Micro Plane Constitutive Model for Concrete

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Analysis for concrete structures under complicated stress conditions based on general purpose FE software and microplane model
Journal of Shenyang Jianzhu University (Natural Science), 2008, 24(1), 49-53.

Abstract: In order to precisely simulate the complicated mechanical behavior of concrete so as to accurately modeling the real complex concrete structures, a novel concrete constitutive model, which is referred as microplane model, is introduced in this paper and integrated into the general purpose finite element (FE) software of MSC.MARC which has outstanding nonlinear capacity. Concrete specimens under uniaixial, biaxial, triaxial and cycle loading are simulated with the proposed program as well as a reinforced concrete (RC) shear wall under cycle loading. Compared the numerical predictions of proposed program to the test results, good agreements can be found. And the problems of concrete models in common FE software are pointed out, when they are used to simulate complicated concrete mechanical behaviors. The results show that the proposed program can precisely simulated the complicated concrete structures.

Keywords: concrete finite element; microplane model; constitutive models; nonlinear analysis

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Nonlinear FE model for RC shear walls based on multi-layer shell element and microplane constitutive model
Proc. Computational Methods in Engineering And Science (EPMESC X), Tsinghua University Press & Springer-Verlag, Aug. 2006, Sanya, Hainan,China, 2006, CDROM.

Abstract: Nonlinear simulations for structures under disasters have been widely focused on in recent years. However, precise modeling for the nonlinear behavior of reinforced concrete (RC) shear walls, which are the major lateral-force-resistant structural member in high-rise buildings, still has not been successfully solved. In this paper, based on the principles of composite material mechanics, a multi-layer shell element model is proposed to simulate the coupled in-plane/out-plane bending and the coupled in-plane bending-shear nonlinear behaviors of RC shear wall. The multi-layer shell element is made up of many layers with different thickness. And different material models (concrete or rebar) are assigned to various layers so that the structural performance of the shear wall can be directly connected with the material constitutive law. And besides the traditional elasto-plastic-fracture constitutive model for concrete, which is efficient but does not give satisfying performance for concrete under complicated stress condition, a novel concrete constitutive model, referred as microplane model, which is originally proposed by Bazant et al., is developed to provide a better simulation for concrete in shear wall under complicated stress conditions and stress histories. Three walls under static push-over load and cyclic load were analyzed with the proposed shear wall model for demonstration. The simulation results show that the multi-layer shell elements can correctly simulate the coupled in-plane/out-plane bending failure for tall walls and the coupled in-plane bending-shear failure for short walls. And with microplane concrete constitutive law, the cycle behavior and the damage accumulation of shear wall can be precisely modeled, which is very important for the performance-based design of structures under disaster loads.

Keywords: shear wall, nonlinear analysis, microplane, finite element, multi-layer shell element

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Uniaixal Compression	Uniaxial Tension

Biaxial Failure Envelope	Triaxial Compression

Hydrostatic Compression	Cycle Compression