Modelling triaxial compression using the Microplane formulation for low confinement

Ghazi, Mohammad; Attard, Mario M.; Foster, Stephen J.

doi:10.1016/s0045-7949(02)00057-3

Cited by 13 publications

(3 citation statements)

References 16 publications

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“…The coefficient #(r V ), in Eqs. (20) and (21), was absent from the original model M4 and has been recently introduced in order to achieve a more realistic response when transverse compressive stresses are applied during tensile softening or when the triaxial compression under low confinement is considered (see also Ghazi et al, 2002).…”

Section: Discussionmentioning

confidence: 99%

A symmetric over-nonlocal microplane model M4 for fracture in concrete

Luzio

2007

International Journal of Solids and Structures

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This paper analyzes the effectiveness of a nonlocal integral-type formulation of a constitutive law such as microplane model M4 in which the yield limits soften as a function of the total strain for prediction of fracture propagation. For a correct regularization of the mathematical problems caused by the softening behavior, an ''over-nonlocal'' generalization of the type proposed by Vermeer and Brinkgreve [Vermeer, P.A., Brinkgreve, R.B.J., 1994. A new effective non-local strain measure for softening plasticity. In: Chambon, R., Desrues, J., Vardoulakis, I. (Eds.), Localization and Bifurcation Theory for Soil and Rocks, Balkema, Rotterdam, pp. 89-100.] is adopted. Moreover, the symmetric weight function, proposed by Borino et al. [Borino, G. Failla, B., Parrinello, F., 2003. A symmetric nonlocal damage theory. International Journal of Solids and Structure 40, 3621-3645.] for damage mechanics, is introduced for the calculation of the nonlocal averaging of the total strain upon which the yield limits depend. The capability of the proposed model for reproducing the stress and strain fields in the vicinity of a notch is also investigated. Finally, the symmetric over-nonlocal generalization of microplane model M4 has been applied for the simulation of a mixed-mode fracture test such as the four-point-shear test and the test of axial tension at constant shear force [Nooru-Mohamend, M.B., 1992. Mixed-mode fracture of concrete: an experimental approach. Doctoral Thesis

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Section: Discussionmentioning

confidence: 99%

A symmetric over-nonlocal microplane model M4 for fracture in concrete

Luzio

2007

International Journal of Solids and Structures

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“…Ghazi et al (2002) observed that the microstructure coefficients of the M4 model do not suitably predict the behaviour of concrete with different uniaxial compressive strengths and different confinement levels. To provide better simulations for an axially loaded FRP-wrapped concrete column using the microplane theory, Ghazi et al (2002) proposed a new formula for the adjustable micromechanics variables ( 1 k to 4 k ) and for the fixed micromechanics constant ( 10 c ) as a function of the level of the confinement lateral pressure (Ghazi et al, 2002). They introduced the factors affecting the post-peak steepness and the stress and strain at the peak of the stress-strain curve of confined concrete as functions of the concrete strength and confinement levels to give a better fit between analytical results and experimental data.…”

Section: Introductionmentioning

confidence: 98%

“…However it has been concluded, through several numerical simulations, that the microplane theory has inconsistent predictions for the concrete behaviour when applying low confinement lateral pressures, as is the case of FRP-wrapped concrete cylinders (Ghazi et al, 2002). Ghazi et al (2002) observed that the microstructure coefficients of the M4 model do not suitably predict the behaviour of concrete with different uniaxial compressive strengths and different confinement levels.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Micromechanics-Based Finite Element Analysis of FRP-Rapped Concrete Columns Subjected to Axial Load

Baky

Demers

Yahiaoui

et al. 2011

Advances in FRP Composites in Civil Engineering

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In this research work, new modifications for the microplane constitutive law are first presented to precisely simulate concrete behaviour under various levels of lateral confinement pressure. A key feature of the suggested formula is to make the microplane theory valid to represent concrete behaviour under both low and high lateral confining pressures. An analysis is then carried out using two different numerical procedures. The first procedure is the use of a three-dimensional finite element analysis with the modified microplane formulations as a user-supplied subroutine into the FE commercial software ADINA to model the concrete behaviour under various stress and strain histories. Here, the sub-objective is to validate the formulated microplane approach that is proposed in the first phase of the research program. In the second analysis; the confinement behaviour is simulated using an in-house code. The code uses the proposed formulations for the microplane theory to represent the concrete characteristics to predict the stress-strain relationships of FRP-wrapped concrete columns up to failure. An accurate equation correlating the axial stiffness of the FRP laminates and the lateral strain of the concrete columns to the confining pressure is incorporated in the in-house code. The two analyses give almost the same predictions, with minor discrepancies due to some numerical aspects. An experimental program consisting of testing thirty eight concrete cylinders under various lateral confinement pressures is carried out to assess the accuracy of the numerical predictions. In the experimental program, the lateral pressure is designed to give almost the same lateral confinement behaviour as that resulting from applying FRP sheets. The numerical predictions are finally compared to experimental results for FRP-wrapped and un-wrapped concrete columns under various levels of lateral pressure. This paper gives an overview for the whole research program with a special emphasis on the theoretical part.

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