• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.241-257
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• 2020

The rapid proliferation of oil/gas drilling and wind turbine installations with jack-up rig-formed structures increases structural safety requirements, due to the greater risks of operational collisions during use of these structures. Therefore, current industrial practices and regulations have tended to increase the required accidental collision design loads (impact energies) for jack-up rigs. However, the existing simplified design approach tends to be limited to the design and prediction of local members due to the difficulty in applying the increased uniform impact energy to a brace member without regard for the member's position. It is therefore necessary to define accidental load estimation in terms of a reasonable collision scenario and its application to the structural response analysis. We found by a collision probabilistic approach that the kinetic energy ranged from a minimum of 9 MJ to a maximum 1049 MJ. Only 6% of these values are less than the 35 MJ recommendation of DNV-GL (2013). This study assumed and applied a representative design load of 196.2 MN for an impact load of 20,000 tons. Based on this design load, the detailed design of a leg structure was numerically verified via an FE analysis comprising three categories: linear analysis, buckling analysis and progressive collapse analysis. Based on the numerical results from this analysis, it was possible to predict the collapse mode and position of each member in relation to the collision load. This study provided a collision strength assessment between attendant vessels and a jack-up rig based on probabilistic collision scenarios and nonlinear structural analysis. The numerical results of this study also afforded reasonable evaluation criteria and specific evaluation procedures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.61-70
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• 2013

This paper presents the response calibration method based on quality control range, which is established from the concept and method of statistical quality control for natural frequency ratio and response ratio. To this end, statistical analysis including descriptive statistics analysis, normality test, ANOVA were performed for response characteristics obtained from loading tests and structural analysis for more than hundred and thirty well-conditioned bridges. Suggested method is based on real structural integrity evaluation case studies and statistical quality control approach, in this respect it is expected to provide scientific criteria and systematic procedure for response calibration and load carrying capacity assessment.

• Structural Engineering and Mechanics
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• v.60 no.2
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• pp.337-350
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• 2016

Even though extensive researches have been performed for steam explosion due to their complex mechanisms and inherent uncertainties, establishment of severe accident management guidelines and strategies is one of state-of-the arts in nuclear industry. The goal of this research is primarily to examine effects of vessel failure modes and locations on nuclear facilities under typical steam explosion conditions. Both discrete and integrated models were employed from the viewpoint of structural integrity assessment of steel components and evaluation of the cracking and crushing in reinforced concrete structures. Thereafter, comparison of systematic analysis results was performed; despite the vessel failure modes were dominant, resulting maximum stresses at the all steel components were sufficiently lower than the corresponding yield strengths. Two failure criteria for the reinforced concrete structures such as the limiting failure ratio of concrete and the limiting strains for rebar and liner plate were satisfied under steam explosion conditions. Moreover, stresses of steel components and reinforced concrete structures were reduced with maximum difference of 12% when the integrated model was adopted comparing to those of discrete models.

• Structural Engineering and Mechanics
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• v.33 no.1
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• pp.31-46
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• 2009

An anisotropic damage mechanics approach is introduced which models the static and dynamic behavior of mass concrete in 3D space. The introduced numerical approach is able to model non-uniform cracking within the cracked element due to cracking in Gaussian points of elements. The validity of the proposed model is considered using available experimental and theoretical results under the static and dynamic loads. No instability and stress locking is observed in the conducted analyses. The Morrow Point dam is analyzed including dam-reservoir interaction effects to consider the nonlinear seismic behavior of the dam. It is found that the resulting crack profiles are in good agreement with those obtained from the smeared crack approach. It is concluded that the proposed model can be used in nonlinear static and dynamic analysis of concrete dams in 3D space and enables engineers to define the damage level of these infrastructures. The performance level of the considered system is used to assess the static and seismic safety using the defined performance based criteria.

• Structural Engineering and Mechanics
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• v.48 no.5
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• pp.661-679
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• 2013

In this work, the safety performance of a commercial motorcycle helmet already placed on the market is assessed. The assessed motorcycle helmet is currently homologated by several relevant motorcycle standards. Impacts including translational and rotational motions are accurately simulated through a finite element numerical framework. The developed model was validated against experimental results: firstly, a validation concerning the constitutive model for the expanded polystyrene, the material responsible for energy absorption during impact; secondly, a validation regarding the acceleration measured at the headform's centre of gravity during the linear impacts defined in the ECE R22.05 standard. Both were successfully validated. After model validation, an oblique impact was simulated and the results were compared against head injury thresholds in order to predict the resultant head injuries. From this comparison, it was concluded that brain injuries such as concussion and diffuse axonal injury may occur even with a helmet certified by the majority of the motorcycle helmet standards. Unfortunately, these standards currently do not contemplate rotational components of acceleration. Conclusion points out to a strong recommendation on the necessity of including rotational motion in forthcoming motorcycle helmet standards and improving the current test procedures and head injury criteria used by the standards, to improve the safety between the motorcyclists.

• Nuclear Engineering and Technology
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• v.53 no.2
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• pp.466-473
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• 2021

Fire protection is one of important issues to ensure safety and reduce risks of nuclear power plants (NPPs). While robust programs to shut down commercial reactors in any fires have been successfully maintained, the concept and associated regulatory requirements are constantly changing or strengthening by lessons learned from operating experiences and information all over the world. As part of this context, it is necessary not only to establish specific fire hazard assessment methods reflecting the characteristics of research reactors and educational reactors but also to make decisions based on advancement encompassing numerical analyses and experiments. The objectives of this study are to address fire simulation in the control room of an educational reactor and to discuss integrity of digital console in charge of main operation as well as analysis results through comparison. Three electrical fire scenarios were postulated and twenty-four thermal analyses were carried out taking into account two turbulence models, two cable materials and two ventilation conditions. Twelve supplementary thermal analyses and six subsequent structural analyses were also conducted for further examination on the temperature and heat flux of cable and von Mises stress of digital console, respectively. As consequences, effects of each parameter were quantified in detail and future applicability was briefly discussed. On the whole, higher profiles were obtained when Deardorff turbulence model was employed or polyvinyl chloride material and larger ventilation condition were considered. All the maximum values considered in this study met the allowable criteria so that safety action seems available by sustained integrity of the cable linked to digital console within operators' reaction time of 300 s.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.4
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• pp.278-287
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• 2023

This study aims to analyze and evaluate the structural strength of a 53ft Liquefied Natural Gas (LNG) tank container according to International Organization for Standardization (ISO) 1496-3, amidst growing global demand for LNG transportation. The research was conducted in two main stages: structural analysis using Finite Element Analysis (FEA) under various load conditions, and structural strength tests following ISO 1496-3 test procedures. The structural analysis was performed considering different loading conditions to assess the structural safety of the tank container. Calculated stresses were compared with allowable stress under specified load conditions. The structural strength tests were conducted at Mokpo National University's Subsea Umbilical cable Riser Flowline R&D Center, which provided a suitable testing environment. The study found that calculated stresses met the allowable stress under specified load conditions, confirming the structural safety of the tank container. Additionally, the maximum deformation and permanent deformation satisfied the design criteria for all test cases, indicating the container's structural strength meets requirements. The research also contributed valuable data for future structural strength tests of similar products and facilitated the development of safe and efficient LNG transportation solutions by developing effective test procedures in accordance with ISO 1496-3 standards.

• The Journal of Sustainable Design and Educational Environment Research
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• v.16 no.2
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• pp.44-53
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• 2017

Facility management is to maintain and develop the primary structural, functional, aesthetic performance of facility in order to guaranty the users' daily convenience and safety. However it is hard to maintain and serve their intended function and safe environment from the beginning as times go by. As present educational government of city and local area has been performing formally facility check and management as well as maintenance of school facility, it is hard to respond a dangerous situation at the suitable time and safety prevention plans are delayed. In addition, educational environment improving budget have been unreasonably decided not according to the allocating criteria. Therefore, this research developed a same, simple, and quantitative evaluation method of deterioration level of elementary, middle, and high School in Korea and verified usability of the method through the case study.

• Journal of Radiation Protection and Research
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• v.26 no.1
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• pp.35-43
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• 2001

All of sealing capsules to transport a special form radioactive material should be designed and fabricated in accordance with the design criteria prescribed in IAEA standards and domestic regulations. The objective of this study is to demonstrate the safety of a shipping capsule for $^{192}Ir$ special form radioisotope which produced in the HANARO. The safety tests were carried out for the impact, percussion, bending and heat test conditions. And leakage tests were carried out before and after the each test. Also, the safety analyses wert performed using computer codes in order to verify the test results. The capsule showed slight scratches and deformation, and maintained its structural and thermal integrities in all tests without any severe damage or melting. It also met the allowable limits of leakage rate after each test. Therefore, it has been verified that the capsule was designed and fabricated to meet all requirements for the special form.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.317-324
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• 2020

In this study, a simplified equation for settlement evaluation suitable for the special conditions of a counter facility is suggested. Recently, counter facilities, especially breakwaters, are constructed on soft ground in distant seas as new-port development projects. A counter facility that resists the external forces by self-weight settles easily when constructed on soft ground. Settlement in a counter facility and breakwater is not an important factor for maintenance than a land facility. On the other hand, the current settlement evaluation criteria are excessive for conducting a safety inspection. A settlement evaluation from a safety inspection followed by "Detailed Guidelines for a safety inspection on a counter facility" is used. A simplified equation was proposed to calculate the maximum settlement by applying the allowable residual settlement or settlement stability evaluation results. The suitability of the simplified equation was assessed compared to the assessed rating from the settlement survey results. The proposed simplified equation showed that the settlement evaluation rating had been upgraded. The proposed simplified equation is expected to be used to evaluate the practical structural stability and functional performance.