• 콘크리트학회논문집
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• 제22권3호
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• pp.313-324
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• 2010

FRP 보강근은 현장 가공이 용이하지 않고 만곡부에서 강도가 저하되는 등 전단보강근으로 사용하기에는 해결해야 할 문제점이 많다. 전단보강을 필요로 하지 않는 구조요소에 FRP 보강근을 휨보강근으로 사용하는 것은 별 어려움 없이 적용할 수 있다. 교량 바닥판이나 복개시설의 슬래브 등은 대부분 판상 구조로 전단보강이 없는 부재들이며, FRP 보강근을 휨보강근으로 사용하는 경우에는 RC구조에 비하여 전단강도가 높지 않은 특성이 있다. 그러나 이러한 형식의 구조물에 대한 신뢰성 있는 전단강도 산정 기준이 확립되지 않은 상태이다. 이 연구에서는 FRP RC의 전단거동을 관찰한 선행연구 결과와 함께 문헌 조사를 통하여 관련 자료 211개를 축적하고, 각국의 전단강도 산정 기준과 비교 검토하였다. 분석 결과 AIJ, ISE 기준이 가장 우수하였으며, ACI 440.1R-06의 기준은 보수적인 설계를 제공하지만 분산 정도는 ISE와 유사하여 항상 일관성 있는 예측 값을 주는 장점이 있었다. 합리적인 새로운 전단강도식을 개발하기 위하여 표본자료의 전단강도를 가장 잘 설명할 수 있는 회귀모형을 구축하였으며 기존 설계식과 비교 검토하였다. 구축된 회귀모형을 기반으로 정확도가 높고 분산도가 작은 새로운 전단강도식을 제안하였다.

• 한국산학기술학회논문지
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• 제16권2호
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• pp.1516-1523
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• 2015

본 연구는 해상풍력 강재타워의 출입문에 발생되는 응력집중에 대해 상세히 기술하고 있다. 원형강재 풍력타워에는 8종류의 하중조합이 작용하며 그 하중조합은 극한한계상태와 사용한계상태를 고려한 정상 및 이상시 운영상태를 고려하고 있다. 유한요소해석 및 변수연구에 범용해석프로그램인 ABAQUS를 사용하였으며 응력값이 변화되는 곳을 고려하여 변위 및 응력을 검토하였다. 출입문 주변의 응력집중현상을 비교분석하기 위하여 출입문이 없는 경우, 출입문은 없으나 보강재가 있는 경우, 출입문 및 보강재가 모두 적용된 경우로 구분하여 해석연구를 수행하였다. 분석내용은 본문에 자세히 기술하고 있으며, 해석결과 응력집중계수 평균값은 1.47, 최대값은 1.81로 분석되었다.

• 방송공학회논문지
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• 제26권7호
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• pp.855-861
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• 2021

Neural Architecture Search (NAS) is cutting-edge technology in the machine learning community. NAS Without Training (NASWOT) recently has been proposed to tackle the high demand of computational resources in NAS by leveraging some indicators to predict the performance of architectures before training. The advantage of these indicators is that they do not require any training. Thus, NASWOT reduces the searching time and computational cost significantly. However, NASWOT only considers high-performing networks which does not guarantee a fast inference speed on hardware devices. In this paper, we propose a multi objectives reward function, which considers the network's latency and the predicted performance, and incorporate it into the Reinforcement Learning approach to search for the best networks with low latency. Unlike other methods, which use FLOPs to measure the latency that does not reflect the actual latency, we obtain the network's latency from the hardware NAS bench. We conduct extensive experiments on NAS-Bench-201 using CIFAR-10, CIFAR-100, and ImageNet-16-120 datasets, and show that the proposed method is capable of generating the best network under latency constrained without training subnetworks.

• Journal of Advanced Research in Ocean Engineering
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• 제3권3호
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• pp.136-148
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• 2017

The paper presents dual arm ROV manipulation using deep reinforcement learning. The purpose of this underwater manipulator is to investigate and excavate natural resources in ocean, finding lost aircraft blackboxes and for performing other extremely dangerous tasks without endangering humans. This research work emphasizes on a self-learning approach using Deep Reinforcement Learning (DRL). DRL technique allows ROV to learn the policy of performing manipulation task directly, from raw image data. Our proposed architecture maps the visual inputs (images) to control actions (output) and get reward after each action, which allows an agent to learn manipulation skill through trial and error method. We have trained our network in simulation. The raw images and rewards are directly provided by our simple Lua simulator. Our simulator achieve accuracy by considering underwater dynamic environmental conditions. Major goal of this research is to provide a smart self-learning way to achieve manipulation in highly dynamic underwater environment. The results showed that a dual robotic arm trained for a 3DOF movement successfully achieved target reaching task in a 2D space by considering real environmental factor.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.383-386
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• 2005

Low frequency heavy-weight impact noise is the most irritating noise in Korean high-rise reinforced concrete apartment buildings. This low frequency noise is generated by foot traffic due to the fact that Koreans do not wear shoes at home. The transmission of the noise is facilitated by a load bearing wall structural system without beams and columns which is used in these buildings. In order to control low frequency heavy-weight impact noise, floating floors using isolation materials such as glass-wool mat and poly-urethane mat are used. However, it was difficult to control low frequency heavy-weight impact sound using isolation material. In this study, reinforcement of concrete slab using beams and plate was conducted. Using the FEM analysis, the effect of concrete slab reinforcement using FRP(fiber-glass reinforced plastic) on the bang machine impact vibration acceleration level and sound were conducted at the standard floor impact sound test building. The $3{\sim}4dB$ floor impact vibration acceleration level and impact sound pressure level were reduced and the natural frequency of slabs were changed.

• Journal of Welding and Joining
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• 제24권5호
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• pp.29-36
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• 2006

In this study, an experimental method for the selection of optimal welding condition was proposed in the fillet weld which was done over the tack weld. This method used the response surface analysis in which the leg length and the reinforcement height were chosen as the quality variables of the weld bead profile. The overall desirability function, which was combined desirability function fur the two quality variables, was employed as the objective function for getting the optimal welding condition. In the experiments, the target values of the leg length and the reinforcement height are 6m and zero respectively for the horizontal fillet weld of 10mm thickness mild steel. The optimal welding conditions could predict the weld bead profile(leg length and reinforcement height) as 6.00mm and 0.19mm without tack weld and 6.00mm and 0.48mm with tack weld. from a series of welding test, it was revealed that a uniform weld bead can be obtained by adopting the optimal welding condition which was determined according to the method proposed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.929-934
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• 2002

Eight full-scale columns were constructed and tested under monotonic axial compression loading to investigate the influence of headed bars on the confinement of the concrete. One column represented a column with no transverse reinforcement and another column had poor detailing and little confinement. A third column contained seismic hoops and crossties, which represented current detailing practice for significant confinement. A fourth column test is conducted to investigate the response with the seismic crossties replaced by headed bars. Two column specimens were constructed and tested with all of the transverse reinforcement provided by headed bars. These six specimens enabled an assesment of the effectiveness of headed bars in confining the concrete. It was found that the use of headed bars improved the confinement of the columns. Two additional specimens were constructed without any transverse reinforcement. These columns were later retrofitted, by drilling horizontal holes in the columns, adding special headed bars (one head fixed and the other head threaded) and then filling the drilled holes with epoxy. These retrofitted specimens with these added headed bars provided insight into the rehabilitation of older structures containing poorly detailed columns. All of the test specimens were instrumented to determine strain localization during failure and to monitor the strain in the longitudinal and transverse reinforcement.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.233-236
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• 2008

본 연구는 슬래브의 하부철근이 포스트 텐션(PT) 플랫 플레이트 골조의 내진성능에 미치는 영향을 평가하였다. 이를 위하여 슬래브-기둥 접합부에 슬래브 하부철근이 있는 경우와 없는 경우의 3층, 9층 골조를 중력하중만 고려하여 설계하였다. 본 연구에서는 대상 건물을 비선형 정적 푸쉬 오버 해석하여 기둥을 관통하는 슬래브 하부철근 유무에 따른 전체 구조시스템 거동을 평가 하였다. 본 연구에서 사용한 접합부 모델은 뚫림 전단과 파괴메커니즘을 예측할 수 있도록 본 연구자들에 의하여 기존 연구에서 제안된 것이다. 본 연구결과에 따르면 기둥을 관통하는 슬래브 하부철근은 PT 플랫 플레이트 골조의 내진성능에 큰 영향을 미치는 것으로 나타났다. 특히 슬래브 하부 철근이 있는 PT 플랫 플레이트 골조는 슬래브 하부철근이 없는 골조에 비하여 최대 강도와 변형 능력이 크게 향상되었다.

• Structural Engineering and Mechanics
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• 제46권6호
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• pp.809-825
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• 2013

In the present study, in reinforced concrete structures, beam-column connections are one of the most critical regions in areas with seismic susceptibility. Proper anchorage of reinforcement is vital to enhance the performance of beam-column joints. Congestion of reinforcement and construction difficulties are reported frequently while using conventional reinforcement detailing in beam-column joints of reinforced concrete structures. An effort has been made to study and evaluate the performance of beam-column joints with joint detailing as per ACI-352 (mechanical anchorage), ACI-318 (conventional hooks bent) and IS-456(full anchorage conventional hooks bent) along with confinement as per IS-13920 and without confinement. Apart from finding solutions for these problems, significant improvements in seismic performance, ductility and strength were observed while using mechanical anchorage in combination with X-cross bars for less seismic prone areas and X-cross bar plus hair clip joint reinforcement for higher seismic prone areas. To evaluate the performances of these types of anchorages and joint details, the specimens were assembled into four groups, each group having three specimens have been tested under reversal loading and the results are presented in this paper.

• Earthquakes and Structures
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• 제18권5호
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• pp.581-598
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• 2020

This paper aims to investigate the seismic behavior and influence parameters of the large-scaled thin-walled reinforced concrete (RC) tubular columns in air-cooled supporting structures of thermal power plants (TPPs). Cyclic loading tests and finite element analysis were performed on 1/8-scaled specimens considering the influence of wall diameter ratio, axial compression ratio, longitudinal reinforcement ratio, stirrup reinforcement ratio and adding steel diagonal braces (SDBs). The research results showed that the cracks mainly occurred on the lower half part of RC tubular columns during the cyclic loading test; the specimen with the minimum wall diameter ratio presented the earlier cracking and had the most cracks; the failure mode of RC tubular columns was large bias compression failure; increasing the axial compression ratio could increase the lateral bearing capacity and energy dissipation capacity, but also weaken the ductility and aggravate the lateral stiffness deterioration; increasing the longitudinal reinforcement ratio could efficiently enhance the seismic behavior; increasing the stirrup reinforcement ratio was favorable to the ductility; RC tubular columns with SDBs had a much higher bearing capacity and lateral stiffness than those without SDBs, and with the decrease of the angle between columns and SDBs, both bearing capacity and lateral stiffness increased significantly.