modelling concrete shrinkage:change in volume due to loss of moisture 1

[aminjamali]

Concrete shrinks because of loss of it's moisture over time. If it's free, it shrinks easily and no stresses develop in it. When it's restrained, tensile stresses develop and cause crackings. I need to model this behavior through finite elements.
There is a block of concrete --lets say 1'x1'x1'--which is restrained at different points. I thought maybe I could simply assign a Thermal Expansion factor to the concrete, and then apply some negative temperature to it. To my mind, it should be ok but my professor doubts it. He wanted me to see if it is possible to model "change in volume" through some special elements or something like that so that I could have modeled the shrinkage more accurately and reliably.
To whom who may read my thread, could you kindly give me some tips on this? Is it basically possible to do such a thing? I have used Ansys for long time for simple problems in mechanics, I am not expert though.

I appreciate your tips.

 

[asixth]

When designing prestressed highway bridges, we calculate the free shrinkage of the concrete and convert this to an equivalent thermal change, doing this will generate an action that is equivalent to the free shrinkage of the concrete, and then modelling the restraining elements will calculate the stresses within the section.

Ansys is a more powerful FE package than what we are using and I wouldn't be surprised if the do have a feature that allows you to impose a volumetric change on a cross-section.

Otherwise there is nothing wrong with the approach you are taking, it is a common approach.