• 대한기계학회논문집
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• 제9권2호
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• pp.174-180
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• 1985

본 논문에서는 등방성 외팔판의 강성계수 및 공유진동수의 관계로 부터 외팔 보강평판의 강성계수와 고유 진동수와의 관계식을 유도하였으며 고유 진동수를 측정하 여 강성계수를 산정하였다. 위의 강성계수 산정법의 타당성을 입증하기 위하여 외팔 판에 집중하중 작용시 하중, 처짐, 강성계수의 관계식을 유도하고 외팔판 처짐 실험을 하였다. 이론해가 없는 임의보강평판에 대해서도 진동수 측정에 의해 강성계수를 산 정하고, 이를 외팔판 처짐실험에 적용하여 처짐의 이론치와 실험치를 비교 검토하였다.

• 한국산학기술학회논문지
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• 제12권2호
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• pp.936-943
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• 2011

ACI 440.1R-06 설계지침에서는 FRP-보강근 콘크리트 부재의 처짐 계산을 위해 Branson에 의해 제안된 유효단면2차모멘트를 수정 보완하여 제시하고 있다. 그러나 다수의 연구자들은 아직까지도 적용범위의 적절성에 대해 의문점을 제기하고 있다. 이에 본 연구에서는 12개의 장방형 단면과 9개의 T형단면의 FRP-보강근 콘크리트 시험체를 제작하여 처짐 실험을 통해 얻어지는 실험값과 제안된 이론식에 의해 얻어진 계산값을 비교 분석하여 합리적인 처짐설계를 위한 기초자료를 제안하고자 하였다. 결과로서 FRP-보강근 콘크리트 보의 처짐값은 장방형단면에서는 계산값이 실험값 보다 과소평가 되었으나, T형단면에서는 계산값이 실험값 보다 다소 과대평가 되어 나타났다.

• Steel and Composite Structures
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• 제43권6호
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• pp.809-819
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• 2022

This paper proposes a method to predict the deflection of prestressed concrete (PC) beams with corrugated steel web (CSW) under constant load concerning time-dependent variation in concrete material. Over time, the top and bottom concrete slabs subjected to asymmetric compression experience shrinkage and creep deformations. Here, the classical Euler-Bernoulli beam theory assumption that the plane sections remain plane is not valid due to shear deformation of CSW. Therefore, this study presents a method based on the first-order shear deformation to find the long-term deflection of the composite beams under bending by considering time effects. Two experimental prestressed beams of this type were monitored under their self-weight over time, and the theoretical results were compared with those data. Additionally, 3D analytical models of the experimental beams were used according to material properties, and the results were compared with two previous cases. There was good consistency between the analytical and numerical results with low error, which increased by wave radius. It is concluded that the proposed method could reliably be used for design purposes.

• Steel and Composite Structures
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• 제45권1호
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• pp.23-38
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• 2022

This paper presents experimental and analytical studies of eccentrically loaded concrete-filled double steel (CFDST) and concrete-filled double skin tube (DCFST) columns having outer stainless steel tube. Eighteen CFDST and DCFST column specimens were manufactured and tested to examine the strength and load-deflection responses. In the study, the main parameters were concrete strength, load eccentricity, cross section and slenderness. The strengths, load-deflection diagrams and failure patterns of the columns were observed. In addition, the tested CFDST and DCFST columns were analyzed to attain the capacity and load versus lateral deflection responses. The obtained theoretical results were compared with the test results. A parametric study was also performed to research the effects of the ratio of eccentricity (e/H_o) slenderness ratio (L/r), H_o/t_o ratio, H_i/t_i ratio and the concrete compressive strength on the behavior of columns. In this work, the obtained results indicated that the ductility and capacity of columns were affected by cross section, concrete strength, steel strength, loading eccentricity and slenderness.

• Wind and Structures
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• 제36권2호
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• pp.133-147
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• 2023

The random vibration of saddle membrane structures under wind load is studied theoretically and experimentally. First, the nonlinear random vibration differential equations of saddle membrane structures under wind loads are established based on von Karman's large deflection theory, thin shell theory and potential flow theory. The probabilistic density function (PDF) and its corresponding statistical parameters of the displacement response of membrane structure are obtained by using the diffusion process theory and the Fokker Planck Kolmogorov equation method (FPK) to solve the equation. Furthermore, a wind tunnel test is carried out to obtain the displacement time history data of the test model under wind load, and the statistical characteristics of the displacement time history of the prototype model are obtained by similarity theory and probability statistics method. Finally, the rationality of the theoretical model is verified by comparing the experimental model with the theoretical model. The results show that the theoretical model agrees with the experimental model, and the random vibration response can be effectively reduced by increasing the initial pretension force and the rise-span ratio within a certain range. The research methods can provide a theoretical reference for the random vibration of the membrane structure, and also be the foundation of structural reliability of membrane structure based on wind-induced response.

• 콘크리트학회논문집
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• 제23권4호
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• pp.413-420
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• 2011

휨 보강근의 종류 및 조합, 섬유 혼입을 변수로 하는 고강도 콘크리트 보의 구조 실험 결과를 균열 모멘트, 극한 모멘트, 처짐 등에 대해 각종 설계기준 및 가이드라인, 여러 연구자들에 의한 예측식과 비교 검토하였다. 섬유를 혼입하지 않은 FRP 보강근 보강 보의 극한 모멘트 이론값은 실험값을 과소평가하였다. 강섬유가 혼입된 FRP 보강근보강보에 대한 ACI 544.4R, Campione의 모델은 섬유 보강 콘크리트의 증가된 극한 압축 변형률을 고려하지 않고 있어 극한 모멘트를 부정확하게 예측하였다. 섬유가 혼입되지 않은 부재에 대해 Bischoff의 처짐 모델은 섬유가 혼입되지 않은 부재들의 사용 하중 하에서의 처짐을 정확하게 예측한 반면, ACI 440 위원회 모델은 사용 하중 하에서의 처짐을 비보수적으로 예측하였다. 이질 보강근이 동시에 적용된 부재에 대해 Bischoff 모델과는 달리 ACI 440 위원회의 처짐 모델은 직접적인 적용이 불가능하기 때문에 ACI 440 위원회 식을 이용하여 이질 보강근이 동시에 적용된 부재의 처짐을 예측하는 방법을 제안하였다. 또한 철근과 FRP 보강근이 동시에 보강된 보에서 철근이 항복한 이후의 처짐을 예측할 수 있는 방법을 제안하였다.

• ETRI Journal
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• 제30권2호
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• pp.282-289
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• 2008

We propose a new mini-slot transmission scheme for a passive optical network (PON) in which each customer can be switched either to access mode or to internetworking mode dynamically. In this paper, we present the system implementation (called LAN-PON) as well as the performance of the proposed transmission scheme to illustrate its feasibility and benefits. A mini-slot scheme can rapidly reduce the queuing delay, which increases due to the flooding of the deflected packets in a deflection scheme. We evaluate the impact of mode switching time on the bandwidth gain (throughput) and delay of local area network (LAN) traffic in the LAN-PON with a mini-slot scheme. We also analyze a theoretical delay model of the proposed scheme. The simulation results demonstrate that switching time has an impact on LAN performance, and the average packet delay of the proposed scheme is significantly improved compared to that of the deflection scheme.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1989년도 가을 학술발표회 논문집
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• pp.43-47
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• 1989

In recent years, it has been found that one of the most significant factors in the reduction of the life of concrete pavements is the presence of voids beneath the slab. In the design of pavement, it is assumed that there is a full support through the length of the pavement. When a void develops, this assumption is no longer vaild. With increasing void size, traffic loads have a very a significant increase in stress. Thus, the combination of existing voids and increasing traffic loads results in significant pavement life reduction. Basea on the results of an experimental deflection using Dynaflect device and a theoretical one on the pavement model, this study presents a rational evaluation technique for detecting voids beneath the plain reinforced concrete pavement.

• 한국자기학회지
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• 제4권2호
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• pp.168-172
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• 1994

박막의 자왜와 그 측정에 연관되는 기판과 박막의 영율 및 자장 중에서 자성체의 영율이 변화하는 ${\Delta}\;E$ 효과 등을 하나의 장치로 측정하는 방법을 연구하였다. 박막이 중착된 기판을 전 극위에 나란하게 외팔보가 되게 지지하면, 전기용량이 형성되고, 그 용량은 시료자체의 무게, 인가된 자장 및 전기장에 의한 굴곡으로 미소변화하며 그것을 미소용량 브리지로 검출하여 역학적 계산으로 박막과 기판의 영율과 자왜 및 ${\Delta}\;E$ 효과를 측정항여 그 결과에 대하여 고찰하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.339-342
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• 2005

This paper presents flexural test results of concrete beams reinforced with GFRP and conventional steel reinforcement for comparison. The beams were tested under static loading to investigate the effects of reinforcement ratio and compressive ,strength of concrete on cracking, deflection, ultimate capacity and mode of failure, This study attempts to establish a theoretical basis for the development of simple and rational design guideline. Test results show that ultimate capacity increases as the reinforcement ratio and concrete strength increase. The ultimate capacity increased up to $8\%-25\%$ by using high strength concrete. The deflection at maximum load of GFRP reinforced beams was about three times that of steel reinforced beams. For GFRP-reinforced beams, the ACI code 440 design method resulted in conservative flexural strength -estimates.