• Steel and Composite Structures
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• 제9권1호
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• pp.39-58
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• 2009

Composite joints, considering the composite action of steel and concrete, exhibit, in general, high strength and high ductility. As a consequence, the use of this type of joint has been increasing in many countries, especially in those that are located in earthquake-prone regions. In this paper, a hysteretic model with pinching is presented that is able to reproduce the cyclic response of steel and composite joints. Secondly, the computer implementation and adaptation of the model in a spring element within the computer code Seismosoft is described. The model is subsequently calibrated using a series of experimental test results for composite joints subjected to cyclic loading. Finally, typical parameters for the various joint configurations are proposed.

• Steel and Composite Structures
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• 제33권5호
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• pp.629-640
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• 2019

This paper presents a theoretical and finite element (FE) study on the stress intensity factors of double-edged cracked steel beams strengthened with carbon fiber reinforced polymer (CFRP) plates. By simplifying the tension flange of the steel beam using a steel plate in tension, the solutions obtained for the stress intensity factors of the double-edged cracked steel plate strengthened with CFRP plates were used to evaluate those of the steel beam specimens. The correction factor α₁ was modified based on the transformed section method, and an additional correction factor φ was introduced into the expressions. Three-dimensional FE modeling was conducted to calculate the stress intensity factors. Numerous combinations of the specimen geometry, crack length, CFRP thickness and Young's modulus, adhesive thickness and shear modulus were analyzed. The numerical results were used to investigate the variations in the stress intensity factor and the additional correction factor φ. The proposed expressions are a function of applied stress, crack length, the ratio between the crack length and half the width of the tension flange, the stiffness ratio between the CFRP plate and tension flange, adhesive shear modulus and thickness. Finally, the proposed expressions were verified by comparing the theoretical and numerical results.

• 한국공간구조학회논문집
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• 제18권4호
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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.

• 한국공간구조학회논문집
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• 제18권3호
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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.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 춘계 학술논문 발표대회
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• pp.10-11
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• 2013

Green Frame is a column-beam system formed by composite precast concrete column and beam connected with steel buried in both members. During the installation of Green columns, the columns of Green Frame, covering 3 floors per each piece and beams, the eccentricity can be observed due to the construction error and the weight of beam itself. Such eccentricity may have a little influence on a single frame, yet, it can develop critical issues to the installation of subsequent beams or beams on the upper floors in the context of a building as a whole that has multiple frames. These issues lead to delay in frame installation, decrease of productivity and increase of cost, etc. Therefore, this study presents a steel-joint connection method in order to solve the issues. The steel-joint connection method exists on slope plane and reinforcing plate in steel frame buried in composite PC members. Through this method, the issues can be resolved without requiring additional equipment or manpower.

• Steel and Composite Structures
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• 제6권3호
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• pp.237-255
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• 2006

This paper presents a novel analytical formulation for the analysis of composite beams with partial shear interaction stiffened by a bolted longitudinal plate accounting for time effects, such as creep and shrinkage. The model is derived by means of the principle of virtual work using a displacement-based formulation. The particularity of this approach is that the partial interaction behaviour is assumed to exist between the top slab and the joist as well as between the joist and the bolted longitudinal stiffening plate, therefore leading to a three-layered structural representation. For this purpose, a novel finite element is derived and presented. Its accuracy is validated based on short-and long-term analyses for the particular cases of full shear interaction and partial shear interaction of two layers for which solutions in closed form are available in the literature. A parametric study is carried out considering different stiffening arrangements to investigate the influence on the short-and long-term behaviour of the composite beam of the shear connection stiffness between the concrete slab and the steel joist, the stiffness of the plate-to-beam connection, the properties of the longitudinal plate and the concrete properties. The values of the deflection obtained from the finite element simulations are compared against those calculated using the effective flexural rigidity in accordance with EC5 guidelines for the behaviour of elastic multi-layered beams with flexible connection and it is shown how the latter well predicts the structural response. The proposed numerical examples highlight the ease of use of the proposed approach in determining the effectiveness of different retrofitting solutions at service conditions.

• 한국산학기술학회논문지
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• 제19권3호
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• pp.130-140
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• 2018

U형 강재보를 근간으로 콘크리트 슬래브와 합성을 위하여 A형의 덮개형 강재앵커를 검토하여 AU합성보를 연구하였다. 이는 노출형의 H형강 강재보에 비해 내부 평면의 자율성을 높일 수 있고 공기 단축과 더불어 층고 절감이 가능하며 튜브구조로서 내부에 콘크리틀 충전하여 휨 강도과 휨 강성를 높였다. 본 연구에서는 AU합성보의 휨실험을 통해 성능을 평가하였다. 실험 결과, 하중 초기에 선형적으로 하중이 증가하면서 콘크리트 슬래브의 파괴에 의해 최대 강도에 도달하고 최대 내력의 85% 이상을 발휘하며 연성적 거동을 하였다. 또한, 덮개형 강재앵커를 통해 합성효과를 발휘하였으며 모든 실험체가 최대 내력에 도달할 때까지 완전 합성거동으로 안정적이었다. 그리고 U형 단면의 강판 두께를 증가시켰을 경우에도 휨 강도와 휨 강성이 증가하였고, U형 단면의 하부에 고강도 강판을 용접 부착하였을 경우에도 성능이 개선되었다. AU합성보의 휨강도는 건축구조기준에 따라 제안된 휨 강도식을 적용할 수 있을 것으로 판단되었다.

• Structural Engineering and Mechanics
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• 제34권5호
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• pp.563-580
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• 2010

Composite beams using bolts to attach steel plates to the side faces of existing reinforced concrete (RC) coupling beams can enhance both their strength and deformability. The behavior of those composite beams differs substantially from the behavior of typical composite beams made up of steel beams and concrete slabs. The former are subjected to longitudinal, vertical and rotational slips, while the latter only involve longitudinal slip. In this study, a mixed analysis method was adopted to develop the fundamental equations for accurate prediction of the load-carrying capacity of steel plate strengthened RC coupling beams. Then, a rigid plastic analysis technique was used to cope with the full composite effect of the bolt group connections. Two theoretical models for the determination of the strength of medium-length plate strengthened coupling beams based on mixed analysis and rigid plastic methods are presented. The strength of the strengthened coupling beams is derived. The vertical and longitudinal slips of the steel plates and the shear strength of the anchor-bolt connection group is considered. The theoretical models are validated by the available experimental results presented in a companion paper. The strength of the specimens predicted from the mixed analysis model is found to be in good agreement with that from the experimental results.

• Structural Engineering and Mechanics
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• 제24권3호
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• pp.307-321
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• 2006

This paper is concerned with the behaviour of steel and concrete composite joints subjected to reversal of loading. Three cruciform composite joint specimens and one bare steel joint specimen were tested so that one side of the beam-to-column connection was under negative moment and another side under positive moment. The steelwork beam-to-column connections were made of bolted end plate with an extended haunch section. Composite slabs employing metal decking were used for all the composite joint specimens. The moment-rotation relationships for the joints were obtained experimentally. Details of the experimental observations and results were reported.

• Steel and Composite Structures
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• 제3권1호
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• pp.65-73
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• 2003

A higher level of engineering standard in the field of construction, is the use of prestressing in building structures. The concept of prestressing steel structures has only recently been widely considered, despite a long and successful history of prestressing concrete members. Several analytical studies of prestressed steel girders were reported in literatures, but much of the work was not studied with reference to the optimal design and behaviour of the prestressed steel plate girder. A plate girder prestressed eccentrically, will behave as a beam-column, which is subjected to axial compression and bending moment which will cause the beam to buckle out. The study of buckling of the prestressed steel plate girder is necessary for stability criteria. This paper deals with the stability of prestressed steel plate girder using concept of "Vlasov's Circle of Stability" under eccentric prestressing force.