• Nuclear Engineering and Technology
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• 제53권7호
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• pp.2268-2276
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• 2021

Spent nuclear fuel, which can degrade during long-term storage, must be transported intact in normal transport conditions. In this regard, many studies, including those involving Multi-Modal Transportation Test (MMTT) campaigns, have been conducted. In order to transport the spent fuel safely, a tie-down structure for supporting and transporting a cask containing the spent fuel is essential. To ensure its structural integrity, a method for finding an optimum conceptual design for the tie-down structure is presented. An optimized transportation test model of a tie-down structure for the KORAD-21 metal cask is derived based on the proposed optimization approach, and the transportation test model is manufactured by redesigning the optimized model to enable its producibility. The topology optimization approach presented in this paper can be used to obtain optimum conceptual designs of tie-down structures developed in the future.

• Ocean Systems Engineering
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• 제1권4호
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• pp.263-283
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• 2011

The performance of a rig tie-down system on a TLP (Tension Leg Platform) is investigated for 10-year, 100-year, and 1000-year hurricane environments. The inertia loading on the derrick is obtained from the three-hour time histories of the platform motions and accelerations, and the dynamic wind forces as well as the time-dependent heel-induced gravitational forces are also applied. Then, the connection loads between the derrick and its substructure as well as the substructure and deck are obtained to assess the safety of the tie-down system. Both linear and nonlinear inertia loads on the derrick are included. The resultant external forces are subsequently used to calculate the loads on the tie-down clamps at every time step with the assumption of rigid derrick. The exact dynamic equations including nonlinear terms are used with all the linear and second-order wave forces considering that some dynamic contributions, such as rotational inertia, centripetal forces, and the nonlinear excitations, have not been accounted for in the conventional engineering practices. From the numerical simulations, it is seen that the contributions of the second-order sum-frequency (or springing) accelerations can be appreciable in certain hurricane conditions. Finally, the maximum reaction loads on the clamps are obtained and used to check the possibility of slip, shear, and tensile failure of the tie-down system for any given environment.

• 한국구조물진단유지관리공학회 논문집
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• 제19권1호
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• pp.62-71
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• 2015

KCI 2012와 ACI318-11에서 확대머리 이형철근에 대한 정착길이 산정식을 제시하고 있지만 확대머리 이형철근을 이용한 겹침이음상세에 대한 규정은 없다. 또한, 정착길이 산정에 있어서 횡보강근 효과는 고려하지 않고 있다. 본연구에서는 400MPa과 500MPa 설계기준항복강도를 가지는 확대머리 이형철근에 대하여 겹침이음구간에 대한 구속상세를 평가하기 위하여 겹침이음실험을 실시하였다. 겹침이음 구간내 적용되는 구속상세는 스터럽과 Tie-down 철근이다. 실험결과, 스터럽만으로 보강된 실험체들에서 겹침이음강도 증가에 큰 영향이 없어 취성적인 파괴를 나타낸 반면에, 스터럽과 Tie-down 철근으로 보강된 실험체들은 공칭휨강도 이상의 실험휨강도와 휨거동을 나타내었다. 따라서 스터럽과 Tie-down 철근 상세는 400MPa과 500MPa의 확대머리 이형철근에 대한 겹침이음 성능향상에 기여할 수 있는 것으로 사료된다.

• Ocean Systems Engineering
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• 제6권2호
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• pp.143-159
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• 2016

Cargo, such as a Tension Leg Platform (TLP), Semi-submersible platform (Semi), Spar or a circular Floating Production Storage and Offloading (FPSO), are frequently dry-transported on a Heavy Lift Vessel (HLV) from the point of construction to the point of installation. The voyage can span months and the overhanging portions of the hull can be subject to frequent wave slamming events in rough weather. Tie-downs or sea-fastening are usually provided to ensure the safety of the cargo during the voyage and to keep the extreme responses of the cargo, primarily for the installed equipment and facilities, within the design limits. The proper design of the tie-down is dependent on the accurate prediction of the wave slamming loads the cargo will experience during the voyage. This is a difficult task and model testing is a widely accepted and adopted method to obtain reliable sea-fastening loads and extreme accelerations. However, it is crucial to realize the difference in the inherent stiffness of the instrument that is used to measure the tri-axial sea fastening loads and the prototype design of the tie-downs. It is practically not possible to scale the tri-axial load measuring instrument stiffness to reflect the real tie-down stiffness during tests. A correlation method is required to systematically and consistently account for the stiffness differences and correct the measured results. Direct application of the measured load tends to be conservative and lead to over-design that can reflect on the overall cost and schedule of the project. The objective here is to employ the established correlation method to provide proper high-frequency responses to topsides and hull design teams. In addition, guidance for optimizing tie-down design to avoid damage to the installed equipment, facilities and structural members can be provided.

• ETRI Journal
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• 제40권5호
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• pp.561-569
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• 2018

Modern communication systems employ wideband antennas with circular polarization (CP) radiation. In this work, asymmetric modified bow-tie (ABT) and symmetric modified bow-tie (SBT) slotted circularly polarized single-point probe-fed circular patch antennas with dimensions of $40mm{\times}40mm$ for wideband applications are proposed. A 10 dB RL bandwidth of 350 MHz with CP, 3 dB axial ratio (AR) bandwidth of 100 MHz, peak gain of 4.9 dBic, and 10 dB RL bandwidth of 530 MHz with CP, 3 dB AR bandwidth of 140 MHz, peak gain of 5 dBic are obtained for ABT and SBT slotted circular patch antennas, respectively. The proposed SBT slotted patch is scaled up and down to $50mm{\times}50mm$ and $30mm{\times}30mm$, respectively. The proposed scaled-up version offers 10 dB RL and 3 dB AR bandwidths of 340 MHz and 80 MHz, with a peak gain of 5 dBic. The scaled-down version offers 10 dB RL and 3 dB AR bandwidths of 710 MHz and 180 MHz, with a peak gain of 5.25 dBic. These prototypes are suitable to work in IEEE 802.11a WLAN, ISM, and IEEE 802.11ac applications. The measured and simulated results are then discussed and compared.

• 대한방사선기술학회지:방사선기술과학
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• 제25권1호
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• pp.39-48
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• 2002

Earthquake are not frequent in korea but exist. The purpose of this study is to make a fixation(tie up) device against earthquake for radiologic department installation. It is considered that the device will prevent the X-ray equipment fall down, slip, Jumping therefor save the X-ray equipment itself and making possible to examine patients even when occuring earthquake, Discussion on how to make and how to set up was researched.

• 한국정밀공학회지
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• 제22권2호
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• pp.148-155
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• 2005

This study was carried out to analyze the effect of direction of wind load and machinery house location on the stability of container crane loading/unloading a container on a vessel. The overturning moment of container crane under wind load at 50m/s velocity was estimated by analyzing reaction forces at each supporting point. And variations of reaction forces at each supporting point of a container crane were analyzed according to direction of wind load and machinery house location. The critical location of machinery house was also investigated to install a tie-down which has an anti-overturning function of container crane at the land side supporting point.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.1000-1003
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• 2014

The primary purpose of this study is to observe the dynamic behavior within a vehicle on chassis dynamometer throughout cleat impact testing with two different constraining setups (Tie-down strap and one point fixation). Throughout this empirical experiment, no outstanding dynamic behavior characteristics are observed between two setups and thus, the performance of the one point fixation device is validated. Neither the interior noise nor acceleration at driver seat rail and knuckle is heavily influenced by two different constraining methods. However, one point fixation is far more advantageous considering its shorter set up time and its capability of measuring traction force with its built in force sensor.

• 한국군사과학기술학회지
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• 제16권6호
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• pp.771-778
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• 2013

Transmission is a core component of helicopter to transmit power from engine to rotor and must have a endurance to be able to show satisfactorily its performance required during its life time. When developing a new helicopter, both military and civil airworthiness authorities require a tie-down test to verify its endurance. Procedure for transmission endurance test is described in FAR part 29 or US military specification but its details are more or less ambiguous. In this paper, we have proposed a proper procedure for transmission endurance test by giving KUH transmission endurance test example including determination of applicable torque, load and test profile.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2005년도 추계학술대회 논문집
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• pp.241-246
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• 2005

본 연구는 컨테이너 크레인이 강풍에 대비하여 크레인을 고정하는 계류 시에 75m/s의 풍하중이 50ton급 컨테이너 크레인에 작용될 때, 풍향변화와 기계실의 위치 변화가 50ton급 컨테이너 크레인의 구조적 안정성에 미치는 영향을 분석하였다.. 본 연구에 적용된 설계 풍하중은 "건축물 하중 기준"에 의거하여 산출하였으며. 풍향은 $0^{\circ}\~180^{\circ}$를 $15^{\circ}$ 간격으로 적용하여 각 지지점에서의 반력을 분석하였다. 그리고 전체 자중의 $15\%$를 차지하는 기계실의 위치 변화가 컨테이너 크레인의 구조 안정성에 미치는 영향을 분석하였다. 그리고 이 결과들을 바탕으로 컨테이너 크레인의 전도방지장치인 타이다운(Tie-down)의 설계기준을 제시하였다.