• Title, Summary, Keyword: 압축변형율

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Analysis of Compressive Strength of Lightweight Air-mixed Soil According to the Properties of Soil (원료토의 특성에 따른 경량기포혼합토의 압축강도 영향인자 분석)

  • Song, Jun-Ho;Im, Jong-Chul;Hong, Seok-Woo
    • Journal of the Korean Geotechnical Society
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    • v.24 no.11
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    • pp.157-166
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    • 2008
  • To investigate the relationship between compressive strength ($q_u$) of Lightweight Air-mixed soil (LAS) and its physical deformation coefficient ($E_{50}$), a series of unconfined compressive tests have been performed on specimens of LAS according to various dredged soil types by percentage of sand, silt and clay. From the results it was found that the cement content ($C_i$) and unit weight (${\gamma}_m$) are most influence factors on strength, and percentage of sand, silt, clay by grain size analysis (KS F2302) have more effect on compressive strength than other physical properties of soil. It was also found that the rate of strength (a) increases with curing time, but it reduces with the increase of percentage of clay ($C_%$).

A Fundamental Study for Development of Corrosion Inhibitor Repair Mortar (저탄소 방청 보수모르타르 개발을 위한 기초연구)

  • Jung, Jae-Eun;Yang, Keun-Hyeok;Go, Jeung-Wan;Yun, In-Gu
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.2 no.2
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    • pp.93-99
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    • 2014
  • The present study prepared 13 mixes to examine fundamental mixture proportions of corrosion inhibitor repair mortars. The mortar mixes were classified into three groups according to the selected test variables which are the substitution level of polymer for Group 1, ground granulated blast-furnace slag (GGBS) and fly ash (FA) for Group 2, and corrosion inhibitor for Group 3. Based on the test results, the optimum substitution levels of GGBS and FA could be recommended as 10% and 20%, respectively, though 1-day strength of mortar significantly decreased with their substitution. Furthermore, the appropriate substitution level of corrosion inhibitor was considered to be less than 1.5%. The flexural strength of mortar tested was higher than the predictions obtained from ACI 318-11 equation. The shrinkage strain of mortar was also conservative after an age of around 10 days compared with the predictions of ACI 209.

Tensile Behavior of Highly Ductile Cementitious Composites Using Normal Sand as Fine Aggregate (일반모래를 잔골재로 사용한 고연성 시멘트 복합체의 인장거동)

  • Lee, Bang Yeon;Kang, Su-Tae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.6
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    • pp.178-184
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    • 2017
  • This study was aimed to investigate the tensile behaviors of PE(Polyethylene) fiber-reinforced highly ductile cementitious composites with different combinations of micro silica sand and normal sand(river sand) with maximum particle size of 4.75 mm. Flow test result indicated the increase of flowability with higher replacement ratio of river sand. There was no noticeable difference in the mean compressive strength with different replacement ratio of river sand, but the variation in the compressive strength increased as higher amount of river sand was adopted for the replacement. The difference in the uniaxial tensile strength was negligible, but the tensile strain capacity was significantly influenced by the replacement ratio of river sand. It is thought that increased density of multiple cracks induced improved tensile strain capacity when higher percentage of river sand was adopted for fine aggregate. The deviation in the strain capacity increased as the replacement ratio of river sand was higher, as in the compressive strength. This study presented the feasibility of using normal sand instead of micro silica sand for highly ductile cementitious composites with equivalent or better uniaxial tensile performance, even though it might increase the deviation in the performance.

Temperature-Dependent Viscoplastic-Damage Constitutive Model for Nonlinear Compressive Behavior of Polyurethane Foam (폴리우레탄 폼 비선형 압축 거동 해석용 온도 의존 손상 점소성 구성방정식)

  • Lee, Jeong-Ho;Kim, Seul-Kee;Lee, Jae-Myung
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.29 no.5
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    • pp.437-445
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    • 2016
  • Recently, polyurethane foam has been used in various industry fields to preserve temperature environment of structures, and a wide range of loads from the static to the dynamic are imposed on the material during a life period. The biggest characteristic of polyurethane foam is porosity as being polymeric material, and it is generally known that insulation performance of the material strongly depends on internal void size. In addition, polyurethane foam's mechanical behavior has high dependence on strain rate and temperature as well as being highly non-linear ductile for compression. In the non-linear compressive behavior, volume fraction of voids and elastic modulus decrease as strain increases. Therefore, in this study, temperature-dependent viscoplastic-damage constitutive model was developed to describe the non-linear compressive behavior with the aforementioned features of polyurethane foam.

Setting Time, Compressive Strength and Drying Shrinkage of Mortar with Alpha-Calcium Sulfate Hemihydrate (α형 반수석고를 치환한 모르타르의 응결 및 압축강도, 건조수축 특성)

  • Lee, Kye-Hyouk;Kim, Gyu-Yong;Lee, Bo-Kyeong;Shin, Kyoung-Su;Nam, Jeong-Soo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.5
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    • pp.117-124
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    • 2017
  • In this study, to evaluate the setting time, compressive strength and drying shrinkage of ordinary Portland cement and Portland blast-furnace slag cement mortar with 0, 10, 20, 30 wt.% alpha-calcium sulfate hemihydrate. As a results, as the replacement ratio of alpha-calcium sulfate hemihydrate increased, the initial setting time of ordinary Portland cement and Portland blast-furnace slag cement mortar was faster. In addition, the compressive strength decreased with increasing replacement ratio of alpha-calcium sulfate hemihydrate in both ordinary Portland cement mortar and Portland blast-furnace slag cement mortar. The strength development of Portland blast-furnace slag cement mortar with alpha-calcium sulfate hemihydrate was effective than that of ordinary Portland cement mortar. On the other hand, in the case of the mortar with alpha-calcium sulfate hemihydrate, it was confirmed that shrinkage deformation was reduced at the early age by growth pressure of needle-shaped ettringite crystals produced by incorporation of alpha-calcium sulfate hemihydrate. However, the effect of inhibiting shrinkage deformation of mortar with alpha-calcium sulfate hemihydrate was not significant as the age passed. Therefore, it is considered that the alpha-calcium sulfate hemihydrate is useful as a construction material.

Lateral Compression and Dowel Bearing Property of Japanese Larch Grown in Korea (국산 낙엽송재의 횡압축과 다우얼 지압 성능)

  • Hwang, Kweonhwan;Park, Byung-Su
    • Journal of the Korean Wood Science and Technology
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    • v.36 no.3
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    • pp.61-69
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    • 2008
  • To examine the compression properties of structural members, the compression and bearing tests were conducted in parallel- and perpendicular-to-grain loading using domestic Japanese larch (Larix kaempferi (Lamb.) Carriere). Compression (bearing) properties with the length of a specimen and the contact length of the bearing plate were investigated, and deformations at each specimen length from the point of bearing force were measured to evaluate the effective end distance tabulated in the present practice (Korean Building Code). Compression (bearing) properties varied with the size of the bearing plate, and the end distance for dowel-type fastener taken into consideration of the specimen's deformation, for the safe design, should be applied with over 7 D.

Stress-Strain Behavior of Clays under Repeated Loading (반복재하(反復載荷)에 의한 점성토(粘性土)의 응력변형특성(應力變形特性))

  • Cho, Jae Hong;Kang, Yea Mook;Ryu, Neung Hwan
    • Korean Journal of Agricultural Science
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    • v.14 no.2
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    • pp.329-344
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    • 1987
  • This paper described the behavior under repeated loading in triaxial compression test on clay. The experiment was conducted to investigate the influence of controlled various over-consolidation ratio and compaction energy, on the stress-strain behavior of clays. 1. The difference of deviator stress during repeated loading was greatly appeared at large strain. And pore water pressure was decreased at initial of unloading, but it was increased again before long. 2. The recoverable elastic strain (${{\Delta}{\varepsilon}e}$) and the slope of un-reloading were decreased with the increment of over-consolidation ratio (OCR). 3. The recoverable elastic strain (${{\Delta}{\varepsilon}e}$) was increased with the increment of strain rate but it was decreased with the increment of strain in strain rate tests. The slope of un-reloading (Eur) tends to increase with the increment of strain rate and it was decreased with the increment of strain. 4. The recoverable elastic strain was greatly increased with the increment of compaction energy and it slightly tends to decrease with the increment of strain on various compaction energy. The slope of un-reloading was not appeared markedly with increment of compaction energy but it tends to decrease with the increment of strain generally.

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The Property Change of Silicone Impression Materials with Change of Storage Temperature (실리콘 인상재의 보관온도에 따른 특성변화)

  • Oh, Sang-Hwan;Moon, Seung-Kyun;Kim, Kyoung-Nam
    • Journal of dental hygiene science
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    • v.10 no.6
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    • pp.459-464
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    • 2010
  • The purpose of this study was to evaluate the physical properties of hydrophilic polyvinyl siloxane impression materials as change of material's storage temperatures. Working time, strain-in-compression, elastic recovery and consistency were tested according to ISO Standard NO. 1563. The results are as followed. 1. Working time decreased in cold storage. 2. Strain-in-compression was different in storage temperatures. Material's strain-in compression in cold temperatures were higher than in room temperature and in incubator. 3. A coefficient of elastic recovery varied by storage temperatures. The rate in cold temperature was the lowest and in incubator was the highest. 4. Consistency of impression substance different in storage temperatures. The extent in cold temperature is the highest and in incubator was the lowest. Statistical analysis(SPSS 14.0k, p>0.05) showed that storage temperature affect to material's physical properties. We recognized that the physical properties of polyvinyl siloxane impression materials were changed according to storage temperature.

Characteristics of Shear Behavior of Remolded Nak-dong River Sandy Silt (재성형된 낙동강 모래질 실트의 전단거동 특성)

  • Kim Young-Su;Tint Khin Swe;Kim Dae-Man
    • Journal of the Korean Geotechnical Society
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    • v.23 no.3
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    • pp.41-50
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    • 2007
  • The results from normally consolidated isotropic drained and undrained triaxial compression tests (NCIU and NCID) on sand with high silt content were presented in this paper. The experiments were performed on specimens of Nak-dong River sand with 63% silt content under effective confined pressures, 100 kPa to 400 kPa. From test results, Sandy silt became initially compressive but eventually appeared to provide dilatancy response throughout the entire stress-strain curve The behavior of sandy silt was more difficult to characterize than that of clay and sand due to lower plastic characteristic. Especially, the samples exhibited dilatancy development during shear after failure. The shear behavior and shear strength parameters of sandy silt can be determined as stress-strain behaviors are described by the Mohr-Coulomb failure criterion. The shear behaviors were observed increasing dilatancy volume change tendency with strain-softening tendency after failure. In this paper, the behavior of dilatancy depends on not only sand content but also fine content with low-cohesion during shear in the samples of sandy silt.

Probabilistic Evaluation on Prediction of the Strains by Single Surface Constitutive Model (확률론에 의한 Single Surface 구성모델의 변형률 예측능력 평가)

  • Jeong, Jin Seob;Song, Young Sun;Kim, Chan Kee
    • Journal of The Korean Society of Civil Engineers
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    • v.13 no.3
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    • pp.163-172
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    • 1993
  • A probabilistic approach for evaluation of prediction of the strains using Lade's single surface constitutive model was employed, based on first-order approximate mean and variance. Several experiments such as isotropic compression and drained triaxial compression tests were conducted to examine the variabilities of soil parameters for Lade's model. By taking into account the results of the experimental data such as mean values and standard deviations of soil parameter's, a new probabilistic approach, which explains the uncertainty of computed strains, is applied. The magnitude of the COV for each parameter and the correlation coefficient between the two parameters can be effectively used for reducing the number of the parameters for the model. It is concluded that Lade's single surface constitutive model is surperior model for the prediction of the strain, because the COV of strains is under the "0.51".

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