• Journal of the Korean Wood Science and Technology
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• 제39권4호
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• pp.318-325
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• 2011

현장에서 시공성이 용이함과 동시에 강도 성능이 뛰어난 steel bar를 이용한 리기다소나무 옹벽을 제작하여 내력평가를 실시하였다. Steel bar를 이용한 목재옹벽은 횡목 4단과 종목 3단으로 적층하였으며, 높이 770 mm, 길이 2,890 mm, 폭 782 mm로 제작하였다. 적층 방법은 18 mm로 선공한 최상단과 최하단 횡목을 Steel bar에 삽입하며, 깊이 64 mm, 폭 18 mm의 슬릿을 낸 나머지 횡목과 종목을 Steel bar에 끼워 넣어 적층하였다. 완성 된 옹벽은 수평 재하 시험을 통한 내력 평가와 화상처리(AlCON 3D OPA-PRO system)를 통하여 구조물의 변형을 측정하였다. Steel bar옹벽에는 1개의 긴 횡목과 2개의 종목으로 구성된 접합부(Type-A)와 반턱으로 이음된 2개의 짧은 횡목이 2개의 종목으로 구성된 접합부(Type-B)가 공존하며, 이들을 각각 3개씩 제작하여 접합부의 압축형 전단내력 평가를 실시하였다. Steel bar옹벽의 수평 재하 시험결과 정각재 목재옹벽(박준철 등, 2010)보다 1.6배 이상의 강도를 나타냈으며, 이때 목재와 접합부의 파단은 발생하지 않았다. 접합부의 압축형 전단 내력 실험결과 Type-A의 평균 최대 하중은 130.13 kN, Type-B의 평균 최대 하중은 130.6 kN으로 측정되었다. 실험 결과 Steel bar를 이용한 목재옹벽은 정각재 목재옹벽보다 시공성이 우수하며 강도 또한 높게 측정되었다.

• 한국지진공학회논문집
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• 제10권5호
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• pp.73-83
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• 2006

이 연구의 목적은 면외방향으로 반복하중을 받는 철근콘크리트 벽식 교각의 지진거동을 파악하고 합리적이면서 경제적인 내진설계기준을 개발하는데 있다. 정확하고 올바른 성능평가를 위하여 신뢰성 있는 비선형 유한요소해석 프로그램을 사용하였다. 사용된 프로그램은 철근콘크리트 구조물의 해석을 위한 RCAHEST이다. 유한요소로서는 면내회전강성도를 갖는 4절점 평면 쉘요소가 사용되었다. 두께방향에 대한 철근과 콘크리트의 재료성질을 고려하기 위하여 층상화기법이 도입되었다. 재료적 비선형성에 대해서는 균열콘크리트에 대한 인장, 압축, 전단모델과 콘크리트 속에 있는 철근모델을 조합하여 고려하였다. 신뢰성 있는 실험결과와 비교를 통하여 이 논문의 제안방법이 면외방향으로 반복하중을 받는 철근콘트리트 벽식 교각의 내진성능평가에 적합한 방법임을 입증하고자 한다.

• Structural Engineering and Mechanics
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• 제60권4호
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• pp.633-653
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• 2016

One of the major threats to the stability of classical columns and colonnades are earthquakes. The behavior of columns under high seismic excitation loads is non-linear and complex since rocking, wobbling and sliding failure modes can occur. Therefore, three dimensional simulation approaches are essential to investigate the in-plane and out-of-plane response of such structures during harmonic and seismic loading excitations. Using a software based on the Distinct Element Method (DEM) of analysis, a three dimensional numerical study has been performed to investigate the parameters affecting the seismic behaviour of colonnades' structural systems. A typical section of the two-storey colonnade of the Forum in Pompeii has been modelled and studied parametrically, in order to identify the main factors affecting the stability and to improve our understanding of the earthquake behaviour of such structures. The model is then used to compare the results between 2D and 3D simulations emphasizing the different response for the selected earthquake records. From the results analysis, it was found that the high-frequency motion requires large base acceleration amplitude to lead to the collapse of the colonnade in a shear-slip mode between the drums. However, low-frequency harmonic excitations are more prominent to cause structural collapse of the two-storey colonnade than the high-frequency ones with predominant rocking failure mode. Finally, the 2D analysis found to be unconservative since underestimates the displacement demands of the colonnade system when compared with the 3D analysis.

• 산업경영시스템학회지
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• 제37권4호
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• pp.72-81
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• 2014

Even though two-hands lifting/lowering activity of manual materials handling tasks are prevalent at the industrial site, many manual materials handling tasks which require the worker to perform one-hand lifting/lowering are also very common at the industrial site, forestry, farming, and daily life. The objective of this study was to compare one-hand lowering activity to lifting activity in terms of biomechanical stress for the range of lowering heights from knuckle height to 10cm above floor level with two workload 7.5kg and 15.0kg. Eight male subjects with LMM were asked to perform lifting/lowering tasks using both a one-handed (left-hand and right-hand) as well as a two-handed technique. Spinal loading was estimated through an EMG-assisted free-dynamic biomechanical model. The biomechanical stress of one-hand lowering activity was shown to be 43% lower than that of one-hand lifting activity. It was claimed that the biomechanical stress for one-hand lifting/lowering activity is almost twice (194%) of the one for two-hands lifting/lowering activity. It was also found that biomechanical stress by one-hand lowering/lifting activity with the half workload of two-hands lowering/lifting activity was greater than that of the two-hands lowering/lifting activity. Therefore, it might be a risk to consider the RWL of one-hand lowering/lifting activity to simply be a half of the RWL of two-hands lowering/lifting activity recommended by NIOSH.

• 한국강구조학회 논문집
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• 제17권4호통권77호
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• pp.481-490
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• 2005

본 논문은 중력하중의 지배를 받는 CFT기둥-RC 무량판 접합부의 실물대 실험결과를 요약한 것이다. CFT구조는 여러 가지 구조 및 시공상의 장점으로 인하여 국내 건설 현장에서 상대적으로 짧은 시간에 폭넓게 수용되고 있다. 주차장 용도로 주로 사용되는 지하층은 철근콘크리트 무량판으로 시공하여 경제성을 도모하는 것이 국내에서 일반적으로 요구되는 시공관행이다. 그러나 CFT기둥-RC 무량판 접합부의 효율적인 디테일은 아직 국내 외적으로 제시된 바가 없어서 이 분야의 연구가 매우 필요한 실정이다. 현장 시공시 경제성을 극대화할 수 있는 몇 가지 전략을 기초로 해서, 여러 가지 접합 상세를 제안하였고 실험을 통하여 검증하였다. 실험결과 본 연구에서 제시된 CFT기둥-RC 무량판 접합 상세의 펀칭강도 및 강성이 RC 무량판 접합부와 동등하거나 이를 상회하는 것을 확인할 수 있었다.

• Smart Structures and Systems
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• 제14권5호
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• pp.869-881
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• 2014

This paper presents the materials analysis for combination of working modes of Magnetorheological (MR) damper. The materials were selected based on the optimum magnetic field strength at the effective areas in order to obtain a better design of MR damper. The design of electromagnetic circuit is one of the critical criteria in designing MR dampers besides the working mechanism and the types of MR damper. The increase in the magnetic field strength is an indication of the improvement in the damping performance of the MR damper. Eventually, the experimental test was performed under quasi-static loading to observe the performances of MR damper in shear mode, squeeze mode and mixed mode. The results showed that the increment of forces was obtained with the increased current due to higher magnetic flux density generated by electromagnetic coils. In general, it can be summarized that the combination of modes generates higher forces than single mode for the same experimental parameters throughout the study.

• Steel and Composite Structures
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• 제34권5호
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• pp.715-732
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• 2020

High-strength steel composite Y-eccentrically braced frame (Y-HSS-EBF) is a novel structural system. In this study, the spatial substructure hybrid simulation test (SHST) method is used to further study the seismic performance of Y-HSS-EBF. Firstly, based on the cyclic loading tests of two single-story single-span Y-HSS-EBF planar specimens, a finite element model in OpenSees was verified to provide a reference for the numerical substructure analysis model for the later SHST. Then, the SHST was carried out on the OpenFresco test platform. A three-story spatial Y-HSS-EBF model was taken as the prototype, the top story was taken as the experimental substructure, and the remaining two stories were taken as the numerical substructure to be simulated in OpenSees. According to the test results, the validity of the SHST was verified, and the main seismic performance indexes of the SHST model were analyzed. The results show that, the SHST based on the OpenFresco platform has good stability and accuracy, and the results of the SHST agree well with the global numerical model of the structure. Under strong seismic action, the plastic deformation of Y-HSS-EBF mainly occurs in the shear link, and the beam, beam-columns and braces can basically remain in the elastic state, which is conducive to post-earthquake repair.

• Structural Engineering and Mechanics
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• 제31권1호
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• pp.39-56
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• 2009

Vibration is an undesirable phenomenon in a dynamic system like lightly damped aerospace structures and active vibration control has gradually been employed to suppress vibration. The objective of the current investigation is to introduce an active torsional magneto-rheological (MR) fluid based damper for vibration control of a typical nose landing gear. They offer the adaptability of active control devices without requiring the associated large power sources. A torsional damper is designed and developed based on Bingham plastic shear flow model. The numerical analysis is carried out to estimate the damping coefficient and damping force. The designed damper is fabricated and an experimental setup is also established to characterize the damper and these results are compared with the analytical results. A typical FE model of Nose landing gear is developed to study the effectiveness of the damper. Open loop response analysis has been carried out and response levels are monitored at the piston tip of a nose landing gear for various loading conditions without damper and with MR-damper as semi-active device. The closed-loop full state feedback control scheme by the pole-placement technique is also applied to control the landing gear instability of an aircraft.

• 한국지반공학회지:지반
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• 제12권1호
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• pp.5-20
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• 1996

연약지반 처리방법으로 압밀을 촉진시키고, 이로 인한 전단강도를 증진시키기 위하여 선행압밀하중공법과 병행된 배수공법이 널리 사용되어 오고 있다. 본 연구에서는 배수재가 설치된 연약지반의 압밀과정동안에 유발되는 간극비의 감소로 인한 압축성과 투수계수의 변화를 고려할 수 있는 축대칭 비선형 압밀이론을 제안하였다. 제안된 축대칭 비선형 압밀이론을 명백한(explicit) 유한차분법을 적용하여 해석용 프로그램(AXICON)을 개발하였으며 현장지반의 교란효과나 층으로 이루어진 지반을 해석할 수 있도록 보완하였다. 또한 현장지반의 단계적 시공절차를 고려하여 하중을 적용할 수 있도록 하였다. AXICON 해석결과를 기존의 Hansbo와 Barren의 해석적인 해와 비교 검토하였으며 현장지반에서 계측된 침하량과 과잉 간극수압의 자료와 비교하였다.

• Advanced Composite Materials
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• 제18권3호
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• pp.233-249
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• 2009

Safe installation and operation of high-pressure composite cylinders for hydrogen storage are of primary concern. It is unavoidable for the cylinders to experience temperature variation and significant thermal input during service. The maximum failure pressure that the cylinder can sustain is affected due to the dependence of composite material properties on temperature and complexity of cylinder design. Most of the analysis reported for high-pressure composite cylinders is based on simplifying assumptions and does not account for complexities like thermo-mechanical behavior and temperature dependent material properties. In the present work, a comprehensive finite element simulation tool for the design of hydrogen storage cylinder system is developed. The structural response of the cylinder is analyzed using laminated shell theory accounting for transverse shear deformation and geometric nonlinearity. A composite failure model is used to evaluate the failure pressure under various thermo-mechanical loadings. A back-propagation neural network (NNk) model is developed to predict the maximum failure pressure using the analysis results. The failure pressures predicted from NNk model are compared with those from test cases. The developed NNk model is capable of predicting the failure pressure for any given loading condition.