• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
• /
• pp.817-820
• /
• 2000

Existence of void or delamination inside building foundation or tunneling lining can cause serious problems in structural safety. Therefore, 0probing of such voids in architectural and civil structures is an important process in evaluating the overall integrity of the structures. In this study, the radar method has been examined in its use in detecting voids inside concrete specimens. The dimensions of the specimens are 1,000 mm(width) $\times$ 600 mm (height) $\times$ 140 mm (thickness). A void is embedded inside concrete specimens with the dimensions of 200 mm(width) $\times$ 600 mm (height) $\times$ 50 mm (thickness). Concrete cover depth of 30 mm, 60 mm is studied for comparison. In both cases, the voids is located with 1 GHz antenna.

• Structural Engineering and Mechanics
• /
• 제77권6호
• /
• pp.745-751
• /
• 2021

Concrete filled double skin tubular members (CFDST) consist of double concentric circular or square steel tubes with concrete filled between the two steel tubes. The CFDST members, having a hollow section inside the internal tube, are generally lighter than ordinary concrete filled steel tubular members (CFT) which have a solid cross-section. Therefore, when the CFDST members are applied to bridge piers, reduction of seismic action can be expected. The present study aims to investigate, experimentally, the behavior of CFDST stub columns with double concentric square steel tubes filled with concrete (SS-CFDST) when working under centric compression. Two test parameters, namely, inner-to-outer width ratio and outer square steel tube's width-to-thickness were selected and outer steel tube's width-to-thickness ratio ranging from 70 to 160 were considered. In the results, shear failure of the concrete fill and local buckling of the double skin tubes having largest inner-to-outer width ratio were observed. A method to predict axial loading capacity of SS-CFDST is also proposed. In addition, the load capacity in the axial direction of stub column test on SS-CFDST is compared with that of double circular CFDST. Finally, the biaxial stress behavior of both steel tubes under plane stress is discussed.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
• /
• pp.379-382
• /
• 2005

Composite behavior between FRP-concrete composite deck and girder is investigated by numerical analysis and parametric experiments. Compared to reinforced concrete deck, the weight of FRP-concrete composite deck is about 64$\%$ but the performance of composition is 90$\%$. Therefore the FRP-concrete composite deck has the advantage of longitudinal section stiffness increase in case of composition to the girder. The experiment, according to the variation of stud diameter, stud length and bedding thickness, is carried out. As a result, the static failure strength increases as stud diameter and length increase and bedding thickness decreases.

• Journal of Radiation Protection and Research
• /
• 제8권1호
• /
• pp.33-37
• /
• 1983

물 또는 콘크리트반사체(反射體)의 두께 및 콘크리트반사체(反射體)와 핵물질용액계(核物質溶液系) 사이의 간격에 따라 변(變)하는 유효증배계수(有效增倍係數)로서의 반사효과(反射效果)를 중성자수송이론(中性子輸送理論)에 기초를 둔 각분할방법(角分割方法)의 전산코드 ANISN으로 계산하였다. 그 결과에 따르면 반사체(反射體)의 두께가 엷을 때, 유효증배계수(有效增倍係數)를 기준으로 한 물 반사체(反射體)의 반사효과(反射效果)는 콘크리트에서보다 크지만 그 두께가 커지면 반대현상도 생기는 것 같았다. 한편 핵물질용액계(核物質溶液系)와 콘크리트반사체(反射體)사이에 물이 채워져 있고 그 간격변화에 따라 산출한 유효증배계수치(有效增倍係數値)는 처음 급격하게 감소하다가 약 15cm를 지나면서부터 서서히 감소하는 것 같았다.

• Computers and Concrete
• /
• 제22권3호
• /
• pp.279-289
• /
• 2018

Shear walls are one of the important structural elements for bearing loads imposed on buildings due to winds and earthquakes. Composite shear walls with high lateral resistance, and high energy dissipation capacity are considered as a lateral load system in such buildings. In this paper, a composite shear wall consisting of steel faceplates, infill concrete and tie bars which tied steel faceplates together, and concrete filled steel tubular (CFST) as boundary columns, was modeled numerically. Test results were compared with the existing experimental results in order to validate the proposed numerical model. Then, the effects of some parameters on the behavior of the composite shear wall were studied; so, the diameter and spacing of tie bars, thickness and compressive strength of infill concrete, thickness of steel faceplates, and the effect of strengthening the bottom region of the wall were considered. The seismic behavior of the modeled composite shear wall was evaluated in terms of stiffness, ductility, lateral strength, and energy dissipation capacity. The results of the study showed that the diameter of tie bars had a trivial effect on the performance of the composite shear wall, but increasing the tie bars spacing decreased ductility. Studying the effect of infill concrete thickness, concrete compressive strength, and thickness of steel faceplates also showed that the main role of infill concrete was to prevent buckling of steel faceplates. Also, by strengthening the bottom region of the wall, as long as the strengthened part did not provide a support performance for the upper part, the behavior of the composite shear wall was improved; otherwise, ductility of the wall could be reduced severely.

• 콘크리트학회지
• /
• 제9권3호
• /
• pp.157-166
• /
• 1997

본 연구에서는 대기 습도변화에 의한 콘크리트 보수체(기층 콘크리트/보수 모르터)의 파괴현상을 조사하기 위해서 보수체내의 비정상적인 습도분포 및 습도응력을 계산하였다. 이러한 계산은 시멘트 모르터로 보수된 접촉면이 없는 보수체에서 보수층 두께(Do=05-2.5cm)와 보수 작업전 기층 콘크리트 표면의 습윤처리 시간(tc=1-5days) 및 대기습도(Ho=50~80%)를 주요변수로 하여 수행되었다. 계산 및 조사 결과에 의하면 접합면의 응력이 압축상태를 유지하기 위해서는 각 대기 습도마다 일정값 이상의 보수층 두께와 습윤처리 시간이 필요함을 알 수 있다.

• Computers and Concrete
• /
• 제28권5호
• /
• pp.497-506
• /
• 2021

Steel-concrete composite structures and precast concrete elements have a common prefabrication process and allow fast construction. The use of hollow-core slabs associated with composite floors can be advantageous. However, there are few studies on the subject, impeding the application of such systems. In this paper, a numerical model representing the considered system using the FE (finite element)-based software DIANA is developed. The results of an experimental test were also presented in Souza (2016) and were used to validate the model. Comparisons between the numerical and test results were performed in terms of the load versus displacement, load versus slip, and load versus strain curves, showing satisfactory agreement. In addition, a wide parametric study was performed, evaluating the influence of several parameters on the behaviour of the composite system: The strength of the steel beam, thickness of the web, thickness and width of the bottom flange of the steel beam and concrete cover thickness on top of the beam. The results indicated a great influence of the steel strength and the thickness of the bottom flange of the steel beam on the capacity of the composite floor. The remaining parameters had limited influences on the results.

• 산업기술연구
• /
• 제16권
• /
• pp.31-38
• /
• 1996

This experimental study was conducted to analyze the characteristics of centrifugal pipes which were made of silica fume concrete. External load tests showed that maximum external load ranged from 1,100~5,300kgf/m with thickness ratio(t/D) of between 4.5%~10.0%. Correlation between thickness ratios and external loads was excellent with $R^2$ of 0.99. Respective correlation between measured and computed vertical deformation was good with $R^2$ of higher than 0.90. And therefore, vertical deformation and tensile stress of centrifugal concrete pipes may be theoretically computed with a good precision.

• 한국화재소방학회논문지
• /
• 제24권4호
• /
• pp.41-46
• /
• 2010

고강도 콘크리트는 대형 사회기반 구조물로서 많이 활용되고 있다. 고강도 콘크리트는 우수한 재료적 성능과 내구성을 확보하고 있지만 반면에 화재에 대한 급작스러운 폭렬현상으로 인하여 구조적인 문제를 야기시키기도 한다. 따라서 본 연구에서는 콘크리트 피복두께에 추가하여 내화피복재를 사용함으로써 내화피복두께에 따른 콘크리트의 내화성능을 평가하고 최적의 내화피복두께를 산정하는 실험적 연구를 수행하였다. 내화피복재를 10mm 간격으로 증가시키면서 실험을 수행한 결과 콘크리트의 내화성능이 크게 향상됨을 볼 수 있었으며, 최적의 내화피복두께는 약 1~3mm로 산정되었다. 또한 폭렬에 의하여 급작스러운 콘크리트 내부의 온도상승 이후 기화열에 의한 열손실로 완만하게 온도가 상승되는 현상이 실험적으로 관측되었다. PP 섬유는 약 $200^{\circ}C$ 부근에서 용해되어 고온에서는 빈 채널만 남게 되므로 내부 증기압을 저감시켜주는 역할도 관측되었다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
• /
• pp.559-565
• /
• 1998

Flexural tests on 2.4m long reinforced concrete beams with epoxy-bonded GFRP plates are reported in these tests. The selected experimental variables are strengthening plate length, plate thickness, plate width and the method of anchoring the plate ends. The effects of these variables in overall behavior are discussed. The results generally indicate that the flexural strength of strengthened beams is increased. The ductile behavior of tested beams in inversely proportional to the plate thickness, plate width. The use of an U-jacket plate provided a proper anchorage system and improved the ductility of beams.