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Experimental study on seismic behavior of RC beam-column joints retrofitted using prestressed steel strips

  • Yang, Yong;Chen, Yang;Chen, Zhan;Wang, Niannian;Yu, Yunlong
    • Earthquakes and Structures
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    • v.15 no.5
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    • pp.499-511
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    • 2018
  • This paper aims to investigate the seismic performance of the prestressed steel strips retrofitted RC beam-column joints. Two series of joint specimens were conducted under compression load and reversed cyclic loading through quasi-static tests. Based on the test results, the seismic behavior of the strengthened joints specimens in terms of the failure modes, hysteresis response, bearing capacity, ductility, stiffness degradation, energy dissipation performance and damage level were focused. Moreover, the effects of the amount of the prestressed steel strips and the axial compression ratio on seismic performance of retrofitted specimens were analyzed. It was shown that the prestressed steel strips retrofitting method could significantly improve the seismic behavior of the RC joint because of the large confinement provided by prestressed steel strips in beam-column joints. The decrease of the spacing and the increase of the layer number of the prestressed steel strips could result in a better seismic performance of the retrofitted joint specimens. Moreover, increasing the axial compression ration could enhance the peak load, stiffness and the energy performance of the joint specimens. Furthermore, by comparison with the specimens reinforced with CFRP sheets, the specimens reinforced with prestressed steel strips was slightly better in seismic performance and cost-saving in material and labor. Therefore, this prestressed steel strips retrofitting method is quite helpful to enhance the seismic behavior of the RC beam-column joints with reducing the cost and engineering time.

Effect of Stern Wedge on the Wave Making Resistance of Chine Hull Form (선미 웨지가 차인선형의 조파저항에 미치는 영향)

  • Lee Dae-Hoon;Lew Jae-Moon;Kang Dae-Sun
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.9 no.2
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    • pp.92-97
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    • 2006
  • Hull forms of a high speed small boat have been developed through numerical studies. A round bilge type hull form has been drived form a using chine hull form with HCAD, a hull form variation software. Wave resistance and the flow fields around the ships have been computed using well-known software, WAVIS. This software employs Rankine source method with non-linear tree surface condition as well as dry transom boundary conditions. The round bilge hull form showed better resistance performance than to the chine hull form for the whole speed range. However, considering the building and labor costs of the small shipyard, the chine hull form has been selected and its wave resistance characteristics has been improved by modifying the bow regions and applying the stem wedge. It is found that the effect of stem wedge is quite satisfactory to improve the resistance characteristics of high speed chine hull form.

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Theoretical Design for the Production of Quinoa (Chenopodium quinoa Willd.) in a Closed Plant Factory

  • Bae, Jong Hyang;Austin, Jirapa;Jeon, Yoon-A;Cha, Mi-Kyung;Cho, Young-Yeol
    • Horticultural Science & Technology
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    • v.34 no.6
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    • pp.840-844
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    • 2016
  • Quinoa (Chenopodium quinoa Willd.) is a grain crop with high nutritional value. The leaves and sprouts of quinoa can also be consumed either raw or cooked, providing considerably nutritional value as well as high antioxidant and anticancer activities. This study was carried out to obtain basic data to assist in the practical design of a plant factory with artificial lighting for the cultivation of quinoa as a leafy vegetable. We estimated the energy content of the quinoa and the electrical energy required to produce this crop. The yield was 1,000 plants per day, with a planting density and light intensity of $0.015m^2$ ($15{\times}10cm$) and $200{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, respectively. The total number of plants, cultivation area, and electricity consumption were estimated to be 25,000, $375m^2$, and $93,750{\mu}mol{\cdot}s^{-1}$, respectively. White fluorescent lamps were used at a power of 20.4 kW from 1,857 fluorescent lamps (FL, 55 W), and the cost for electricity was approximately 1,820 dollars (exchange rate of $1 = 1,200 won) per month. For a daily harvest of 1,000 plants per day in a closed plant factory, the estimated light installation cost, total installation cost, and total production cost would be 15,473, 46,421, and 55,704 dollars, respectively. The calculated production cost per plant, including labor costs, would be 27 cents for the 25-day cultivation period, with a marketable ratio of 80%. Considering the annual total expenses, income, and depreciation costs, the selling price per plant was estimated to be approximately 56 cents.

A Thermal Analysis for the Underground Power Transmission Cable by a Water Pipe Cooling Method with Trough in Tunnel (전력구트라프간접수냉방식에서의 지중송전케이블에 대한 열해석)

  • Park, Man-Heung
    • Solar Energy
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    • v.15 no.3
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    • pp.59-73
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    • 1995
  • The thermal analysis is accomplished with the route for the underground power transmission system which adopts the water pipe cooling with trough in tunnel. As a result, in case of a cooling system based on a refrigerator, the optimum condition for the flow rate of cooling water and the air velocity are calculated as the $2{\sim}3{\ell}/s/pipe$ and $1{\sim}2m/s/fan$, respectively. On the other hand, in case of cooling tower the optimum condition for them are calculated as the $2{\sim}3{\ell}/s/pipe$ and 6 m/s/fan, respectively. But the cooling system based on a cooling tower has the problem of enlarging the size of cooling fan and suppressing the labor of operator in tunnel. Therefore, to meet all the cooling conditions for a given cooling section, the cooling system based on a refrigerator is more acceptable.

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Status and Response Strategies of Carbon Labeling in Landscape Architecture (조경분야 탄소성적표지제도 적용실태 및 대응전략)

  • Kim, Jeong-Ho;Yoon, Yong-Han
    • Journal of Environmental Science International
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    • v.24 no.6
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    • pp.709-720
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    • 2015
  • After analyzing the actual acquisition status of carbon labeling by year and by product for the past four years, as well as its certification in the construction-related sectors of greenhouse gas emission, this study attempted to present the problems and coping strategies upon issuing the carbon labeling certification in the landscape architecture. During the period of this analysis, the carbon labelings were acquired by 134 enterprises, 267 workplaces, and 735 products, while the percentage of acquisition was highest in the regular non-durable goods(49%), followed by energy-consuming durable goods(26%), regular production goods (19%), regular durable goods(3%), and service(3%). Furthermore, the acquisition certifications in construction sectors, were highest in the various pipes/panel(8 cases), followed by concrete(6 cases), gypsum board(4 cases), and landscape architecture materials(2 cases). The landscape architecture only had two cases in the acquisition certification for the first time in 2012, which accounted for 0.27% of the entire certification products, due to the uncertainty in the process, the lack of professionalism, and the lack of comprehension. However, the study conducted on the coping strategies for carbon labeling in the landscape architecture revealed the following: (1) regular reporting system management through the division of labor in the head office and factories, (2) the building of objective DB through the adoption of data management programs such as SAP, (3) continuous promotion and vitalization of the incentive system, (4) the adoption of mandatory or preferential application system in landscaping projects, management, and bidding, (5) enhancement of elasticity in deliberation of certification by recruiting experts in the landscape architecture sectors, and (6) provision of incentives for the cooperative firms acquiring the certification and support for their participation.

A Study on the Formation Plan of Green Cluster by Sectoral Type for the Enhancement of Regional Competitiveness in Green Industry (녹색산업의 지역경쟁력 확보를 위한 산업유형별 클러스터 형성방안에 관한 연구)

  • Kim, Soo-Kyung;Lee, Joo-Hyung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.3
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    • pp.1081-1089
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    • 2013
  • The purpose of this paper is to suggest the formation plan of green cluster for the enhancement of green industry competitiveness in Korea. For this reason, this paper has the analysis to find out regional competitiveness and effective factors in the green industry. The major findings are as follows. First, the renewable energy industry was competitive at Gyeonggi, Gyeongnam, Chungbuk, Chungnam, Ulsan, Jeonnam, and the carbon reduction industry was competitive at Ulsan, Gyeonggi, Gyeongbuk,, Chungnam, Seoul, Chungbuk, Inchon. Second, the most important factors of the renewable energy industry was factor condition, such as business, labor, research and development; while in the carbon reduction industry was sector of structure and rivalry, such as performance, policy and institution, market share, industry specialization. Third, it showed that the green industry was more competitive at the local area with the better industrial infrastructure. So, we need to focus on the green of existing industry-infrastructure, and the strategy of selection and concentration, for the enhancement of green industry competitiveness in Korea.

Comparison of Safety Perception between Foreign and Local Workers in the Construction Industry in Republic of Korea

  • Korkmaz, Serdar;Park, Dal Jae
    • Safety and Health at Work
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    • v.9 no.1
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    • pp.53-58
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    • 2018
  • Background: Since the Republic of Korea became a labor-force-importing country, the number of foreign workers has increased gradually, especially in the construction industry. The main objective of this study was to examine the differences in safety perception between domestic and foreign workers at Korean construction sites. Methods: A total of 891 Korean and foreign workers were surveyed: 140 foreign and 751 Korean workers. The general characteristics and 25 factors influencing safety perception were considered in the questionnaire. Regression and correlation analyses were conducted to examine the variables of workers' safety perception. Results: Differences of nationality (F = 7.379, p < 0.001) and workplace accidents were statistically significant for both domestic (F = 1.503, p < 0.05) and foreign workers (F = 7.868, p < 0.05). In contrast, age, education, and Korean language level were significant variables only for foreign workers. Correlation coefficients of $0.428^{**}$ for Korean and 0.148 for foreign workers between two items - namely, "management's commitment to safety" and "blaming staff when they make mistakes" - support the conclusion that foreign workers do not trust management's commitment to safety, while Korean workers have confidence in these commitments. Conclusion: Foreign workers' level of safety perception should rise to the same level as Korean workers, especially in terms of obeying safety rules, safety education performance, and safety beliefs. Therefore, an improvement plan for the Korean construction industry is suggested in order to have a better safety level at construction sites with foreign workers.

Analysis of Traditional Process for Yukwa Making, a Korean Puffed Rice Snack (I): Steeping and Punching Processes (전통 유과가공공정의 분석(I): 수침 및 꽈리치기 공정)

  • Kang, Sun-Hee;Ryu, Gi-Hyung
    • Korean Journal of Food Science and Technology
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    • v.34 no.4
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    • pp.597-603
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    • 2002
  • The analysis of traditional process for a Korean puffed rice snack (Yukwa) is needed to develop an advanced process for Yukwa-making. Steeping and punching (Koarichigi) processes, consume time and labor in Yukwa-making, were analyzed on this study. Steeping of waxy rice at $15^{\circ}C$ for 3 days was required to equilibrate moisture absorption in waxy rice kernel. However, steeping for more than 6 days was required soft texture and small air cell distribution of Yukwa. Protein content at pericarp on endosperm of waxy rice kernel was decreased and starch granule was damaged during steeping. RVA paste viscosity was the highest at 6 day steeping after than decreased. Expansion ratio of Yukwa was increased with the increase in steeping time. Air bubbles in dough after punching were uniformly distributed and kneading energy input was decreased with the increase in steeping time. Soft texture, unique texture of Yukwa could be controlled by controlling steeping time and kneading energy input during punching process.

Experimental study on seismic behavior of reinforced concrete column retrofitted with prestressed steel strips

  • Zhang, Bo;Yang, Yong;Wei, Yuan-feng;Liu, Ru-yue;Ding, Chu;Zhang, Ke-qiang
    • Structural Engineering and Mechanics
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    • v.55 no.6
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    • pp.1139-1155
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    • 2015
  • In this study, a new retrofitting method for improving the seismic performance of reinforced concrete column was presented, in which prestressed steel strips were utilized as retrofitting stuff to confine the reinforced concrete column transversely. In order to figure out the seismic performance of concrete column specimen retrofitted by such prestressed steel strips methods, a series of quasi-static tests of five retrofitted specimens and two unconfined column specimen which acted as control specimens were conducted. Based on the test results, the seismic performance including the failure modes, hysteresis performance, ductility performance, energy dissipation and stiffness degradation of all these specimens were fully investigated and analyzed. And furthermore the influences of some key parameters such as the axial force ratios, shear span ratios and steel strips spacing on seismic performance of those retrofitted reinforced concrete column specimens were also studied. It was shown that the prestressed steel strips provided large transverse confining effect on reinforced concrete column specimens, which resulted in improving the shearing bearing capacity, ductility performance, deformation capacity and energy dissipation performance of retrofitted specimens effectively. In comparison to the specimen which was retrofitted by the carbon fiber reinforced plastics (CFRP) strips method, the seismic performance of the specimens retrofitted by the prestressed steel strips was a bit better, and with much less cost both in material and labor. From this research results, it can be concluded that this new retrofitting method is really useful and has significant advantages both in saving money and time over some other retrofitting methods.

Utilizing Mean Teacher Semi-Supervised Learning for Robust Pothole Image Classification

  • Inki Kim;Beomjun Kim;Jeonghwan Gwak
    • Journal of the Korea Society of Computer and Information
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    • v.28 no.5
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    • pp.17-28
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    • 2023
  • Potholes that occur on paved roads can have fatal consequences for vehicles traveling at high speeds and may even lead to fatalities. While manual detection of potholes using human labor is commonly used to prevent pothole-related accidents, it is economically and temporally inefficient due to the exposure of workers on the road and the difficulty in predicting potholes in certain categories. Therefore, completely preventing potholes is nearly impossible, and even preventing their formation is limited due to the influence of ground conditions closely related to road environments. Additionally, labeling work guided by experts is required for dataset construction. Thus, in this paper, we utilized the Mean Teacher technique, one of the semi-supervised learning-based knowledge distillation methods, to achieve robust performance in pothole image classification even with limited labeled data. We demonstrated this using performance metrics and GradCAM, showing that when using semi-supervised learning, 15 pre-trained CNN models achieved an average accuracy of 90.41%, with a minimum of 2% and a maximum of 9% performance difference compared to supervised learning.