• 한국지반공학회지:지반
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• 제8권4호
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• pp.67-80
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• 1992

동적인 문제를 해석하는 데 있어서 최대전단탄성계수의 결정은 어떤 변형률에서의 전단응력을 추정하는데 필연적이라 할 수 있다. 그동안 실리카질 모래에 관한 모델이 준시되어 왔지만 그러한 모델을 부서지는 모래에 직점적으로 적용하는 데는 모래의 부서짐(crushability)때문에 어려움이 있다. 본 연구에서는 부서지는 모래의 미소변형률에서의 동적인 거동이 평가되었으며 실험한 모래의 최대 전단탄성 계수에 관한 모델이 제시되었다. 부서지는 모래의 전단탄성 계수는 느슨한 모래의 경우는 실리카질 모래와 유사한 값을 보이나 밀도가 증가하면 입자간의 접촉면적이 커져서 비틀력 (torsional force)으로 인해 모래가 부서져 전단저항이 작아지는 것으로 보인다. 그리고 계수치 (modulus number) 가 Been과 Jefferies (1985)의 상태 정수 (state parameter)로 표현되었다.

• 대한기계학회논문집A
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• 제29권11호
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• pp.1551-1559
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• 2005

This paper explains manufacturing process and experimental studies on a composite carbody of Korean tilting train. The composite carbody with length of 23m was manufactured as a sandwich structure composed of a 40mm-thick aluminium honeycomb core and 5mm-thick woven fabric carbon/epoxy face. In order to evaluate structural behavior and safety of the composite carbody, the static load tests such as vertical load, end compressive load, torsional load and 3-point support load tests have been conducted. These tests were performed under Japanese Industrial Standard (JIS) 17105 standard. From the tests, maximum deflection was 12.3mm and equivalent bending stiffness of the carbody was 0.81$\times$10$^{14}$ kgf$\cdot$mm$^{2}$ Maximum stress of the composite body was lower than 12.2$\%$ of strength of the carbon/epoxy. Therefore, the composite body satisfied the Japanese Industrial Standard.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.173-178
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• 2004

The estimation of springing responses for recent ships are carried out and application to a ship design are described. To this aim, springing effects on hull girder were re-evaluated including non-linear wave excitations and torsional vibrations of the hull. The Timoshenko beam model was used to calculate stress distribution on the hull girder by the superposition method. The strip method was employed to calculate the hydrodynamic forces and moments on the hull. In order to remove the irregular frequencies, we adopted 'rigid lid' on the hull free surface level and added asymptotic interpolation along the high frequency range. Several applications to the existing ships were carried out. They are Bishop and Price's container ship, S-175 container ship, large container, VLCC and ore carrier. One of them is compared with ship measurement result while another with that of model test. Comparison between analytical solution and numerical one for homogeneous beam type artificial ship shows good agreement. It is found that most springing energy came from high frequency waves for the ships having low natural frequency and North Atlantic route etc. Therefore, the high frequency tail of the wave spectrum should be increased by $\omega^{-3}\;instead\;of\;\omega^{-4}\;or\;\omega^{-5}$ for springing calculation.

• 한국소음진동공학회논문집
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• 제19권2호
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• pp.155-161
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• 2009

Engine builders have separately developed and applied torsional, axial and structural vibration monitoring system on most marine engines. These systems displayed their results for engine or ship operation engineers and were not regularly stored at the hardware of computer. So, the history and trend of various engine and hull vibrations were not supported for preventive maintenance and to protect the failure of these activity or function. The integrated vibration or stress monitoring system(EVAMOS : engine vibration analysis and monitoring system) in marine diesel engine, its accessories and hull structure have been developed by the dynamics laboratory of Mokpo Maritime University during last 3 years. This paper introduces the design conception and ability of commercial software EVAMOS with field data on several actual tests.

• 항공우주시스템공학회지
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• 제14권6호
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• pp.18-25
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• 2020

This study investigated the structural behaviors and safety of an electro-mechanical linear actuator and a load simulator with a plate spring. The material and dimensions of the plate spring were determined by theoretically calculating the stress and torsional angle for the rating load of the actuator. Thereafter, a flexible multibody dynamics (FMBD) analysis was conducted on the linear actuator and load simulator to confirm the performance of the load simulator and acquire the reaction forces acting on the actuator and simulator. The structural safety of the linear actuator and load simulator was evaluated via finite element analysis using the aforementioned reaction forces. Consequently, the proposed linear actuator and load simulator were determined to be structurally safe; however, the safety factors for the actuation rod and the housing on the actuator were excessively high. Therefore, the weight and cost must be reduced to improve their design parameters in the future.

• Geomechanics and Engineering
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• 제30권5호
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• pp.449-460
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• 2022

Safe underground construction in a rock mass requires adequate ground investigation and effective determination of rock conditions. The estimation of rock mass behavior is difficult, because rock masses are innately anisotropic and heterogeneous at different scales and are affected by various environmental factors. Quantitative rock mass classification systems, such as the Q-system and rock mass rating, are widely used for characterization and engineering design. The measurement of rock classification parameters is subjective and can vary among observers, resulting in questionable accuracy. Geophysical investigation methods, such as seismic surveys, have also been used for ground characterization. Torsional shear wave propagation characteristics in cylindrical rods are equal to that in an infinite media. A probabilistic quantitative relationship between the Q-value and shear wave velocity is thus investigated considering long-wavelength wave propagation in equivalent continuum jointed rock masses. Individual Q-system parameters are correlated with stress-dependent shear wave velocities in jointed rocks using experimental and numerical methods. The relationship between the Q-value and the shear wave velocity is normalized using a defined reference condition. This relationship is further improved using probabilistic analysis to remove unrealistic data and to suggest a range of Q-values for a given wave velocity. The proposed probabilistic Q-value estimation is then compared with field measurements and cross-hole seismic test data to verify its applicability.

• Steel and Composite Structures
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• 제49권5호
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• pp.473-486
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• 2023

A through-railway bridge with an inclined girder has recently been applied to optimize the cross-section of a slender bridge structure in railway bridges. To achieve the additional cross-section optimization effect by the bolted end-plate connection, it is necessary to investigate the application of the bolted end-plate tension connection between the inclined girder and the crossbeam. This basic study was conducted on the application of the bolted end-plate moment connection of crossbeams to half-through girders with inclined webs. The combined behavior of vertical deflection and rotational behavior was observed due to the effect of the web inclination in the inclined girder where the steel crossbeam was connected to the girder by the bolted end-plate moment connection. Therefore, in the experiment, the deflection of the inclined girder was 1.77-2.93 times greater than that of the vertical girder but the lateral deflection of the inclined girder was 0.4 times less than that of the vertical girder. Moreover, the tensile stress of the upper bolts in the inclined girder with low crossbeams was clearly 0.81 times lower than that of the vertical girder. According to the results, the design formula for vertical girders does not reflect the influence of the web inclination. Therefore, this study proposed the design procedures for the inclined girder to apply the bolted end-plate moment connection of the crossbeam to the inclined girder by reflecting the design change factors according to the effect of the web inclination.

• Journal of Advanced Marine Engineering and Technology
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• 제15권4호
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• pp.29-45
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• 1991

Lip type stern tube sealing systems have used in almost all the middle or large ships which are being constructed in these days. It seems that the pressure fluctuation of the seal ring interspace, the cross-section profile and the materials quality of the seal rings have great effects on the sealing fuction of this sealing system. In this paper, the mechanical movement of lip seal ring which plays the most important role in stern tube sealing system and the possibility of leakage caused by pressure fluctuation are studied by theory and experiment. Using the finite element method for the axi-symetric object which receives the torsional load, the displacement and stress analysis of the seal rings, and also the possibility of crack occurance is checked by theoretical analysis. If the force which seal ring lip periphery receives is too small, there will be the possibility of leakage caused by the pressure fluctuation of the seal ring interspace, and if this force is too large, the frictional force between the seal ring and the liner will become problematical. The possibility of leakage caused by hardening of seal ring materials and creep phenomena of tested seal rings are also examined. The trial seal rings were designed and manufactured using the program of displacement and stress analysis developed in this study and the experimental apparatus to test the trial seal rings was also designed and manufactured. This trial seal rings were fitted in the experimental apparatus which was made in the same form as an actual stern tube. The one side of this apparatus was filled with sea water and the other side of it was filled with the lubricating oil. The leakage of oil and sea water was checked and the temperature was measured, rotating the propeller shaft at the constant velocity by D.C. motor. It was proved that the trial seal rings made in Viton rubber functioned excellenty but the trial seal rings made in N.B.R. rubber had problem in its durability.

• 한국지반공학회논문집
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• 제21권2호
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• pp.137-144
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• 2005

직접전단시험은 측방변위 구속형의 일면·단순전단시험과 측방변위 비구속형의 비들림 전단시험으로 대별된다. 현재까지도 가장 많이 사용되고 있는 직접전단시험은 시험기 및 시험방법과 결과의 해석 등에 몇 가지의 문제점이 있었으며, 특히 사질토에서는 강도가 과대하게 평가되는 등의 지적이 있었다. 또한 시험기구상의 제약으로부터 전단과정 중 진행성 파괴를 일으키는 점, 공시체내의 전단변형량과 전단응력이 일정하지 않기 때문에 전단변형량을 정의할 수 없는 점 등이 있다. 한편 단순전단시험은 직접전단시험의 장점을 그대로 가지면서, 공시체에 일정한 전단변형을 전달할 수 있기 때문에 전단에 대한 응력-변형량 관계를 얻을 수 있는 이상적인 시험법이라고 할 수 있다. 그러나 단순전단시험은 그 구조상, 시험기제작이 어려운 점 등 아직도 실용적인 시험기의 완성에는 도달하지 못하고 있는 실정이다. 본 논문에서는 간이 전단시험방법 및 시험기의 문제점을 개선한 개량형 일면전단 시험기의 제작과 일본 지반공학회 토질시험법의 기준화과정에서 얻은 시험결과를 바탕으로 시험기의 개요와 시험법의 개선, 정압조건의 시험결과에 대해 서술하였다.

• 해양환경안전학회지
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• 제24권5호
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• pp.597-603
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• 2018

본 연구는 수중 및 여가활동에 대한 수요 증가에 따른 다이버들을 위한 보트의 구조 건전성에 관한 것이다. 대상 선박은 선체 중앙부에 Moon Pool 구조를 갖추고 있는 소형 쌍동선이며, 연구수행은 ISO Rule 기반의 허용응력 산정을 통한 유한요소 해석법을 이용하여 연구를 수행하였다. 연구수행 방법은 ISO 12215-5와 TC118.1225-7에서 정의하고 있는 계수를 산정하고, 종방향굽힘 모멘트, 비틀림 모멘트, 선저슬래밍 하중 등을 적용하여 ISO 기준과 허용응력 설계법(ASD)에 의한 적합성 여부를 판정하고 유한요소해석(FEA)를 활용한 극한강도 설계법을(LFRD)를 적용하여 수행하였다. 연구결과 문풀형 구조를 가진 선박도 ISO규정, KR규정을 적용하여 설계시 구조적 건전성을 확보하는 것으로 사료된다.