• Fire Science and Engineering
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• v.29 no.1
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• pp.1-6
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• 2015

In this study, the damages of high strength concrete exposed to high temperature have been evaluated by the impact echo method. Elastic wave velocity and dynamic modulus of elasticity were measured by the impact echo method, and the compressive strength and the static modulus of elasticity were measured by the compression testing method after exposure to high temperature. The results showed that elastic wave velocity has a linear correlation with the compressive strength and dynamic modulus of elasticity has a linear correlation with static modulus of elasticity. Based on results, it is concluded that the impact echo method can be effectively applied to evaluate the mechanical properties of fire damaged high strength concrete.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.189-189
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• 2016

To generate information that contributes to climate change risk management, it is important to perform a precise assessment on the impact in diverse aspects. Considering this academic necessity, Japanese government launched continuous research project for the climate change impact assessment, and one of the representative project is Program for Risk Information on Climate Change (Sousei Program), Theme D; Precise Impact Assessment on Climate Change (FY2012 ~ FY2016). In this research program, quantitative impact assessments have been doing from a variety of perspectives including natural hazards, water resources, and ecosystems and biodiversity. Especially for the natural hazards aspect, a comprehensive impact assessment has been carried out with the worst-case scenario of typhoons, which cause the most serious weather-related damage in Japan, concerning the frequency and scale of the typhoons as well as accompanying disasters by heavy rainfall, strong winds, high tides, high waves, and landslides. In this presentation, a framework of comprehensive impact assessment with the worst-case scenario under the climate change condition is introduced based on a case study of Theme D in Sousei program There are approx. 25 typhoons annually and around 10 of those approach or make landfall in Japan. The number of typhoons may not change increase in the future, but it is known that a small alteration in the path of a typhoon can have an extremely large impact on the amount of rain and wind Japan receives, and as a result, cause immense damage. Specifically, it is important to assess the impact of a complex disaster including precipitation, strong winds, river overflows, and high tide inundation, simulating how different the damage of Isewan Typhoon (T5915) in 1959 would have been if the typhoon had taken a different path, or how powerful or how much damage it would cause if Isewan Typhoon occurs again in the future when the sea surface water temperature has risen due to climate changes (Pseudo global warming experiment). The research group also predict and assess how the frequency of "100-years return period" disasters and worst-case damage will change in the coming century. As a final goal in this research activity, the natural disaster impact assessment will extend not only Japan but also major rivers in Southeast Asia, with a special focus on floods and inundations.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.13-13
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• 2011

The Rio Grande Compact Commission, in collaboration with local water management entities, water users and universities established a three state Rio Grande The Rio Grande Compact Commission, in collaboration with local water management entities, water users and universities established a three state Rio Grande Salinity Management Program. The objectives of the Rio Grande Project Salinity Management Program are to reduce salinity concentrations, loading, and salinity impacts in the Rio Grande basin for the 270 mile river reach from San Acacia, New Mexico to Fort Quitman, Texasto increase usable water supplies for agricultural, urban, and environmental purposes. The focus of this first phase of the program is the development of baseline salinity and hydrologic information and a preliminary assessment of the economic impacts of salinity. An assessment of the economic impacts of salinity in this region was conducted by scientists at Texas A&M University's AgriLife Research Center at El Paso and New Mexico State University. Economic damages attributable to high salinity of Rio Grandewater were estimated for residential, agricultural, municipal, and industrial uses. The major impact issues addressed were: who is being affected the types of economic impacts the magnitude of economic damages overall and by user category and identification of threshold-effect levels for different types of water use. Salinity concentrations in this 270 mile reach of the river typically range from 480 ppm to 1,200 ppm, but can exceed 3,000 ppm in the lower section of this reach. Economic impacts include reductions in agricultural yields, reduced water appliance life, equipment replacement costs, and increased water supply costs. This preliminary economic assessment indicates annual damages of $10.5 million from increased water salinity. Under current water uses, municipal and industrial uses account for 75% of the total estimated impacts. However, agricultural impacts are based on current crop pattern yield reductions and, salinity leaching requirements and do not account for the impacts of reduced revenue from having to grow salinity tolerant, lower value crops. Actual damages are anticipated to be significantly higher with the inclusion of these additional agricultural impacts plus the future impacts from the growing population in the region. A more comprehensive economic analysis is planned for the second phase of this program. Results of the economic analysis are being used to determine the feasiblity of salinity control alternatives and what salinity reduction control measures will be pursued.

• Journal of the Korean Institute of Gas
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• v.15 no.5
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• pp.1-6
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• 2011

It is required to construct the pipelines to eliminate pressure drop at the end of transmission line under limitation of maximum operation pressure of 6.86 MPa, however, it highly costs to build the pipelines and takes time-consuming job. Higher operation pressure compared to current operating pressure has been considered to resolve the problem of pressure drop without modification of the existing pipelines and facilities. As a result of the integrity evaluation, the existing pipelines can be operated up to 7.85 MPa in terms of wall thickness and have higher Charpy impact energy than required value in the ASME B31.8. However, Increment of operation pressure gives rise to increase potential impact area if the pipelines burst due to third party damages.

• Journal of the Korean Society for Nondestructive Testing
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• v.37 no.2
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• pp.91-98
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• 2017

Recently, composite materials have been mainly used in the main wings, ailerons, and fuselages of aircraft and rotor blades of helicopters. Composite materials used in rapid moving structures are subject to impact by hail, lightning, and bird strike. Such an impact can destroy fiber tissues in the composite materials as well as deform the composite materials, resulting in various problems such as weakened rigidity of the composite structure and penetration of water into tiny cracks. In this study, experiments were conducted using a 2 kW halogen lamp which is most frequently used as a light source, a 2 kW near-infrared lamp, which is used for heating to a high temperature, and a 6 kW xenon flash lamp which emits a large amount of energy for a moment. CFRP composite sandwich panels using Nomex honeycomb core were used as the specimens. Experiments were carried out under impact damages of 1, 4 and 8 J. It was found that the detection of defects was fast when the xenon flash lamp was used. The detection of damaged regions was excellent when the halogen lamp was used. Furthermore, the near-infrared lamp is an effective technology for showing the surface of a test object.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.5
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• pp.349-357
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• 2015

The piezoelectric paint sensor is a paint type sensor comprising of an epoxy and piezoelectric powder, which is the main component of a piezoelectric material. This sensor can be easily attached to any type of structure as compared to other sensors because it is viable to directly apply it on structures, as in the case with a typical paint. In this study, the capability of piezoelectric paint sensor for impact detection was evaluated. In Particular, the applications of the piezoelectric paint sensor for railroad vehicles were considered. There have been various cases reported about the damages caused by flying gravel to the under-cover of the railroad vehicle during operation. In order to prevent this, real-time monitoring of the large under-cover surface of the railroad vehicle is unavoidable. Under the assumption of vehicle application, sensor sensitivities were measured after multiple and prolonged exposure to thermal cycle environment $-20{\sim}60^{\circ}C$). Sensitivity evaluation of paint sensor under environmental conditions was conducted in an aluminum specimen. In results, despite the small variations in sensitivity, we could confirm the applicability of this paint sensor for impact detection even after a severe environmental exposure test.

• Ecology and Resilient Infrastructure
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• v.3 no.2
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• pp.80-91
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• 2016

Diverse types of meteorological disasters that are frequently occurring at the present time, such as urban flooding, draught, heat waves, or tropical nights do not only cause casualties and property damages but also make it difficult to preserve the natural environment of the city. That is why Low Impact Development or Green Infrastructure has recently received lots of attention as a means to minimize meteorological disasters, adapt to climate change and to leave a better urban environment for the next generation. As of now, Korea's low impact development and green infrastructure technology are standing at the stage of incubation or demonstration. Both central and provincial governments have accelerated the updating of laws and regulations, which allows us to turn the Gray City with Gray Infrastructure that only uses water into a Green City with Green Infrastructure that manages the water. To spread and distribute such a notion in a systemic way, it requires new technology development tailored to Korea, verification of technology, and maintenance of related technological standards, cooperation with other industries, training & promotion, and the participation of citizens.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.5
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• pp.371-378
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• 2018

Internal detonation of a warhead inside a compartment of naval vessel can result in serious blast damages including plastic deformation and rupture of the structural members especially bulkhead due to the huge explosive impact pressure, fragments and high temperature flame. To secure watertight integrity and to prevent the domino-type flooding of neighbouring compartments caused by the rupture of bulkheads, it is necessary to develop the structural design technology of Blast Hardened Bulkheads(BHB) which can resist the blast impact pressure of threatening weapons to increase the survivability of naval vessels. This study dealt with the simplified structural response analysis of BHB under impact pressure of confined explosion and aimed to develop the efficient and rational design method of BHB and joint structures which can be applied at initial design stage. The present 1st report dealt with the phenomena of explosive detonation surveying the preceding experimental/theoretical research and the characteristics of time history of blast pressure including the peak value and duration time were examined. And to predict the large plastic deformation behaviors of BHB by the huge blast pressure reasonably, the plastic hinge method including the membrane effects was formulated. It was applied to the simplified structural design equations. The following report will deal with the application and adjustment process of the structural scantling equations to the actual BHB design and verification of validity of them.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.3
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• pp.187-195
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• 2018

Ship's bottom slamming has been studied by many researchers for a very long time. But still some ships suffer structure damages caused by the bottom slamming impacts. This paper presents a practical computation method of the design impact pressure due to ship's bow bottom slamming. Large heave and pitch motions of a rigid hull ship are simulated by the nonlinear strip method in time domain and the relative colliding velocity between the bow bottom and the water surface is calculated using the simulated ship motions. The bottom slamming impact pressure is calculated as a product of the relative colliding velocity squared and the bottom slamming pressure coefficient that is obtained by modification of the SNAME pressure coefficients based on Ochi's slamming experiments. Not only the bottom slamming pressures but also the required bottom plate thicknesses are calculated and compared with those of the classification society rules. The comparisons show good agreements and it is confirmed that the present method is practically very useful for the bottom structure design against ship's bow bottom slamming impacts.

• Smart Structures and Systems
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• v.6 no.5_6
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• pp.731-748
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• 2010

Impact detection and health monitoring are very important tasks for civil infrastructures, such as bridges. Piezoceramic based transducers are widely researched for these tasks due to the piezoceramic material's inherent advantages of dual sensing and actuation ability, which enables the active sensing method for structural health monitoring with a network of piezoceramic transducers. Wireless sensor networks, which are easy for deployment, have great potential in health monitoring systems for large civil infrastructures to identify early-age damages. However, most commercial wireless sensor networks are general purpose and may not be optimized for a network of piezoceramic based transducers. Wireless networks of piezoceramic transducers for active sensing have special requirements, such as relatively high sampling rate (at a few-thousand Hz), incorporation of an amplifier for the piezoceramic element for actuation, and low energy consumption for actuation. In this paper, a wireless network is specially designed for piezoceramic transducers to implement impact detection and active sensing for structural health monitoring. A power efficient embedded system is designed to form the wireless sensor network that is capable of high sampling rate. A 32 bit RISC wireless microcontroller is chosen as the main processor. Detailed design of the hardware system and software system of the wireless sensor network is presented in this paper. To verify the functionality of the wireless sensor network, it is deployed on a two-story concrete frame with embedded piezoceramic transducers, and the active sensing property of piezoceramic material is used to detect the damage in the structure. Experimental results show that the wireless sensor network can effectively implement active sensing and impact detection with high sampling rate while maintaining low power consumption by performing offline data processing and minimizing wireless communication.