Journal of Constructional Steel Research62(2006)
463–471
https://www.doczj.com/doc/023988619.html,/locate/jcsr
Experimental investigation on behaviour of steel–concrete composite bridge
decks with perfobond ribs
Hyeong-Yeol Kim?,Youn-Ju Jeong
Structure Research Department,Korea Institute of Construction Technology,2311Daewha-Dong Ilsan-Gu Goyang,Gyeonggi-Do411-712,Republic of Korea
Received17March2005;accepted24August2005
Abstract
This paper introduces a test program conducted for steel–concrete composite bridge decks with perfobond rib shear connectors.The composite deck consists of pro?led steel sheeting,perfobond ribs,steel reinforcements,and concrete.To provide longitudinal shear resistance between the pro?led sheeting and the concrete,perfobond ribs were used.For a prototype steel-box girder bridge,two types of deck pro?les with deck-to-girder connections were designed.To validate the effectiveness of the proposed deck system for bridge application,push-out,full-scale?exural, and deck-to-girder connection tests for each deck pro?le have been conducted.The results of tests have shown that the perfobond ribs can be effectively used for shear connection in the steel–concrete composite decks.
c 2005Elsevier Ltd.All rights reserved.
Keywords:Steel–concrete composite;Bridge deck;Perfobond rib shear connector;Pro?led sheeting;Connection;Experiment
1.Introduction
Different types of steel–concrete composite deck systems are used to construct buildings and highway bridges.Among the composite deck systems,the concrete composite deck with pro?led steel sheeting may be the most widely used form. The pro?led steel sheeting acts as a permanent formwork for erection and as a tensile reinforcement for the hardened concrete.If the composite action between the pro?led sheeting and the concrete can be obtained,the cross-sectional area of the composite deck can be signi?cantly reduced.
To achieve the desired composite action,longitudinal shear force needs to be transferred between the pro?le sheeting and the concrete.Among the several different types of shear connectors used to provide composite action,the headed shear stud is the most common.However,the stud might cause spatial obstacles during erection,and some fatigue problems of headed studs during service life have been reported[1].
In1987,a German consulting engineering?rm introduced the perfobond rib shear connector for composite beams to overcome the fatigue problem of the studs under live load[2]. The perfobond rib shear connector consists of a steel plate ?Corresponding author.Tel.:+82319100582;fax:+82319100578.
E-mail address:hykim1@kict.re.kr(H.-Y.Kim).with a number of uniformly spaced holes.In this case,the ribs were directly welded onto the top?ange of a steel beam.If the holes in the perfobond rib are?lled with concrete,concrete dowels are formed,which provide longitudinal shear resistance between the steel and the concrete.The potential advantages of the perfobond rib shear connectors are:they are easy to customize and fabricate;there are smaller obstacles than the studs during erection;and a perfobond rib could replace a number of headed studs[3].
There has been a lot of research[1–5]in the area of composite beams with perfobond ribs.Recently,a test program was conducted using perfobond ribs and lightweight concrete[6].However,this research project was concerned with the cast-in-place concrete slab deck that rests on a steel beam.
This paper deals with an experimental investigation on the behaviour of steel–concrete composite decks with perfobond rib shear connectors.This study mainly aims to investigate the usability of perfobond rib shear connectors for composite bridge decks with pro?led steel sheeting and application of the proposed deck system for a bridge.For a prototype steel-box girder bridge,two different types of composite deck pro?les with deck-to-girder connections were designed.In order to validate the effectiveness of the proposed deck systems,a series of structural tests were conducted.A total of17test specimens were put to test and the results were discussed in this paper,of
0143-974X/$-see front matter c 2005Elsevier Ltd.All rights reserved. doi:10.1016/j.jcsr.2005.08.010
464H.-Y.Kim,Y.-J.Jeong /Journal of Constructional Steel Research 62(2006)
463–471
Fig.1.Schematic of proposed deck
pro?le.
Fig.2.Cross-section of steel-box girder bridge.
which,four were push-out tests to examine the shear capacity of the perfobond rib shear connectors,nine full-scale ?exural tests to examine the bending behavior of the deck with sheet-to-sheet connection,and four deck-to-girder connection tests to examine the connection behavior of the deck-to-girder connection.2.Design of deck pro?les
Fig.1shows a schematic of the composite bridge deck system proposed in this study.The deck consists of pro?led steel sheeting,perfobond rib shear connectors,steel reinforcements,and concrete.The perfobond rib acts as a shear connector and as a longitudinal stiffener within the pro?led sheeting.Since the pro?led sheeting is considered as tensile reinforcement in the design of the deck,bottom reinforcing bars are no longer necessary.For the practical application,the pro?led sheeting must be galvanized to resist corrosion.
A steel-box girder bridge shown in Fig.2was selected to design the deck pro?le.Only the middle portion of the deck was to be designed as a composite deck with pro?led steel sheeting.The effective span length of the composite deck was 3.5m excluding the bearing length of 75mm above each girder.The standard design truck load speci?ed in the Speci?ca-tions [7]was used as the design live load and the self-weight of the deck including the 50mm thick asphalt wearing surface was considered for the dead loads.The design truck load spec-i?ed in [7]is approximately 1.33times heavier than an HS20truck load of AASHTO [8].The ultimate strength method was employed for the deck design.The overall design process was driven by the bending and vertical shear strengths of the deck since the longitudinal shear capacity can be obtained from the test information.A de?ection limit of span/800was employed.Fig.3shows a cross-sectional shape of the composite deck pro?le assumed in this study.In order to design the
deck
Fig.3.Cross-section of proposed deck pro?le.
Table 1
Dimensions of deck pro?les Type b o b 1b 2b 3h o h 1t (mm)(mm)(mm)(mm)(mm)(mm)(mm)Deck-A 2501002550200506Deck-B
500
200
50
100
200
70
6
Table 2
Required and design strength per unit width of decks Description
Required Design strength strength Deck-A Deck-B RC deck Positive bending (kN m)100.5250.8192.889.5Negative bending (kN m)94.3108.4108.488.7Vertical shear (kN)
245.8
396.9
308.4
–
pro?le more ef?ciently,two cross-sections of the deck pro?le with different wavelengths of pro?led sheeting were assumed and the corresponding deck pro?les were named Deck-A and Deck-B.The Deck-A type was given a wavelength of sheeting (b o )250mm wide,and Deck-B’s was 500mm wide.The widths of top and bottom ?anges,b 3and b 1in the ?gure,were also assumed appropriately.Therefore,the design process for deck pro?le is reduced to determine the overall depth of the deck (h o ),the thickness of the sheeting (t ),and the depth of the pro?led sheeting (h 1).The viable dimensions of the deck pro?les were determined based on an extensive structural analysis and the results are summarized in Table 1.The perfobond ribs were excluded in the calculations of the design strength of the deck.
The depth of pro?led sheeting is in?uenced by the design requirements for vertical shear strength of the deck.On the other hand,the thickness of the steel sheeting affects both the overall depth of the deck and the depth of the pro?led sheeting.Except for the depth of the pro?led sheeting,if the thickness of the steel sheeting is over 5mm,the shape of the pro?led sheeting is not an important factor for the bending strength of the deck.If the overall depth of the deck is limited to 200mm,a reasonable thickness for the steel plate becomes 6mm.In our nation,the depth of a typically designed cast-in-place concrete deck for steel-box girder bridges is about 240mm.We decided to go with an overall depth of 200mm for both the deck pro?les.The required and design strengths per unit width of the deck pro?les are summarized in Table 2.The design strengths of
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Fig.4.Description of perfobond rib shear connector. typically designed cast-in-place reinforced concrete deck(RC deck)are also provided in the table.
To date,no design information has been provided for a composite deck with perfobond ribs welded onto the pro?led sheeting.Existing studies by others[1,3–6]on composite beams with a perfobond rib shear connection indicate that the longitudinal shear resistance of perfobond ribs is mainly in?uenced by the diameter and spacing of holes,and the concrete strength.The commonly used diameter of hole is about half the height of the perfobond rib.The spacing of holes that produces the maximum shear resistance ranges from2D to 2.5D,where D is the diameter of the hole.In this study,as shown in Fig.4,the diameter and center-to-center spacing of holes for the perfobond rib were chosen as55mm and125mm, respectively.Half-circle holes were fabricated on top of the perfobond rib for easy placement of transverse reinforcement.
3.Fabrication of specimens
3.1.Pro?led sheeting and materials
An SM400-grade mild steel plate of6mm thickness was pro?led through the press braking process to form the desired shapes of pro?led sheeting for Deck-A and Deck-B.The perfobond ribs were fabricated by cutting the same steel plate and cutting holes using a Plasma Jet https://www.doczj.com/doc/023988619.html,ing an automatic welding machine,the perfobond ribs were welded onto the pro?led sheeting.Fig.5(a)illustrates a spot-welded perfobond rib on the sheeting before complete welding.On the other hand,Fig.5(b)shows a perfobond rib welded on the sheeting for the push-out test specimen.The pro?led sheeting and perfobond ribs were fabricated in a metal workshop.
The material properties of the steel sheeting were identi?ed through three coupon tests,and the mean values obtained for yield strength and tensile strength were368MPa and488MPa, respectively.The reinforcing steel used for the specimens was standard deformed bars with diameters of16and19mm.The mean yield strength of reinforcing bars of16and19mm diameter was obtained as431MPa and412MPa,respectively. The normal density concrete with the design strength of 30MPa,a slump of120mm,and an entrained air of5.1%was used.The compressive strength of the concrete was identi?ed through three cylinder tests,and the mean value was35.1MPa.
Table3summarizes characteristics of the specimens fabricated in this study.
3.2.Push-out test specimens
The load and deformation characteristics of shear connection can be identi?ed by a small-scale test known as a
push-out Fig.5.Perfobond rib welded on:(a)pro?led sheeting;and(b)push-out
specimen.
Fig.6.Description of push-out specimen(units:mm).
test[9].In this study,to investigate the usability of perfobond rib shear connectors for a composite deck,a series of push-out
tests were conducted.Fig.6(a)and(b)respectively show the cross-section and side views of a test specimen with perfobond
rib.Except for the width of the specimen(b o),all of the other dimensions were the same.The width of each specimen is the
same as that of a wavelength of the deck pro?le.
Two of the composite specimens were independently cast
and cured in the horizontal position,and then were connected by bolting and held in the vertical position,as shown in Fig.6(b).In the transverse direction of the concrete slab, reinforcing bars of16mm diameter were uniformly spaced at 125mm to reinforce the concrete slab.The reinforcing bars are not connected to the perfobond rib.Two push-out specimens for each deck type were fabricated and the specimens
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Table 3
A summary of test specimens Deck type
Push-out Full-scale ?exural Deck-to-girder connection specimen Specimen Sheet-to-sheet Specimen Connection details ID ID connection ID Deck-A
PTA-1SAF-1None SAC-1Detail-A PTA-2
SAF-2Top SAC-2
Detail-A
SAF-3Top SAF-4Bottom Deck-B
PTB-1SBF-1None SBC-1Detail-B PTB-2SBF-2None SBC-2Detail-B
SBF-3Top SBF-4Top SBF-5
Bottom
(a)Deck-A
type.
(b)Deck-B type.
Fig.7.Cross-section of full-scale ?exural test specimens.
corresponding to Deck-A and Deck-B were respectively named as PTA and PTB.
3.3.Full-scale ?exural test specimens
Although the longitudinal shear resistance of the shear connectors used in the steel–concrete composite members can be identi?ed by a simple push-out test,the push-out specimen is subject to normal force only.Therefore,a full-scale ?exural test under combined action of shear and bending is required to verify the effectiveness of the shear connectors used for the composite decks.To examine the load and de?ection behaviour of a composite deck with perfobond ribs,nine full-scale test specimens were fabricated,among which,four specimens were for Deck-A and ?ve were for Deck-B.The specimen groups corresponding to Deck-A and Deck-B were named as SAF and SBF,respectively.
Fig.7shows the cross-sectional shapes of 3.7m long full-scale test specimens.The perfobond ribs were welded onto the bottom ?ange of the steel sheeting.A 19mm diameter reinforcing bar was used as the primary reinforcement and a 16mm bar was used as transverse reinforcement to control the crack.The reinforcing bars were uniformly spaced at 125mm in each direction of the specimens.
In practice,sheet-to-sheet connections are necessary during the erection of pro?le sheeting since the size of sheeting
is
Fig.8.Schematic of connections for sheeting on (a)top;and (b)
bottom.
Fig.9.Description of deck-to-girder connection specimen (units:mm).
limited.During the fabrication of the specimens,a method of sheet-to-sheet connection for the pro?led sheeting was also considered.As shown in Fig.8,a sheet-to-sheet connection can be placed either on the top ?ange or on the bottom ?ange of the sheeting.High tension bolts of 14mm in diameter with center-to-center spacing of 125mm were used for the sheet-to-sheet connection shown in Fig.8(a).As shown in Fig.8(b),holes were positioned on the edge of each sheet to be connected then two of the sheets were folded vertically inward to face each other.The diameter and spacing of the holes were the same as those of the perfobond ribs.The center-to-center spacing of the top and bottom bolts was 500mm and 250mm,respectively.3.4.Deck-to-girder connection specimens
In order to examine the behaviour of deck-to-girder connections,two specimens for each deck type were fabricated and tested.The specimen groups corresponding to Deck-A and Deck-B were named as SAC and SBC,respectively.As illustrated in Fig.9,the connection specimen consists of a 1.0m ×2.0m steel-box block and a 1.0m ×4.35m composite deck.The stiffened steel-box block was used to simulate the top ?ange of the steel-box girder.Two prefabricated pro?led sheetings with perfobond ribs were placed on either side of the steel-box in order to perfectly in?ll between the deck concrete and the steel-box.The headed studs were welded onto the top
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(a)Side
view.
(b)Plan view.
Fig.10.Deck-to-girder connection with Detail-A (units:
mm).
(a)Side
view.
(b)Plan view.
Fig.11.Deck-to-girder connection with Detail-B (units:mm).
?ange of the steel-box to provide composite action between the deck concrete and the steel-box.The headed studs were installed in accordance with the Speci?cations [7]by assuming full-shear connection for the steel-box girder bridge.Figs.10and 11show the details of the deck-to-girder connections for Deck-A and Deck-B,respectively.To resist the compressive stress induced by transverse bending of the deck,the concrete section above the steel-box was reinforced
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463–471
Fig.12.Set-up for push-out test.
by steel reinforcement.Since limited space is available for bottom reinforcement,deck-to-girder connection specimens SAC with Detail-A were reinforced with the perfobond ribs that extended from the deck to the steel-box as shown in Fig.10. The extended perfobond rib was not connected to the steel-box.On the other hand,as shown in Fig.11,reinforcing bars of 19mm in diameter were placed for deck-to-girder connection specimens SBC with Detail-B.
A19mm diameter reinforcing bar was used as the primary reinforcement and a16mm bar was used as the transverse reinforcement.For each specimen the reinforcing bars were uniformly spaced at125mm in each direction.After the reinforcements were placed,normal density concrete was placed to the specimens.
4.Test program
4.1.Push-out test
Fig.12shows a set-up for the push-out test.A vertical monotonic load with displacement control of0.03mm/s was applied to the specimens using a servo-controlled universal testing machine with a1000kN capacity.Two LVDTs(Linear Variable Differential Transducers)were installed on either side of the specimen to measure the longitudinal slip at the interface.
As the load increased,the concrete slabs began to crack.For the specimen with Deck-A,a longitudinal crack occurred on the side of the concrete and further loading caused splitting of the concrete slab,as illustrated in Fig.13(a).On the other hand, for the specimen with Deck-B,a longitudinal crack occurred at the top side of the concrete slab along the perfobond rib as illustrated in Fig.13(b)and the crack progressively grew until the failure occurred.In both cases,the observed failure was associated with the failure of the concrete.After the test, the specimen was demolished to observe the condition of perfobond ribs but the ribs showed no visible
deformation.
(a)Deck-A
type.
(b)Deck-B type.
Fig.13.Typical failure mechanism of push-out
specimens.
Fig.14.Load–slip curves for push-out specimens.
Fig.14shows the load–relative slip curves for the push-out test specimens.Since the specimen for each deck type was different in width,the applied load was divided by the area of the steel–concrete interface and denoted as the shear stress in the?gure.Although the initial behaviour of the specimens was similar to each other until the load(shear stress in the?gure) reached3MPa,the ultimate load–slip behaviour was quite different.Overall,Specimens PTB-1and PTB-2were more ductile than Specimens PTA-1and PTA-2.For the specimens with Deck-B,no distinct ultimate load can be identi?ed.This may be due to the fact that the friction between the cracked
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469
Fig.15.Set-up for full-scale ?exural
test.
Fig.16.Load–displacement curves for specimens with Deck-A type.concrete surfaces continued to resist the applied load even after the concrete dowels were broken.On the other hand,the failure of Specimens PTA-1and PTA-2is associated with vertical separation of concrete at the layer of reinforcing bars.As expected,the ultimate shear resistance of specimens with Deck-A type was approximately 1.8times greater than that of Deck-B.
4.2.Full-scale ?exural test
Fig.15shows a typical set-up for four-point ?exural testing.The deck specimen was simply supported with an effective span of 3.5m.Two equal concentrated loads were applied through 250mm ×500mm rigid blocks.The center-to-center distance of the rigid blocks was 1.75m (span /2).Neoprene sheeting was placed between the rigid blocks and the deck specimen.
Two LVDTs were positioned at both ends of the specimen to measure the end slip in the longitudinal direction.An LVDT was placed at the mid-span of the specimen so that vertical displacement of the specimen can be measured at different loading stages.A number of strain gauges were mounted on the different locations of the concrete and pro?led sheeting to measure the stains.A crack-width gauge was installed at the sheet-to-sheet connection to measure the separation of connection.A vertical monotonic load was applied in increment to the specimens using a hydraulic jack with a 2000kN
capacity.
Fig.17.Load–displacement curves for specimens with Deck-B
type.
Fig.18.Load–end slip of deck specimens.
Figs.16and 17show the load versus vertical displacement curves for the specimens with Deck-A and Deck-B types,respectively.The test results along with the position for the sheet-to-sheet connection are also summarized in Tables 4and 5.Two deck systems showed similar load–displacement behaviour up to failure.As the load increased,the cracking of concrete occurred near the support of the specimen.A number of cracks began at the bottom of the concrete near the support
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Fig.19.Typical failure mechanism of full-scale ?exural test specimens.
Table 4
Results of full-scale ?exural tests for Deck-A type specimens Specimen Load (kN)
ID Cracking of concrete Yielding of sheeting Ultimate SAF-1461No yielding 785.0SAF-2441540731.1SAF-3294640855.5SAF-4461343
710.5Average
414
770.5
Table 5
Results of full-scale ?exural tests for Deck-B type specimens Specimen Load (kN)
ID Cracking of concrete Yielding of sheeting Ultimate SBF-1411645
664.4SBF-2245No yielding 553.7SBF-3392450712.5SBF-4353640712.3SBF-5343480
663.5Average
348
661.3
and progressively spread towards the top of the concrete at quarter span,as the load further increased.For the specimens with Deck-A type,cracks were observed on top of the concrete slab before the pro?led sheeting yielded.On the other hand,for the specimens with Deck-B type,cracks were observed on top of the concrete slab after the yielding of pro?led sheeting,in which the load causing the crack on top of the concrete was almost 1.5times greater than that which caused the initial crack at the bottom of the https://www.doczj.com/doc/023988619.html,ing the measured strains,the location of the neutral axis for the specimen was estimated.The neutral axes of the specimens with Deck-A and Deck-B types were located in the concrete slab and locations were identi?ed as 120mm and 90mm from the bottom,respectively.
As shown in Fig.18,except for Specimen SAF-1the measured end slip of specimens was nearly zero until the load reached 230kN.A small amount of vertical separation between the concrete and steel sheeting was observed before the ultimate load was reached.The failure of Specimen SBF-2occurs in association with the vertical separation of concrete at the layer of reinforcing bars.The maximum load was reached just before the failure that showed brittle behaviour.Except for Specimens SAF-1and SBF-2,the yielding of pro?led steel sheeting accelerated the failure of deck
specimens.
Fig.20.Set-up for deck-to-girder connection
test.
Fig.21.Load–displacement curves for connection specimens.
Fig.19illustrates a typical failure mechanism of the specimens tested.After the test,a selected number of specimens were demolished to observe the condition of the perfobond ribs but the perfobond ribs showed no visible deformation.The test results further indicated that the specimens with a sheet-to-sheet connection had no in?uence on the load–de?ection behaviour and no visible deformation or separation on the connection was observed.The maximum separation of sheet-to-sheet connection measured at a quarter span was less than 1.0mm.Therefore,the connection details chosen in this study can be effectively used for the proposed deck system.
The results for the full-scale specimens under ?exural loading indicated that the ultimate load of specimens with Deck-A type was about 17%greater than those with Deck-B type.This result may be because the design strength of the specimen with Deck-A type is 23%greater than that with Deck-B type,as provided in Table 2,and the number of perfobond ribs in Deck-A type is double that of Deck-B type.
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Fig.22.Typical failure mechanism of connection specimen.
4.3.Deck-to-girder connections test
After the concrete has cured,the deck-to-girder connection specimen was inverted for testing as illustrated in Fig.20. The specimen was simply supported with an effective span of 4.15m.Except for the test set-up,the testing procedure used for the connection test was the same as that used for the full-scale ?exural test described in Section4.2.
Fig.21shows the load–vertical displacement curves for the connection specimens.Excepting Specimen SAC-1,Specimens SAC-2,SBC-1,and SBC-2behave in a similar manner.As expected,failure was initiated by the cracking of concrete at the connection between the steel-box and the composite deck.The cracking pattern of the concrete slab is illustrated in Fig.22.The load level causing an initial crack of concrete was approximately15%of the ultimate load.
5.Concluding remarks
The usability of perfobond rib shear connectors in a steel–concrete composite deck and the application of the proposed deck system for a steel-box girder bridge were experimentally investigated in this study.Based on the test program outlined in this paper,several conclusions can be drawn and are summarized in the following.
The results of the push-out tests indicated that the perfobond ribs were effective for longitudinal shear force.The results of the full-scale?exural tests for the deck specimens have shown that measurable end slip has not occurred under the service load level.The ultimate load of the deck specimen was at least two times greater than the load level causing a measurable end slip. In Eurocode4[9],the behaviour of composite decks can be de?ned as ductile if the failure load exceeds the load causing the end slip of0.1mm by more than10%.Therefore,the behaviour of the composite deck tested in this study is considered ductile. Overall,the performance of specimens with Deck-A type was slightly better than that with Deck-B type.
The?exural strength of the proposed deck system under positive bending is approximately two times greater than that of a typically designed cast-in-place concrete deck,as provided in Table2,with the deck weighing35%less.This may be attributed to the potential advantages of the proposed deck system over the conventional one.The proposed steel–concrete composite decks behave as partial-shear connection and should be designed with the design method considering partial-shear connection,such as the m–k method in[9].Therefore,in order to determine the longitudinal shear resistance of the composite deck under?exural loading and to draw practical design guideline based on the empirical m–k method described in[9],further full-scale test program with different shear spans has to be conducted in the future study.
The failure of the deck-to-girder connection specimens was associated with the yielding of the primary reinforcing bars. The tensile reinforcement under negative bending yielded at 45%of the ultimate load.No slip was measured at the bedding between the pro?led sheeting and the steel-box.Both deck-to-girder connection details considered in this study can be effectively used for connection between the pro?led sheeting and the steel box in the composite decks.
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