• Journal of the Korea Concrete Institute
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• v.26 no.6
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• pp.761-769
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• 2014

Ultra high performance concrete (UHPC) has been developed to overcome the low strengths and brittleness of conventional concrete. Considering that UHPC, owing to its composition and the use of steel fibers, develops a compressive strength of 180 MPa as well as high stiffness, the top flange of the steel girder may be superfluous in the composite beam combining a slab made of UHPC and the steel girder. In such composite beam, the steel girder takes the form of an inverted-T shaped structure without top flange in which the studs needed for the composition of the steel girder with the UHPC slab are disposed in the web of the steel girder. This study investigates experimentally and analytically the flexural behavior of this new type of composite beam to propose details like stud spacing and slab thickness for further design recommendations. To that goal, eight composite beams with varying stud spacing and slab thickness were fabricated and tested. The test results indicated that stud spacing running from 100 mm to 2 to 3 times the slab thickness can be recommended. In view of the relative characteristic slip limit of Eurocode-4, the results showed that the composite beam developed ductile behavior. Moreover, except for the members with thin slab and large stud spacing, most of the specimens exhibited results different to those predicted by AASHTO LRFD and Eurocode-4 because of the high performance developed by UHPC.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.1
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• pp.64-71
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• 2016

In this paper, when the composite beam is made with UHPC deck and steel girder, the steel girder takes the form of the inverted-T shape without top flange because of high strength and stiffness of UHPC deck. There is no evaluation by experiment and analysis about the shear connector behavior on the web of steel girder and flexural behavior of inverted-T shape composite beam. By this reason, this study compares between experiment and analysis by using tension softening model of UHPC on the basis of flexural test results of 16 members considering compressive strength of UHPC, spacing of stud and thickness of deck as variables. The results of tensile strength of UHPC by inverse analysis were 6.57 MPa(in case of 120 MPa) and 9.57 MPa(in case of 150 MPa). In case of the test members with small stud spacing, the results of analysis and test were close clearly, and the test members with thick deck and low UHPC compressive strength also similar, but effects were small. As it compared between analysis and experiment totally, the results of analysis and experiment agree well. So the tension softening model of UHPC is reasonably reflected on the real behavior of composite beam of UHPC.

• Journal of Korean Society of Steel Construction
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• v.20 no.2
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• pp.333-345
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• 2008

concrete deck bridges are increasingly aplied to twin- girder bridges and open-stel box girder bridges.One of the most dificult isues in the design of shear conect ors is the mater of achieving ful composite action. Many connectors in smal area require a significant section los of precast decks resulting in difficult reinforcement details. In this closer spacing than the required minimum spacing in the design codes was evaluated through static tests. Test results s howed that the ultimate strength decreased as the conector spacing was reduced. The strength enhancement was observed due to aditional reinforcement for precast slabs or for shear pockets. Thus, the design of group stud shear connection needs to anticipate failure modes and the conector failure should be induced. Based on the test results, an empirical equation consi dering stud spacing was proposed to evaluate the ultimate strength of group stud shear conection. Fatigue tests showed n o reduction in fatigue life of the group stud shear conection in the range of this research. Details of the precast decks wer e enhanced using the findings of the study.

• Journal of the Korea Concrete Institute
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• v.27 no.2
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• pp.185-193
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• 2015

Ultra high performance concrete (UHPC) has been developed to overcome the low tensile strengths and brittleness of conventional concrete. Considering that UHPC, owing to its composition and the use of steel fibers, develops a compressive strength of 180 MPa as well as high stiffness, the top flange of the steel girder may be superfluous in the composite beam combining a slab made of UHPC and the steel girder. In such composite beam, the steel girder takes the form of an inverted-T shaped structure without top flange in which the studs needed for the composition of the steel girder with the UHPC slab are disposed in the web of the steel girder. This study investigates experimentally and analytically the flexural behavior of this new type of composite beam to propose details like stud spacing and slab thickness for further design recommendations. To that goal, eight composite beams with varying stud spacing and slab thickness were fabricated and tested. The test results indicated that stud spacing running from 100 mm to 2 to 3 times the slab thickness can be recommended. In view of the relative characteristic slip limit of Eurocode-4, the results showed that the composite beam developed ductile behavior. Moreover, except for the members with thin slab and large stud spacing, most of the specimens exhibited results different to those predicted by AASHTO LRFD and Eurocode-4 because of the high performance developed by UHPC.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.803-811
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• 2002

Current composite steel and concrete bridges are designed using full-interaction theory assuming there is no relative slip, between the steel and concrete components along their interface, because of the complexities of partial-interaction analysis techniques. However, in the assessment of existing composite bridges this simplification may not be warranted as it is often necesary to extract the correct capacity and endurance from the structure. This may only be achieved using partial-interaction theory which tuly reflects the behaviour of the structure. In this paper, Parametric analyses have been carried out in order to confirm the partial-interaction curvatures with deflection effect using the finite element method. Therefore, the model is considered for simply supported steel and concrete composite bridges with a uniform distribution of connectors subjected to a single concentrated load. For the case studies, this study applicate a parameters such as the number and space of stud shear connector and elastic modulus of concrete slabs. From this study, it is known that partial-interaction effect was in the increase to the increasing the deflection of composite bridges, and stiffness and strength of slab concrete considering the occurrence of crack effect seriously to the partial-interaction behavior.

• Journal of Korean Society of Steel Construction
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• v.19 no.5
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• pp.473-482
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• 2007

When the material strength and ductility of shear studs is sufficient to carry the interface shear force, the composite beam can behave safely without premature structural failure in the interface and without ultimate moment reduction. In this study, the influence of the deformation capacity of shear studs embedded in high-strength concrete on structural behavior and design condition of composite beam is analyzed using FEM. In the analysis, load type, degree of shear connection and arrangement of studs are considered as analysis parameters. According to analysis results, in the case of partial interaction,the deformation capacity of studs embedded in high-strength concrete should be considered together with material strength. Especially in the case of uniform arrangement of studs and uniformly distributed load, a minimum available degree of shear connection is restricted by the deformation capacity of studs. In this case,shear studs should be arranged in consideration of the distribution of shear force at the composite section.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.400-413
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• 2016

The horizontal shear capacity when the flange of a steel girder is replaced with 80 MPa concrete is important for its structural safety. In this study, 6 specimens with different interface conditions were designed and fabricated based on the Limit State Design Code on Korean Highway Bridges and static tests were performed to measure the horizontal shear capacity. Not only the resistance factors of the stud shear connector, concrete and reinforcement, but also the surface conditions of the casing concrete and spacing of the horizontal shear reinforcements were used as the experimental variables. The experiments showed that the interfaces between the steel girder and the concrete flange have stronger joint performance than those between the concrete flange and deck slab. To ensure the composite action in the plastic zone, the conservative horizontal shear reinforcement is more important than the roughness in the concrete face.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.1-8
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• 2008

This research carried out to optimize crossbeams and stringers of steel box girder bridges, which are parts of floor system and support loading from the bridge deck. In the current design practice, the crossbeam is densely deployed with a spacing of 6 meters, and the stringer is placed between the crossbeams. The crossbeams and stringer are connected to the deck through slab anchors but the allowable stress of the compression flange is determined by the lateral-torsional buckling. To increase economic efficiency of the steel box girder bridges. the increased spacing of the crossbeam was studied. The study shows that the spacing can be increased up to 10 meters. However, higher strength steel plates are necessary. Shear studs rather than slab anchors are also recommended to prevent lateral-torsional buckling strength of the crossbeams and stringer.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.463-471
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• 2016

A shear strength model for the high-shear ring anchor consisting of a steel ring and a rod was developed based on the shear tests on single high-shear ring anchors. The shear strength was found to be proportional to $f_{ck}{^{0.75}}$ which is a similar characteristic to the strength of shear connectors used in composite structures. The effects of the compressive strength of concrete, edge distance, and embedment length of rod are included in the proposed model. Comparison with 22 tests shows that the average and the coefficient of variation of test-to-prediction ratios are 1.01 and 7.57%, respectively. Push tests on the specimens having four high-shear ring anchors at each face were conducted and the measured shear strengths were compared with the predictions by the proposed model. For the specimen with an edge distance of 100 mm, a splitting failure occurred and for the specimens with an edge distance of 150 mm, a failure mode mixed with splitting and bearing occurred, which were very similar to the failures of shear tests on single high-shear ring anchors. In case of a splitting failure, the overlap of failure surfaces could be prevented by providing the longitudinal spacing of 400 mm which is four times of the edge distance. In case of a bearing failure, the failure area is less than 150 mm from the center of the anchor and therefore the overlap of failure surfaces could be prevented by providing the longitudinal spacing of 200 mm. The average of the test-to-prediction ratios of Push tests is 98%, which means that the proposed mode can be applied to predict the shear strength of the multiple high-shear rings.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.593-604
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• 2007

Although composite construction has more mechanical advantages compared to noncomposite construction, the design of noncomposite construction for skew bridges with large skew angels has been often checked because composite construction may cause large stresses in the bridge deck. In this study, the analytical model considered dynamic behaviors for noncomposite skew bridges was proposed. Using the proposed analytical model, the validity of the application of noncomposite construction to skew bridges was checked. Also, the effects of interactions between the concrete deck and steel girders such as composite construction, partial composite construction, and noncomposite construction on the dynamic characteristics and dynamic behaviors of simply supported skew bridges were investigated. A series of parametric studies for the total 27 skew bridges was conducted with respect to parameters such as girder spacing, skew angle, and deck aspect ratio. Although the slip at the interfaces between the concrete deck and steel girders results in the reduction of seismic total base shear in the transverse direction due to period elongation, it causes an undesirable behavior of skew bridges by the modification in mode shapes and distributions of stiffness. Shear connectors placed by minimum requirements for partial composite action have an effect on reducing the girder stresses and deck stresses; except case of some skew bridges, the magnitude of the girder stresses and deck stresses obtained from partial composite skew bridges is similar to or slightly more than those acquired from composite skew bridges.