• Title, Summary, Keyword: compressive strain

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Flexural analysis of steel fibre-reinforced concrete members

  • Chalioris, Constantin E.;Panagiotopoulos, Thomas A.
    • Computers and Concrete
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    • v.22 no.1
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    • pp.11-25
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    • 2018
  • A numerical approach for the evaluation of the flexural response of Steel Fibrous Concrete (SFC) cross-sections with arbitrary geometry, with or without conventional steel longitudinal reinforcing bars is proposed. Resisting bending moment versus curvature curves are calculated using verified non-linear constitutive stress-strain relationships for the SFC under compression and tension which include post-peak and post-cracking softening parts. A new compressive stress-strain model for SFC is employed that has been derived from test data of 125 stress-strain curves and 257 strength values providing the overall compressive behaviour of various SFC mixtures. The proposed sectional analysis is verified using existing experimental data of 42 SFC beams, and it predicts the flexural capacity and the curvature ductility of SFC members reasonably well. The developed approach also provides rational and more accurate compressive and tensile stress-strain curves along with bending moment versus curvature curves with regards to the predictions of relevant existing models.

A Study on the Compressive Properties of Seawater-absorbed Carbon-Epoxy Composites - Hydrostatic Pressure Effect (해수가 흡수된 Carbon-Epoxy 적층복합재의 압축특성에 대한 연구- 정수압력 영향)

  • Lee Ji Hoon;Rhee Kyong Yop;Kim Hyun ju
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.16 no.4
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    • pp.191-195
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    • 2004
  • This study investigated the effect of deep-sea environment on the compressive characteristics of polymer matrix composite. The specimens used in the experiment were thick Carbon-Epoxy composites that were made from Carbon-Epoxy prepregs. The specimens were immersed into seawater for thirteen months. The seawater content at saturation was about 1.2% of the specimen weight. The hydrostatic pressures applied were 0.1 MPa, 100 MPa, 200 MPa, and 270 MPa. It was found that the compressive elastic modulus increased about 10% as the hydrostatic pressure increased from 0.1 MPa to 200 MPa. The modulus increased additional 2.3% as the pressure increased to 270 MPa. It was also found that compressive fracture strength and compressive fracture strain increased with pressure in a linear behavior. Compressive fracture strength increased 28% and compressive fracture strain increased 8.5% as the hydrostatic pressure increased from 0.1 MPa to 270 MPa.

Characteristic responses of critical current in REBCO coated conductor tapes under tensile/compressive bending strains at 77 K

  • Diaz, Mark Angelo;Shin, Hyung Seop;Lee, Jae-Hun
    • Progress in Superconductivity and Cryogenics
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    • v.20 no.4
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    • pp.31-35
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    • 2018
  • When REBCO coated conductors (CCs) are applied to superconducting devices such as coils and magnets, they are subjected to deformation in various modes such as compression/tension bending, uniaxial/transverse tension and torsion. Despite outstanding performances by REBCO CC tapes, their electromechanical properties have been evaluated primarily under uniaxial tension, therefore data about the critical current ($I_c$) response in the compressive strain region are lacking. In this study, the characteristic responses of $I_c$ in REBCO CC tapes under bending strains in the range from tensile to compressive were evaluated. The springboard bending beam was used, wherein the CC tape sample was soldered onto the surface of the springboard. A Goldacker-type bending test rig, which lacks a support holding the sample during testing, was used as a comparator. Degradation in $I_c$ behaviors, including strain sensitivity, in differently processed REBCO CC tapes were examined based on the test rig used.

Critical Compressive Strain of Concrete under a Long-Term Deformation Effect Part I. Experiments

  • Nghia, Tran Tuan;Chu, In-Yeop;Kim, Jin-Keun
    • International Journal of Concrete Structures and Materials
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    • v.4 no.2
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    • pp.89-96
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    • 2010
  • This paper focuses on the effect of creep on the critical compressive strain (CCS) of concrete. The strain of concrete corresponding to the peak compressive stress is crucial in the selection of the ultimate yield strength of the reinforcing bar used in reinforced concrete columns. Among the various influencing factors, such as the creep, shrinkage, loading rate and confinement, the effect of creep and shrinkage is the most significant. So far, investigations into how these factors can affect the CCS of concrete have been rare. Therefore, to investigate the effect of creep and shrinkage on CCS, an experimental (part I) and a parametric study (part II) were conducted, as presented in these papers (part I considers creep effect, part II considers effect of creep and shrinkage). In part I, experiments pertaining to the loading age, loading rate, loading duration and loading and creep levels were conducted to study the effect of these variables on the CCS of concrete. It was found that the effects of the loading rate, loading age, and level and duration on the CCS of concrete were negligible. However, it is very important to consider the effect of creep.

Experimental study on axial compressive behavior of hybrid FRP confined concrete columns

  • Li, Li-Juan;Zeng, Lan;Xu, Shun-De;Guo, Yong-Chang
    • Computers and Concrete
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    • v.19 no.4
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    • pp.395-404
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    • 2017
  • In this paper, the mechanical property of CFRP, BFRP, GFRP and their hybrid FRP was experimentally studied. The elastic modulus and tensile strength of CFRP, BFRP, GFRP and their hybrid FRP were tested. The experimental results showed that the elastic modulus of hybrid FRP agreed well with the theoretical rule of mixture, which means the property of hybrid composites are linear with the volumes of the corresponding components while the tensile strength did not. The bearing capacity, peak strain, stress-strain relationship of circular concrete columns confined by CFRP, BFRP, GFRP and hybrid FRP subjected to axial compression were recorded. And the confinement effect of hybrid FRP on concrete columns was analyzed. The test results showed that the bearing capacity and ductility of concrete columns were efficiently improved through hybrid FRP confinement. A strength model and a stress-strain relationship model of hybrid FRP confined concrete columns were proposed. The proposed stress-strain model was shown to be capable of providing accurate prediction of the axial compressive strength of hybrid FRP confined concrete compared with Teng et al. (2002) model, Karbhari and Gao (1997) model and Miyachi et al. (1999) model. The modified stress-strain model was also suitable for single FRP confinement cases and it was so concise in form and didn't have piecewise fitting, which would be easy for use in structural design.

Cyclic compressive behavior of polyurethane rubber springs for smart dampers

  • Choi, Eunsoo;Jeon, Jong-Su;Seo, Junwon
    • Smart Structures and Systems
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    • v.20 no.6
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    • pp.739-757
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    • 2017
  • The main goal of this study is to investigate the hysteretic behavior of polyurethane rubber springs in compression with and without precompression. The precompression is introduced to provide rigid force in the behavior, and thereby a precompressed rubber spring can be used for a restoring element. For the goal, this study prepares nine rubber springs for three suites which are all cylindrical in shape with a hole at the center. The rubber springs in each suite have different dimensions of diameter and length but have similar shape factors; thus, they are designed to have a similar compressive stiffness. Three rubber springs from the nine are tested with increasing compressive strain up to 30% strain to investigate the behavior of the rubber springs without precompression as well as the effect of the loading strain. The nine springs are compressed up to 30% strain with increasing precompressive strain from 0 to 20% at increments of 5%. The study analyzes the effective stiffness and damping ratio of the rubber springs with and without precompression, and the rigid force of the precompressed rubber springs is discussed. Finally, this study suggests a regression method to determine the minimum required precompression to eliminate residual strain after unloading.

Moment Capacity of Reinforced Concrete Members Strengthened with FRP (FRP 보강 철근콘크리트 부재의 휨모멘트)

  • Cho, Baik-Soon;Kim, Seong-Do;Back, Sung-Yong;Choi, Eun-Soo;Choi, Yong-Ju
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.23 no.3
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    • pp.315-323
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    • 2010
  • Five concrete compressive stress-strain models have been analyzed to check the validity of the strength method for determining the nominal moment of strengthened members using commercially available computer language. The results show that the concrete stress-strain models do not influence on the flexural analysis. The moment of a strengthened member obtained from the flexural analysis at concrete compressive strain reaching 0.003 is well agreed with nominal moment using the strength method. The flexural analysis results show that when the steel reinforcement, FRP ratio, FRP failure strain, and concrete failure compressive strain are relatively lower, the strength method overestimates the flexural capacity of the strengthened members.

Autofrettage Analysis of Compound Cylinder with Power Function Strain Hardening Model (멱함수 가공경화 모델을 이용한 복합실린더의 자긴가공해석)

  • Park, Jae-Hyun;Lee, Young-Shin;Shim, Woo-Sung;Kim, Jae-Hoon;Cha, Ki-Up;Hong, Suk-Kyun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.6
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    • pp.488-495
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    • 2008
  • In order to achieve long fatigue lifetimes for cyclically pressurized thick cylinders, multi-layered compound cylinder has been proposed. Such compound cylinder involves a shrink-fit procedure incorporating a monobloc tube which has previously undergone autofrettage. The basic autofrettage theory assumes elastic-perfectly plastic behaviour. Because of the Bauschinger effect and strain-hardening, most materials do not display elastic-perfectly plastic properties and consequently various autofrettage mo dels are based on different simplified material strain-hardening models, which is assumed that combination of linear strain-hardenig and power strain-hardening model. This approach gives a more accurate prediction than the elastic-perfectly plastic model and is suitable for different strain-hardening materials. In this paper, a general autofrettage model that incorporates the material strain-hardening relationship and the Bauschinger effect, based upon the actual tensile-compressive stress-strain curve of a material was proposed. The model was obtained using the von Mises yield criterion and plane strain condition. The tensile-compressive stress-strain curve was obtained by experiment. The parameters needed in the model were determined by fitting the actual tensile-compressive curve of the material. Finally, strain- hardening model was compared with elastic-perfectly plastic model.

Modeling and Analysis of Strain Localization in Concrete (콘크리트 변형률국소화 모형 및 해석)

  • 송하원;김인순;나웅진
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.375-382
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    • 1997
  • In this paper, a unified micromechanics-based model which can be applied to both tensile and compressive member of concrete is suggested and to the analysis of the strain-localization in concrete. From the comparison of the analysis results obtained from different size of concrete members with experimental data, it id shown that the model in this paper can be applied to the analysis of the strain localization concrete. For the finite element analysis of the strain-localization in concrete, the localized zone in concrete under strain localization is modeled as ad plastic model which can consider nonlinear strain softening and the non-localized zone is modeled as a nonlinear elastic-damage model. Using developed finite element analysis program. strain localization behaviors under compressive force for the different sizes of concrete having different sizes of the localized zone are simulated.

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