R. Lackner:
"Ein anisotropes Werkstoffmodell für Beton auf der Grundlage der Plastizitäts- und der Schädigungstheorie"; Institute for Strength of Materials, TU Wien, Vienna, Austria, 1995.
This master's thesis is concerned with an anisotropic 2D constitutive model for plain concrete based on plasticity and damage theory stress-strain-relation of concrete when subjected to compressive loading. The use of a particular damage theory developed by Simo, Oliver and Armero [1] allows consideration of anisotropic material stiffness degradation induced by crack growth. In this work a material model for cracked concrete is developed which is characterized by a combination of anisotropic damage and isotropic plasticity theory. This combination allows modelling of permanent strains after closure of cracks.The different failure mechanisms of concrete under tension and compression, respectively, are accounted for by two different models Rankine damage surface is employed. For concrete subjected to compressive or mixed tensile compressive stresses an elasto-plastic hardening Drucker-Prager model is used. Chapter 4 contains the calibration of both models.
In chapter 5 and 6 the positive and negative aspects of the model are investigated in the context of one and two dimensional problems.
The presented model for concrete was implemented into the Finite Element Program MARC. Chapter 7 contains selected results of a cylinder splitting test. A comparison with results obtained from an isotropic elasto-plastic model and a "fixed crack" model shows a relatively small influence of the specific model on the predicted ultimate load capacity.
[1]J.C. SIMO, J. OLIVER and F. ARMERO, 'An analysis of strong discontinuities induced by strain-softening in rate-independent inelastic solids.', Computational Mechanics, Vol. 12, 277-296, (1993)
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