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  • Title/Summary/Keyword: 연성도 평가

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Estimation of fracture toughness of X65 and X70 steels by DWTT (X65 및 X70강 가스배관의 DWTT 및 파괴인성평가)

  • Cho, Ye-Won;Song, Young-Ho;Kim, Jeong-Min;Kim, Woo-Sik;Park, Joon-Sik
    • Journal of the Korean Institute of Gas
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    • v.16 no.3
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    • pp.54-64
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    • 2012
  • DWTT (Drop Weigh Tearing Test) is one critical method that can exhibit the fracture properties of line pipe steel, since it estimates the properties with real pipe steel. In this study, the ductile portion, inverse fracture ratio and absorbed energy of API X65 and X70 line pipe steels were estimated with temperature variation. Both steels showed that the ratio of ductile area and absorbed energy were decreased with respect to decreasing the test temperature. However, while the ductile fracture behavior exhibited until 40C for the X70 steel, but it showed until 30C for the X65 steel. The fracture properties were discussed with respect to test temperatures.

Estimation of Response Modification Factor and Nonlinear Displacement for Moment Resisting Reinforced Concrete Frames (철근콘크리트 연성 모멘트골조에 대한 반응수정계수와 비선형 변위량의 평가)

  • 김길환;전대한;이상호
    • Journal of the Earthquake Engineering Society of Korea
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    • v.6 no.2
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    • pp.29-37
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    • 2002
  • The purpose of this study is to provide a fundamental data of earthquake resistant design through the estimation of the response modification factor and nonlinear displacement for moment resisting reinforced concrete frames by linear and nonlinear static analysis. The analysis models are designed in accordance with AIK code and then, estimated the response modification factor and nonlinear displacement of the buildings. The parameters such as story numbers(10, 20, 30), plan ratios(1:1, 1:2) and analysis types(2D, 3D) of building structure are chosen for use in this study. After comparing the results of linear and nonlinear static analysis, the response modification factor is obtained as the product of four factors: ductility factor, strength factor, damping factor and redundancy factor. The response modification factor are close to 3.5 in case of 2 span, 4.3 in case of 3 span and 5.0 in case 4 or more span models regardless number of stories and plan ratios. The nonlinear displacement is evaluated from the ratio of story drift angle(nonlinear drift/linear drift). The ratio of story drift angle increases as story numbers increase and the value varies from 5.85 to 9.34.

Evaluation on Cyclic Flexural Behavior of HSRC (Hybrid H-steel-reinforced Concrete) Beams Connected with Steel Columns (강재 기둥과 하이브리드 강재 보-RC 보 접합부의 반복 휨 거동 평가)

  • Kwon, Hyuck-Jin;Yang, Keun-Hyeok;Hong, Seung-Hyun
    • Journal of the Korea Concrete Institute
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    • v.29 no.3
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    • pp.291-298
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    • 2017
  • The objective of the present study is to evaluate the cyclic flexural behavior of a hybrid H-steel-reinforced concrete (HSRC) beam at the connection with a H-steel column. The test parameter investigated was the configuration of dowel bars at the joint region of the HSRC beam. The HSRC beam was designed to have plastic hinge at the end of the H-steel beam rather than the RC beam section near the joint. All specimens showed a considerable ductile behavior without a sudden drop of th applied load, resulting in the displacement ductility ratio exceeding 4.6, although an unexpected premature welding failure occurred at the flanges of H-steel beams connecting to H-steel column. The crack propagation in the RC beam region, flexural strength, and ductility of HSRC beam system were insignificantly affected by the configuration of dowel bars. The flexural strength of HSRC beam system governed by the yielding of H-steel beam could be conservatively evaluated from the assumption of a perfect plasticity state along the section.

Pseudo Dynamic Test for the Seismic Performance Enhancement of Circular RC Bridge Piers Retrofitted with Fibers (섬유보강 원형 철근콘크리트 교각의 내진성능 향상에 관한 유사동적 실험)

  • 정영수;박종협;박희상;조창백
    • Journal of the Korea Concrete Institute
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    • v.14 no.2
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    • pp.180-189
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    • 2002
  • The objective of this experimental research is to assess the seismic performance of circular RC bridge pier specimens retrofitted with fibers which were designed as a prototype of Hagal bridge in the city of Suwon, Korea. Pseudo dynamic test has been done for four(4) test specimens which were nonseismically or seismically designed by the related provisions of the Korea roadway bridge design specification, and four nonseisemic test specimens retrofitted with fibers in the plastic hinge region. Glass and carbon fiber sheets were used for the seismic capacity enhancement of circular test specimens. Important test parameters were confinement steel ratio, load pattern, and retrofitting. The seismic behavior has been analyzed through the displacement ductility, energy analysis, and capacity spectrum. Approximate 7.7 ∼8.7 displacement ductility was observed for nonseismic test specimens retrofitted with fibers subjected to Korea Highway Cooperation artificial earthquake motions. It is concluded that these retrofitted test specimens could have sufficient seismic capacity in the region of moderate seismic zone.

Flexural Behavior of Layered RC Slabs, which Bio-Mimics the Interface of Shell Layers, Produced by Using 3D Printable Highly Ductile Cement Composite (3D 프린팅용 고연성 시멘트 복합체를 활용한 패류 껍질층 경계면 모방형 적층 RC 슬래브의 휨 거동)

  • Chang-Jin Hyun;Ki-Seong Kwon;Ji-Seok Seo;Yun-Yong Kim
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.28 no.1
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    • pp.90-97
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    • 2024
  • In this study, we employed Highly Ductile Cement Composite (HDCC) to evaluate the flexural performance of a RC slab that simulates the laminating structure of a seashell. To evaluate flexural performance, we produced conventional RC slab specimens, HDCC slab specimens, and HDCC-M slab specimens which biomimics a seashell's layered structure by inserting PE mesh inside the slab made of HDCC. A series of 4-point bending tests were conducted. Experimental results shows the flexural strength of the HDCC-M slab specimen was 1.7 times and 1.2 times higher than that of the RC and HDCC slab specimens, respectively. Furthermore, the ductility was evaluated using the ratio of yield deflection to maximum deflection, and it was confirmed that the HDCC slab test specimen exhibited the best ductility. This is most likely due to the fact that the inserted PE mesh separates the layers and increases ductility, while the HDCC passing through the mesh prevents the loss of load carrying capacity due to layer separation.

An Experimental Study on the Strengh and Ductility of High-Strength Flexural Members (고강도 휨재의 강도와 연성에 관한 실험적 연구)

  • Lee, Seung-Joon
    • Journal of Korean Society of Steel Construction
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    • v.13 no.1
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    • pp.19-28
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    • 2001
  • The strength and ductility of steel flexural members are investigated experimentally in this study. As for the performance evaluation of flexural members. experimental studies on the 9 test specimens were carried out. Four specimens were fabricated from SM490 and five specimens were fabricated from SM570. The experimental results of the specimens were analyzed with focus on the flexural strength and ductility. The experimental results exhibited that all the specimens provided sufficient flexural strengthes which exceeded the nominal flexural strengthes specified in the current Limit State Design Specification by average ratio of 1.22. However. the experimental results showed that the compact-section specimens fabricated from SM570 did not provide the required rotational ductility. The yield-to-tensile strength ratio(YR) of SM570 of about 0.9 might be the causes of such insufficient capacities.

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Seismic Performance Evaluation of RC Bridge Piers with Limited Ductility by the Pseudo-Dynamic Test (한정연성 철근콘크리트 교각의 유사동적 실험에 의한 내진 성능 평가)

  • Chung, Young-Soo;Park, Chang-Kyu;Park, Jin-Young
    • Journal of the Korea Concrete Institute
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    • v.15 no.5
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    • pp.705-714
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    • 2003
  • Even though Korean peninsula is located in regions of moderate seismic risks, current seismic design provisions of the roadway bridge design code have adopted the AASHTO code which is based on the requirements for high seismic regions. The objective of this research is to investigate the seismic performance of circular reinforced concrete (RC) bridge piers with limited ductility, which may be desirable in low or moderate seismic regions, such as in Korea. Four test specimens were designed and constructed. The reference specimen was designed with longitudinal steel ratio as 1.01% and the confinement reinforcement ratio as 0.13% without considering earthquake, and three other test specimens were designed in accordance with a limited-ductility concept as 0.3% for the confinement steel ratio. This confinement ratio is 0.32 times of minimum lateral reinforcement specified in current seismic design provisions, and 2.3 times of lateral reinforcement required in nonseismic design provisions. The pseudo-dynamic test was carried out to evaluate the seismic performance of full-scale specimens in size of 1.2m diameter and 4.8m height. Judging from the experiment, the reference specimen was not satisfactory for the demand displacement ductility μ=5.0, but three limited-ductility specimens appeared to have the displacement ductility of more than 5.

Characterization of tissue conditioner containing chitosan-doped silver nanoparticles (키토산-은나노 복합체가 함유된 의치 연성이장재 특성에 관한 연구)

  • Nam, Ki Young;Lee, Chul Jae
    • The Journal of Korean Academy of Prosthodontics
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    • v.58 no.4
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    • pp.275-281
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    • 2020
  • Purpose: Development of a latent antimicrobial soft liner is strongly needed to overcome a possible inflammation related with its dimensional degrade or surface roughness. Modified tissue conditioner (TC) containing chitosan-doped silver nanoparticles (ChSN) complexes were synthesized and assessed for their characterizations. Materials and methods: ChSN were preliminarily synthesized from silver nitrate (AgNO3), sodium borohydride (NaBH4) as a reducing agent and chitosan biopolymer as a capping agent. Ultraviolet-visible and Fourier transform infrared spectroscopy were conducted to confirm the stable reduction of nanoparticles with chitosan. Modified TC blended with ChSN by 0 (control), 1.0, 3.0 and 5.0 % mass fraction were mechanically tested by ultimate tensile strength (UTS), silver ion elution and color stability (n=7). Results: At 24 hour and 7 day storage periods, UTS values were not significant (P>.05) as compared with pristine TC (control) and silver ion was detected with the dose-dependent values of ChSN incorporated. Color stability of TC were influenced by ChSN add, with the higher doses, the significantly greater color changes (P<.05). Conclusion: A stable synthesized ChSN was acquired and modified TC loading ChSN was characterized as silver ion releasing without detrimental physical property. For its clinical application, antimicrobial test, color control and multifactor investigations are still required.

Experimental Study on the Performance Improvement of Velcro Reinforcement through Internal Filling (내부충진을 통한 벨크로 보강재의 성능향상에 대한 실험적 연구)

  • Jeong, Yeong-Seok;Kwon, Minho;Kim, Jin-Sup;Nam, Gwang-Sik
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.41 no.4
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    • pp.347-355
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    • 2021
  • During the earthquake, for multi-story structure, if the first floor is soft, the deformation will concentrate on that floor causing a serious damage to the column members which might leads to the collapse of the whole structure like Piloti structure during the Pohang earthquake in Korea. According to the 2016 National Disaster Management Research Institute's "Investigation of Seismic Reinforcement and Cost Analysis of Domestic Non-seismic Buildings", the rate of seismic resistance of private reinforced concrete buildings was 38.3 %. Among them, it was reported that the seismic-resistance ratio of the two to five-story structures was less than 50 %. Accordingly, the government is trying to improve the seismic rate through support projects, but the conventional seismic reinforcement methods are still expensive, and emergency construction is difficult. Therefore, in this study, the field applicability was evaluated by improving the reinforcement method using Velcro, which was developed through the research project of the Ministry of Land, Transport and Maritime Affairs in 2014. In order to improve the performance of the Velcro reinforcement method, introducing the initial tension of Velcro using high foaming rigid urethane filling between the Velcro and concrete of the columns was applied. Additionally, an experiment was conducted to evaluate the ductility of Velcro specimen from the concrete confinement effect. As a result, the ductility of the Velcro specimen was improved compare to Normal specimen. However, the energy dissipation capacity of VELCRO2 is better than VELCRO1, yet the maximum ductility of those two specimens did not show a significant difference. Therefore, the improvement of the internal filler material is still needed to have a better maximum ductility.

Numerical Study on the Coupled Responses of the Steel Lazy Wave Riser (SLWR) Based on the Basis of Design and Moored FPSO (BoD 기반의 Steel Lazy Wave Riser(SLWR)와 계류된 FPSO와의 연성해석에 관한 수치해석 연구)

  • Kwon, Yong-Ju;Nam, Bo Woo;Park, Byeong-Won;Oh, Seung-Hoon;Jung, Jae-Hwan;Jung, Dongho
    • Journal of Navigation and Port Research
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    • v.43 no.6
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    • pp.344-352
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    • 2019
  • A coupled analysis was performed between the riser to develop oil and gas in ultra-deepwater and the moored floating body. In general, the safety of the riser is conservatively evaluated by considering the maximum offset excluding the coupled analysis with the floating body. In this study, the safety of the riser was analyzed by considering the coupled motion analysis of the moored floating body. The riser is considered steel lazy wave riser (SLWR) applied in the deep sea, and the floating body is determined to FPSO. The methodology was presented on coupled and uncoupled analysis. The coupled effects were analyzed according to the incident wave headings in intact and damaged conditions of mooring lines. The tension of mooring lines, the motion of the floating body, and riser responses were analyzed according to the loading conditions.