structural behaviour of perforated shear connectors with flange heads in composite girders: an...

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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


Figure 4. Details of the test specimens (unit: mm).


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.


Figure 7. Load-slip curves of all the specimens.


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;


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


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).


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


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


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


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.


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


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.


4.7. Effect of concrete strength


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.


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


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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