• Smart Structures and Systems
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• 제18권3호
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• pp.601-623
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• 2016

Precast concrete elements are widely used in the construction of buildings and civil infrastructures as they provide higher construction quality and requires less construction time. However, any abnormalities in precast concrete surfaces such as non-flatness or distortion, can influence the erection of the elements as well as the functional performance of the connections between elements. Thus, it is important to undertake surface flatness and distortion inspection (SFDI) on precast concrete elements before their delivery to the construction sites. The traditional methods of SFDI which are conducted manually or by contact-type devices are, however, time-consuming, labor-intensive and error-prone. To tackle these problems, this study proposes techniques for SFDI of precast concrete elements using laser scanning technology. The proposed techniques estimate the $F_F$ number to evaluate the surface flatness, and estimate three different measurements, warping, bowing, and differential elevation between adjacent elements, to evaluate the surface distortion. The proposed techniques were validated by experiments on four small scale test specimens manufactured by a 3D printer. The measured surface flatness and distortion from the laser scanned data were compared to the actual ones, which were obtained from the designed surface geometries of the specimens. The validation experiments show that the proposed techniques can evaluate the surface flatness and distortion effectively and accurately. Furthermore, scanning experiments on two actual precast concrete bridge deck panels were conducted and the proposed techniques were successfully applied to the scanned data of the panels.

• 건축구조
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• 제11권2호
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• pp.76-77
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• 2004

• 한국건설순환자원학회논문집
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• 제8권3호
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• pp.269-275
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• 2020

본 연구에서는 초고성능 콘크리트를 적용한 경량 프리캐스트 패널 개발의 일환으로 단면 두께와 철근 배근 유무에 따른 패널의 휨 재하 실험을 수행하였다. 일반 콘크리트 패널 1개와 초고성능 콘크리트를 사용한 경량 프리캐스트 패널 3개로서 총 4개의 패널을 제작하였다. 초고성능 콘크리트를 사용하고 철근을 보강하지 않은 패널은 단면 크기와 상관없이 일반 콘크리트 패널에 비해 휨 성능이 저하되는 것으로 나타났다. 초고성능 콘크리트를 적용한 속빈 단면에 콘크리트 양을 감소시킨 패널은 일반 콘크리트 패널에 비해 휨 성능이 150% 향상되었다. 이는 초고성능 콘크리트를 사용한 프리캐스트 패널의 단면 최적화 설계를 통해 더욱 경량화가 가능할 것으로 판단된다. 초고성능 콘크리트를 사용한 경량 프리캐스트 패널을 실제 구조물에 적용하기 위해서는 전단 성능과 연결 상세에 대한 추가 검토가 필요할 것으로 판단된다.

• 한국도로학회논문집
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• 제10권2호
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• pp.229-239
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• 2008

콘크리트 슬래브를 공장에서 제작하여 도로포장의 신설 또는 보수에 사용하는 공법인 프리캐스트 콘크리트 포장의 하중전달 성능을 평가하기 위하여 연구를 수행하였다. 실내실험을 통해 다웰바 연결 부분의 그라우팅 효과를 측정할 수 있는 방법을 고안하였으며 이러한 실험을 위해 실험체를 제작하여 실험하였다. 실험을 수행한 결과 그리우팅을 한 다웰바의 전단강도는 콘크리트와 일체식으로 된 다웰바의 전단강도에 비해 떨어지지 않음을 알 수 있었다. 이울러 현장에서의 시험시공을 통해 설치된 보수용 프리캐스트 콘크리트 포장에 대해서도 FWD 시험을 실시하여 하중전달 성능을 평가하였다. 현장 실험 결과 기존 콘크리트 포장에 비해 슬래브 중앙부에서의 처짐은 다소 크게 나타나나, 줄눈부에서의 하중전달율은 거의 유사한 것으로 나타났다.

• Computers and Concrete
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• 제25권3호
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• pp.273-282
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• 2020

A new seismic design methodology for precast concrete diaphragms has been developed and incorporated into the current American seismic design code. This design methodology recognizes that diaphragm inertial forces during earthquakes are highly influenced by higher dynamic vibration modes and incorporates the higher mode effect into the diaphragm seismic design acceleration determination using a first mode reduced method, which applies the response modification coefficient only to the first mode response but keeps the higher mode response unreduced. However the first mode reduced method does not consider effects of diaphragm flexibility, which plays an important role on the diaphragm seismic response especially for the precast concrete diaphragm. Therefore this paper investigated the effect of diaphragm flexibility on the diaphragm seismic design acceleration for precast concrete shear wall structures through parametric studies. Several design parameters were considered including number of stories, diaphragm geometries and stiffness. It was found that the diaphragm flexibility can change the structural dynamic properties and amplify the diaphragm acceleration during earthquakes. Design equations for mode contribution factors considering the diaphragm flexibility were first established through modal analyses to modify the first mode reduced method in the current code. The modified first mode reduced method has then been verified through nonlinear time history analyses.

• 한국안전학회지
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• 제27권2호
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• pp.25-32
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• 2012

In this study, the effect of blast furnace slag on precast concrete culvert was assessed by measuring the flexural strength using to full scaled box culvert. As a result, the initial cracking load and yield load of reinforced concrete box converts are increased in comparison with those of the normal concrete box culvert, but the ultimate load is decreased slightly. It can be concluded that use of blast furnace slag induce to flexural strength in precast concrete box culvert greatly improved the serviceability.

• Computers and Concrete
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• 제5권6호
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• pp.525-544
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• 2008

In this research, the self-centering effect in precast and prestressed reinforced concrete structures was investigated experimentally. The reinforced concrete beams and columns were precast and connected by post-tensioning tendons passing through the center of the beams as well as the panel zone of the connections. Three beam-to-interior-column connections were constructed to investigate parameters such as beam to column interfaces (steel on steel or plastic on plastic), energy dissipating devices (unbonded buckling restrained steel bars or steel angles) and the spacing of hoops in the panel zone. In addition to the self-centering effect, the shear strength in the panel zone of interior column connections was experimentally and theoretically evaluated, since the panel zone designed by current code provisions may not be conservative enough to resist the panel shear increased by the post-tensioning force.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.619-622
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• 2004

In this study, a moment resisting precast concrete beam-column connection is proposed. An experimental study was carried out to investigate the connection behavior subjected to cyclic loading. Three precast beam-column interior connections and one monolithic connection were tested. Variable included the detailing used at the joint to achieve structural constructability and the location of mild steel reinforcement and high strength bar. During specimen fabrication, the joint details enables ease and speed of construction. Connection performance is evaluated on the basis of ductility, energy dissipation capacity, connection strength, and drift capacity. Based on test results, the precast concrete beam-column connection is capable of matching or exceeding the performance of the monolithic connection.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.469-474
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• 2003

Recently, to overcome the disadvantages of RC decks, advanced countries such as Japan and USA, and Europe are using prestressing connection precast decks and loop connection precast decks. The prestressing connection precast deck, however, has a weakness against steel corrosion, because of unreliable enforced grouting. The relatively low loading and fatigue capacities of the loop connection precast deck make it difficult to be used for the bridge that requires high fatigue resistance due to the frequent over loaded vehicles. This research proposes the improved connecting method for the precast decks to minimize its shortcomings based on both numerical analyses and full scale model tests. The proposed method maximizes the advantages of precast decks and extends it's service life.

• 복합신소재구조학회 논문집
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• 제6권2호
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• pp.8-16
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• 2015

Prestressed concrete (PSC) is a method in which prestressed tendon is placed inside and/or outside the reinforced concrete member and the compressive force applied to the concrete in advance to enhance the engineering properties of concrete member which is weak under tension. In this paper we suggested the precast PSC girder assembled with segments of portable size and weight at the factory. The segments of precast PSC girder will be delivered and assembled as a unit of PSC girder at the site. Consequently, we suggested new-type of precast segmented PSC girder with different shapes of segment cross-section (i.e., I-shape, Box-shape). To mitigate the problems associated with the field splice between the segments of precast PSC girder anchor system is attached near the neutral axis of the girder and relatively uniform compression throughout the girder cross-section is applied. Prior to the experimental investigation, analytical investigation on the structural behavior of precast PSC girder was performed and the serviceability (deflection) and safety (strength) of the girder were confirmed. In addition, 4-point bending test on the girder was conducted to investigate the structural performance under bending. From the experimental investigation, it was found that the precast PSC girder spliced with 3 and 5 segments has sufficient in serviceability and safety conditions and it was also observed that the point where the segments spliced has no defects and the girder behaves as a unit.