• 제목/요약/키워드: Reduction of construction period

검색결과 222건 처리시간 0.034초

Control effect and mechanism investigation on the horizontal flow-isolating plate for PI shaped bridge decks' VIV stability

  • Li, Ke;Qian, Guowei;Ge, Yaojun;Zhao, Lin;Di, Jin
    • Wind and Structures
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    • 제28권2호
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    • pp.99-110
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    • 2019
  • Vortex-Induced-Vibration (VIV) is one kind of the wind-induced vibrations, which may occur in the construction and operation period of bridges. This phenomenon can bring negative effects to the traffic safety or can cause bridge fatigue damage and should be eliminated or controlled within safe amplitudes.In the current VIV studies, one available mitigation countermeasure, the horizontal flow-isolating plate, shows satisfactory performance particularly in PI shaped bridge deck type. Details of the wind tunnel test are firstly presented to give an overall description of this appendage and its control effect. Then, the computational-fluid-dynamics(CFD) method is introduced to investigate the control mechanism, using two-dimensional Large-Eddy-Simulation to reproduce the VIV process. The Reynolds number of the cases involved in this paper ranges from $1{\times}10^5$ to $3{\times}10^5$, using the width of bridge deck as reference length. A field-filter technique and detailed analysis on wall pressure are used to give an intuitive demonstration of the changes brought by the horizontal flow-isolating plate. Results show that this aerodynamic appendage is equally effective in suppressing vertical and torsional VIV, indicating inspiring application prospect in similar PI shaped bridge decks.

이중버블시트를 이용한 단열양생공법의 한중콘크리트 현장적용 (Field Application of Insulation Curing Method with Double Bubble Sheets Subject to Cold Weather)

  • 홍석민;백대현;김종;전충근;한민철;한천구
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2008년도 춘계 학술논문 발표대회
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    • pp.57-60
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    • 2008
  • This study investigated the results of insulation heat curing method using double layer bubble sheet in slab concrete and mass concrete in cold weather environment. First of all, when double bubble sheets are applied, it was shown that slab concrete was protected from early freezing by remaining between 6 and 15℃ even in case outside temperature drops -9℃ below zero until the 2nd day from piling, and in the case of mass concrete, with the maximum temperature difference between the center and surface less than 4℃, crack occurrence index was close to 2 and no hydration heat crack occurred by internal constraint. The insulation heat preservation curing method using the double bubble sheet applied in this field prevented early freezing owing to stable curing temperature management, deterring concrete strength development delay at low temperature, and obtained the needed strength. Also, it was proven that the method is highly effective and economic for cold weather concrete quality maintenance through curing cost reduction like construction period shortening and labor cost reduction, etc by reducing the process of temporary equipment installation and disassembling.

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이중버블시트를 이용한 단열보온 양생공법의 한중콘크리트 현장적용 (Field Application of Insulation Curing Method for the Concrete applying Double Layer Bubble Sheets Subjected to Cold Weather)

  • 홍석민;손호정;오치현;한민철;한천구
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2011년도 춘계 학술논문 발표대회 1부
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    • pp.83-85
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    • 2011
  • This study investigated the results of insulation heat curing method using double layer bubble sheet in concrete in cold weather environment. First of all, when double bubble sheets are applied, it was shown that concrete was protected from early freezing by remaining between 7℃ and 3℃ even in case outside temperature drops -7℃ below zero until the 3d day from piling. The insulation heat preservation curing method using the double bubble sheet applied in this field prevented early freezing owing to stable curing temperature management, deterring concrete strength development delay at low temperature, and obtained the needed strength. Also, it was proven that the method is highly effective and economic for cold weather concrete quality maintenance through curing cost reduction like construction period shortening and labor cost reduction, etc by reducing the process of temporary equipment installation and disassembling.

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이중버블시트를 이용한 단열양생공법의 한중콘크리트 현장적용 (Field Application of Insulation Curing Method with Double Bubble Sheets Subject to Cold Weather)

  • 홍석민;이일선;백대현;김종;한민철;한천구
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2009년도 춘계 학술논문 발표대회 학계
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    • pp.25-28
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    • 2009
  • This study investigated the results of insulation heat curing method using double layer bubble sheet in slab concrete in cold weather environment. First of all, when double bubble sheets are applied, it was shown that slab concrete was protected from early freezing by remaining between 5 and $l0^{\circ}C$ even in case outside temperature drops $-11^{\circ}C$ below zero until the 4nd day from piling. The insulation heat preservation curing method using the double bubble sheet applied in this field prevented early freezing owing to stable curing temperature management, deterring concrete strength development delay at low temperature, and obtained the needed strength. Also, it was proven that the method is highly effective and economic for cold weather concrete quality maintenance through curing cost reduction like construction period shortening and labor cost reduction, etc by reducing the process of temporary equipment installation and disassembling.

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페인트 도장공사의 색관리에 관한 연구 (A study on the color controlled of painter's work)

  • 심명섭;이현정
    • 한국건축시공학회지
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    • 제3권1호
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    • pp.107-114
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    • 2003
  • This study aims to find methods that prevents aging of buildings paint coating and that limits defects in construction. Defects in painting can occur in four stages: pure paint, during painting, after the paint coating has dried, and after some period of time has passed after coating. Paint may become bad due to precipitation of pigments, formation of membranes, and seeding during manufacturing. Therefore, it is important that the paint is well mixed and kept airtight at a cool, dark place. Indents, paint brush strokes, orange peel, separation of colors, and paint running and spreading during the paint work process can be prevented by using high quality materials and applying a high-level of construction method. After the paint coating has dried, boiling, yellowing, poor drying, poor bonding, and/or glen deficiency may occur. These are influenced by the levels of cleanness of the dried product, drying temperature and hydration. Then, when the coating has been left dried for some period of time, cracking, peeling, scaling, swelling, discoloring, and/or rusting may develop due to the ultraviolet and contaminants in the air. Since these defects occur due to inappropriate construction schedule and/or hot and humid condition, one must use weatherproof materials. Furthermore, poor paint color may be caused by contamination in the sample plate, discoloration, and/or discrepancies in colors which are due to material differences, level of glossiness, degree of dispersion, dual color property of metallic colors, precipitation of pigments, etc. One should achieve reduction in construction cost and effectiveness in paint work by limiting contaminations in the construction site and strictly observing to construction regulations.

굴삭기 요소수 탱크 커버의 신규 모델 개발을 위한 CAE 기반 프레스 성형 공정 설계 (Stamping process design to develop a urea tank cover for excavators based on sheet metal forming analysis)

  • 전용준;허영무;윤석현;김동언
    • Design & Manufacturing
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    • 제14권2호
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    • pp.49-55
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    • 2020
  • Recently, when a new component of construction equipment is designed, a stamping process capable of producing parts having high appearance quality and precision has been gaining attention. However, in general, as it is developed based on existing parts made by welding metal sheets and tubes, frequent to die modification occurs, which increases the time and cost of developing new parts. Thus, it is necessary to reduce the cost by shortening the die development period. In this study, a stamping process was designed for the urea tank cover, which is a part for excavators, to reduce the die development period through sheet metal forming analysis. The stamping process was designed by determining the blank holding force after selecting the initial blank shape and size. The round value at the corner was modified such that formability is ensured. After selecting process parameters, the thickness reduction rate and spring-back effect were reviewed.

적산온도 기법을 활용한 콘크리트구조물의 강도관리모델 개발에 관한 연구 (A Study on the Development of Strength Control Model of Concrete Structure using Maturity Method)

  • 길배수;윤종기;김재환;김정일;남재현;김무한
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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    • pp.711-716
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    • 2002
  • The purpose of this study is to develop a strength control model for application of variety internal condition at construction field. The results of this study were shown as follows ; 1) According to results of compressive strength of concrete by using equivalent age, new curve is applicable of construction field because there is similar relation with logistic curve. 2) It is shown that the construction period is shorten by reduction of the formwork removal time, because a predicted compressive strength of using the new curve is high than proposed compressive strength of standard.

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동절기 고강도콘크리트의 시공에 있어서 초기동해 방지에 관한 실험적 연구 (An Experimental Study on the Early Frost Resistance Properties of High-Strength Concrete in Winter Concreting)

  • 권영진
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2001년도 학술논문발표회
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    • pp.76-81
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    • 2001
  • Recently, the structure is higher and larger, so that the application of high-strength concrete is increased, And as the development of construction skills, it is possible to place during the winter. Concrete work during winter is indispensible to shorten time of completion and cut costs. When concrete work during winter is placed, it has anxiety that concrete freeze at low temperature. As repetition of concrete's freezing cause reduction of durability, it is necessary for mixing to pay attention to air content and W/C ratios. Accordingly, in this study, we estimate the frost resistance by air content and W/C ratios, and development of strength after early-frost damage in the high-strength concrete during the cold weather. In this study, it could be confirmed that factors which were air content, W/C ratios and early curing period, affected on the frost resistance.

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초기 재령에서 초음파 속도법을 활용한 보통 및 경량 골재 콘크리트의 강도 발현 평가 (Evaluation of Strength of Normal and Lightweight Aggregate Concrete Using Ultrasonic Velocity Method in Early Age)

  • 남영진;김원창;최형길;류정림;이태규
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2023년도 봄 학술논문 발표대회
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    • pp.55-56
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    • 2023
  • Recently, large and high-rise buildings are increasing, and accordingly, concrete weight reduction is required. Lightweight aggregate concrete can provide economic feasibility and large space, but safety can be reduced due to problems such as low strength and poor durability. Since the development of such low strength of concrete is important in the early construction stage, it is necessary to evaluate the vertical formwork demolding period at the early age. The correlation was analyzed by measuring the compressive strength and ultrasonic pulse velocity. As a result, the ultrasonic pulse rates of normal and lightweight aggregate concrete at the time of 5 MPa expression, which is the time of vertical mold deformation, were 3.07 km/s and 2.77 km/s for W/B 41, and 2.89 km/s and 2.73 km/s for W/B 33.

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등가재령방식에 의한 조기강도 예측기술의 적용성 검토 (Application Review of the Prediction Method of Early-age Strength with Equivalent Age Method)

  • 이재현;정양희;김용로;김옥종;이도범;정재수
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2010년도 춘계 학술논문 발표대회 2부
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    • pp.51-52
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    • 2010
  • In this study, it is confirmed that the use of equivalent age method can be applied to predict the early-age strength in case of using the new early strength concrete developed for the reduction of construction work period by our company, in apartment.

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