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Young hardening concrete, increasing material stiffness ABAQUS

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themaninblue

Petroleum
Aug 16, 2011
9
I am trying to model the curing process of a mass concrete structure. We have a 6m diameter, 60m high steel cylinder which is to be filled with a high strength concrete mix (approx 40GPa 28 day stiffness).

There are a number of processes occuring during the curing phase which I'm trying to capture:

Axial expansion up the column due to thermal expansion
Radial expansion, restrained by the steel
Increasing stiffness of the concrete (varying with time/space)
Stress concentrations around local details

Ideally, I would also like to capture the viscoelastic creep response as well as the cracking response, but at this stage the most important parameter is the effective material stiffness and these latter parameters would need additional test data.

I can change the stiffness using the field variable dependency ie:

*Elastic, dependencies=1
5000000000, 0.19, , 1
40000000000, 0.19, , 2

However, when it is altered, it causes changes in the stress and strain. In reality, the initial stress/strain should remain constant as the concrete sets.

I have tried to carry out stiffness changes in a single step with simultaneous temperature changes.

I also tried using the *import function and discretizing the stiffness changes (imagining that I could retain the stress from the previous step but adjust the initial stiffness for the next step).

I would very much appreciate any insight on the capabilities of Abaqus to perform this work.

Thomas
 
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