Quantifying Deflection Variation in RC Beams Propagated from Microstructural Variability in Concrete using Homogenization Technique

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Title: Quantifying Deflection Variation in RC Beams Propagated from Microstructural Variability in Concrete using Homogenization Technique

Author(s): J.J. Kim, T. Fan and M.M. Reda Taha

Publication: Special Publication

Volume: 284

Issue:

Appears on pages(s): 1-14

Keywords: deflection, homogenization, ITZ, Monte Carlo simulation, RVE, uncertainty

Date: 3/1/2012

Abstract:
Deflection of reinforced concrete (RC) beams is affected by the mechanical properties of concrete, which directly affect the structural stiffness of the element and indirectly define the moment redistribution due to cracking. Therefore, it is important to incorporate uncertainty of the mechanical properties of concrete in deflection calculations for robust prediction of RC deflection. In this study, inherent variations of mechanical properties of concrete are evaluated using the finite element (FE) method. Considering concrete as discrete particles of aggregate and cement paste connected by interfacial transition zone (ITZ), a non-linear representative volume element (RVE) of concrete is developed based on concrete section images. Tension and compression behaviors in concrete are simulated by modeling the cohesive response of ITZ and considering contact mechanics within the RVE. The concrete RVE is validated with a theoretical concrete constitutive model based on compressive strength. The proposed RVE model is then used to describe the constitutive properties of concrete. The mechanical properties of cement paste and ITZ are used as sources of uncertainties in concrete. The homogenization approach allows for considering uncertainties due to concrete microstructure randomness. These uncertainties are reflected in the macro properties of concrete derived from the RVE. The deflection variations of RC beams are then propagated from the variations in macro properties of concrete using Monte Carlo (MC) simulation based on a non-linear FE beam model incorporating cracking and tension stiffening.