• Journal of the Korean Society of Safety
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• v.32 no.4
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• pp.34-39
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• 2017

Typical flow regime of overflow at barrier or weir constructed in mid and small streams becomes as the submerged flow during most flood events. One of major causes of barrier failure has been reported as the levee-scour near the conjuction node between barrier and levee. However, most related design guidelines in Korea have not mentioned about the protection of levee around barrier or weir in detail. Furthermore, most previous researches have focused on the flow characteristics of overflow around several types of weirs but they did not have considered the material properties of levee itself. In this study, local scour near barrier was investigated with different material properties of levee under the submerged overflow condition which is assumed to reenact a flood event. Based on results from Fritz et al. and Mavis et al., a theoretical formula was also proposed in initial stage of laboratory experiments. And hydraulic experiments were carried out for the verification of the proposed formula. Levee was installed in the prismetic trapezoidal open channel and most parts were made of concrete except for movable section in which scour was expected to occur for the efficiency of experimental procedure. Each compaction of movable section in levee was followed by the basis of the KS F 2312. Further, after performing the experiments to find the optimum water content for each sediment, the specific amount of water was injected before flowing water. The difference between the proposed theoretical formula and experiment results was not much but considerable, which might be caused by the effect of compaction. For theoretical approach, it seemed that the formula did not take into account the compaction of levee, thus the correction coefficient for levee compaction determined in the literature was considered. Finally, the formula for the length of scour around barrier or weir was proposed, which can be useful to predict a levee in the reference design of revetment in mid and small streams. As shortly future study, scour length of levee around barrier or weir under different flow conditions such as perfect overflow condition will be studied and it will be able to contribute to suggest the design formula or criteria under all overflow conditions near barrier or weir.

• Journal of the Korean Society of Safety
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• v.31 no.2
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• pp.83-89
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• 2016

As the world's industrial development quickens, the highways and regional expressways have been expanding to serve the logistics and transportation needs of people. The burgeoning road construction has led to a growing interest in roadside installations. These must have reliable performance over long periods, reduced maintenance and high durability. Steel roadside barriers are prone to corrosion and other compromises to their functionality. Therefore, using high anti-corrosion steel material is now seen as a viable solution to this problem. Thus, the objective of this paper is to expand the scope of applications for high anti-corrosion steel material for roadside barriers. This paper assesses the impact safety such as structural performance, occupant protection performance and post-impact vehicular response performance by a simulation review on roadside barriers built with high strength anti-corrosion steel materials named as hot-dip zinc-aluminium-magnesium alloy-coated steel. The simulation test results for the roadside barriers built with high strength anti-corrosion steels with reduced sectional thickness meet the safety evaluation criteria, hence the proposed roadside barrier made by high strength and high anti-corrosion hot-dip zinc-aluminium-magnesium alloy-coated steel will be a good solution to serve safe impact performance as well as save maintenance cost.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.5
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• pp.30-41
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• 2017

Types of noise barrier installed for noise attenuation are largely divided into noise-absorbing format and noise-proofing format. In these days, installation of transparent noise barrier is general trend to solve problems that hinder sunshine and landscape. Some kinds of transparent boards are used to one of components in noise barriers, but in some cases, less transparency and worse pollution due to yellowing phenomena, and severe material deformation are to harm the urban aesthetics Therefore laminated-tempered glass board in that yellowing phenomena does not occur can be replaced as a transparent one to secure those shortcomings. In this paper, the structural safety against train induced vibration and the resistibility to wind load are analyzed for laminated-tempered glass system as a component of noise barrier installed on Metro railway elevated bridges. Also the appropriateness is evaluated through flexural bending performance test, compressive strength test, modulus of elasticity tests, and impact test for the system or the glass material itself. All of these processes are intended to present the deployment of logic to evaluate the adequacy for the system.

• Journal of the Korean Institute of Gas
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• v.24 no.3
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• pp.20-26
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• 2020

In this study, experimental study was conducted to examine the influence of explosion pressure and flame propagation velocity of methane-air mixtures due to the obstacles placed in the explosion space. We used the quantified parameter named barrier ratio in order to generalize the effect of explosion pressure and flame propagation velocity in the closed explosion space with obstacles. From experimental observations, the explosion pressure and flame propagation velocity regardless of the number of obstacles increased with barrier ratio. In the same methane concentration of 10% methane, the flame propagation velocity without obstacle (barrier ratio = 0) was 3.46 m/s but 24.24 m/s (increase about 7 times) with 3 obstacle and barrier ratio of 0.98. In the same barrier ratio, explosion pressure and flame propagation velocity increased sharply with increasing of the number of obstacles.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.2
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• pp.217-223
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• 2013

Population aging is a shift in the distribution of a country's population towards older ages. This is usually reflected in an increase in the population's mean and median ages, a decline in the proportion of the population composed of children, and a rise in the proportion of the population that is elderly. Population ageing is widespread across the world. Barrier-free or Design for All concept consists of modifying buildings or facilities so that they can be used by people who are disabled or have physical impairments. Design for All criteria are aimed at ensuring that everyone can participate in the Information society. Safety-related products being easy to adapt according to different needs, or using standardized interfaces that can be accessed simply by using assistive technology. To this end, policy makers and service providers, especially in the ubiquitous technologies, produce new technologies, products, services and applications for pedestrians.

• International Journal of Highway Engineering
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• v.19 no.6
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• pp.13-21
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• 2017

PURPOSES : In this research, an SB3-level roadside barrier for a highway transition zone that meets the newly established guide Installation and Management Guide for Roadside Safety Appurtenance is developed. Its performance is evaluated by a numerical simulation and real-scale vehicle impact test. METHODS : The commercial explicit dynamic software LS-DYNA is utilized for impact simulation. An FE model of a passenger vehicle developed and released by the National Crash Analysis Center (NCAC) at George Washington University and a heavy goods vehicle (HGV) model developed by the TC226/CM-E Work Group are utilized for impact simulation. The original vehicle models were modified to reflect the conditions of test vehicles. The impact positions of the passenger vehicle and truck to the transition guardrail were set as 1/2 and 3/4 of the transition region, respectively, according to the guide. RESULTS : Based on the numerical simulation results of the existing transition barrier, a new structural system with improved performance was suggested. According to the result of a numerical simulation of the suggested structural system, two sets of transition barriers were manufactured and installed for real-scale vehicle impact tests. The tests were performed at a test field for roadside safety hardware of the Korea Highway Corporation Research Institute. CONCLUSIONS : The results of both the real-vehicle impact tests and numerical simulations of the developed transition barrier satisfied the performance criteria, and the results of numerical simulation showed good correlation with the test results.

• Journal of The Korea Institute of Healthcare Architecture
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• v.22 no.4
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• pp.29-36
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• 2016

Purpose: Considering the proportion of the population such as the elderly, pregnant women, infants companion and constantly increasing foreign tourists, there is a high need for implementing an environment without barriers. In terms of policy and institutional aspects, Jeju Special Self-Governing Province is striving to create an environment without barriers and to promote the safety and convenience of Vulnerable Pedestrians. But it is not enough to create a viable barrier-free environment. Methods: Method of this research is to analyze the general population status and installed facilities status for the disabled in Jeju. And analysis of policy research needs and level of barrier-free. By applying the barrier-free environment certification standards should conduct an assessment of the level of the current public office buildings in Jeju. It presents the environmental improvement of public office buildings for barrier-free environment. Result: Barrier-free environment status of the five public office buildings research surveyed all buildings have shown low levels of installed facilities for the disabled. In particular, it was analyzed that represents a very low level in the intermediate facilities and other facilities. The development of a specific installation manual for the facilities for the disabled is required to improve public office buildings. And barrier-free criteria need to reflect on the implementation of regulations. Implications: Through continuous research to analyze the barrier-free level and problems of public office buildings, it will be made to improve the comprehensive and reasonable alternative.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.3
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• pp.49-57
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• 2009

To minimze the degree of damage for the SMART highway's punctuality and safety after car-barrier collisions, the impact condition for longitudinal barriers of SMART highway was determined to be quite larger than the existing maximum impact condition. The impact condition consists of impact vehicles, impact velocities, and impact angles. To consider the occupant safety of passenger cars as much as possible, a small car with high risk during impact was selected as the impact vehicle for the evaluation of occupant risk. The impact velocity was determined to be 20% larger than the existing maximum impact velocity in order to include accident impact velocities as much as possible. The impact angle was determined to include most of expected accident impact angles. Computer simulations using various impact conditions were conducted for the existing domestic highest-performance medium and roadside barrier. How the suggested impact condition has an effect on the occupant safety was investigated. The existing domestic highest-performance medium and roadside barriers could not satisfy the suggested impact condition. New high-performance longitudinal barriers are required to minimize the degree of damage for the SMART highway's punctuality and safety after car-barrier collisions.

• The Journal of Korea Robotics Society
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• v.17 no.1
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• pp.76-85
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• 2022

One of the most fundamental challenges when designing controllers for dynamic systems is the adjustment of controller parameters. Usually the system model is used to get the initial controller, but eventually the controller parameters must be manually adjusted in the real system to achieve the best performance. To avoid this manual tuning step, data-driven methods such as machine learning were used. Recently, reinforcement learning became one alternative of this problem to be considered as an agent learns policies in large state space with trial-and-error Markov Decision Process (MDP) which is widely used in the field of robotics. However, on initial training step, as an agent tries to explore to the new state space with random action and acts directly on the controller parameters in real systems, MDP can lead the system safety-critical system failures. Therefore, the issue of 'safe exploration' became important. In this paper we meet 'safe exploration' condition with Control Barrier Function (CBF) which converts direct constraints on the state space to the implicit constraint of the control inputs. Given an initial low-performance controller, it automatically optimizes the parameters of the control law while ensuring safety by the CBF so that the agent can learn how to predict and control unknown and often stochastic environments. Simulation results on a quadrotor UAV indicate that the proposed method can safely optimize controller parameters quickly and automatically.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4120-4124
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• 2023

High-level radioactive waste produced by nuclear power plants are disposed subterraneously utilizing an engineered barrier system (EBS). A gap inevitably exists between the disposal canisters and buffer materials, which may have a negative effect on the thermal transfer and water-blocking efficiency of the system. As few previous experimental works have quantified this effect, this study aimed to create an experimental model for investigating differences in the temperature changes of bentonite buffer in the presence and absence of air gaps between it and a surrounding stainless steel cell. Three test scenarios comprised an empty cell and cells partially or completely filled with bentonite. The temperature was measured inside the buffers and on the inner surface of their surrounding cells, which were artificially heated. The time required for the entire system to reach 100℃ was approximately 40% faster with no gap between the inner cell surface and the bentonite. This suggests that rock-buffer spaces should be filled in practice to ensure the rapid dissipation of heat from the buffer materials to their surroundings. However, it can be advantageous to retain buffer-canister gaps to lower the peak buffer temperature.