 A,B,C TPS-13-1 1167 10.8 A,B,C
TPS-5-3 1383 10.0 A,B,C TPS-13-2 1223 7.8 A,B,C
TPS-6-1 1411 26.2 A,B,C TPS-13-3 1358 16.4 A,B,C
TPS-6-2 1402 24.8 A,B,C TPS-14-1 1194 17.5 A,B,C
TPS-6-3 1182 17.4 A,B,C TPS-14-2 1095 15.3 A,B,C
TPS-7-1 1336 18.0 A,B,C TPS-14-3 1194 19.0 A,B,C
TPS-7-2 1349 20.8 A,B,C TPS-15-1 1381 38.0 B,C
TPS-7-3 1359 20.5 A,B,C TPS-15-2 1406 34.0 B,C
TPS-8-1 1293 33.7 A,B,C TPS-15-3 1402 18.0 B,C
TPS-8-2 1300 20.5 A,B,C
Note: Pu : Ultimate bearing capacity (unit: kN); Su : Slip between the connector and the concrete slab corresponding to Pu (unit:mm); Failure mode- A represents concrete slipping, B represents flange distortion, C represents web plastic deformation, Drepresents web fracture;
158 Qing-Tian Su et al. / International Journal of Steel Structures, 14(1), 151-164, 2014
Although the dimension and the material of three
specimens in each group were completely identical in
design, the slightly different testing results about P-S
curve of three specimens were appeared. This mainly
caused by the dimension error of specimen during the
manufacture process and experimental error of specimen
during the testing process and these errors were often
occurred in stud connector push-out test and in Perfobond
connector push-out test (Hu et al., 2006; Shim, 2004). In
the following content, in order to investigate the influence
of aforementioned parameters and eliminate the inevitable
errors, the loading values of the three specimens in a
group corresponding to the same slip value were averaged.
4.1. Effect of plate thickness
Figure 9 shows the P-S curves of the PSCFH with the
main variable being the plate thickness and all the other
variables being kept constant. The results showed increases
of the PSCFH bearing capacity with increasing the plate
thickness. In the variation of the thickness from 12 to 16
mm and from 12 to 20 mm, the bearing capacities of the
connector increase 23.7 percent and 31.9 percent,
respectively. Therefore, the ultimate bearing capacity of
PSCFH has close relationship with the thickness of the
steel plate. The ultimate bearing capacity increases
amplitude is not linear to the thickness increases amplitude,
due to the bearing capacity of the specimen was also
controlled by the splitting of the concrete slabs. So in
PSCFH increasing the plate thickness can improve the
bearing capacity properly, while when the thickness reach
to a certain value the bearing capacity will dominated by
the concrete strength.
4.2. Effect of the height of PSCFH
Figure 10 shows the P-S curves of the PSCFH with the
main variable being the connector height and all the other
variables being kept constant. Figure 10 shows that the
height of the connector in the range of 150~200 mm has
no obvious influence on the structural performance of
PSCFH when the applied load is less than 600 kN. When
the loads exceeded 800 kN the connector height has a
Figure 10. Effect of connector height.
Figure 9. Effect of plate thickness.
Figure 8. Comparison between conventional perfobondconnecters (PS) and PSCFH (TPS).
Structural Behaviour of Perforated Shear Connectors with Flange Heads in Composite Girders: An Experimental Approach 159
slight influence on the structural behavior of PSCFH. As
illustrated in Fig. 10, compared with the connector with
the height of 150 mm, the ultimate bearing capacities of
the connector with the height of 175 and 200 mm increase
6.06 percent and 6.38 percent respectively which shows
the bearing capacity varying of the connector with the
height changed from 175 to 200 mm is very slight.
4.3. Effect of the flange length of PSCFH
Figure 11 shows the P-S curves of the PSCFH with the
main variable being the flange length and all the other
variables being kept constant. As shown in Fig. 11, the P-
S curves of PSCFH with the length of flange 140, 180,
and 220 mm are close very much. The bearing capacity
increases 1.2 percent when the flange length changed
from 140 to 180 mm and the bearing capacity increase
1.4 percent when the flange length changed from 140 to
220 mm. So the flange length in the range of 140~220
mm has no obvious influence on the ultimate bearing
capacity of PSCFH. It also indicates that the flange length
of 140 mm could provide enough gripping force between
the steel and concrete. The minimum flange length which
can effect the bearing capacity of PSCFH need further
experiments to verified.
4.4. Effect of the flange number of PSCFH
Figure 12 shows the P-S curves of the PSCFH with the
main variable being the flange number and all the other
variables being kept constant. In all specimens the total
length of PSCFH was 300 mm being kept constant, so the
flange number is 3, 4 and 5 and the corresponding single
flange width is 100, 75, and 60 mm respectively. As
shown in Fig. 12, the bearing capacity of PSCFH is
growing with increasing the flange number in a certain
extant. The bearing capacity improves 6.7 percent when
the flange number changed from 3 to 4 and the bearing
capacity improve 7.1 percent when the flange number
changed from 3 to 5. The main reason is that the increase
of flange number could enhance the connecting area
between steel and concrete.
4.5. Effect of the hole diameter of PSCFH
Figure 13 shows the P-S curves of the PSCFH with the
main variable being the diameter of holes on the web of
the connector and all the other variables being kept
constant. As shown in Fig. 13, the holes diameter on the
web affects the bearing capacity of PSCFH significantly.
With the variation of the diameter of rib hole from 50 to 60
mm, the ultimate bearing capacity increases correspondingly,
while in the case of the variation from 60 to 75 mm the
ultimate bearing capacity decreases on the contrary. The
main reasons exist that the increase of the diameter of
hole can improve size of the concrete dowel to enhance
the shear capacity of the connector; on the other hand, the
Figure 12. Effect of flange number.
Figure 11. Effect of flange length.
160 Qing-Tian Su et al. / International Journal of Steel Structures, 14(1), 151-164, 2014
increase of the hole weakens the effective web area of
connector to decrease the bearing capacity of the connector.
Therefore, under the premise that there is no damage
caused by web, increasing the hole diameter can be
appropriate to improve the bearing capacity of the connector,
on the contrary, when the web destroy controlled conditions,
to increase the hole diameter will reduce the bearing
capacity of the connector.
4.6. Effect of transverse reinforcement
Figure 14 shows the P-S curves of the PSCFH with the
main variable being the diameter of transverse reinforcement
and all the other variables being kept constant. Diameters
of reinforcing bars through the holes on the web plate of
the connector in group TPS-13, TPS-12 and TPS-1 were
15.08, 17.28, and 19.95 mm respectively. As shown in
Fig. 14, the diameter of transverse reinforcement affects
the mechanical behavior of PSCFH in a certain extant. In
the variation of the diameter of reinforcing bar from
15.08 to 17.28 mm and from 15.08 to 19.95 mm, the
ultimate bearing capacity increases 4.8 percent and 7.8
percent respectively. The bearing capacity of specimen is
enhanced with the increasing the diameter of transverse
reinforcing bar.
Figure 14. Effect of transverse reinforcement.
Figure 13. Effect of rib hole diameter.
Figure 15. Effect of concrete strength.
Structural Behaviour of Perforated Shear Connectors with Flange Heads in Composite Girders: An Experimental Approach 161
4.7. Effect of concrete strength
Figure 15 shows the P-S curves of the PSCFH with the
main variable being the concrete strength and all the other
variables being kept constant. Cubic compressive strength
of the concrete in group TPS-14, TPS-1 and TPS-15 were
36.9, 53.1, and 59.3 MPa respectively. As illustrated in
Fig. 15, the influence of concrete strength on the ultimate
bearing capacity is significant, and the bearing capacity of
specimen increases with increasing the concrete strength.
In the variation of the concrete strength from 37 to 53
MPa and from 37 to 59 MPa, the increase amplitude of
ultimate bearing capacities are about 16 percent and 20.3
percent respectively. As mentioned in the above paragraph,
the failure mode of many specimens is the splitting of the
concrete slabs, so the increase of the concrete strength
can efficiently improve the bearing capacity of PSCFH.
On the other hand, when the failure mode of the specimen
is controlled by steel material, improving the concrete
strength can not make the bearing capacity of the
specimen grow.
5. Shear Bearing Capacity
5.1. Shear bearing capacity of Perfobond
The previous researchers concluded that the shear
resistance of Perfobond connectors was consisted of three
mainly contributions (Hosaka et al., 2002; Oguejiofor and
Hosain, 1994): the bearing concrete resistance at the
connector face, the steel reinforcement bars in the concrete
slab, and the concrete cylinders in shear. Most certainly
there is an interaction between these resistance components,
and an analytical expression to predict the global resistance
surely should not be based on the linear sum of these
contributions. In fact it should be centered on reduction
factors affecting each other contribution, to take into account
the interaction. According to this rule, the ultimate shear
capacity for Perfobond connectors has been proposed
in(Hosaka, 2002), (Oguejiofor and Hosain, 1994)and
(Oguejiofor and Hosain, 1997) respectively as follows.
(1)
(2)
(3)
where dh is holes diameter on the web of the connector
(mm), dpr is diameter of reinforcing bars (mm), fc is axial
compressive strength of concrete obtained from cylinder
specimens (MPa), fy is reinforcement yield strength
(MPa), hp is height of the connector (mm), tp is thickness
of the steel plate of the connector (mm), Ar is the cross
section area of reinforcing bars through holes (mm2), Nh
is number of hole in the web, Bt is the width of the beam
flange of the steel profile (mm), Lt is the length of the
contract area between the steel profile and the concrete
slab (mm).
Learned from the three equations, bearing capacity of
Perfobond connector is mainly determined by the size of
the connector, the material strength of the concrete and
the reinforcing bars, which is corresponding with the test
results by Ahn (2008). The common failure mode of
Perfobond connector is the failure of the concrete without
obvious plastic deformation on the steel plate.
5.2. Shear bearing capacity of PSCFH
Chemical bonding and friction (cohesive behavior)
existed at the interface between the steel flange and the
concrete slab, and this effect takes a great role during the
early stage of push-out test. However, when the relative
slip between steel and concrete appears, the effect of
chemical bonding and friction becomes very tiny. Therefore,
the bonding and friction force can be neglected in the
determination of the ultimate bearing capacity of the
connector and can be considered as a safety reservation
for actual project. All specimens tested in this paper,
grease is smeared the contact face of I-shape beam flange
to eliminate the chemical bonding and friction. Based on
the configuration feature of PSCFH, the load transferring
route of PSCFH can be shown in Fig. 16. For PSCFH in
composite girder, longitudinal shear force is mainly carried
by the following four parts: (1) concrete dowel in the
holes on the web plate of the connector, (2) reinforcement
bars through the holes, (3) concrete on the flange, and (4)
concrete on the T-shaped end face of the connector. The
vertical uplift force is mainly borne by the following three
parts: (5) concrete dowel in the holes, (6) reinforcing bars
through the holes, and (7) flange of the connector. Compared
with Perfobond connector, PSCFH has additional separate
flanges embedded in concrete, which increases the efficient
interaction between the steel and concrete. Therefore, the
load bearing capacity of PSCFH is higher than that of
conventional Perfobond connector.
According to the test results, action of the concrete
between the flange heads and action of the concrete on
the end of the connector can be seem as same contribute
to bearing capacity of PSCFH. In the analysis of the
ultimate capacity of the connector, linear multivariate
regression analysis method was adopted to obtain the
calculation formula of PSCFH with reinforcing bar through
Qu 1.45 dh2dpr
2–( )fc dpr
2fy+[ ]= 26100–
Qu 4.5 hp tp fc⋅ ⋅ ⋅= 0.91 Ar fy⋅ ⋅ 3.31 Nh dh2
fc⋅ ⋅ ⋅+ +
Qu 0.75 tp hp fc⋅ ⋅ ⋅= 0.9 Ar fy⋅ ⋅ 1.304 Nh dh2
fc⋅ ⋅ ⋅+ +
0.41 Bt Lt⋅ ⋅+
Figure 16. Load bearing mechanism of PSCFH.
162 Qing-Tian Su et al. / International Journal of Steel Structures, 14(1), 151-164, 2014
the hole. Integrated variable x1, x2 and x3 represent the
action of concrete dowel in rib hole, the action of reinforcing
bar through the rib hole and the action of compression
concrete bearing capacity respectively. The expressions
of variable are:
(4)
(5)
(6)
where Nh is number of hole in the web, dh is hole
diameter of web, dpr is diameter of reinforcing bars, fcu is
concrete cubic strength, fy is reinforcement yield strength,
B is total flange length, bp is connector height.
The expression for calculating the ultimate bearing
capacity of PSCFH can be given as below,
(7)
k1, k2 and k3 are the critical parameters to be
determined. Based on the experimental results and
regression analysis of the ultimate capacity in Table 2 of
39 specimens in 13 groups without the failure mode of
steel rupture, the coefficients can be obtained, k1=0.9637,
k2=1.2741 and k3=0.8682. In the regression analysis, the
standard deviation is 87 kN, which is satisfied.
Therefore, expression of the equation for ultimate
bearing capacity of PSCFH is:
(8)
or
(9)
where Ac is the cross section area of the concrete dowel
equivalent to the difference of cross section area between
rib holes and reinforcing bars; Apr is the cross section area
of reinforcing bars through holes.
In group TPS-4 with thinner thickness and group TPS-
11 with large rib hole in the web, the failure mode is the
fracture of the steel plate, which is different from the
failure modes of other specimens. Therefore, the equation
of ultimate capacity for PSCFH with the failure mode of
steel fracture is proposed as follows:
(10)
where Aw is shear area of the rib web, which is taken as
the area of center section of rib holes conservatively
, tp is the thickness of PSCFH and lp is
the total length of PSCFH; γ is the ratio of the yield
strength to the ultimate strength of the steel of rib plate,
in this paper γ =541 MPa/347 MPa=1.559. Based on the
regression analysis of 6 specimen in group TPS-4 and
group TPS-11, the factor α is 0.9295.
Therefore, the minimum value of Eq. (9) and Eq. (10)
can be adopted to estimate the ultimate bearing capacity
of PSCFH.
(11)
Comparison of ultimate bearing capacity of the 15
x1
2Nhπ
4--- dh
2dpr
2–( )fcu=
x2
2Nhπ
4---dpr
2 fy
3
------=
x3
1
2---Bhp fcu=
Qu k1x1
⋅= k2x2
⋅ k3x3
⋅+ +
Qu 1,0.9637= 2Nh
π
4--- Dh
2dpr
2–( )fcu× 1.2741+
2Nhπ
4---dpr
2 fy
3
------ 0.86821
2---Bhp fcu×+×
Qu 1,1.9274Ac fcu= 1.4712Apr fy 0.4341bf hp fcu+ +
Qu 2,αAwγ fy=
Aw tp lp Nh– dh⋅( )=
Qu min Qu 1,Qu 2,,( )=
Table 3. Ultimate bearing capacity of specimens (unit: kN)
SpecimenTest
Cal. (2) (2)/(1)Coupon 1 Coupon 2 Coupon 3 Average (1)
TPS-1 1312 1288 1442 1347 1361 1.01
TPS-2 1373 1131 1305 1270 1316 1.04
TPS-3 1341 1377 1335 1351 1407 1.04
TPS-4 1055 1099 1114 1089 1081 0.99
TPS-5 1387 1525 1383 1432 1361 0.95
TPS-6 1411 1402 1182 1331 1290 0.97
TPS-7 1336 1349 1359 1349 1432 1.06
TPS-8 1293 1300 1192 1262 1361 1.08
TPS-9 1364 1343 1344 1351 1361 1.01
TPS-10 1267 1289 1310 1289 1184 0.92
TPS-11 1140 1206 1271 1206 1201 1.00
TPS-12 1309 1331 1290 1310 1222 0.93
TPS-13 1167 1223 1358 1250 1174 0.94
TPS-14 1194 1095 1194 1161 1106 0.95
TPS-15 1381 1406 1402 1397 1441 1.03
Structural Behaviour of Perforated Shear Connectors with Flange Heads in Composite Girders: An Experimental Approach 163
groups of specimens between the experimental results
and predicted results is listed in Table 3. The comparisons
show that the estimation based on the proposed Eq.(9)
agrees well with the test results.
6. Conclusions
Forty-five push-out tests of PSCFH were carried out
and the results obtained allow the following conclusions
to be drawn:
(1) Structural behaviors of PSCFH during the full
loading process are obtained and the failure modes are
investigated by quantities of push-out tests. The test results
indicate that PSCFH behaves higher shear capacity and
better ductility compared with Perfobond connector.
(2) Influences of various parameters on the bearing
capacity of PSCFH were studied. It can be concluded that
thickness of the steel plate, diameter of the hole on the
web and concrete strength have great influences on the
failure mode and bearing capacity of PSCFH connector.
(3) Calculation expressions for the ultimate bearing
capacity of PSCFH were proposed and the calculation
results agree well with the test results. It is expected that
the results presented in this paper would be useful as
references for the further research and the design of
PSCFH in composite structures.
Acknowledgments
The authors are indebted to WANG Rui for assistance
with the conduction of the experiments. This research is
sponsored by Key Project of Chinese National Programs
for Fundamental Research and Development (973 Program,
Grant No: 2013CB036303). These supports are gratefully
acknowledged.
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