• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.111-118
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• 2020

The U-shaped composite beam used in this study consist of a reinforced concrete structure, a beam steel structure supporting the slab, a reinforced concrete structure, and a U-shaped steel plate. The U-shaped composite beam was developed for the purpose of using it as a parking lot because it is highly constructible and has low floor height and long span. For the improvement of constructivity, the U-shaped composite beam ends are planned with standardized H-shaped steel and connected directly to the columns, and the middle of the U-shaped composite beam consists of U-shaped steel plates folded in U-shaped form using thin steel plates (t=6) instead of H-shaped steel. In the middle of the composite beam, where U-shaped steel plates are located, the depth of U-shaped beam may be planned to be small so as to satisfy the height limit of the parking lot. It is important to grasp the structural performance according to the change of depth because low beam depth is advantageous for the reduction of the floor height, but it is a inhibitor to the structural behaviors of U-shaped composite beam. In addition, since U-shaped composite beams are a mixture of steel frame structures, reinforced concrete structures and U-shaped steel plates, securing unity has a great influence on securing structural performance. Therefore, in this study, a structural experiment was conducted to understand the structural performance according to the depth change for U-shaped composite beam. A total of three specimens were planned, including two specimens that changed the depth using a criteria specimen planned for a general parking lot. The results of the experiment showed that the specimens who planned the depth greatly had better structural performance such as yield strength, maximum strength, and energy than the standard specimen.

• Steel and Composite Structures
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• v.43 no.3
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• pp.311-325
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• 2022

For multi-story structural systems, Korean steel industry has fostered development of a steel-concrete composite beam. Configuration of the composite beam is characterized by steel angle shear connectors welded to a U-shaped cold formed-steel beam. Effects of shear connector orientation and spacing were studied to evaluate current application of the angle shear connector design equation in AC495. For the study, interfacial shear resistance behavior was investigated by conducting 24 push-out tests and attuned using unreinforced push-out specimens. Interfacial shear to horizontal slip response was reported along with corresponding failure patterns. Pure shear connector strength was also evaluated by excluding concrete shear contribution, which was estimated in relation to steel beam-slab interface separation or interfacial crack width.

• Steel and Composite Structures
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• v.34 no.3
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• pp.441-452
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• 2020

Within the French CIFRE research project COMINO, an innovative type of composite beam was developed for buildings that need fire resistance with no additional supports in construction stage. The developed solution is composed of a steel U-shaped beam acting as a formwork in construction stage for a reinforced concrete part that provides the fire resistance. In the exploitation stage, the steel and the reinforced concrete are acting together as a composite beam. This paper presents the investigation made on the load bearing capacity of this new developed steel-concrete composite section. A full-scale test has been carried out at the Laboratory of Structural Engineering of the University of Luxembourg. The paper presents the configuration of the specimen, the fabrication process and the obtained test results. The beam behaved compositely and exhibited high ductility and bending resistance. The shear connection in the tension zone was effective. The beam failed by a separation between the slab and the beam at high deformations, excessive shear forces conducted to a failure of the stirrups in this zone. The test results are then compared with good agreement to analytical methods of design based on EN 1994 and design guidelines are given.

• Steel and Composite Structures
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• v.19 no.3
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• pp.735-757
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• 2015

Composite bonding steel plate (CBSP) is a newly developed type of structure strengthened technique applicable to the existing RC beam. This composite structure is applicable to strengthening the existing beam bearing high load. The strengthened beam consists of two layers of epoxy bonding prestressed steel plates and the RC beam sandwiched in between. The bonding enclosed and prestressed U-shaped steel jackets are applied at the beam sides. This technique is adopted in case of structures with high longitudinal reinforcing bar ratio and impracticable unloading. The prestress can be generated on the strengthening steel plates and jackets by using the CBSP technique before loading. The test results of full-scale CBSP strengthened beams show that the strength and stiffness are enhanced without reduction of their ductility. It is demonstrated that the strain hysteresis effect can be effectively overcome after prestressing on the steel plates by using such technique. The applied plates and jackets can jointly behave together with the existing beam under the action of epoxy bonding and the mechanical anchorage of the steel jackets. The simplified formulas are proposed to calculate the prestress and the ultimate capacities of strengthened beams. The accuracy of formulas was verified with the experimental results.

• Journal of Korean Association for Spatial Structures
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• v.17 no.3
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• pp.99-105
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• 2017

The SLIM AU composite beam consists of U-shaped steel plate, A-shaped steel cap and infilled concrete. The bottom steel plate acts as tension bars, and the top steel cap takes roles of shear connector and compression bars in the conventional reinforced concrete section. In this paper the shear strength of this composite beam with closed steel section has been evaluated through the concentrated loading shear experiments. Test results under the symmetrical and asymmetrical loading conditions were compared with the predicted values based on the KBC 2016. The composite beam showed the greater shear strength capacities than those of the theoretical evaluation.

• Computational Structural Engineering
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• v.24 no.2
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• pp.37-42
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• 2011

• Journal of Korean Association for Spatial Structures
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• v.18 no.4
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• pp.123-130
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• 2018

U-flanged truss beam is composed of u-shaped upper steel flange, lower steel plate of 8mm or more thickness, and connecting lattice bars welded on the upper and lower sides. The hybrid beam with U-flanged steel truss is made in the construction site through pouring the concrete, and designated as U-flanged truss hybrid beam. In this study the structural experiments on the 4 hybrid beams with the proposed basic shapes were performed, and the flexural capacities from the tests were compared with those from the theoretical approach. The failure modes of each specimen were quite similar. The peak load was reached with the ductile behavior after yielding, and the failure occurred through the concrete crushing. The considerable increasement of deformation was observed up to the concrete crushing. The composite action of concrete and steel member was considered to be reliable from the behavior of specimens. The flexural strength of hybrid beam has been evaluated exactly using the calculation method applied in the boubly reinforced concrete beam. The placement of additional rebars in the bottom instead of upper side is proposed for the efficient design of U-flanged truss hybrid beam.

• Journal of Korean Association for Spatial Structures
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• v.18 no.3
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• pp.57-66
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• 2018

Recently various composite beams in which concrete is filled in the U-shaped steel plate have been developed for saving story height and reducing construction period. Due to the high flexural stiffness and strength, they are widely being used for the building with large loads and long spans. The semi-slim AU composite beam has proven to take highly improved stability compared to the existing composite beams, because it consists of the closed steel section by attaching cap-type shear connectors to the upper side of U-shaped steel plate. In this study the finite element analyses were performed to evaluate the safety of the AU composite beam with unconsolidated concrete which were sustained through the closed steel section during the construction phase. The analyses were performed on the two types of cross section applied to the fabrication of AU composite beams, and the results were compared to the those of 2-point bending tests. In addition, the flexural performance according to the space of intermittent cap-type shear connectors and the location of reinforcing steel bars for compression was comparatively investigated. Through the results of analytical studies, it is preferable to adopt the yield moment of AU composite beam for evaluating the safety in the construction phase, and to limit the space of intermittent shear connectors to 400 mm or less for the construction load.

• Journal of Korean Association for Spatial Structures
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• v.16 no.4
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• pp.133-140
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• 2016

SLIM AU(A plus U-shaped) composite beam had been developed for not only reducing the story height in residential and commercial building, but also saving the cost of floor construction. The structural performance and economic feasibility was sufficiently approved by means of structural experiments and analytical studies. Even though fire resistance of the SLIM AU composite beam was evaluated throughout furnace fire test, the fire performance of the composite beam using finite element analysis is not analysed yet. Therefore the predictions of fire resistance simulations with loading as well as temperature distribution of the composite beam are summarized in this paper.

• Journal of Korean Association for Spatial Structures
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• v.19 no.3
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• pp.77-83
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• 2019

AU(A plus U-shaped) composite beam was developed for reducing the story height in the residential buildings, and saving the cosrtuction cost of floor structures. Structural performance and economic feasibility of the composite beam have been sufficiently approved through the structural experiments and the analytical studies. Fire safety for the practical application of the composite beam has also been verified through the fire resistance tests and the heat transfer analyses. In this study 2-points bending tests were performed on the four specimens already tested for fire resistance to evaluate the residual bending strength of AU composite beam after fire accident. The same bending test was performed on the one fresh specimen having the same section and span of the specimens for practically comparative study.