• Journal of the Korean Institute of Gas
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• v.27 no.4
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• pp.27-33
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• 2023

In a petrochemical plant, various mechanical equipments and structures are interconnected to ensure operability. Since the production activities of petrochemical plants have a great impact on the national economy, it is very important to maintain not only structural safety but also the operability of the facilities. However, the current seismic design standards present the design requirements of facilities mainly aimed at preventing collapse, and do not provide the requirements for securing operability of facilities. Depending on the behavioral characteristics of the facility, operability of the facility can be secured by seismic performance levels other than the collapse prevention level, so it is necessary to present seismic design methods that can apply various seismic performance levels. Spherical (ball) storage tanks are supported by columns and braces and exhibit complex nonlinear behavior because of buckling and yielding of support members. In this study, nonlinear seismic behavior characteristics were statistically analyzed and a new performance-based seismic design method was proposed based on them.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.3
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• pp.328-336
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• 2002

decrease in efficiency due to cavity fluid fluctuation. The purpose of this study is to examine erosion aspect on the SS400 specimen by cavitation and the effect of impact pressure generated from the demolition of the cavity of ultrasonic vibrator horn in the marine sludge oil environment. The erosion damage of specimen was investigated mainly on weight loss, weight loss rate and maximum erosion rate with variation of the vibration amplitude of $50{\mu}m, 24{\mu}m$ as well as the change of space between transducer horn and specimen. The experimental results showed that as the space between ultrasonic vibrator horn and specimen disk increased, the weight loss and weight loss rate decreased and the values were larger in SFO than in SLO. These findings would help interpret the aspect of cavitation erosion damage in metallic materials of different operating environment and material characteristics.

• Earthquakes and Structures
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• v.22 no.3
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• pp.289-304
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• 2022

During strong ground motions, adjacent structures with insufficient separation distances collide with each other causing considerable architectural and structural damage or collapse of the whole structure. Generally, existing design procedures for determining the separation distance between adjacent buildings subjected to structural pounding are based on approximations of the buildings' peak relative displacement. These procedures are based on unknown safety levels. This paper attempts to evaluate the influence of foundation flexibility on the structural seismic response by considering the variability in the system and uncertainties in the ground motion characteristics through comprehensive numerical simulations. Actually, the aim of this study is to evaluate the influence of foundation flexibility on probabilistic evaluation of structural pounding. A Hertz-damp pounding force model has been considered in order to effectively capture impact forces during collisions. In total, 5.25 million time-history analyses were performed over the adopted models using an ensemble of 25 ground motions as seismic input within OpenSees software. The results of the study indicate that the soil-structure interaction significantly influences the pounding-involved responses of adjacent structures during earthquakes and generally increases the pounding probability.

• Journal of Wetlands Research
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• v.25 no.4
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• pp.345-352
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• 2023

Recently, the risk of snow disasters has been increasing South Korea. The damages of heavy snow were categorized into direct and indirect. Direct damage is usually the collapse of buildings as houses, greenhouse or barns. Indirect damage is various, for example, traffic congestion, traffic acident, drop damage, and so on. In South Korea, direct damage is severe in rural area, mosty collapse of greenhouse or barns. However, indirect damage such as traffic accident is mostly occurred in urban area. Therefore, the regional characteristics should be considered when vulnerability is evaluated. Therefore, in this study, the PSR and DPSIR method were applied by regional scale in South Korea. The PSR evaluation method is divided into pressure, state, and reaction index. however, the DPSIR evaluation method is divided into Driving force, Pressure, State, Impact, and Response index. the DPSIR evaluation method is divided into Driving force, Pressure, State, Impact, and Response index. Data corresponding to each indicator were collected, and the weight was calculated using the entropy method to calculate the snowfall vulnerability index by regional scale in South Korea. Calculated heavy snow damage vulnerabilities from the two methods were compared. The calculated vulnerabilities were validated using the recent snow damage in South Korea from 2018 to 2022. Snow vulnerability index calculated using the DPSIR method showed more reliable results. The results of this study could be utilized as an information to prepare the mitigation of heavy snow damage and to establish an efficient snow removal response system.

• Journal of Advanced Research in Ocean Engineering
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• v.3 no.1
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• pp.1-14
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• 2017

The safety analysis of an earthquake is carried out during the operation of a subsea pipeline and an onshore pipeline. Several cases are proposed for consideration. In the case of a buried pipeline, permanent ground deformation by the earthquake and an increase of internal pressure by the acceleration of the earthquake should be considered. In the case of a subsea pipeline, a bending moment is caused by liquefaction of the backfill material on a trenched seabed, etc., which results in a high bending moment of the buried pipeline. The bending moment causes the collapse of the subsea pipeline or a leak of crude oil or gas, which results in economic loss due to enormous environmental contamination and social economic loss owing to operation functional failure. Thus, in order to prevent economic loss and operation loss, structurally sensitive design with regard to seismic characteristics must be performed in the buried pipeline in advance, and the negative impact on the buried pipeline must be minimized by conducting a thorough analysis on the seabed and backfilling material selection. Moreover, it is proposed to consider the selection of material properties for the buried pipeline. A more economical review is also required for detailed study.

• Structural Engineering and Mechanics
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• v.12 no.4
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• pp.347-362
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• 2001

The paper deals with preventing the collapse of by the means of supporting the bridges by rubber bearings and pedeck structures of skew and curved bridges during earthquakes, rmitting pounding between the decks and the abutments. Seismic response during pounding is characterized by various phenomena, such as the caging of bridge decks between abutments during an earthquake or decks popping out. These behaviors depend on only a small difference in seismic intensity. Regarding the global characteristics of a seismic response, smaller clearance between a deck and its abutments results in smaller impact damage of the abutments as well as lesser deformation of the rubber bearings. Similarly, smaller clearance between a deck and the side blocks results in smaller damage. The stiffnesses of the bearings and the stiffness ratio between them control the deck displacement. In short to medium length bridges, zero clearance between a deck and the abutments or the deck and the side blocks is the most effective way in preventing the deck from falling and limits the damage to the abutments or the side blocks.

• Journal of the Korea Concrete Institute
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• v.25 no.5
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• pp.485-496
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• 2013

In recent years, frequent terror or military attacks by explosion or impact accidents have occurred. Examplary case of these attacks were World Trade Center collapse and US Department of Defense Pentagon attack on Sept. 11 of 2001. These attacks of the civil infrastructure have induced numerous casualties and property damage, which raised public concerns and anxiety of potential terrorist attacks. However, a existing design procedure for civil infrastructures do not consider a protective design for extreme loading scenario. Also, the extreme loading researches of prestressed concrete (PSC) member, which widely used for nuclear containment vessel, gas tank, bridges, and tunnel, are insufficient due to experimental limitations of loading characteristics. To protect concrete structures against extreme loading such as explosion and impact with high strain rate, understanding of the effect, characteristic, and propagation mechanism of extreme loadings on structures is needed. Therefore, in this paper, to evaluate the impact resistance capacity and its protective performance of bi-directional unbonded prestressed concrete member, impact tests were carried out on $1400mm{\times}1000mm{\times}300mm$ for reinforced concrete (RC), prestressed concrete without rebar (PS), prestressed concrete with rebar (PSR, general PSC) specimens. According to test site conditions, impact tests were performed with 14 kN impactor with drop height of 10 m, 5 m, 4 m for preliminary tests and 3.5 m for main tests. Also, in this study, the procedure, layout, and measurement system of impact tests were established. The impact resistance capacity was measured using crack patterns, damage rates, measuring value such as displacement, acceleration, and residual structural strength. The results can be used as basic research references for related research areas, which include protective design and impact numerical simulation under impact loading.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.5
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• pp.481-487
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• 2012

Recently, the construction of the small Al alloy ships is an increasing trend in viewpoint such as the disposal issue of a retired ship, the enhancement of environmental regulation and resources recycling etc. for FRP ships. However, Al alloy ship which can achieve high speed by light weight in marine environment is exposed to a problem on materials damage by cavitation-erosion which is generated by large impact pressure with the collapse of air bubbles due to cavitation. Consequently, in this study, water cavitation peening technology was applied in Al alloy for ship to enhance durability life by preventing cavitation damage. So, the water cavitaton peening application time that presented the excellent cavitation characteristic investigated. The weight-loss of 5456-H116, 5083-H321 and 5052-O Al alloy at the optimum water cavitation peening time were improved to 42.11 %, 50.0 % and 25.7 %, respectively.

• Ocean and Polar Research
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• v.45 no.3
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• pp.155-172
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• 2023

The collapse of ice shelves is a process that can severely increase the rise of global sea-levels through the reduction of the buttressing effect of ice shelves and the consequent acceleration of the ice flow of ice sheets. In recent years, the West Antarctic ice shelves in the Amundsen Sea, whose buttressing effect is essential for a great part of the West Antarctic ice sheet, have been experiencing the most rapid melting and thinning in the world. The melting of the West Antarctic ice shelves is caused primarily by heat transported by Circumpolar Deep Water (CDW). For this reason, it is important to investigate ice-ocean interactions that could influence the melting of ice shelves and evaluate the stability of West Antarctic ice shelves. A lot of researchers have been actively investigating the West Antarctic ice shelves in the Amundsen Sea. High-impact journals have recognized the importance of and published studies on ice-ocean interactions occurring near and under the ice shelves as well as the connections among ice shelves. However, in situ observations are limited due to extreme weather and sea-ice conditions near the ice shelves; therefore, many scientific questions remain unanswered. This study introduces the characteristics of the Amundsen Sea and investigate the past and latest research issues in this region. This study also gives suggestions regarding important scientific questions and directions for future research that should help early-career scientists take the lead in future research on the melting dynamics of the West Antarctic ice shelves in the Amundsen Sea.

• Journal of Wetlands Research
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• v.21 no.1
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• pp.9-15
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• 2019

The Daegi-cheon watershed is located in the upper part of the Han River, which has the representative highland vegetable growing complexes. This watershed has a large impact on the water quality and aquatic ecosystem in the upstream of the Han River by discharging a large amount of turbid water during rainfall season. For proposing an efficient turbid water management and policy, the analysis of the characteristics of flow rate and SS and its causes needs to be carried out preferentially. In this study, the relationship between flow rate and SS concentration was analyzed in the Daegi-cheon watershed, and in turn the turbidity characteristics were analyzed. As a result of the study, in the normal flood flow condition, it was shown that SS concentration changed arbitrarily due to various environmental factors. On the other hand, the SS concentration was considerably high in the very high flow condition. Based on the field survey, this could be the reason why the effects of the steep valley and slope collapse according to the very high flow rate as well as the source in the agricultural fields were greatly contributed. Therefore, it is necessary to develop a structural best management practice that can stabilize the steep slope and reduce river bed loss along with the typical source managements plans.