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The coupling effect of drying shrinkage and moisture diffusion in concrete
A. Suwito,Ayman Ababneh,Yunping Xi,Kaspar Willam 한국계산역학회 2006 Computers and Concrete, An International Journal Vol.3 No.2
Drying shrinkage of concrete occurs due to the loss of moisture and thus, it is controlled by moisture diffusion process. On the other hand, the shrinkage causes cracking of concrete and affects its moisture diffusion properties. Therefore, moisture diffusion and drying shrinkage are two coupled processes and their interactive effect is important for the durability of concrete structures. In this paper, the two material parameters in the moisture diffusion equation, i.e., the moisture capacity and humidity diffusivity, are modified by two different methods to include the effect of drying shrinkage on the moisture diffusion. The effect of drying shrinkage on the humidity diffusivity is introduced by the scalar damage parameter. The effect of drying shrinkage on the moisture capacity is evaluated by an analytical model based on non-equilibrium thermodynamics and minimum potential energy principle for a two-phase composite. The mechanical part of drying shrinkage is modeled as an elastoplastic damage problem. The coupled problem of moisture diffusion and drying shrinkage is solved using a finite element method. The present model can predict that the drying shrinkage accelerates the moisture diffusion in concrete, and in turn, the accelerated drying process increases the shrinkage strain. The coupling effects are demonstrated by a numerical example.
Masoud Dehghani Champiri,Mir Mohammad Reza Mousavi,Kaspar Jodok Willam,Bora Gencturk 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.3
This paper investigates the effect of concrete degradation due to alkali-silica reactivity (ASR) and its effect on the performance of vertical concrete casks in the case of a hypothetical tip-over event. ASR is one of the major problems in certain concrete structures exposed to high relative humidity and temperature. Using the first order kinetic model, the mechanical and environmental effects of degradation are modeled for a dry-cask storage structure under the conditions that ASR is completely extended. Following the degradation, a tip-over impact simulation was performed and compared with that of an intact cask in terms of failure modes, damage patterns, stresses, and accelerations. It was seen that concrete crushing and shear banding are major failure modes in the cask with intact concrete, but in the case of the ASR affected cask, the concrete is fully damaged and a longitudinal crack which separates the cask into two parts propagates through the outerpack.