• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.1A
• /
• pp.27-33
• /
• 2010

This study addresses a methodology to use small wind turbines for dual purposes, improving aerodynamic performance of flexible bridges and wind energy harvesting. A way to proper placement of small wind turbines on flexible bridges were proposed according on the analogy of conventional aerodynamic appendages. From the wind tunnel tests, it was found that the wind turbine attached like fairing was effective to reduce the vortex-induced vibration of bridge and the optimal spanwise interval of the wind turbine was 3-4.5 time of turbine diameter. Moreover the aerodynamic coefficients of the bridge were improved after installation of the wind turbines. Present results showed the general availability of wind turbine for improvement of aerodynamic performance and energy supply of flexible bridges although the capacity of wind power generation was strongly dependent on wind characteristics of the bridge site.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.3A
• /
• pp.241-256
• /
• 2010

This study intends to develop an aerodynamic girder for suspension bridge with width corresponding to 1/70 of the main span length. In the first step of present study, parametric study for the effects of major structural properties on aerodynamic stability of bridges was performed. The span length and natural frequency of bridges were found to be free from girder width, girder height, and aspect ratio of width to height. The empirical equation according to confidence interval was proposed to estimate the natural frequencies of bridges from span length. From the sensitivity analysis, it was revealed that the torsional frequency was dominant parameter among various structural properties that affected flutter velocity mostly. The final aerodynamic bridge section which satisfied the flutter criteria was found from section wind tunnel tests for 30 cross sectional models. The aerodynamic stability of the developed cross section was verified by multimode flutter analysis. The present economical cross section can be used for long span suspension bridge.

• Journal of the Korean Society of Industry Convergence
• /
• v.27 no.4_2
• /
• pp.833-840
• /
• 2024

According to recent data from the Korea Meteorological Administration(KMA), the frequency of typhoons around the Korea Peninsula is almost unchanged, but the intensity is on the rise due to climate change. A typhoon that has become so powerful can cause partial or complete damage to the traffic signal structures, limiting the operation of the vehicle and causing traffic congestion. If the traffic signal structure fails to function properly due to the influence of the typhoon, not only the v ehicle operation will be disrupted, but also direct damage to the traffic signal structure will occur. In addition, if the social overhead cost of traffic congestion is included, the recovery cost caused by the typhoon will increase to an extent that it is difficult to estimate. Therefore, in this study, a wind tunnel experiment was performed by producing a wind tunnel model of an existing fixed traffic signal structure and a traffic signal structure in which signs and traffic lights are hinged. Also, The fixed and hinge structures were modeled as 3D finite elements, and wind-resistant analysis was performed by wind speed, and, wind-resistant safety of traffic signal structures were analyzed and examined through wind-resistant analyses. From the comparative analysis of the results of experiment and FE analysis, it was known that the stress reduction rate of the hinge connection structure was at least 30% compared to that of the fixed connection structure from the results of the wind tunnel experiment and FE analysis. And As a result of finite element analysis for the maximum design wind speed of 50m/s, it was found that the maximum stress generated in the existing structure exceeded all the yield stress, but the maximum stress of the hinge connection structure was within the yield stress. Finally The hinge connection structure showed a relatively large stress reduction rate as the wind speed increased and the length of the lateral beam was shorter at the same wind speed.

• Journal of Aerospace System Engineering
• /
• v.18 no.4
• /
• pp.34-42
• /
• 2024

This study developed a morphing technology applicable to unmanned aerial vehicles (UAVs) with diverse flight characteristics. Existing morphing technologies require additional mechanisms and driving devices, posing challenges in constructing features such as ribs and spars within the wing structure, leading to structural instability. To address this, we developed a Variable-Camber and Variable-Chord (VCC) morphing flap that could maintains a continuously transforming surface during deformation, altering both camber shape and chord length simultaneously. Furthermore, we conducted design and fabrication of UAV wings incorporating these morphing flaps, ensuring structural stability by developing specialized shapes. Furthermore, structural experiments were conducted to simulate flight loads, followed by actual flight tests to validate performances of both morphing mechanism and wings. Finally, wind tunnel tests were conducted to compare results with aerodynamic analysis, confirming the effective applicability of this morphing technology.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.28 no.2
• /
• pp.153-160
• /
• 2015

The objective of this study is to construct the TPU aerodynamic database with wind tunnel test data of overall wind loads and responses on tall buildings. In this study, wind tunnel tests were conducted to investigate characteristics of wind forces and the effect of wind load combination by cross-correlation analysis among along-wind overturning moment, across-wind overturning moment and torsional moment on a tall building with various side ratios(D/B=0.33, 0.50, 0.77, 0.83, 0.91, 1.0, 1.1, 1.2, 1.3, 2.0 and 3.0) for different terrain roughnesses. The results of wind tunnel tests were compared with those of past literatures. As a result, there was no significant effects of changing of terrain roughnesses on moment coefficients and power spectral densities of across-wind overturning moment coefficients and torsional moment coefficients with various side ratios. Further, these results were good agreement with those of past literatures. From cross-correlation analysis, the across-wind overturning moment coefficients were highly correlated with the torsional moment coefficients. The results of this study will be helpful for practical designers in preliminary design stage.

• Journal of Bio-Environment Control
• /
• v.5 no.2
• /
• pp.160-166
• /
• 1996

Objective of this study was to investigate the effects of all current speed on the microclimates above and inside the plug stand under artificial light. Maximum air temperature appeared near the top of the plug stand. Difference in air temperature inside the plug stand increased with the decreasing air current speed. Difference in relative humidity(DRH) to the relative humidity at the Inlet of the main air flow conditioner Inside and above the plug stand decreased with the increasing air current speed. Relative humidity inside the plug stand was 10-15% higher than that above the plug stand. DRH inside a stand of plug at air current speed of 0.3m s$^{-1}$ was about two times as many as that at air current speed of 0.9 m s$^{-1}$ . DRH inside the plug stand was 2.8-6.5% higher at LAI of 2.6 than that at LAI of 0.5. Gradient for the vapour pressure deficit was distinctly appeared at the low air current speed. Direction of vapour pressure flux is from the medium surface upwards. Difference in vapour pressure(DVPD) to the vapour pressure deficit at the inlet of the main air flow conditioner inside and above the plug stand decreased with the increasing height above the medium surface. DVPD inside the plug stand was 0.3-0.4㎪ higher at air current speed of 0.9m s$^{-1}$ than that at air current speed of 0.3m s$^{-1}$ . Results for the effects of air current speed on the relative humidity and vapour pressure deficit indicated that the microclimates above and inside the plug stand at the rear region in plug trays were slightly unfavorable compared to those at middle region.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.23 no.5
• /
• pp.473-481
• /
• 2017

Seafarer sea survival training, such as basic safety refresher training and advanced safety refresher training, in accordance with the STCW Convention, is an indispensable program that can increase the crew survival rate during emergency situations at sea. It is important for crew members to carry out theoretical and practical training with various safety equipment in order to effectively train according to IMO model courses. Therefore, this study suggests the following measures to improve safety training facilities for seafarers by reviewing survival training requirements based on the IMO model course and comparing and analyzing related facilities based on operating cases from domestic and overseas training institutes. First, it is necessary to establish a training environment where seafarers can practice utilizing various, updated safety equipment such as marine evacuation equipment (slides, chutes, etc.). Second, it is necessary to construct an educational environment in which learners can directly or indirectly experience realistic emergency situations by installing marine environment simulation facilities with such equipment as a wave generator, rain fall device, wind generating device, etc. Third, it is also necessary to develop and expand customized training using virtual reality equipment in addition to experiential training, audiovisual training and simulation training.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.3 no.3
• /
• pp.27-37
• /
• 1983

A method of dynamic analysis is developed for torsional free vibrations of elliptical-box girder type or stiffening truss system suspension bridge. In this study, the method based on a finite element technique using a digital computer, is illustrated by two numerical examples, the Namhae Bridge which is located in Kyungsang nam-do opened on June, 1973, and the Mt. Chunma Bridge is simple span pedestrian's suspension bridge with lateral bracing system in Mt. Chunma, Kyungki-do, are used. In general, dynamic modes of complex suspension bridges are three-dimensional in form, i.e., coupling between vertical and torsional motions. However, introduced that amplitudes of oscillation are infinitesimal for coincidence with the purpose of it's use, thereupon, the torsional vibration analyses are treated without coupling terms. A sufficient number of natural frequencies and mode shapes for torsional free vibration are presented in this paper. In the case of Mt. Chunma Bridge, the natural frequencies and periods are computed with and without reinforcement, respectively, and compared their discrepancies. The influence of the auxiliary reinforcing cables is prevailing in the first few modes, namely, 1st and 2nd in symmetric and 1st, 2nd and 3rd in antisymmetric vibration, and conspicuous in the symmetric compared with the antisymmetric motion, but in the higher modes, this kind of simple accessory elucidates rether converse effects. In the Namhae Bridge, the results are compared with the Manual's obtained by wind tunnel test. It reveals commendable agreement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1993.04a
• /
• pp.35-39
• /
• 1993

항공기의 플러터 현상을 예방키 위한 개발시의 주요 공학적 임무로는 플러 터 해석, 풍동 플러터 시험, 실기체에 대한 지상진동시험 및 비행 플러터 시 험이 있다. 이들 업무는 군용 항공기의 경우에는 군사 규격서, 민간 항공기 의 경우는 FAR 규정 등에 항공기 개발 및 개조시에는 필히 수행토록 명시 되어 있으며, 특히 개발항공기의 인증을 받기 위해서는 초도 비행전까지 필 수적으로 완료되어야 하는 업무이다. 이중 항공기 지상진동시험은 개발항공 기의 초도 비행전에 실기체를 대상으로 하는 구조 동특성 규명시험으로써 플러터 해석 모델의 정확도를 입증하고 그 해석모델을 수정하거나 개선시키 는데 필요한 구조의 동특성 변수들을 실험적으로 규명하는 시험이다. 이 시 험은 개발된 항공기의 초도비행허가를 획득하고 비행속도제한을 설정키 위 해서 초도비행 직전에 초도 개발 비행기를 대상으로 필수적으로 수행되어야 하는 필수적 시험이다. 이에 따라 개발된 항공기의 전기체 지상진동시험을 수행하였고, 시험데이터의 모달해석을 하였다. 이 시험을 수행하기 위해 3개 의 가진기를 사용하였고, 모두 159개의 지점에서 주파수응답 함수를 얻었다. 최대 48 채널의 데이터 획득시스템을 사용하였으므로, 네번에 걸쳐 측정위치 를 옮겨 전체데이타를 획득하였다. 지상진동 시험의 최종해석 결과는 유한요 소 모델의 유효성을 검토하는데 사용되었고, 시험 데이타를 이용한 가진응답 해석(Forced Response Analysis)을 통하여 비행플러터 시험시에 사용되는 플러터 가진기의 위치선정 및 가진력의 크기를 결정하는데 이용하였다.ncy)가 저주 파수대로 천이(Lower Shift)하는 현상이 나타났으며, 일정한 작업량이라도 작업중량을 줄이고 작업 빈도를 높여서 작업할 경우에 이러한 현상이 더욱 두드러졌다. 작업시간의 경과에 따른 MVIS의 감소 현상은 작업빈도가 높고 비대칭형 작업일 때 가장 크게 나타났다. 총손실을 줄이고, 상대적 비용절감효과를 갖게할 수 있다고 하였다. 따라서 본 연구에서는 성인 여성기성복의 치수적합성을 높이기위하여 출산 후 중년에 접어 들면서 체형이 변화되는 것을 고려하여 연령을 분류하고(18세-34세, 30세-51세), 각 연령 집단에 따른 체형을 각각 3가지로 분류하였다. 이에 따라 의복 생산시의 총손실을 줄이기위한 상의, 하의생산시 필요한 부위별 최적규격치 간격을 제시하였다.적인 기능으로 보여지는 것에 좁혀서 작업능력의 연령증가 변화에 대하여다원적 평가를 하는 것이 실제적이라고 할 수 있다. 따라서 본 연구에서는 인간이 가지고 있는 다수의 기능중에서 수지교 치성과 연령증가와의 관계를 조사한다. 만약 연령증가 만으로 수지교치성을 평가 할 수 없는 경우에는 어떠한 요인이 수지기민성의 변화에 영향을 미치는가를 검토한다.t list)에서 자동적으로 사건들의 순서가 결정되도록 확장하였으며, 설비 제어방식에 있어서도 FIFO, LIFO, 우선 순위 방식등을 선택할 수 있도록 확장하였다. SIMPLE는 자료구조 및 프로그램이 공개되어 있으므로 프로그래머가 원하는 기능을 쉽게 추가할 수 있는 장점도 있다. 아울러 SMPLE에서 새로이 추가된 자료구조와 함수 및 설비제어 방식등을 활용하여 실제 중형급 시스

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.24 no.3
• /
• pp.171-179
• /
• 2014

Sunroof buffeting is one of the most critical issues in the vehicle wind noise phenomena. The experimental approach to solve this issue typically requires a lot of time and resources. To reduce time and cost, the numerical approach could be taken, which can also privide more insights into physical phenomena involved in sunroof buffeting, only if the accuracy in its predictions are guranteed. The benchmark test of various numerical solvers is carried out for the buffeting behavior of a simplified vehicle body, the Hyundai simplified model(HSM). The results of each solver are compared to the experimental measurements in a Hyundai aeroacoustic wind tunnel(HAWT) at various wind speeds. In particular, acoustic response tests were performed and the results were provided prior to all simulations in order to consider the real world effects that could introduce discrepancies between the numerical and experimental approaches. Through this study, most solvers can demonstrate an acceptable accuracy level for actual commercial development and high precision experimental data and computational prediction priories can be shared in order to promote the numerical accuracy level of each numerical solver.