Experimental shear resistance evaluation of Y-type perfobond rib shear connector

Journal of Constructional Steel Research 82 (2013) 1–18

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Journal of Constructional Steel Research

Experimental shear resistance evaluation of Y-type perfobond rib shear connector Sang-Hyo Kim a, Kyu-Tae Choi b, Se-Jun Park c, Seung-Min Park d, Chi-Young Jung e,⁎ a

Department of Civil and Environmental Engineering, Yonsei University, Seoul, 120-749, Republic of Korea Yooho Development & Construction Co. Ltd., Seoul, 135-907, Republic of Korea Department of Civil and Environmental Engineering, Yonsei University, Seoul, 120-749, Republic of Korea d Hyundai Engineering & Construction, Seoul, 110-920, Republic of Korea e Department of Civil and Environmental Engineering, Yonsei University, Seoul, 120-749, Republic of Korea b c

a r t i c l e

i n f o

Article history: Received 9 May 2012 Accepted 1 December 2012 Available online 29 December 2012 Keywords: Y-type perfobond rib shear connector Shear connection Push-out test Shear resistance equation

a b s t r a c t Recently due to the increase in the construction of the steel–concrete composite structures, researches on shear connector which is capable of composite behavior of two members have been widely studied. This study evaluated the behavior of Y-type perfobond rib shear connector which is superior in shear resistance and ductility than conventional perfobond rib shear connector. Also, it suggested a shear resistance equation based on the push-out test. Firstly, various types of the proposed Y-type perfobond rib shear connectors have been examined to evaluate the effect on design variables such as strength of concrete, transverse rebar, thickness of rib, and Y-shape angle. As a result, the experiment showed that the higher the concrete strength, the shear resistance increased, while ductility decreased. In addition, transverse rebar significantly impacted both shear resistance and ductility to increase. Moreover, as thickness of ribs increased, shear resistance increased and ductility decreased. It was also proven that Y-shape angle has an effect on shear resistance and ductility to grow. Furthermore, it was indicated that Y-type perfobond rib shear connector has higher shear resistance and ductility than the conventional perfobond rib shear connector by comparing and estimating the experimental results. Lastly, the effect of bearing resistance, transverse rebar, dowel resistance by holes, and dowel resistance by Y-shape ribs on shear resistance was estimated by regression analysis. Through the result, the shear resistance equation was suggested to predict shear resistance of Y-type perfobond shear connector. © 2012 Elsevier Ltd. All rights reserved.

1. Introduction Steel and concrete composite structures are widely used in building and bridge structures. It has been proven that composite structure has economical and structurally efficiency by combining the advantages of both concrete and steel materials. Shear connector is required for the composite structures to prevent vertical and horizontal separation of steel and concrete. Also it can ensure composite behavior by transferring force between steel and concrete. A considerable amount of research has been carried out to study the behavior of different types of shear connectors in composite structures to improve the composite behavior efficiency and applicability. Shear connectors can be divided into ductile and rigid shear connector. Ductile shear connectors such as stud shear connector show ductile fracture behavior. It has many advantages like an identified ⁎ Corresponding author. Tel.: +82 2 2123 2804; fax: +82 2 313 2804. E-mail addresses: [email protected] (S.-H. Kim), [email protected] (K.-T. Choi), [email protected] (S.-J. Park), [email protected] (S.-M. Park), [email protected] (C.-Y. Jung). 0143-974X/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jcsr.2012.12.001

structural mechanism, a simple design process, and ease of calculation. However, stud shear connectors have some disadvantages. As a large number of stud shear connectors are welded, construction and welding quality control are difficult and it has fatigue problem at weld collar [1,2]. Also it is very weak to pull-out forces due to the geometric characteristics of the stud. To solve the problems of the stud shear connector, which is used most widely today, a German design company developed in 1987 perfobond rib shear connector that has received worldwide attention because of its high shear resistance and ease of manufacture. Rigid shear connectors such as perfobond rib shear connector are more applicable in a narrow space than ductile shear connectors because it has high shear resistance. However the rigid shear connector has a brittle fracture behavior characteristic which is caused by fracture of concrete. It is because if shear connector has high enough shear resistance, the concrete fracture is a dominant failure mechanism [3–5]. For this reason Eurocode-4 defines minimum slip capacity to ensure the ductility of shear connectors and prevent brittle failure behavior of structures [6]. As the types of composite structures become more varied, the mechanical behavior of the shear connection gets more complex, the design and construction get more

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constrained, and higher workability on the construction site is required [7–10]. Thus, a new type of shear connector which has advantage of both ductile shear connector and rigid shear connector is needed. In this study, Y-type perfobond rib shear connector is proposed with the aim of improving ductility of the perfobond rib shear connector and workability of the transverse rebars which placed in dowel holes. Behavioral characteristics of the newly proposed and conventional perfobond rib shear connectors were compared by evaluating the shear resistance of the proposed Y-type perfobond rib shear connector and estimating behavioral differences caused by certain variables. In this study, evaluation was carried out on design variables such as the strength of concrete (fck = 30, 40 MPa), the presence of transverse rebars, the angle of the Y-shape (Y-shape angle = 0, 60°), and the thickness of rib (rib thickness= 8, 10 mm). Experiments performed in this study are the push-out test defined in the Eurocode-4 and behavior was evaluated based on the relationship between the load and slip obtained from the tests. In addition, based on the results of the push-out tests, a shear resistance equation is proposed for the Y-type perfobond rib shear connector by regression analysis.

(a) Bearing resistance

2. Y-type perfobond rib shear connector 2.1. Conventional perfobond rib shear connector A perfobond rib shear connector is a steel plate with multiple holes. It is welded upright at the center of the top flange of the steel girder top surface, in the longitudinal direction of the girder. Then concrete is poured in the floor slab and the hole becomes filled with concrete which forms concrete dowel and resists the horizontal shear force and vertical separation force acting between the steel and concrete. Fig. 1 shows shear resistance characteristics of a perfobond rib shear connector, which are important variables affecting shear resistance. As shown in Fig. 1, the shear resistance of a perfobond rib shear connector is determined by (a) bearing resistance at the tip of the concrete slab; (b) shear resistance of the rebars penetrating the hole; and (c) horizontal and (d) vertical shear resistance, both caused by dowel action of the hall installed in the perfobond rib [3]. Oguejiofor and Hosain performed push-out tests with perfobond ribs and proposed two regression analysis equations for predicting the shear resistance of perfobond-rib shear connectors. The first equation, Eq. (1), overestimates the shear resistance of a perfobond rib because it over-evaluates the contribution of end-bearing resistance as well as the contribution of the rebar in the concrete slab. The second equation, Eq. (2), which considers the height and thickness of the rib, was proposed by Oguejiofor and Hosain after the numerical analysis of the push-out tests [3,11]. qffiffiffiffiffiffi qffiffiffiffiffiffi 2 Q ¼ 0:59⋅b⋅h⋅ f ck þ 1:233⋅Atr ⋅f y þ 2:87⋅n⋅π⋅d f ck

2

Q ¼ 4:5⋅h⋅t⋅f ck þ 0:91⋅Atr ⋅f y þ 3:31⋅n⋅π⋅d

qffiffiffiffiffiffi f ck

(b) Longitudinal resistance by transverse rebar

(c) Longitudinal resistance by concrete dowel

ð1Þ

ð2Þ

where Q (N) is the shear resistance at the shear connector, fck (MPa) is the compressive concrete strength, Acc (mm 2) is the shear area of the concrete slab, Atr (mm 2) is the area of the transverse rebars in the rib holes, fy (MPa) is the yield strength of the transverse rebar, n is the number of rib holes, d (mm) is the diameter of the rib hole, h (mm) is the height of the rib, and t (mm) is the thickness of the rib. Sara and Bahram proposed another equation, Eq. (3), for predicting the shear resistance of perfobond-rib shear connectors. The equation

(d) Vertical resistance by concrete dowel Fig. 1. Shear resistance characteristics of perfobond rib shear connector.

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included the effect of the chemical bond between the steel and the concrete face in the equations of Oguejiofor and Hosain [3,11,12]. Q ¼ 0:747⋅b⋅hecs þ 0:9⋅Atr ⋅f y

qffiffiffiffiffiffi qffiffiffiffiffiffi 2 f ck þ 0:413⋅bf ⋅Lc þ 1:66⋅n⋅π f ck ðd=2Þ ð3Þ

where b (mm) is the thickness of the concrete slab, hecs (mm) is the distance between the end of the perfobond rib and the end of the concrete slab, bf (mm) is the width of the steel beam flange, and Lc (mm) is the contact length between the concrete slab and the steel beam flange. Veríssimo et al. proposed a modified shear resistance equation, Eq. (4), based on that of Oguejiofor and Hosain [13,14].

h 2 Q ¼ 4:04⋅ ⋅h⋅t⋅f ck þ 2:37⋅n⋅d b 6  10 ðAtr =Acc Þ

qffiffiffiffiffiffi qffiffiffiffiffiffi f ck þ 0:16⋅Acc f ck þ 31:85 ð4Þ

3

where Acc (mm2) is the longitudinal concrete shear area per connector. Ahn et al. (2010) studied shear resistance of the perfobond rib shear connector depending on concrete strength and rib arrangement and also suggested shear resistance equations for single perfobond shear connector (Eq. (5)) and double perfobond shear connectors (Eq. (6)) [15]. 2

qffiffiffiffiffiffi f ck

ð5Þ

2

qffiffiffiffiffiffi f ck

ð6Þ

Q ¼ 3:14⋅h⋅t⋅f ck þ 1:21⋅Atr ⋅f y þ 3:79⋅n⋅π⋅ðd=2Þ Q ¼ 2:76⋅h⋅t⋅f ck þ 1:06⋅Atr ⋅f y þ 3:32⋅n⋅π⋅ðd=2Þ

Kim et al. [16] suggested corrugated perfobond rib shear connector for corrugated web PSC girder system. Push-out tests were conducted to evaluated shear resistance of the corrugated perfobond rib shear connector by conducting experimental evaluations. Eq. (7) was

(a) Bearing resistance

(d) Concrete dowel resistance by Y-shape rib

(b) Longitudinal resistance by transverse rebar

(e) Vertical resistance by Y-shaperib

(c) Concrete dowel resistance by holes Fig. 2. Mechanical characteristics of Y-type perfobond rib shear connector.

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proposed to consider additional concrete bearing at contact surfaces of corrugated rib.

qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi Q ¼ Af 1 ⋅ Af 2 =Af 1 ⋅f ck =γ c

ð7Þ

where Af1 is the front bearing area of the shear connector, Af2 is the front bearing area of the shear connector amplified by the inclination rate, γc is the safety factor. 2.2. Y-type perfobond rib shear connector The Y-type perfobond rib shear connector is a new type of perfobond rib shear connector proposed by this study to complement the structural characteristics and workability of conventional perfobond rib shear connectors. To manufacture the Y-type perfobond rib shear connector, the top of the rib of a conventional perfobond rib shear connector is bent to Y-shape, and to replace the conventional circular hole where the transverse rebars are placed for dowel resistance, the rib is cut into a semicircle and the top of the rib is removed so that it would provide sufficient space for workability. Fig. 2 describes the mechanical characteristics of the Y-type perfobond rib shear connector. The Y-type perfobond rib shear connector has the following advantages. First the workability of the transverse rebars is improved as shown in Fig. 3. Placing transverse rebars through the hole of perfobond rib shear connectors is difficult when the hole is closed. On the contrary, each bend of the Y-type perfobond rib shear connector is not closed, making it easier to place a rebar mesh, manufactured in a factory or at the construction site, vertically through the shear connector. This improves workability at the construction site. Second, the Y-type perfobond rib shear connector shows ductile fracture behavior. One of the disadvantages of conventional perfobond rib shear connectors is that the shear connection shows brittle fracture after ultimate load. Eurocode-4 requires the slip capacity of the shear connection to be at least 6 mm so that the shear connection can have some degree of ductility. This indicates that ductile behavior of the shear connection must be secured to ensure the safety of the structure. With that regard, the Y-type perfobond rib shear connector demonstrates sufficient ductile behavior made possible by the individual Y-shaped bend part. As the area where concrete and steel are attached has increased, stress concentration is prevented, and as the effective area of the concrete part has increased, the failure of the concrete part is delayed longer than the conventional perfobond rib shear connector. In addition, the ratio of length to height at each Y-shaped bend part is smaller than the conventional perfobond rib shear connector and the difference of the strength of concrete and rib are relatively smaller than the conventional perfobond rib shear connector. It causes that strength ratio between shear connector and concrete is balanced. Therefore, the concrete in the Y-type perfobond rib shear connector is less dominant for fracture behavior characteristic than the conventional perfobond rib shear connector. Thus, unlike the conventional perfobond rib for which the fracture behavior of the shear connection is determined by the brittle fracture of the concrete, Y-type perfobond rib shear connectors have the balance between the concrete fracture and the individual bend part and thus can prevent brittle fracture of the shear connection. Third, the resistance to vertical separation force is excellent. The conventional perfobond rib shear connectors are composed in a straight form and thus have a small area of resistance in the vertical direction and the resisting performance against vertical separation force is limited. Due to this characteristic, the conventional perfobond rib shear connectors are not suitable to be applied to structures with hogging moment. However, the Y-type perfobond rib shear connector

(a) Stud

(b) Conventional perfobond rib

(c) Y-type perfobond rib Fig. 3. Insert direction of transverse rebars.

can secure resisting performance against vertical separation force because of the individual bend part bent at a particular angle as Y-shape. The proposed Y-type perfobond rib shear connector has a wide range of applicability. Fig. 4 shows an example. Like the conventional perfobond rib shear connector, the Y-type perfobond rib shear connector can be welded to the H-beam flanges (Fig. 4(a)). In addition, by extending the web of steel, the Y-type perfobond rib shear connector can be manufactured without any welded connection between the web and shear connectors (see Fig. 4(b)). These various methods enable application to a variety of structure formats as described in Fig. 4(c).

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(a) Welded on a flange

5

(b) Extended from a web

Steel-concrete hybrid box

Steel-concrete hybrid girder

(c) Practical application examples Fig. 4. Application of Y-type perfobond rib shear connector.

3. Shear resistance of Y-type perfobond rib shear connector 3.1. Details of experiments 3.1.1. Specimens In this study, various design variables which can affect shear resistance such as concrete strength, transverse rebar, rib thickness and Y-shape angle were set as variables to evaluate the shear resistance of the Y-type perfobond rib shear connector. The effect of the variables on the shear resistance and the behavioral differences with conventional perfobond rib shear connectors were assessed through push-out experiments presented by Eurocod-4. The range of each variable applied to the specimens was determined in accordance with Korea Highway Bridge Specifications (KHBS) [17]. First, 40 MPa and 30 MPa of concrete compressive strength were used to see the effect of the concrete strength, as they are generally applied to a girder structure. Second, the spacing of the transverse rebars was made less than 600 mm in accordance with the KHBS for the interval of concrete girders and slabs. To evaluate the effect of the number of transverse rebars, evaluation was conducted for both cases with and without the transverse rebars. Third, decisions on the Y-shaped angle were made based on the spacing standards for main reinforcement proposed by KHBS. According to the standards, the spacing of the main rebars should not exceed 400 mm. To make sure that the construction of the Y-type perfobond rib shear connector is not interfered with the main rebars, the angle of the Y-shape was set for 60° in this study. Evaluation was also conducted on a case where the angle of the Y-shape is 0° to consider cases with no bending. Fourth, 8 mm and 10 mm rib thickness were applied, considering the minimum requirement for the structural steel thickness is 6 mm. Of the two, 10 mm was selected to be a standard variable. Finally, in the tests on the conventional perfobond rib shear connector, the strength of concrete, transverse rebars, and rib thickness were applied in the same way as in the tests on the Y-type perfobond rib shear connector, so that changes in behavior could be observed

under the same conditions. Table 1 summarizes the conditions of variables for each specimen. For each variable condition, three specimens with the same specifications were manufactured to make sure the test results are reliable. Fig. 5 shows the details of each specimen. 3.1.2. Fabrication of specimens and material properties All specimens were fabricated in advance in a manufacturing plant to maintain consistency in materials and shapes. Fabrication processes of the specimens are as follows. First the rebar mesh was assembled. Second, shear connectors are welded to the beams. Third, the assembled rebar mesh and transverse rebars are placed on the beams. For the transverse rebar 16 mm-diameter rebars (fy = 400 MPa) were used. A 70 mm-long styrofoam was attached at the bottom end of the rib of the shear connector to prevent the concrete from pouring in. This was done to reflect the fact that concrete bearing resistance would not occur except in the dowel hole and the bending part of the Y-shape because the Y-type perfobond rib shear connectors will be placed continuously without any break. Also, to remove the adhesive force caused by the chemical bonding between the concrete and steel rib, grease was applied to the steel rib before pouring concrete. Styrofoam was installed at the bottom end in the opposite direction of the applied load of the steel rib in order to prevent concrete bearing resistance in all parts except in the Y-shape and dowel hole. To maintain consistent strength in the top and bottom part of the concrete slab, concrete was poured while the specimen was held horizontally. After the concrete was completely cured, the specimens on the right and the left were held upright and the center of the beam was welded. Fig. 6 shows fabrication processes of specimen The concrete compressive strength and steel tensile strength were performed to check quality of materials. For concrete, a cylinder specimen was manufactured using a cylinder of 100 mm in diameter and 200 mm in height. A total of 21 cylinder specimens were manufactured for 40 MPa concrete, and 12 for 30 MPa concrete. Cylinder specimens were cured under the same conditions as the specimens. Evaluation of concrete compressive strength was conducted right before the

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Table 1 Variations of specimens. Variations

Concrete strength (fck, MPa)

Number of transverse rebar

Y-shape angle (°)

Rib thickness (mm)

Number of specimens

Y-type perfobond rib (Representative) Y-type perfobond rib (fck = 30) Y-type perfobond rib (Rib thickness = 8) Y-type perfobond rib (Rebar = 0) Y-type perfobond rib (Y-shape angle = 0) Conventional perfobond

40

4

60

10

3

30

4

60

10

3

40

4

60

8

3

40

0

60

10

3

40

4

0

10

3

40

4

0

10

3

Y-type perfobond (1) Representative, 2) fck = 30, 3) Rib thickness = 8)

5) Y-type perfobond (Y-shape angle = 0)

concrete age reaches 28th day and the push-out tests. Table 2 shows the average value of the results of concrete compressive strength tests. Tensile strength evaluation was conducted on the SS400 steel used in the manufacture of the specimens. According to KHBS the yield point of the shear connectors (0.2% strength) should be 240 MPa or more, tensile strength should be 410 to 560 MPa, and the coefficient of expansion should be 20% or more [17]. Table 3 shows the results of the inspections of the tensile strength, which indicates that the steel applied in this study is suitable to be a specimen of shear connectors. 3.1.3. Push-out test In this study, the shear resistance of the Y-type perfobond rib shear connector and the behavioral characteristics depending on each variable will be analyzed based on the results of push-out tests proposed by Eurocode-4. For loading, 2500 kN actuator was used. To measure the relative slip between the concrete and steel, L-shaped angle was attached at 350 mm below the top of the concrete slab and four 50 mm LVDTs were installed. Loading was

4) Y-type perfobond (Transverse rebar = 0)

6) Conventional perfobond

conducted by controlling the displacement. The speed of the increase in the displacement was controlled according to the methods proposed by Eurocode-4 to prevent the failure of the specimen in less than 15 min [6]. The speed of the displacement increase was controlled at 0.05 mm/s until the load becomes 500 kN, and after that it was maintained at 0.02 mm/s. The development of the surface cracks during the loading was observed at each level of loading. The test was finished when the load decreased 20% from its ultimate load. Fig. 7 shows the test set-up of the push-out tests. Test results were evaluated based on the results of the relative displacement caused by loading. Fig. 8 explains the criteria of result evaluation used in this study. The concepts of slip capacity (δu) and characteristic load value (PRK) presented by Eurocode-4 were used in this study. However, it is difficult to use conventional PRK and δu to evaluate the initial stiffness and ductile behavior that change in a variety of Y-type perfobond rib shear connectors. Thus, this study defines the initial relative displacement (δ90) based on PRK, and δu/δ90 was compared. δu/δ90 refers to the ratio of slip capacity to the initial relative displacement. The larger the ratio, the bigger the ductility of the shear

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connector compared to the initial stiffness. Each variable for the Y-type perfobond rib shear connector and the ratio of ductile section to the initial stiffness and overall displacement of the conventional perfobond rib shear connector were compared. 3.2. Test results and comparisons Push-out tests were conducted to evaluate the shear resistance, slip capacity and ductile behavior of the Y-type perfobond rib shear

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connector. The behavior of the standard specimen of the Y-type perfobond rib shear connector is as follows. The standard specimen of the Y-type perfobond rib shear connector was composed of concrete with 40 MPa strength, four transverse rebars, 60° Y-shaped angle, and 10 mm-thick ribs. Fig. 9 describes the relationship between load and relative slip of three representative specimens with the same specifications. The average ultimate load of the three specimens was 1803.3 kN. Differences in the test results of each specimen were less than 10%, proving the validity of the test results. The Eurocode-4

Fig. 5. Layout of specimens.

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Fig. 5 (continued).

requires the ductile behavior of the shear connector to be at least 6 mm of δuk = 0.9× δu. Thus, the Y-type perfobond rib shear connector proposed by this study satisfies such requirement. δu/δ90 was 8.5 on average. Table 4 is results of push-out tests. Table 4 describes the relationship between load and relative slip, characteristic load, and characteristic relative slip results of all of specimens. As shown in Fig. 9 and Table 5, the three specimens show similar behavior. Of the three, the Y-type perfobond (Representative)-03 shows results closest

to the average. Thus, the Y-type perfobond (Representative)-03 is used as the representative specimen for comparison for each variable. When comparing the test results, the average value of the three specimens was used. 3.2.1. Results of concrete strength variation specimens To evaluate the effect of the concrete strength on the behavior of the Y-type perfobond rib shear connector, three specimens with

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Fig. 5 (continued).

30 MPa concrete strength were manufactured and push-out tests were conducted. Test results were compared to the representative specimen (fck = 40 MPa). Fig. 10 shows test results of the three specimens with 30 MPa concrete strength (Y-type perfobond (fck = 30)– Nos.1, 2, 3). The average ultimate load of the three specimens was 1671.9 kN. Differences in the test results of each specimen were about 3%, meaning the test results were valid. δu/δ90 was 11.4 on average.

In Fig. 11 and Table 5, test results were compared between Y-type perfobond (Representative, fck = 40) and Y-type perfobond (fck = 30). As shown in the comparison, when the concrete strength falls from 40 MPa to 30 MPa, the shear resistance of the specimen drops about 8% and the initial relative displacement (δ90) decreases 15%. Therefore, the shear resistance and initial stiffness of the Y-type perfobond rib shear connector change in proportion to concrete strength. However, the δu of the Y-type perfobond (fck = 30) was 15% higher,

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(a) Assembly of rebars

(b) Formwork

(c) Applying grease to steel rib

(d) Styrofoam installation

(e) Pouring concrete

(f) Compaction of concrete

(g) Removal of form

(h) Specimen completed

Fig. 6. Fabrication processes of specimens.

indicating that it is in inverse proportion to concrete strength. Also the δu/δ90 of the Y-type perfobond (fck = 30) was 34% higher. This indicated that the ductility of the Y-type perfobond rib shear connector

Table 3 Results of steel tensile strength test.

Table 2 Results of concrete cylinder compressive strength. Evaluation time

28-day strength Before push-out test

changes in inverse proportion to the concrete strength. It appears that such fracture behavior has been caused due to the characteristics of concrete—the stronger the concrete is, the lower the strain capacity.

Specimen

Yield strength (MPa)

Ultimate strength (MPa)

Elongation (%)

Young's modulus (MPa)

S1 S2 S3 Average

356 349 352 352.3

440 418 427 428.3

33 35 33 33.6

2.13Exp + 5 2.13Exp + 5 2.13Exp + 5 2.13Exp + 5

Compressive strength (MPa) fck = 30.0

fck = 40.0

29.6 30.4

40.4 42.2

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11

2000 1800 1600

Load(kN)

1400 1200 1000 800 600 400

Y-type (Representative)-1 Y-type (Representative)-2 Y-type (Representative)-3

200 0

0

5

10

15

20

25

30

35

40

45

50

Relative slip(mm) Fig. 9. Load-relative slip relationships of representative specimens.

Fig. 7. Test set-up of push-out test.

3.2.2. Results of transverse rebar variation specimens The shear resistance and ductility were estimated based on the presence of the transverse rebar. Test results were compared with the representative specimen (rebar= 4). Fig. 12 shows the test results of the three specimens with no transverse rebar (Y-type(Rebar= 0)–1, 2, 3). The average ultimate load of the three specimens was 1034.7 kN. The ultimate load of the Y-type (Rebar= 0)–3 was 904.7 kN, about 13% less than the average value. The result does not seem to be reliable. But the ultimate loads of Y-type (Rebar= 0)–1 and 2 are similar at 3%. Thus, the test result of Y-type (Rebar= 0)–3 seems to have some error due to the uncertainty of concrete as a material. However, the behavioral characteristics of the three specimens show very similar tendency and thus explain well the effect of the transverse rebar. Fig. 13 and Table 6 compare the test results of Y-type perfobond(Representative, Rebar=4) and Y-type perfobond(Rebar=0). Without the transverse rebar, the ultimate load of the specimen decreased about 43% and the initial relative displacement (δ90) decreased 80%. This indicates that the transverse rebar has a significant influence on the shear resistance performance. As shown in Fig. 13, the shear resistance performance of the Y-type perfobond (Rebar= 0) falls sharply after the ultimate load. Also, the δu of the Y-type perfobond (Rebar= 0) is 2.7 mm, much less than the 6 mm required by the Eurocode-4. Thus, it is proved that without the transverse rebar, the shear connection shows brittle fracture behavior. Therefore, when applying the Y-type perfobond rib shear connector to the composite section, the transverse rebar must be placed to enhance durability and safety of shear connection.

3.2.3. Results of rib thickness variation specimens In this part, the effect of the rib thickness was evaluated on the behavior of the shear connector by performing the push-out tests with three specimens which have 8 mm rib thickness. Test results of the three specimens (Y-type(Rib thickness = 8)–1, 2, 3) are shown in Fig. 14. The average ultimate load for the three specimens is 1645.6 kN. Differences in the test results of each specimen were similar at 5%. δu/δ90 was 9.6 on average. Fig. 15 and Table 7 show comparison of test results between Y-type perfobond (Representative, Rib thickness = 10) and Y-type perfobond (Rib thickness = 8). As the rib thickness decreased 2 mm, the ultimate load dropped 9%. The initial relative displacement (δ90) and slip capacity (δu) increased 32% and 52% respectively. δu/δ90 increased 13%. Thus, for practical application, an optimized design for rib thickness is needed to obtain adequate shear resistance and ductility of the shear connection. 3.2.4. Results of Y-shape angle variation specimens Three specimens with 0° Y-shape angle were made and push-out tests were conducted to evaluate the effect of the Y-shape angle of the Y-type perfobond rib shear connector on the behavior of the

Table 4 Results of push-out tests. Specimens

No.

Pmax (kN)

PRK (kN)

δ90 (mm)

δu (mm)

δu/δ90

Y-type perfobond (Representative)

1 2 3 Avg. 1 2 3 Avg. 1 2 3 Avg. 1 2 3 Avg. 1 2 3 Avg. 1 2 3 Avg.

1811.1 1789.1 1809.8 1803.3 1687.4 1636.8 1691.3 1671.9 1079.1 1120.2 904.7 1034.7 1698.7 1630.4 1607.7 1645.6 1680.7 1619.4 1674.0 1658.0 1780.2 1748.1 1752.0 1760.1

1630.0 1610.2 1628.8 1623.0 1518.7 1473.1 1522.2 1504.7 972.5 1010.0 814.5 932.3 1528.8 1467.4 1446.9 1481.1 1512.6 1457.5 1506.6 1492.2 1602.2 1573.3 1576.8 1584.1

3.2 3.5 3.3 3.4 2.8 2.9 3.0 2.9 0.7 1.0 0.8 0.8 4.3 4.2 5.0 4.5 3.8 3.2 3.8 3.6 11.1 9.1 7.0 9.0

30.9 25.6 28.5 28.3 33.0 33.0 31.5 32.5 2.4 2.6 2.1 2.7 44.4 42.0 43.0 43.1 29.3 26.8 26.1 27.4 26.1 30.6 29.2 28.6

9.6 7.3 8.5 8.5 11.8 11.6 10.7 11.4 3.55 2.67 2.71 3.0 10.3 10.0 8.6 9.6 7.8 8.4 6.9 7.7 2.4 3.4 4.2 3.3

Y-type perfobond (fck = 30)

P Y-type perfobond (Rebar = 0)

Pmax PRK(=Pmaxx0.9)

Y-type perfobond (Rib thickness = 8)

Y-type perfobond (Y-shape angle=0)

Conventional perfobond 90

Fig. 8. Evaluation method of test results.

U

12

S.-H. Kim et al. / Journal of Constructional Steel Research 82 (2013) 1–18

2000

Table 5 Comparison of concrete strength variation.

1800

Pmax (kN)

PRK (kN)

δ90 (mm)

δu (mm)

δu/δ90

1600

(A) Y-type perfobond (fck = 30 MPa) (B) Y-type perfobond (Representative, fck = 40 MPa) Ratio (A/B)

1645.6

1481.1

4.5

43.1

9.6

1400

1803.3

1623.0

3.4

28.3

8.5

0.91

0.91

1.32

1.52

Load(kN)

Specimens

1.13

1200 1000 800 600 400 Y-type (fck=30) Y-type (Representative, fck=40)

200 0

25

30

35

40

45

50

Y-type (Rebar=0)-1 Y-type (Rebar=0)-2 Y-type (Rebar=0)-3

1800 1600 1400 1200 1000 800 600 400 200 0

0

5

10

15

20

25

30

35

40

45

50

Relative slip(mm) Fig. 12. Load-relative slip relationships of transverse rebar variation specimens.

1800

1600

1600

1400

1400 1200 1000 800 600

600 400

400

Y-type (fck=30)-1 Y-type (fck=30)-2 Y-type (fck=30)-3

200 0

20

2000

2000

800

15

displacement, the shear resistance of the conventional perfobond was 88% of the shear resistance of Y-type perfobond. This indicates that the Y-type perfobond has higher initial stiffness. The most important part in a composite structure is the shear connector. The strength and stiffness of the shear connector determine the degree of shear connection and the degree of interaction. Thus, it is necessary to use a shear connector with high ultimate load and initial stiffness for a composite structure. Also in terms of the safety of the structure, it is necessary to use a shear connector that shows ductile fracture behavior after the ultimate load. Therefore, the Y-type perfobond rib shear connector is better to be used in a composite structure than the conventional perfobond rib shear connector.

1800

1000

10

Fig. 11. Comparison of concrete strength variation.

2000

1200

5

Relative slip(mm)

Load(kN)

Load(kN)

3.2.5. Results of conventional perfobond rib specimens For the comparison of the conventional perfobond rib shear connector and the Y-type perfobond rib shear connector, the push-out tests were conducted. Test results were compared to the representative specimen. The test results of the three conventional perfobond rib specimens are shown in Fig. 18. The average ultimate load of the three specimens was 1760.3 kN. Ultimate loads of the three specimens were similar with only about 2% difference. δu was 28.6 mm on average, satisfying 6 mm requirement set by the Eurocode-4. δu/δ90 was 3.3 on average. Comparison between test results of Y-type perfobond (Representative) and conventional perfobond is shown in Fig. 19 and Table 9. The ultimate load of the Y-type perfobond was 2% higher than that of the conventional perfobond. However, the conventional perfobond showed 265% higher δ90 than the Y-type perfobond. There was no significant difference in δu. Thus, the δu/δ90 was 40% of the Y-type perfobond. As shown in Table 10, when compared at 6 mm of relative

0

Load(kN)

shear connector. Test results were compared with the standard specimen (Y-shape angle = 60). The test results of the tree specimens (Y-type(Y-shape angle = 0)–1, 2, 3) are shown in Fig. 16. The average ultimate load of the three specimens was 1658.0 kN. Differences in the ultimate loads of the three specimens were about 3%, meaning they have similar results. δu/δ90 was 7.7 on average. In Fig. 17 and Table 8, test results are compared between Y-type perfobond (Representative, Y-shape angle = 60) and Y-type perfobond (Y-shape angle= 0). When the Y-shape angle is 0°, the ultimate load decreased 8% compared to the standard specimen (Y-shape angle= 60). The initial relative displacement (δ90) increased 6%, slip capacity (δu) decreased 3%, and δu/δ90 decreased 9%. As indicated in the test results, both cases of the Y-shape angles (60° and 0°) showed high ultimate load and ductile behavior. However, the 60° angle showed higher ultimate load, initial stiffness and ductile behavior. The reason is that the Dowel area, caused by the concrete filling between ribs, increases as the top of the rib is bent.

0

5

10

15

20

25

30

35

40

45

Y-type (Rebar=0) Y-type (Representative, Rebar=4)

200 50

Relative slip(mm) Fig. 10. Load-relative slip relationships of concrete strength variation specimens.

0

0

5

10

15

20

25

30

35

40

Relative slip(mm) Fig. 13. Comparison of transverse rebar variation.

45

50

S.-H. Kim et al. / Journal of Constructional Steel Research 82 (2013) 1–18 Table 6 Comparison of transverse rebar variation specimens. Specimens

Pmax (kN)

(A) Y-type perfobond 1034.7 (Rebar = 0) (B) Y-type perfobond 1803.3 (Representative, Rebar=4) Ratio (A/B) 0.57

Table 7 Comparison of rib thickness variation specimens. δu/δ90

Specimens

Pmax (kN)

PRK (kN)

δ90 (mm)

δu (mm)

δu/δ90

932.3

0.8

2.7

3.0

1645.6

1481.1

4.5

43.1

9.6

1623.0

3.4

28.3

8.5

(A) Y-type perfobond (Rib thickness = 8) (B) Y-type perfobond (Representative, Rib thickness = 10) Ratio (A/B)

1803.3

1623.0

3.4

28.3

8.5

PRK (kN)

0.57

δ90 (mm)

0.23

δu (mm)

0.08

0.35

2000 1800 1600

Load(kN)

1400 1200 1000 800 600 400

Y-type (Rib thickness=8)-1 Y-type (Rib thickness=8)-2 Y-type (Rib thickness=8)-3

200 0

0

5

10

15

20

25

30

35

40

45

50

Relative slip(mm) Fig. 14. Load-relative slip relationships of rib thickness variation specimens.

3.3. Concrete crack patterns and failure of specimens

2000 1800

1600

1600

1400

1400

800

1.32

1.52

1.13

Shear resistance equations for perfobond rib shear connector have been studied by many researchers. However, existing equations are not suitable to estimate the shear resistance of the proposed Y-type perfobond rib shear connector. Thus, a new evaluation equation is

1800

1000

0.91

4. Shear resistance equation for Y-type perfobond rib shear connector

2000

1200

0.91

concrete and steel. The splitting cracks on the conventional perfobond rib shear connector (Fig. 21(f)) appeared in a vertical direction, closer to the center that the Y-type perfobond rib shear connector (Y-shape angle = 0) (Fig. 21(e)) as the rib is placed in a straight row. In the case of the Y-type perfobond rib shear connector (rebar = 0) (Fig. 21(c)), no splitting cracks in a horizontal direction were observed, but two splitting cracks in a vertical direction were observed along the top of the rib. Considering the amount and distribution of the cracks in the concrete, it was determined that load transfer to the concrete would not be effective if transverse rebars are not placed in a full-scale structure. Fig. 22 shows the deformed shape of the shear connector after the test was completed. After the test, the concrete slabs of the specimen were crushed to check the deformation of the transverse rebars and ribs. It was observed that the Y-type perfobond (Representative) had deformed transverse rebars and ribs and the dowel hole, caused by the transverse rebars, was also deformed. In particular, ribs had both the bending deflection and buckling distortion. The Y-type perfobond (Rebar = 0) had buckling distortion in the ribs but no deformation in the dowel hole. Unlike in the cases of bending, the Y-type perfobond (Y-shape angle = 0) had no buckling distortion, but only showed bending deflection. Also, the dowel hole, caused by the transverse rebars, was deformed. In the case of the conventional perfobond, no bending deflection and buckling distortion were observed. But the dowel hole caused by the transverse rebars was deformed. Unlike the Y-type perfobond specimen, the transverse rebars were ruptured. The reason seems to be that the transverse rebars of the conventional perfobond rib shear connector have relatively higher resistance effect and thus the transverse rebars were affected by a bigger shear force than the Y-type perfobond rib shear connector.

Load(kN)

Load(kN)

Most of the specimens started to show cracks at the lower part of the interface of the concrete and the H-beam flange at about 75% of the ultimate load. In both of the shear connectors, cracks appeared first at the location where the rib was placed. Fig. 20 describes the characteristics of initial cracks of the Y-type perfobond rib shear connector and the conventional perfobond rib shear connector. Fig. 21 shows the development of cracks after the ultimate load. The Y-type perfobond rib shear connector showed similar crack patterns for three variables—representative (Fig. 21(a)), fck = 30 (Fig. 21(b)), and rib thickness = 8 (Fig. 21(d)). Two rows of splitting cracks occurred in a vertical direction along the line of Y-shape rib, and multiple splitting cracks occurred in a horizontal direction depending on how the transverse rebars are placed. In addition, some splitting cracks developed into shear cracks. Cracks spread widely across the concrete slab. This seems to be caused by the increase in the effective resistance area of the concrete as the rib is bent in Y-shape. Such characteristics will be beneficial to secure composite behavior of the

1200 1000 800 600

600

400

400 Y-type (Rib thickness=8) Y-type (Representative, Rib thicknessr=10)

200 0

13

0 0

5

10

15

20

25

30

35

Relative slip(mm) Fig. 15. Comparison of rib thickness variation.

40

45

Y-type (Y-shape angle=0)-1 Y-type (Y-shape angle=0)-2 Y-type (Y-shape angle=0)-3

200 50

0

5

10

15

20

25

30

35

40

45

Relative slip(mm) Fig. 16. Load-relative slip relationships of Y-shape angle variation specimens.

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S.-H. Kim et al. / Journal of Constructional Steel Research 82 (2013) 1–18

2000

2000

1800

1800

1600

1600

1400

1400

1200

Load(kN)

Load(kN)

14

1000 800 600

1000 800 600

400

400 Y-type (Y-shape angle=0) Y-type (Representative, Y-shape angle=60)

200 0

1200

0

5

10

15

20

25

30

35

40

45

Y-type (Representative) Conventional perfobond

200 50

0

0

5

10

Relative slip(mm)

15

20

25

30

35

40

45

50

Relative slip(mm)

Fig. 17. Comparison of Y-shape angle variation.

Fig. 19. Comparison of Y-shape angle variation.

Table 8 Comparison of Y-shape angle variation specimens.

Table 9 Comparison of shear connector types.

Specimens

Pmax (kN)

PRK (kN)

δ90 (mm)

δu (mm)

δu/δ90

Specimens

Pmax (kN)

PRK (kN)

δ90 (mm)

δu (mm)

δu/δ90

(A) Y-type perfobond (Y-shape angle = 0) (B) Y-type perfobond (Representative, Y-shape angle = 60) Ratio (A/B)

1658.0

1492.2

3.6

27.4

7.7

1760.1 1803.3

1584.1 1623.0

9.0 3.4

28.6 28.3

3.3 8.5

1803.3

1623.0

3.4

28.3

8.5

(A) Conventional perfobond (B) Y-type perfobond (Representative) Ratio (A/B)

0.92

0.92

1.06

0.97

0.98

0.98

2.65

1.01

0.39

0.91

proposed in this study, using regression analysis. The proposed shear resistance equation is composed as described in Eq. (8). The first term indicates the end bearing by Y-type perfobond rib; the second term, resistance by transverse rebar; the third term, concrete dowel resistance by holes; and the fourth term, concrete dowel resistance by Y-shaped form. qffiffiffiffiffiffi 2 Q ¼ β1 ⋅ðd=2 þ 2hÞ⋅t⋅f ck þ β2 ⋅Atr ⋅f y þ β3 ⋅n⋅π⋅ðd=2Þ ⋅ f ck qffiffiffiffiffiffi þ β4 ⋅m⋅h⋅s⋅ f ck

ð8Þ

where, the Q (kN) represents the shear resistance of Y-type perfobond rib shear connector, d (mm) is dowel hole's diameter, h (mm) is individual rib height, t (mm) is rib thickness, fck (MPa) is concrete compressive strength, Atr (mm 2) is transverse rebar's section area, fy (MPa) is transverse rebar's yield strength, n is the number of dowel holes, m is the number of dowel areas formed between ribs bent in Y-shape, and s (mm) is net distance between ribs that are

bent in same direction. β1, β2, β3, and β4 are values acquired by the regression analysis on the test results. The parameters are shown in Fig. 23. The shear resistance equation determined by this study is described in Eq. (9). In Table 11 and Fig. 24, the measured shear resistances which have been divided by the number of shear connector and the predicted shear resistances of the Y-type perfobond rib shear connector specimens were compared to verify the proposed

Table 10 Comparison of shear load at relative slip = 6 mm. Specimens

P6mm (kN)

(A) Conventional perfobond (B) Y-type perfobond (Representative) Ratio (A/B)

1543.2 1761.6 0.88

2000 1800 1600

Load(kN)

1400 1200 1000 800 600 400

Conventional perfobond-1 Conventional perfobond-2 Conventional perfobond-3

200 0

0

5

10

15

20

25

30

35

40

45

50

Relative slip(mm) Fig. 18. Load-relative slip relationships of conventional perfobond specimens.

(a) Y-type perfobond

(b) Conventional perfobond

Fig. 20. Characteristics of initial cracks by type of perfobond rib shear connector.

S.-H. Kim et al. / Journal of Constructional Steel Research 82 (2013) 1–18

(a) Y-type perfobond (Representative)

(b) Y-type perfobond (fck=30)

(c) Y-type perfobond (Rebar=0)

(d) Y-type perfobond (Rib thickness=8)

(e) Y-type perfobond (Y-shape angle=0)

(f) Conventional perfobond

15

Fig. 21. Cracks after push-out test.

shear resistance equation, Eq. (9). The coefficient of determination, R 2, was 0.958. It can be seen that the measured shear resistances and the predicted shear resistances of the Y-type perfobond rib shear connector specimens were in reasonable agreement. Therefore,

the proposed equation not only estimates the shear resistance of Y-type perfobond rib shear connection accurately within the margin of error, but also enables safe designing of the shear connection. However, accounting for all characteristics of the Y-type perfobond shear

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S.-H. Kim et al. / Journal of Constructional Steel Research 82 (2013) 1–18

(a) Y-type perfobond (Representative)

(b) Y-type perfobond (Rebar=0)

(c) Y-type perfobond (Y-shape angle=0)

(d) Conventionalperfobond Fig. 22. Deformation of shear connectors.

connector with only four variables has its limits. Thus, further study is needed to consider the characteristics of the Y-type perfobond rib shear connector in more diverse perspectives, so that more accurate shear resistance equation will be developed. qffiffiffiffiffiffi 2 Q ¼ 3:428⋅ðd=2 þ 2hÞ⋅t⋅f ck þ 1:213⋅Atr ⋅f y þ 1:9⋅n⋅π⋅ðd=2Þ ⋅ f ck qffiffiffiffiffiffi ð9Þ þ 0:438⋅m⋅h⋅s⋅ f ck

5. Conclusions In this study, push-out tests were conducted on the Y-type perfobond rib shear connector to propose a new shear connector with improved workability and higher shear resistance and ductility that can be applied to various types of composite structures. Shear connector specimens were fabricated according to Eurocode-4 requirements and push-out tests were conducted. Concrete strength,

transverse rebar, rib thickness, and Y-shape angle were considered as variables to evaluate the effect of various design variables on the Y-type perfobond rib shear connector. In addition, to compare the behavior with conventional perfobond, specimens with the same design variables were assigned. Based on test results, the shear resistance and ductile behavior characteristics, caused by changes in variables, were evaluated and a shear resistance equation for Y-type perfobond rib shear connector was proposed. The conclusions obtained in this study are as follows. The results of the push-out tests indicated that the Y-type perfobond rib shear connector has better shear resistance performance and ductility than the conventional perfobond rib shear connector. Under the same initial relative slip, the Y-type perfobond showed 12% higher shear resistance. Also, the ductility of the Y-type perfobond rib shear connector was 255% of that of the conventional perfobond specimen. Therefore the Y-type perfobond rib shear connector demonstrated more idealized behavior than the conventional perfobond rib shear connector, by achieving higher initial stiffness and ductile behavior.

S.-H. Kim et al. / Journal of Constructional Steel Research 82 (2013) 1–18

17

Table 11 Comparisons between measured shear resistance and predicted shear resistance of Y-type perfobond rib shear connector. Specimens

No

Measured shear resistance (A)

Predicted shear resistance (B)

Ratio (B/A)

Representative

1 2 3 1 2 3 1 2 3 1 2 3

905.6 894.6 904.9 843.7 818.4 845.7 539.6 560.1 452.4 849.4 815.2 803.9

819.9

0.91 0.92 0.91 0.86 0.89 0.86 0.81 0.78 0.96 0.89 0.93 0.94

h fck = 30

d/2 Transverse rebar = 0

(a) Bearing resistance (1st term)

Rib thickness = 8

Atr

(b) Longitudinal resistance by transverse rebar (2nd term)

d/2

(c) Concrete dowel resistance by holes (3rd term)

726.6

435.6

759.6

shear connector. When the rib thickness increased, the shear resistance increased 9% whereas the ductility decreased. Also, as the number of the transverse rebars increased, the shear resistance and ductility of the Y-type perfobond rib shear connector increased. This shows that the transverse rebars improve the concrete dowel performance and directly affects the changes in stiffness after the cracking load. Meanwhile, through the push-out test conducted to observe the effect of the Y-shape angle, it was found that the specimen without the bending has lower shear resistance and ductility than the specimen with bending. Based on the test results of this study, a new shear resistance equation is proposed for the Y-type perfobond rib shear connector. The equation considered effects on end bearing by Y-type perfobond rib, transverse rebar, concrete dowel by rib holes and Y-shaped form. Through comparison between the predicted shear resistance by proposed equation and measured shear resistance by push-out tests, the validity of the proposed equation was verified. From this study, it was found that the Y-type perfobond rib shear connector has more sufficient ductility as well as high shear resistance than the conventional perfobond rib shear connector. Also the Y-type perfobond rib shear connector has improved workability and resistance to pull-out forces than the conventional perfobond rib shear connector. Therefore, the Y-type perfobond rib shear connector can be used as a shear connector in a composite structure.

S 1000

h

(d) Concrete dowel resistance by Y-shape rib (4th term) Fig. 23. Parameters of shear resistance equation.

Also, through the evaluation of behavioral changes of the Y-type perfobond rib shear connector, it was found that when the concrete strength increases from 30 MPa to 40 MPa, the shear resistance of the Y-type perfobond rib connection increases 8%. However, despite the increase in the concrete strength, the ductile behavior after the ultimate load decreased. Thus, it was proved that the concrete strength has effect on the shear resistance and ductility of the Y-type perfobond

Measured shear resistance (kN)

900

800

700

600

500 Predicted shear resistance Measured shear resistance 400 400

500

600

700

800

900

Predicted shear resistance (kN) Fig. 24. Evaluation of proposed shear resistance equation.

1000

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S.-H. Kim et al. / Journal of Constructional Steel Research 82 (2013) 1–18

Acknowledgment This study also has been supported in part by Yonsei University, Center for Future Infrastructure System, a Brain Korea 21 program, Korea. This work was also supported by the Innovations in Nuclear Power Technology (Development of Nuclear Energy Technology) of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (2010 T100101065). References [1] Ahn JH, Kim SH, Jeong YJ. Fatigue experiment of stud welded on steel plate for a new bridge deck system. Steel Compos Struct 2007;7(5):391–404. [2] Kim SH, Jung CY, Ahn JH. Ultimate strength of composite structure with different degrees of shear connection. Steel Compos Struct 2011;11(5):375–90. [3] Oguejiofor EC, Hosain MU. A parametric study of perfobond rib shear connectors. Can J Civ Eng 1994;21:614–25. [4] Machacek J, Studnicka J. Perforated shear connectors. Steel Compos Struct 2002;2(1):51–66. [5] Ahn JH, Kim SH, Jeong YJ. Shear behaviour of perfobond rib shear connector under static and cyclic loadings. Mag Concr Res 2008;60(50):347–57. [6] European Committee for Standardization. prEN 1994-1-1 Design of composite steel and concrete structures Part 1-1: General rules and rules for buildings. Brussels: CEN; 2002.

[7] Kim SH, Yoon JH, Kim JH, Choi WJ, Ahn JH. Structural details of steel girder-abutment joints in integral bridges: an experimental study. J Constr Steel Res 2012;70:190–212. [8] Baran E, Topkaya C. An experimental study on channel type shear connectors. J Constr Steel Res 2012;74:108–17. [9] Qureshi J, Lam D, Ye J. Effect of shear connector spacing and layout on the shear connector capacity in composite beams. J Constr Steel Res 2011;67:706–19. [10] Valente IB, Cruz PJS. Experimental analysis of shear connection between steel and lightweight concrete. J Constr Steel Res 2009;65:1954–63. [11] Oguejiofor EC, Hosain MU. Numerical analysis of push-out specimens with perfobond rib connectors. Comput Struct 1997;62(4):617–24. [12] Sara BM, Bahram MS. Perforbond shear connectors for composite construction. Eng J 2002:2–12 (First Quarter). [13] Verissimo GS. Development of a shear connector plate gear for composite structures of steel and concrete and study their behavior [In Portuguese]. Ph.D. thesis, Universidade Federal de Minas Gerais Belo Horizonte; 2007. [14] Vianna J da C, Costa-Neves LF, Vellasco PCG da S, Andrade SAL de. Experimental assessment of Perfobond rib and T-Perfobond shear connectors' structural response. J Constr Steel Res 2009;65:408–21. [15] Ahn JH, Lee CG, Won JH, Kim SH. Shear resistance of the perfobond-rib shear connector depending on concrete strength and rib arrangement. J Constr Steel Res 2010;66:1295–307. [16] Kim SH, Ahn JH, Choi KT, Jung CY. Experimental evaluation of the shear resistance of corrugated perfobond rib shear connections. Adv Struct Eng 2011;14(2): 249–63. [17] Korea Highway Bridge Specifications. Korean Ministry of Construction and Transportation; 2005.