• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.9 no.2
• /
• pp.43-54
• /
• 1989

In this paper, measured and calculated responses are compared in order to give how the static and dynamic responses occurred in steel railway bridges due to train loads could be calculated appropriately. From this, it is investigated how the impact factors are varied by changing the train speed above 100km/h Field measurement is carried out by the steel strain gages and displacement transducers at the main design points, and then the static and dynamic response, fundamental frequencies, damping ratios and impact factors of the bridges are obtained. Static analysis is done using the computer program developed according to three dimensional matrix structural analysis in which the trains and bridges are modelled as 1,2 and 3 dimensions. Dynamic analysis is done according to 2 approaches, the moving force and mass problem. In moving force problem, the solutions are obtained by the modesuperposition-method and in moving mass problem by the direct integration method. From this study, it is known that in order to obtain the static response in the railway bridges, the bridge could be modelled by 1 or 2 dimension as in the highway bridge, however the response ratio(measured/calculaled) is high comparing to the highway bridges. By the way, the dynamic response should be obtained by the moving mass problem. And by comparing the measured and code specified impact factors, it is known that the factors specified in the present railway bridge code are very safe under the present service speed below 100km/h. However, because the factors become very high under the speed above 100km/h, especially in the simple plate girder bridge, it is thought that the code specification on impact factor should be discussed enough under the rapid transit system.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.33 no.5
• /
• pp.287-296
• /
• 2020

The wave-impact load on offshore structures can be divided into green-water and wave-slamming impact loads. These wave impact loads are known to have strong nonlinear characteristics. Although the wave impact loads are dealt with in the current classification rules in the shipping industry, their strong nonlinear characteristics are not considered in detail. Therefore, to investigate these characteristics, wave-impact loads induced by a breaking wave on a circular cylinder were analyzed. A model test was carried out to measure the wave-impact loads due to breaking waves in a two-dimensional (2D) wave tank. To generate a breaking wave, the focusing wave method was applied. A series of 2D tank tests under a horizontal wave impact was carried out to investigate the structural responses of the cylindrical structure, which were obtained from the measured model test data. According to the results, we proposed a structural damage-estimation procedure of an offshore tubular member due to a wave impact load. Furthermore, a recommended wave-impact load is suggested that considers the minimum required thickness of each member. From the experimental results, we found that the required minimum thickness is dependent on the impact pressure located in a three-dimensional space on the surface of a tubular member.

• 한국정보통신설비학회:학술대회논문집
• /
• 2006.08a
• /
• pp.111-116
• /
• 2006

통신용 지하 관로 자재로는 주로 100mm관(PVC관, FC관)과 50mm관(FC관)이 사용되고 있으며, 이들 관자재의 품질은 관로 시공 품질 뿐 아니라 케이블 포설을 위한 선로 구성에 큰 영향을 미치고 있어, 관자재의 품질 확보는 매우 중요하다고 할 수 있다. 관자재의 품질 성능을 나타내는 방법으로는 편평시험(5% 및 100% 변형하중)과 충격시험 결과를 많이 사용하고 있으나, 관로 시공 현장에서 이러한 성능 시험을 한다는 것은 현실적으로 불가능하여, 대부분의 현장에서는 관자재의 두께나 무게와 같은 물성치 측정으로 품질관리를 하고 있다. 이에 본 논문에서는 관자재의 물성치와 품질 성능간 상호 관계를 분석한 후, 상관성이 높은 항목들을 도출함으로써, 관종 별의 관자재의 물성치와 품질 성능간에는 상관성이 매우 높은 인자들이 있다는 것을 규명하였으며, 이를 통하여 관자재의 물성치 만으로도 품질 성능을 객관적으로 판단할 수 있는 근거를 제시하였다. 이를 이용하여 관로 시공 현장에서 관자재 품질관리와 시공 품질 향상에 활용할 수 있도록 하였다.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.11
• /
• pp.1506-1512
• /
• 2000

Control of shock may be important in the hydraulic system and necessary to avoid failure and to improve the efficiency of operation. This study addresses the design and use of an orifice to provide the desired control of the hydraulic actuator system. The experimental apparatus is an idealization of an automobile shift system. Control is accomplished by installing three different types of orifices at appropriate locations in the system. Experimental results show that the orifice can be used to obtain the control of shock and control level depends on the orifice size, orifice type, operating pressure and flow rate.

• Proceedings of the KSME Conference
• /
• 2000.11b
• /
• pp.621-626
• /
• 2000

Reduction in pressure transients may be important in the hydraulic system and necessary to avoid failure and to improve the efficiency of operation. This study addresses the design and use of an orifice to provide the desired control of the hydraulic actuator system. The experimental apparatus is a model of an automobile shift system. Control is accomplished by installing four different diameter ratio of orifices at appropriate locations in the system. Experimental results show that the orifice can be used to obtain the control of shock and the control level depends on the orifice size, orifice type, operating conditions.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.8 no.4
• /
• pp.247-256
• /
• 2004

The damage curves for the 2-story shear building to the impulsive rectangular loads were established with the peak load and Impulse ratio producing the critical displacement. The convolution integrations with the Impulse response matrix and the loads were used to find the responses of the building. The impulse response matrix required in the calculations of the convolution integration were found with the mode superposition method It is shown from the established damage curves that the responses of the top and bottom floor are sensitive to the magnitude and the impulse of the loads respectively.

• Journal of Ocean Engineering and Technology
• /
• v.2 no.1
• /
• pp.150-162
• /
• 1988

The dynamic fracture toughness, $K_{Id}$,is measured in the heat-treated and ion-nitrided Cr-Mo, Ni-Cr-Mo steel using standard and Precracked Charpy specimens an imstrumented impact machine. The value of $K_{Id}$and both the energy of initiate fracture, and the total energy of fracture. Since the $K_{Id}$values of the precraked impact specimens are in accord with their theoretical ones, this testing method is sufficently practical. The effect of ion-nitriding are found to be larger than the heat-treaded specimen.

• Journal of Ocean Engineering and Technology
• /
• v.25 no.5
• /
• pp.40-46
• /
• 2011

This study carried out a series of experiments involving impact tests (Drop weight type & Charpy type with a standard specimen and newly designed I-type specimen), hardness tests, and fracture surface observations of French-made roll shell steel (F), abnormal roll shell steel (M), reheated roll shell steel (R), and S25C steel under heat treatment conditions ($570^{\circ}C$) to analyze the cause and prevent the roll shell steel's brittle fracture and its damage.

• Journal of Ocean Engineering and Technology
• /
• v.25 no.5
• /
• pp.33-39
• /
• 2011

This study involved a series of experiments, which included impact tests (drop weight & Charpy) and hardness tests under various heat treatment conditions, followed by fractography observations of Normal Roll Shell steel (NRS), Abnormal Roll Shell steel (ARS), and S25C steel, in order to analyze the cause of brittle fracture and damages in Roll Shell steel. The optimal tempering temperature was characterized for ARS and NRS.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1992.10a
• /
• pp.8-13
• /
• 1992

최근 우리 나라도 자동차의 수요가 급격히 늘어나고 있고, 생산량도 급증하 고 있어 자동차 공업이 산업의 최고의 위치를 확보하게 되었다. 자동차는 최 신 종합 기계 구조물로서 전기, 전자, 제어에 이르기까지 거의 모든 분양의 학문적 이론과 기술을 도입하는 최첨단의 기계 장비인것이다. 따라서 그 부 가가치 또한 매우 큰 것이다. 자동차의 성능을 결정짓는 가장 커다란 요소는 주행 성능과 안정성 및 조종성이다. 주행성능이라 함은 자동차의 종방향 운 동에 관한 성능으로서 기관의 동력에 지배적인 영향을 받는 성능(동력 성능) 과 그 밖의 성능(타향 성능, 제동 성능)으로 구분된다. 또 안정성과 조종성이 라함은 자동차의 횡방향 운동에 관한 성능으로서 로울링과 요우잉을 포함시 킨 곡선 운동에 관한 성능을 일컫는다. 이러한 운동 성능을 좌우하는 것은 구조적인 설계의 양부와 스프링이나 댐퍼의 성능일 것이다. 자동차의 수많은 부품 중의 다수가 국산화 되어 있지 아니하고, 또한 이러한 부품들의 성능을 시험할 수 있는 장비의 수입 의존도가 높은 것은 업계나 학계 등에서 앞으 로 많은 연구가 이루어져야 할 점이다. 자동차의 충격 흡수기(shock absorber)의 검사기도 또한 수입 시험기에 의존하고 있었던 것이 현실이었 다. 이에 본 연구진은 이 검사기의 국산화에 착수 한 것이다. 자동차에 있어 서 충격 흡수기는 지면에서 오는 충격을 급속히 흡수하는 역할을 하여 자동 차의 주행 성능과 안정성을 높혀 주며, 승차감을 높혀 주는 중요한 부품이 다. 따라서 충격 흡수기의 양부의 판정은 대단히 중요한 것이다. 본 연구에 서는 충격 흡수기의 충격 흡수력(감쇠력)을 측정하여 감쇠 특성을 정도 높게 파악할 수 있는 시험기를 만드는데 그 목적을 두고 있다. 연구는 시험기의 구동부를 제작하는 기계부와, 제어 및 계측의 하드웨어를 담당하는 전기.전 자부및 실제로 기계를 구동, 제어하고 측정 결과를 기록하고 출력하는 부분 을 담당하는 소프트웨어 개발부로 나누어서 진행하였다.