• Title/Summary/Keyword: PS 도입량

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Analytical Evaluation of Behavior of Precast PSC Box Curve Bridge Based on Design Variables (프리캐스트 PSC 중공 박스 곡선교의 설계변수에 관한 해석적 거동 평가)

  • Kim, Sung-Bae;Kim, Sung-Jae;Park, Jeong-Cheon;Uhm, Ki-Ha;Kim, Jang-Ho Jay
    • Journal of the Korea Concrete Institute
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    • v.26 no.3
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    • pp.267-275
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    • 2014
  • Recently, the construction of curved bridge has increased, thus researchers perform the analytic studies on PSC curved bridge. However, the grid analysis method that are mostly used in the construction industry is not adequate to acquire the precise behavior evaluation of curved PSC briges. Therefore, the precise finite element analysis considering the effective variables were performed to establish the basis for the design method of curved PSC bridge by using 3D elements and bar element. The evaluated variables in this analysis were the number of girders, loading point, section figure, change of prestressing force. The results show the load carrying capacity of the 3 girder type bridge is 200% of that of the 2 girder type, and that applying load on outer girder makes the load resistance capacity and the deflection deviation of 2 girders smaller. The structural capacity of the bridge is improved when the section size is increased, but the efficiency of it is not sufficient enough compare to that of the change of prestressing forces. The change of prestressing forces shows that the camber and the load carrying capacity are linearly increased as PS force is increased. Moreover, when the PS force applied on outer girder is increased than that of inner girder, the deviation of deflection the girders decreases, thereby the stability of the bridge is enhanced.

Slip Behavior of Anchorage Unifying Both PS Strand and Bar (강봉과 강연선이 일체화된 정착구의 슬립거동 평가)

  • Lee, Pil-Goo;Kim, Choong-Eon
    • Proceedings of the Korea Concrete Institute Conference
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    • 2009.05a
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    • pp.147-148
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    • 2009
  • The anchorage system unified both PS strand and bar effectively introduced a prestress into a flexural concrete members. This study examined the relation between the anchorages of both ends and the introduced force and derived the equation for design.

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Detection of Fracture Signals of Low Prestressed Steel Wires in a 10 m PSC Beam by Continuous Acoustic Monitoring Techniques (연속음향감지기법을 이용한 긴장력이 감소된 10 m PSC보의 PS 강선 파단음파 감지)

  • Youn, Seok-Goo;Lee, Chang-No
    • Journal of the Korea Concrete Institute
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    • v.22 no.1
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    • pp.113-122
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    • 2010
  • Corrosion of prestressing tendons and wire fractures in grouted post-tensioned prestressed concrete bridges have been considered as a serious safety problem. In bridge evaluation the condition of prestressing tendons should be inspected, and if corroded tendons are found, the loss of tendon area should be included when we calculate the ultimate strength. In the previous study, it was evaluated that continuous acoustic monitoring techniques could be considered as a reliable non-destructive method for detecting wire fractures of fully grouted post-tensioned prestressing tendons. In the present study, an experimental test was performed for detecting wire fractures of post-tensioned prestressing tendons which are prestressed lower than current design level. A 10 m prestressed concrete beam was fabricated, which included two tendons prestressed 66 percentage and 40 percentage of tensile strength, respectively. The corrosion of two tendons was induced by an accelerated corrosion equipment and the test beam was monitored by using seven acoustic sensors and a continuous acoustic monitoring system. From each prestressing tendon, two acoustic signals of wire fractures were successfully detected and source locations were estimated within 20 mm error. Based on the test results, it is considered that continuous acoustic monitoring techniques can be applied to detect low-prestressed wire fracture in fully grouted post-tensioned prestressed concrete beams.

Synthesis of Polystyrene-b-Poly(ethylene oxide)-b-Polylactide Copolymers via Sequential Anionic and Ring-Opening Polymerizations (순차적 음이온 및 개환중합반응을 통한 폴리스티렌-폴리에틸렌옥사이드-폴리락티드 블록공증합체의 합성)

  • Song, Jie;Cho, Byoung-Ki
    • Polymer(Korea)
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    • v.33 no.5
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    • pp.458-462
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    • 2009
  • We have synthesized ABC linear triblock copolymers, i.e., polystyrene-b-poly(ethylene oxide)-b-polylactide, via sequential anionic and ring-opening polymerizations. In the first anionic polymerization step, styrene was polymerized in cyclohexane using sec-butyllithium as the initiator. Poly (styryl) lithium was hydroxylated by the addition of ethylene oxide, and the subsequent protonation with methanolic HCl. In the second anionic polymerization step, potassium naphthalenide was used to deprotonate the hydroxyl group of the PS to generate the macroinitiator of PS-$O^-K^+$. Polymerization of ethylene oxide was performed in THF and terminated with methanolic HCl. In the ring-opening polymerization step, the PS-b-PEO-$AlEt_2$ macroinitiator was prepared from an $AlEt_3$/pyridine system in THF, and the polymerization of lactide was performed at $90^{\circ}C$. The resulting block copolymers showed well-defined molecular weights and narrow molecular weight distributions as revealed by $^1H$- NMR spectroscopy and gel permeation chromatography (GPC).

A Study on the Compatibilization of Blends Based on Poly(phenylene ether) and Polyamide (Poly(phenylene ether)/Polyamide 블렌드의 상용화에 관한 연구)

  • 김형수;임종철
    • Polymer(Korea)
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    • v.25 no.3
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    • pp.441-449
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    • 2001
  • Compatibilization of blends based on poly(phenylene ether) (PPE) and polyamide (PA) has been practiced with the incorporation of a copolymer formed by grafting polystyrene onto polybutadiene latex (g-BS) which is further functionalized with maleic anhydride (MAH) (g-BS*) to impart reactivity with amine groups of PA. The major focus has been placed on the effect of the various structural factors in g-BS8 on the phase morphology and mechanical performance of the blends. For the balance of impact strength and heat resistance, it was important to locate g-BS n particles inside of the PPE phase, which was accomplished by the proper control of the molecular weight and amount of PS in g-BS*. For g-BS*'s having constant molecular weight and amount of PS, the reduction of MAH content or increase of rubber particle size in g-BS* resulted in the increase of domain size and consequently loss in mechanical properties. Based on the comparison made with the conventional PPE/PA blend comprising MAH grafted PPE as a compatibilizer, it was confirmed that the comparable level of mechanical performance can be achieved by an appropriate g-BS* type material with improved whiteness index.

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Application of a New Scaling Parameter to Chain Expansion in the Systems of Polystyrene/Mixed Solvents (폴리스티렌/혼합용매 계에서 사슬의 팽창에 대한 새로운 스케일링 파라미터의 적용)

  • Park, Il-Hyun;Lee, Dong-Il;Hwang, Mi-Ok;Yu, Young-Chol;Park, Ki-Sang
    • Polymer(Korea)
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    • v.31 no.2
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    • pp.98-104
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    • 2007
  • The expansion behavior of polystyrene (PS) chains with various molecular weights has been investigated above Flory $\Theta$temperature by viscometry after dissolving in the three different mixed solvents systems such as benzene/n-heptane, 1,4-dioxane/isopropanol, and 1,4-dioxane/n-heptane. Two different regimes are observed as increasing temperature: one regime is for the expansion of chain and the other is for the contraction. For the higher molecular weight sample of PS, the higher peak temperature showing its maximum expansion is obtained. Within a certain system of Ps/mixed solvents, the $\tau/\tau_c$ parameter shows universality for the variation of molecular weight. But while each system of Ps/mixed solvents has shown its own different slope, the universality breaks down in the overall system of mixed solvents. However after introducing a new empirical $b^{2/3}\tau/\tau_c$ parameter, all data points of three different systems have dropt on one master curve and the universality of chain expansion has recovered again. Here $\tau$ and $\tau_c$ are defined as $(T-\Theta)/\Theta$ and $(\Theta-T_c)/T_c$, respectively and $T_c$ is the critical solution temperature, and b of Schultz-Flory equation is corresponding to the effective slope in the plot of $1/T_c$ against $1/M_w^{1/2}$.

Study on Performance Comparison in Carbon Nanotube Embedded Electrospun Membranes for Particulate Matter Removal (탄소나노튜브가 첨가된 전기방사 멤브레인의 미세입자 제거 성능 비교에 관한 연구)

  • Gu, Minkyung;kim, Dongwan;Han, Sangil
    • Korean Chemical Engineering Research
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    • v.56 no.1
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    • pp.56-60
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    • 2018
  • There have been a lot of study to improve the performance of membrane filters as the removal of particulate matter has been of great interest due to the negative effects. Among the membrane fabrication techniques, the electrospinning technique is the most promising because it can produce uniform fibers ranging from nano to micrometer size. The electrospun membranes will greatly improve the filtration performance due to the high ratio of surface area to volume and the high porosity. In the present study, polystyrene (PS) and cellulose acetate (CA) polymers were used to produce the membranes with carbon nanotube (CNT), showing the filtration performances were improved with the optimal amounts of CNT.

Overview and Recent Development of Recycling Waste Refrigerators (폐(廢) 냉장고(冷藏庫) 재활용(再活用) 현황(現況)과 기술(技術) 전망(展望))

  • Yang, Hyunseok;Kim, Geon-Hong;Kong, Man-Sik;Park, Kiejin;Lee, Gwang Weon;Kim, Bo Saeng
    • Resources Recycling
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    • v.22 no.4
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    • pp.70-80
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    • 2013
  • Waste refrigerator is the most large amount of item being recycled and the recycling process is the most complicated in WEEE (Waste Electrical and Electronic Equipment) because refrigerator is biggest product and consists of various parts and materials such as ferrous, non-ferrous, and plastics. Recently, recycling process of waste refrigerator has been being more complex since large capacity 2 door refrigerators and standing Kimchi refrigerators with various material are distributed on custom market. In addition, recycling of valuable resource from waste refrigerator is mandatory by WEEEs recycling legislation; therefore, high efficiency recycling enough for economic and environment-friendly recovery of valuable resource through present technical situation analysis and comparison of recycling technologies of waste refrigerator with advanced country.

Comparative Study on Energy Consumption in Steam-Humidification- and Water-Spray-Humidification-Type Outdoor Air-Conditioning Systems for Semiconductor Manufacturing Clean Rooms (반도체 클린룸용 증기가습 및 수분무가습 외기공조시스템의 에너지소비량 비교연구)

  • Kim, Hyung-Tae;Song, Gen-Soo;Kim, Ki-Cheol;Yoo, Kyung-Hoon;Son, Seung-Woo;Shin, Dae-Kun;Park, Dug-Jun;Kwon, Oh-Myung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.12
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    • pp.1249-1255
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    • 2011
  • In modern large-scale semiconductor manufacturing clean rooms, the energy consumed by the outdoor air-conditioning system during heating, humidification, cooling, and dehumidification of the incoming outdoor air represents about 45% of the total air-conditioning load required to maintain a clean-room environment. In particular, the energy required for humidification of the outdoor air in winter is very high. Therefore, evaluation and comparison of the energy consumption in key humidification systems, viz., steam-humidification and water-spray-humidification systems, used in outdoor air-conditioning systems would be useful to reduce the outdoor air-conditioning load in clean rooms. In the present study, an experiment with an outdoor air flow of 1000 $m^3$/h was conducted to compare the air-conditioning process and energy consumption in outdoor air-conditioning systems with electrodeboiler steam humidifiers and air-washer water spray humidification systems. The experimental results showed that the water-spray-humidification-type outdoor air-conditioning system consumed less electrical power than did the steam-humidification-type system and was more energy efficient during winter.