• Title/Summary/Keyword: Modulus ratio

Search Result 1,301, Processing Time 0.032 seconds

Compressive Behavior of Hybrid Steel Fiber Reinforced Ultra-High Performance Concrete (하이브리드 강섬유 보강 초고성능 콘크리트의 압축거동)

  • Lim, Woo-Young;Hong, Sung-Gul
    • Journal of the Korea Concrete Institute
    • /
    • v.28 no.2
    • /
    • pp.213-221
    • /
    • 2016
  • Uniaxial compression tests for ultra-high performance hybrid steel fiber reinforced concrete (UHPC) were performed to evaluate the compressive behavior of UHPC. The UHPC for testing contains hybrid steel fibers with a predetermined ratio using a length of 19 mm and 16 mm straight typed steel fibers. Test parameter was determined as a fiber volume ratio to investigate the effect of fiber volume ratio on the strength and secant modulus of elasticity. Test results showed that the compressive strength and elastic modulus of UHPC increased with increasing the fiber volume ratio. Based on the test results, the compressive strength and modulus of elasticity equations were proposed as function of the compressive strength of unreinforced and fiber reinforced UHPC, respectively. The simplified equations for predicting the mechanical properties of the UHPC were a good agreement with the test data. The proposed equations are expected to be applied to the SFRC and UHPC with steel fibers.

The Effect on the Properties of Concrete by Fine Aggregate Fineness Modulus and Grain Shape of Coarse Aggregate (잔골재 조립율 및 굵은골재 입형이 콘크리트의 특성에 미치는 영향)

  • 정용욱;윤용호;이승한
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2003.11a
    • /
    • pp.102-105
    • /
    • 2003
  • The purpose of this study is to examine the influence of the flowability and the compressive strength of concrete after the improving of grain shape of the coarse aggregate and fine aggregate fineness modulus. According to the experimental results, the coarse aggregate after improvement of grain shape it lead to be down by 6% fine aggregate ratio, from 47% to 41%. The 0.5% increase of fine aggregate fineness modulus lead to 3% increase of concrete slump, and 1% reduction of concrete air content. While compressive strength on fine aggregate fineness modulus, it was increased until fineness modulus 3.0, but after it reached by 3.5 it was decreased. The compressive strength of the coarse aggregate after improving the grain shape was decreased by 6% due to loss of the adhesion of cement paste.

  • PDF

Prediction of Equivalent Elastic Modulus for Flexible Textile Composites according to Waviness Ratio of Fiber Tows (섬유다발의 굴곡도에 따른 유연직물복합재료의 등가탄성계수 예측)

  • Suh, Young-W.;Kim, Sung-Joon;Ahn, Seok-Min
    • Aerospace Engineering and Technology
    • /
    • v.9 no.2
    • /
    • pp.73-79
    • /
    • 2010
  • In this study, the equivalent elastic modulus of flexible textile composites was predicted by nonlinear finite element analysis. The analysis was carried out considering the material nonlinearity of fiber tows and the geometrical nonlinearity during large deformation using commercial analysis software, ABAQUS. To account for the geometrical nonlinearity due to the large shear deformation of fiber tows, a user defined material algorithm was developed and inserted in ABAQUS. In results, nonlinear stress-strain curve for the flexible textile composites under uni-axial tension was predicted from which effective elastic modulus was obtained and compared to the test result. The effective elastic moduli were calculated for the various finite element models with different waviness ratio of fiber tow.

Mechanical Properties and Modeling of Amorphous Metallic Fiber-Reinforced Concrete in Compression

  • Dinh, Ngoc-Hieu;Choi, Kyoung-Kyu;Kim, Hee-Seung
    • International Journal of Concrete Structures and Materials
    • /
    • v.10 no.2
    • /
    • pp.221-236
    • /
    • 2016
  • The aim of this paper is to investigate the compressive behavior and characteristics of amorphous metallic fiber-reinforced concrete (AMFRC). Compressive tests were carried out for two primary parameters: fiber volume fractions ($V_f$) of 0, 0.3, 0.6 and 0.8 %; and design compressive strengths of 27, 35, and 50 MPa at the age of 28 days. Test results indicated that the addition of amorphous metallic fibers in concrete mixture enhances the toughness, strain corresponding to peak stress, and Poisson's ratio at high stress level, while the compressive strength at the 28-th day is less affected and the modulus of elasticity is reduced. Based on the experimental results, prediction equations were proposed for the modulus of elasticity and strain at peak stress as functions of fiber volume fraction and concrete compressive strength. In addition, an analytical model representing the entire stress-strain relationship of AMFRC in compression was proposed and validated with test results for each concrete mix. The comparison showed that the proposed modeling approach can properly simulate the entire stress-strain relationship of AMFRC as well as the primary mechanical properties in compression including the modulus of elasticity and strain at peak stress.

Microstructure and shear modulus in concentrated dispersions of bidisperse charged spherical colloids

  • Chun, Myung-Suk;Lee, Sangwoo;Lee, Tae-Seok;Cho, Jae-Seol
    • Korea-Australia Rheology Journal
    • /
    • v.16 no.1
    • /
    • pp.17-26
    • /
    • 2004
  • We examine rigorous computations on microstructural as well as rheological properties of concentrated dispersions of bidisperse colloids. The NVT Monte Carlo simulation is applied to obtain the radial distribution function for the concentrated system. The long-range electrostatic interactions between dissimilar spherical colloids are determined using the singularity method, which provides explicit solutions to the linearized electrostatic field. The increasing trend of osmotic pressure with increasing total particle concentration is reduced as the concentration ratio between large and small particles is increased. From the estimation of total structure factor, we observe the strong correlations developed between dissimilar spheres. As the particle concentration increases at a given ionic strength, the magnitude of the first peak in structure factors increases and also moves to higher wave number values. The increase of electrostatic interaction between same charged particles caused by the Debye screening effect provides an increase in both the osmotic pressure and the shear modulus. The higher volume fraction ratio providing larger interparticle spacing yields decreasing high frequency limit of the shear modulus, due to decreasing the particle interaction energy.

The Rearch of Stress Route for Concrete Structure using Advanced Progressive Optimization (개선된 점진적 구조 최적화 기법을 이용한 콘크리트 구조물의 응력경로 탐색)

  • Kim, Shi-Hwan;Yoon, Seong-Soo;Park, Jin-Seon;Jeon, Jeong-Bae
    • Journal of The Korean Society of Agricultural Engineers
    • /
    • v.53 no.6
    • /
    • pp.153-163
    • /
    • 2011
  • This research describe improved algorithm that is able to decide terminal criterion of Evolutionary Structural Optimization (ESO), reducing load of calculation to search load path of concrete beam, and apply to agricultural facilities. The ESO method is that make to discrete structure, structural analyze each element stress through FEM. And repeat generation with next material condition to become for most suitable composing. Individual element introduces concept of zero stiffness, but zero stiffness decisions are gone to direction of exclusion. In this stduy, improve algorithm to be convergence by 'Rule of Alive or Die' in arrival because is most suitable. Also, existing terminal criterion lack consistency because that used depend on experience of researcher. This research procedure is fellowed. First, all modulus of elasticity assume a half of elasticity modulus of material, Second, structural analysis by FEM, Third, apply to the remove ratio and restoration ratio for the 'rule of alive or die'. Forth, reconstruct the element and material conditions. And repeat the first to forth process. The terminal time of evolutional procedure is the all elastic modulus of element changed to blank value or elasticity modulus value of original. Therefore, in this study, consist the algorithm for programming, and apply to the agricultural facilities with concrete.

Characteristics of Dynamic Properties of Granite Specimen from Chungnam Yeongi Area (충남 연기군 지역 화강암 시험편의 동적물성 특성에 관한 연구)

  • Min, June-Hyun;Lee, Seung-Joong;Choi, Sung-O.
    • Tunnel and Underground Space
    • /
    • v.21 no.6
    • /
    • pp.480-493
    • /
    • 2011
  • Dynamic rock property is one of most important parameters in design of earthquake-resistant structures. In this study, free-free resonant column test has been conducted to obtain dynamic Young's modulus, dynamic shear modulus, and damping ratio among dynamic properties with granite specimen of Chungnam Yeongi area. The dynamic properties obtained from this test were compared with the physical properties from static rock tests, and their relationship has been analyzed. From our study, it has been concluded that the dynamic Young's modulus and the dynamic shear modulus are linearly proportional to the elastic wave velocity. And also the damping ratio has been identified to be in non-linear inverse proportion to the elastic wave velocity.

Fundamental Characteristics of Concrete According to Fineness Modulus and Replacement Ratio of Crushed Sand (부순모래의 조립률 및 치환률에 따른 콘크리트의 기초 특성)

  • Yun, Yong-Ho;Choi, Jong-Oh;Lee, Dong-Gyu;Jung, Yong-Wook
    • Journal of the Korean Recycled Construction Resources Institute
    • /
    • v.3 no.3
    • /
    • pp.244-251
    • /
    • 2015
  • The paper evaluates the effect of the physical property, fineness modulus (FM) and replacement ratio of crushed sand on the characteristics of concrete. This is intended to use crushed sand from Daegu-Kyungbuk region as the fine aggregate of concrete. The experimental result indicates that the replacement ratio of crushed sand needs to be less than 50% to satisfy the mixed gradation of both natural and crushed sand when their FMs are 2.0 and 3.2, respectively. The slump of concrete with crushed sand increased as the replacement ratio of crushed sand increased, while the workability of concrete with the replacement ratio of more than 75% was significantly reduced. The air content and bleeding rate of concrete was reduced as the replacement ratio increased. Furthermore, due to the enhancement of the concrete adhesive regardless of the FM of crushed sand, compressive strength of concrete tended to improve as the replacement ratio increased.

An Experimental Study for Crack Prevention of Floor Mortar (바닥용 모르타르의 균열방지를 위한 실험적 연구)

  • 정재동;김진근;최응규;이칠성;이상순
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 1996.04a
    • /
    • pp.202-207
    • /
    • 1996
  • Recently, the mortar crack on floor is very serious in construction field, e.g. the crack due to plastic shrinkage and the crack due to drying shrinkage. To prevent this kind of crack, optimum mix propertions not only satisfying the required workability but also minimizing the unit water content were selected. And the expansion admixtures were used to compensate the shrinkage of mortar. This study shows that water/cement ratio used in construction field is about 64%. Even if we reduce water/cement ratio of mortar by the appropriate use the fine aggregate with high fineness modulus and superplastizer, floor mortar can have the required workability. The equations between mortar flow and water/cement ratio, sand/cement ratio, fineness modulus of fine aggregate were proposed in this study. And this equation may provide available mix proportions of floor mortar.

  • PDF

Behavior of High-Speed Rail Roadbed Reinforced by Geogrid under Cyclic Loading (지오그리드로 보강한 고속철도 노반의 거동 특성)

  • 신은철;김두환
    • Journal of the Korean Society for Railway
    • /
    • v.3 no.2
    • /
    • pp.84-91
    • /
    • 2000
  • The general concept of reinforced roadbed in the high-speed railway is to cope with the soft ground for the bearing capacity and settlement of foundation soil. The cyclic plate load tests were performed to determine the behavior of reinforced ground with multiple layers of geogrid underlying by soft soil. With the test results, the bearing capacity ratio, elastic rebound ratio, subgrade modulus and the strain of geogrids under loading were investigated. Based on these plate load tests, laboratory model tests under cyclic loading were conducted to estimate the effect of geogrid reinforcement in particular for the high-speed rail roadbed. The permanent settlement and the behavior of earth pressure in reinforced roadbed subjected to a combination of static and dynamic loading are presented.

  • PDF