• 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.

• Steel and Composite Structures
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• 제31권6호
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• pp.541-558
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• 2019

In Special Concentrically Braced Frames (SCBFs), vertical and horizontal components of the brace force must be resisted by column and beam, respectively but normal force component existing at the gusset plate-to-column and beam interfaces, creates out-of-plane action making distortion in column and beam faces adjacent to the gusset plate. It is a main concern in Hollow Structural Section (HSS) columns and beams where their webs and gusset plate are not in the same plane. In this paper, a new gusset plate passing through the HSS columns and beams, named as through gusset plate, is proposed to study the force transfer mechanism in such gusset plates of SCBFs compared to the case with conventional gusset plates. For this purpose, twelve SCBFs with diagonal brace and HSS columns and twelve SCBFs with chevron brace and HSS columns and beams are considered. For each frame, two cases are considered, one with through gusset plates and the other with conventional ones. Based on numerical results, using through gusset plates prevents distortion and out-of-plane deformation at HSS column and beam faces adjacent to the gusset plate helping the entire column and beam cross-sections to resist respectively vertical and horizontal components of the brace force. Moreover, its application increases energy dissipation, lateral stiffness and strength around 28%, 40% and 32%, respectively, improving connection behavior and raising the resistance of the normal force components at the gusset plate-to-HSS column and beam interfaces to approximately 4 and 3.5 times, respectively. Finally, using such through gusset plates leads to better structural performance particularly for HSS columns and beams with larger width-to-thickness ratio elements.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.729-732
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• 1999

In this paper, the Mohr-Coulomb criterion was adopted to predict the bonding failure load of the reinforced concrete beams strengthened by the externally bonded steel plates. Based on this criterion, a nonlinear analysis program of APSB(Analysis Program for Strengthened Beams) and nonlinear finite element analysis program of RCSD-SB (Reinforced Concrete Structural Design - Strengthened Beams) were developed. Numerical results were then compared with experimental results and good agreements were obtained.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.72-75
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• 2004

Carbon Fiber Reinforced Polymer(CFRP) composites are widely applied to strengthen deteriorated concrete structures. This paper presents the experimental results of the performance of reinforced concrete(RC) beams strengthened with externally prestressed CFRP plates. Simple beams with 3 m span length were tested to investigate the effect of prestressing force of CFRP plates on the flexural behavior of externally strengthened RC beams.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.739-744
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• 2000

The aim of this research is to investigate and to compare the shear strengthening effects of steel plates and glass fiber sheets(GFS). Shear damaged beams were repaired by steel plates and GFS. Thickness of steel plates and strengthening type of GFS were taken as the parameters. With loading, the development and propagation of cracks, failure mode and deformation of strengthening materials were checked. The ultimate load was compared with formulas proposed by previous researchers.

• Structural Engineering and Mechanics
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• 제10권3호
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• pp.211-226
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• 2000

A procedure has been developed for bolting steel plates to the sides of existing reinforced concrete beams which can be used to increase the shear strength of beams, increase the flexural strength of beams with enhanced ductility or with only a small loss of ductility, and increase the stiffness of beams in order to reduce deflections and crack widths. It will be shown in this paper, through a qualitative analysis and through the results of testing eight large scale beams, that standard rigid plastic analysis techniques which are commonly used in the design of reinforced-concrete, steel, and composite steel and concrete beams cannot be used directly to design composite bolted-plated reinforced-concrete beams. In the companion paper, quantitative procedures will be used to adapt the standard rigid plastic analysis techniques for this relatively new form of retrofitting.

• Steel and Composite Structures
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• 제22권1호
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• pp.183-201
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• 2016

Perforated steel beams can be optimised by increased beam depth and the moment of inertia combined with a reduced web thickness, favouring the use of original I-section beams. The designers are often confronted with situations where optimisation cannot be carried out effectively, taking account of the buckling risk at web posts, moment-shear transfers and local plastic deformations on the transverse holes of the openings. The purpose of this study is to suggest solutions for reducing these failure risks of tested optimal designed beams under applying loads in a self-reacting frame. The design method for the beams is the hunting search optimisation technique, and the design constraints are implemented from BS 5950 provisions. Therefore, I have aimed to explore the strengthening effects of reinforced openings with ring stiffeners, welded vertical simple plates on the web posts and horizontal plates around the openings on the ultimate load carrying capacities of optimally designed perforated steel beams. Test results have shown that compared to lateral stiffeners, ring and vertical stiffeners significantly increase the loadcarrying capacity of perforated steel beams.

• KCI Concrete Journal
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• 제14권1호
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• pp.51-60
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• 2002

Strengthening of existing concrete structures is a major concern in recent years as the number of degraded structures increases. The purpose of this paper is to investigate the static and fatigue behavior of reinforced concrete (RC) beams strengthened with steel plates. To this end, a comprehensive test program has been set up and many series of strengthened beams have been tested. The major test variables include the plate thickness, adhesive thickness, and the shear-span to depth ratio. The test results indicate that the separation of plates is the dominant failure mechanism even for the full-span-length strengthened beams with steel plate. The theoretical ultimate load capacities for strengthened beams based on the full composite action of concrete beam and steel plate are found to be larger than the actual measured load capacities. The strengthened beams exhibit more dominant shear cracking as the shear-span to depth ratio decreases. The ultimate capacity of strengthened beams increases slightly with the increase of adhesive thickness, which may be caused by the late initiation of plate separation in the beams with thicker adhesive. A realistic concept of ductility for plate-strengthened beams is proposed in this study. It is seen that the strengthened beams show relatively low ductility compared with unstrengthened beams. The present study indicates that the strengthened beams exhibit much higher fatigue resistance than the unstrengthened beams. The increase of deflections of strengthened beams according to the number of load cycles is much smaller than that of unstrengthened beams. The present study provides very useful results for the realistic application of plate-strengthening method in reinforced concrete structures.

• 콘크리트학회논문집
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• 제26권2호
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• pp.171-179
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• 2014

이 연구는 DH beam의 구조성능을 평가하는 것을 목적으로 하였다. DH beam을 사용하는 DH 공법은 얇은 철판을 성형하여 거푸집 및 구조적 역할을 할 수 있는 철판을 철근과 함께 공장에서 선조립하여 현장으로 반입하여 콘크리트를 타설하는 공법이다. 이 때 DH 판이 거푸집 역할 뿐 아니라 휨강도에 기여할 것으로 여겨져서 이 연구에서는 DH 판의 휨강도 기여도를 평가하고자 하였다. 총 5개의 실험체를 대상으로 실험 및 해석적 연구를 수행하였다. 실험체는 2개의 정모멘트 실험체, 2개의 부모멘트 실험체, 그리고 1개의 RC 실험체로 구성되었다. RC 실험체는 DH beam과 비교를 목적으로 제작하였다. DH beam에 대한 실험 결과는 휨강도를 산정하는 설계식 그리고 RC 실험체에 대한 실험 결과 등과 비교를 통하여 DH beam은 철판이 항복하면서 충분히 휨강도에 기여하고 있음을 알 수 있었다. 그리고 비선형 구조해석에서는 두 개의 실험체에 대하여 DH 판이 있는 경우와 없는 경우를 대상으로 휨강도, 콘크리트의 주인장변형률, 그리고 철근의 응력을 비교하였으며, 해석에서도 DH 판이 휨강도에 충분히 기여함을 알 수 있었다. 이상과 같은 실험 및 해석적 연구의 결과 DH beam의 철판은 콘크리트와 합성단면을 형성하여 충분한 휨강도를 갖는 것으로 보였다.

• 콘크리트학회논문집
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• 제19권4호
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• pp.467-474
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• 2007

본 논문에서는 부착 유무, 정착장치 유무, 긴장량, 경간 길이 등을 실험 변수로 하여 총 13개의 시험체를 제작하여 휨 성능 실험과 유한요소해석을 수행하였다. 1개의 표준시험체, 2개의 긴장력을 도입하지 않는 보강시험체, 4개의 긴장력을 도입한 비부착보강시험체, 4개의 긴장력을 도입한 부착시험체와 2개의 경간 길이가 다른 보강시험체를 제작하였다. 또한, 콘크리트의 비선형, 철근 및 탄소섬유와 콘크리트와의 계면 특성을 고려한 DIANA 프로그램을 이용하여 비선형 유한요소해석을 수행하였다. 긴장력을 도입한 보강된 시험체는 박리 파괴가 아닌 FRP 파단에 의하여 최종파괴가 되었다. 특히, 긴장력을 도입한 부착시험체는 1차, 2차 박리가 발생 후, 정착장치의 고정으로 인하여 부착시스템에서 비부착시스템으로 전환되었다. 또한, 탄소섬유판으로 보강된 시험체의 해석 결과와 실험 결과를 비교 분석하였다. 긴장력을 도입한 탄소섬유판으로 보강된 모든 시험체는 연성지수가 3이상 나타나 어느 정도 이상의 연성을 확보하고 있는 것으로 알 수 있었다. 그리고 박리하중과 항복하중 및 극한하중에서 실험값과 해석값이 잘 일치하는 것으로 나타났다.