A Study on Detection of a Critical Spot and the Securing Safety Method of CFRP Bicycle Forks by Finite Element Method
Lee, Su-Yeong;Lee, Nam Ju;Choi, Ung-Jae;Kim, Hong Seok;Shin, Ki-Hoon;Cheong, Seong-Kyun 1
https://doi.org/10.14346/JKOSOS.2016.31.6.1 PDF KSCI
A bicycle is one of the most popular sporting goods in view of a sport activity and a human health. Metallic materials such as steel, aluminum, etc. were mainly used to the bicycle fork in the past. Nowadays, the carbon fiber reinforced composite materials are widely used to the manufacturing of a bicycle fork to reduce the weight and to increase the efficiency. Safety is a most important design parameter of a bicycle fork even if the weight and cost reduction are important. Bicycle failure may happen at the critical spot of a bicycle fork and cause the accident. In this paper, the composite bicycle fork will be analyzed to secure the safety and detect a critical spot by using the finite element method with Tsai-Wu failure criterion. The stress data were obtained for the laminated composites with various number of plies and fiber orientation under the bending load. Thus, design concept of a bicycle fork was proposed to secure the safety of a bicycle. The finite element analysis results show that the connection area between a steer tube and a fork blade is critical spot, and 75 or more layers of 0 degree are needed to secure the safety of a bicycle fork.
Penetration Fracture Characteristics of Orthotropic CFRP Laminates Shells according to Curvature
Yang, Yong Jun;Pyeon, Seok Beom;Cha, Cheon Seok;Yang, In Young 6
CFRP composite laminates are widely used as structural materials for airplanes, automobile and aerospace vehicles because of their high strength and stiffness. This study aims to examine an effect of curvature on the penetration fracture characteristic of an orthotropic composite laminated shell. For the purpose, we manufactured orthotropic CFRP shell specimen with different curvatures, and conducted a penetration test using an air-gun. Those specimens were prepared to varied curvature radius(${\infty}$, 200mm, 150mm and 100mm)and were stacked to $[O^{\circ}{_3}/90^{\circ}{_3}]_s$. When the specimen is subjected to transverse impact by a steel sphere(${\Phi}10$), the velocity of steel sphere was measured both before and after impact by determining the time for it to pass two ball-screen sensors located a known distance apart. As the curvature increases, the absorption energy and the critical penetration energy increased linearly because the resistance to the bending moment. Patterns of cracks caused by the penetration of CFRP laminated shells included fiber breakage, lamina fracture, matrix crack interlaminar crack and intralaminar crack.
A Study on an Optimal Design of Electric Snow Melting Mat for Vulnerable Walk Zone
Kwon, Jin Wook;Jang, Chul;Hwang, Myung Whan 12
https://doi.org/10.14346/JKOSOS.2016.31.6.12 PDF KSCI
This paper describes an optimal design of electric snow melting mat on vulnerable walk zone. In order to design an optimal electric power of snow melting mat and protect pedestrians with a nonslip mat, with considering protection of environmental pollution from abusing of the de-icing salts added calcium chloride. We analyzed nine snow melting mats through verification experiment in the condition of $-5^{\circ}C$, depending on three different kinds of heating material, electric heating cable, carbon heating film and carbon textile film. As a consequence, the $150W/m^2$ carbon textile film mat for snow melting was identified as an optimal power input and functional performance for pedestrians' safety on vulnerable walk zone. It is expected that the $150W/m^2$ carbon textile film mat would be useful to reduce slip down accidents by human error.
Design and Implementation of Wideband Grounding Impedance Measurement Device using IQ Demodulation Method
Kim, Young-Jin;Gil, Hyung-Jun;Kim, Sung-Ju;Kim, Jae Hyung 19
One of key parameters on lightning protection system design of electric, information and communication system is grounding impedance. Earth impedance includes numerous information about earthing performance of grounding system. This paper suggests grounding impedance measuring device which is comprised of wideband current source, voltage and current measuring components. We used IQ Demodulation to measure more accurate phase difference of voltage and current. The range of frequency is up to 1 MHz that is IEEE defined as the range of lightning surge. We compared developed grounding impedance measuring device with existing one to test its performance, and we used grounding system while we implemented measurement and analysing by using fall of potential method IEEE Std.81 proposed.
The Resistance Characteristics and Reliability Evaluation of an Insulation Ring Type of Corrugated Stainless Steel Tubing(CSST)
Lee, Jang-Woo;Kim, Jeom-Sik;Choi, Chung-Seog 25
This paper has analyzed the structure, applicable regulations and the resistance characteristics of insulation ring type of CSST (Corrugated Stainless Steel Tubing for Gas). With the flammability test conducted in accordance with KS C IEC 60811-1-1, the evaluation of insulation resistance, temperature characteristics, and reliability has been conducted. An insulation ring type CSST consists of protective coating, tube, nut, insulation ring, packing, socket, and ball valve. Connecting an insulation ring type CSST to gas tubings for gas appliance is not permitted, moreover, the product shall be installed inside a sleeve pipe in case of buried installation such as the ceiling. Damages on protective coating and tube were detected when fire was applied to the test sample with a portable torch for 60 seconds. The insulation resistance of a normal product was $49.59M{\Omega}$, while that of the product completed the flammability test reduced to $9.21M{\Omega}$. The mean insulation resistance within the confidence Interval of 95% using the mini tap program 17 was $49.59M{\Omega}$ and the mean insulation resistance within the confidence interval reduced to $9.21M{\Omega}$. In the normal distribution analysis of 95% confidence interval, the value-P of the normal product was stable at 0.075 and AD(Anderson-Darling) statistic value was turned out to be 0.063, which is very normal, and the standard deviation was analyzed as 0.2586. The value P of the product completed the flammability test resulted in 0.005, the AD was 1.355 and the standard deviation reduced to 0.07908.
A Study of Emergency Response for the Leakage Accident of Hazardous and Noxious Substances in a Port
Woo, Young Jin;Lee, Chang Jun 32
In general, lots of containers including various dangerous materials are transported to the port located in big cities such as Busan where massive residents live. Thus, it's really important how to make the emergency response for the leak accidents of dangerous materials and evaluate the direct or indirect damages to adjacent areas. In this study, in order to make reasonable emergency plans, CA (Consequence Analysis) is employed after selecting a key hazardous and noxious material, hydrogen fluroide. This material accounts for the third largest portion of cargo volume among all dangerous materials and can cause a huge damage in case of leakages. As a case study, Busan North port is selected as a test port since the portion of dangerous materials is higher than that of other ports in Busan. It is assumed that 1 ton of hydrogen fluoride is spilled at Busan North port. CA is performed to assess the impact of this accident. Throughout CA, the ERPG-2 range of a leak accident can be evaluated and this result can be used for decision making tools for mitigating the impact of a leak accident. To mitigate the damage of this accident, suitable a protective equipment and resident evacuation procedures should be prepared. Finally, this study can provide a systematic approach to make the emergency plan for reducing economical and personal losses.
Bubble Point Calculation using Experimental Flash Points of Binary Solutions
Ha, Dong-Myeong;Lee, Sungjin 39
Suitable design and operation of distillation process is very dependent on vapor-liquid equilibrium calculation. The usual calculation method is use binary interaction parameter. Flash points of n-propanol+n-butanol and 2-butanol+n-butanol were measured by Seta-flash closed cup tester. Experimental Flash points were compared with those calculated by the method based on Raoult's law and the optimization method using Wilson equation. The binary interaction parameters obtained by the optimization method are then used to calculate the bubble points of n-propanol+n-butanol and 2-butanol+n-butanol.
Evaluation of Behavior of Direct Fixation Track and Track Girder Ends on Yeongjong Grand Bridge
Choi, Jung-Youl;Chung, Jee-Seung;Kim, Jun-Hyung;Lee, Kyu-Yong;Lee, Sun-Gil 45
The purpose of this study is to investigate the influence of train-induced end rotation of simple supported track girder on the performance of a direct fixation track system (DFTS) in Yeongjong grand bridge. In this study, the influences of deflection of a DFTS and track girder on dynamic rail-track girder interaction forces for the track girder ends currently employed in airport express lines were assessed by performing field tests using actual vehicles running along the service lines. Therefore, the dynamic displacement of rail and track girder and the fastener stress on the center and ends sections of DFTS were measured for two different trains (AREX and KTX) running in Yeongjong grand bridge. A three-dimensional finite element analysis (FEA) model using the time-history function based on the design wheel load was used to predict the train-induced track and track girder displacement, and the FEA and field test results were compared. The analytical results reproduced the experimental results well within about 3-7% difference in the values. Therefore, the FEA model of DFTS on track girder is considered to provide sufficiently reliable FEA results in the investigation of the behavior of DFTS. Using the analytical and experimental results, the influence of train-induced end rotation of simple supported track girder on the interaction behavior of rail and track girder installed on a simple supported track girder ends, i.e., upward displacement of rail-track girder and the fastener stress, was investigated. It was found that the train-induced end rotation effect of track girder was not significantly affected by the upward displacement of rails and the fastener stresses of track girder ends. Further, the interaction behavior of rail and track girder were similar to or less than that of the general railway bridge deck ends, nevertheless the vertical displacement of track was higher than that of conventional DFTS on the general railway bridge. From the results, the dynamic responses of the DFTS on track girder ends were not significantly affected by the safety and stability of DFTS ends.
Performance Test and Numerical Model Development of Restoring Viscous Damper for X-type Damper System
Kim, David;Park, Jangho;Ok, Seung-Yong;Park, Wonsuk 52
In this study, a restoring viscous damper is introduced for X-type damper system which is designed for the seismic response control of large spatial structures. A nonlinear numerical model for its behavior is developed using the result of dynamic loading tests. The X-type damper system is composed of restoring viscous dampers and connecting devices such as adjustable wire bracing, where the damping capacity of the system is controllable by changing the number of the dampers. The restoring viscous damper is devised to exert main damping force in tension direction, which is effective to prevent the buckling of bracing subjected to compressive axial force. To evaluate the performance of the proposed damper, dynamic cyclic loading tests are performed by using manufactured dampers at full scale. In order to construct the numerical model of the damper system, its model parameters are first identified using a nonlinear curve fitting method with the test data. The numerical simulations are then performed to validate the accuracy of the numerical model in comparison with the experimental test results. It is expected that the proposed system is effectively applicable to various building structures for seismic performance enhancement.
Failure Probability Assessment for Risk Analysis of Concrete Gravity Dam under Flood
Cho, Soojin;Shin, Sung Woo;Sim, Sung-Han;Lim, Jeong-Yeul 58
This study aims to estimate the failure probability of concrete gravity dams for their risk analysis under flood situation. To the end, failure modes of concrete gravity dams and their limit state functions are proposed based on numerous review of domestic and international literatures on the dam failure cases and design standards. Three failure modes are proposed: overturning, sliding, and overstress. Based on the failure modes the limit state functions, the failure probability is assessed for a weir section and a non-weir section of a dam in Korea. As water level is rising from operational condition to extreme flood condition, the failure probability is found to be raised up to the warning condition, especially for overturning mode at the non-weir section. The result can be used to reduce the risk of the dam by random environmental variables under possible flood situation.
A Study on User Experience Survey for Development of New Full Body Harness in Heavy and Construction Industry
Kim, Daesik;Kim, Yuchang 67
According to industrial accident analysis of the Ministry of Employment and Labor in 2013, 38 workers were injured by fall accidents on average per day, and one worker died on average per day among them. In various industries such as heavy and construction industry, the full body harness is commonly used to prevent the fall accident. In developing full body harness, the designer considered only the workers' safety, without taking into account comfort and workability. The survey was conducted so as to search the problems of full body harness currently used by workers in heavy and construction industry. The survey questionnaire was given to 565 workers wearing full body harness in heavy and construction industry. The results of study showed that the development of new full body harness considering body size of korean was needed. The impotent factors for developing of new full body harness were the size and the weight of the full body harness. The full body harness taking into account body size was judged to contribute to more comfortable work, work efficiency and safety. The result of this study can be utilized as useful data in the development of new full body harness considering the body size of korean workers.
Educational and Ecological Factors Associated with Workers' Participation to Safety and Health Education at Work - Based on the PRECEDE Model -
Park, Kyoung-Ok 74
The purpose of this study was to identify the educational and ecological factors (environment and infra-structure) associated with workers' participation to safety and health education at work (SHEW) based on the PRECEDE constructs. A total of 590 workers (484 in manufacturing and 106 in construction companies) finished the self-administered survey. Survey packets were delivered to the safety and health manager (SHM) in survey companies and the SHMs conducted the self-administered survey in their companies. The questionnaire includes demographics, epidemiological constructs, and educational and ecological constructs based on the PRECEDE model. Participation to SHEW was better in the manufacturing sector than in the construction sector (p<.001). Environmental, reinforcing, and enabling factors were better in the manufacturing companies than in the construction companies. Male worker, better perceived efficacy of SHEW, higher social support for SHEW, assignment of SHM at work, and better safety and health management level at work were significantly associated with workers' better participation to SHEW (p<.05). Those factors accounted for 45.9% of total variance of workers' participation to SHEW.
Public's Recognition of the Space Object's Re-entry Situations and the National Space Disaster Management Policy
Kim, Syeun;Cho, Sungki;Hong, Jeongyoo 84
Since the mankind started its space mission, the number of artificial space objects has been increasing exponentially. It contains not just the space machines which are in use but the machines which are out of order. Meantime, those dead machines are being a serious danger, a real threat to human's lives and property because of it could re-enter into the earth's atmosphere and fall to the ground causing mega-disaster. As the number of space activities gets growing so far, the re-entry of the space objects will be a lot more happened in the future. Therefore, not just natural space object like asteroids but the artificial space object like artificial satellite and space station can cause the disaster by falling to the ground. To protect our nation and our property, the government has set up the space disaster management center in Korea astronomy and Space science Institute. In this study, we surveyed public's recognition of the space object's re-entry situation and analyzed it to contribute building national space disaster management policy.
Inflow Characteristics of Debris Flow and Risk Assessment for Different Shapes of Defensive Structure
Oh, Seung Myeong;Song, Chang Geun;Lee, Seung Oh 93
This study analyzed the inflow characteristics of debris flow according to shape of defensive structure and computed risk index. In order to simulate debris flow, two shapes of defensive structure were considered. Initial mass distribution was set with a rectangular shape and defensive structures were set semi-circular shape and rectangular shape, respectively. It was found that a defensive structure with semicircular shape was more vulnerable to debris impact compared with rectangular shape because the flow mass became concentrated in quadrant part of the inner circle. If the velocity of the debris flow was less than 1 m/s, the risk assessment by FII (Flood Intensity Index) was much appropriate. However, when the movement of debris runout was faster than 1 m/s, the risk index of FHR (Flood Hazard Rating) provided improved classification due to its subdivided hazardous range.
Deriving Strategic Agenda for Response of Road Sink Phenomenon
Seong, Joo Hyun;Park, Won Joo;Lee, Jong Gun;Choi, Byoung Il 99
Road Sink Phenomenon (RSP) is one of the major issues in South Korea. National and local governments are trying to develop effective preventive measures against the RSP. Developing the policy-oriented RSP management is most important to minimize possible losses induced by RSP. In this study, we employed the Futures Wheel (FW) method to derive influence factors for RSP management. FW method is widely used for predicting future social-environmental condition. In addition, RAND Corporation's method is used to derive potential strategic agenda based on derived influence factors by FW method. These derived strategic agenda can contribute to develop the policies related with RSP management.
Disaster Victims' Post-trauma Risk, Posttraumatic Growth and Subjective Well-being - Social Support as a Mediator and Income as a Moderator -
Sim, Olivia S.;Sohn, Young Woo;Park, Sang Hyun;Yoon, Ji Won 105
The current study examined the relationships between disaster victims' post-trauma risk and posttraumatic growth, and the mediational role of social support for this relationships. In addition, we tested the hypothesis that income status would moderate the relationship between post-trauma risk and subjective well-being. Two hundred disaster victims completed Post-trauma Risk Checklist (PRC), Posttraumatic growth scale, Social support scale and Concise Measure of Subjective Well-Being (COMOSWB) as well as questions about their demographic characteristics. Results showed that those with high post-trauma risk demonstrated significantly higher levels of posttraumatic growth as compared to those with low post-trauma risk and social support partially mediated this relationship. Also, high levels of post-trauma risk predicted low levels of recent subjective well-being. Participants with high income obtained higher subjective well-being than did those with low income among high post-trauma risk groups. Implications for post-trauma risk and posttraumatic growth are discussed.
Research of Emotion Model on Disaster and Safety based on Analyzing Social Media
Choi, Seon Hwa 113
People use social media platforms such as Twitter to leave traces of their personal thoughts and opinions. In other words, social media platforms retain the emotions of the people as it is, and accurately understanding the emotions of the people through social media will be used as a significant index for disaster management. In this research, emotion type modeling method and emotional quotient quantification method will be proposed to understand the emotions present in social media platforms. Emotion types are primarily analyzed based on 3 major emotions of affirmation, caution, and observation. Then, in order to understand the public's emotional progress according to the progress of disaster or accident and government response in detail, negative emotions are broken down into anxiety, seriousness, sadness, and complaint to enhance the analysis. Ultimately, positive emotions are further broken down into 3 more emotions, and Russell emotion model was used as a reference to develop a model of 8 primary emotions in order to acquire an overall understanding of the public's emotions. Then, the emotional quotient of each emotion was quantified. Based on the results, overall emotional status of the public is monitored, and in the event of a disaster, the public's emotional fluctuation rate could be quantitatively observed.
The Detection Model of Disaster Issues based on the Risk Degree of Social Media Contents
Social Media transformed the mass media based information traffic, and it has become a key resource for finding value in enterprises and public institutions. Particularly, in regards to disaster management, the necessity for public participation policy development through the use of social media is emphasized. National Disaster Management Research Institute developed the Social Big Board, which is a system that monitors social Big Data in real time for purposes of implementing social media disaster management. Social Big Board collects a daily average of 36 million tweets in Korean in real time and automatically filters disaster safety related tweets. The filtered tweets are then automatically categorized into 71 disaster safety types. This real time tweet monitoring system provides various information and insights based on the tweets, such as disaster issues, tweet frequency by region, original tweets, etc. The purpose of using this system is to take advantage of the potential benefits of social media in relations to disaster management. It is a first step towards disaster management that communicates with the people that allows us to hear the voice of the people concerning disaster issues and also understand their emotions at the same time. In this paper, Korean language text mining based Social Big Board will be briefly introduced, and disaster issue detection model, which is key algorithms, will be described. Disaster issues are divided into two categories: potential issues, which refers to abnormal signs prior to disaster events, and occurrence issues, which is a notification of disaster events. The detection models of these two categories are defined and the performance of the models are compared and evaluated.
A Study on the Probabilistic Safety Assessment and Sensitivity Analysis of Success Criteria of Large LOCA for APR+
Moon, Horim;Kim, Han Gon 129
Standard design of APR+(advanced power reactor plus) was certified at 2014 by Korea regulatory body. Based on the experience gained from OPR1000 and APR1400, the APR1400 was being developed as a 1,500MWe class reactor using Korean technologies for design code, reactor coolant pump, and man-machine interface system. APR+ has been basically designed to have the seismic design basis of safe shutdown earthquake (SSE) 0.3g, a 4-train safety concept based on N+2 design philosophy, and a passive auxiliary feedwater system (PAFS). Also, safety issues on the Fukushima-type accidents have been extensively reviewed and applied to enhance APR+ safety. APR+ provides higher reliability and safety against tsunami and earthquake. The purpose of this paper is to implement probabilistic safety assessment considering these design features and to analyze sensitivity of core damage frequency for large loss of coolant accident of APR+.