Creep and Shrinkage

[Edu09]

Hi all,

How does one consider creep and shrinkage in analysis of a structural element? For example, do you actually check different design stages by adding the strains due to shrinkage and creep to the strains present in the section from loading to increase the stresses?

So, for the long term case, I add the final shrinkage strain(calculated according to BS EN 1992-1-1) as an imposed deformation? Because it is an indirect action similar to temperature.

And a final question, does this apply for all load cases? ULS, SLS characteristic, quasi permanent?

If anyone has a good reference that explains these things I'm happy to plough through it myself, I'm not asking anyone to do my work here, I just want to understand! It doesn't matter about the code, it's more the principle I'm trying to properly grasp.

as always, Thanks chaps

 

[klaus.]

Well basically you have to consider everything which is relevant for your structure
If creep is relevant...yes..you have to consider
same for all other possible loads and situations



best regards
Klaus

 

[Edu09]

Thanks for your time Klaus,

To extend this further, if I have calculated a total strain due to autogenous and drying shrinkage, how do I apply this to a section?

Do I add these strains to the existing strain due to load in the section and check the effects?

Sorry, if the first question or this one is not too clear.

 

[MotorCity]

Take a look at your load combinations. Is the strain from load due to dead load, live load, both, etc? I would classify drying shrinkage as a temperature induced load and include it accordingly in the load combinations that include temperature. Either way, creep and shrinkage generate a force in your members. Calculate that force and apply it as a load to the appropriate members in your model.

 

[SethGuthrie]

Here's an interesting read (though you'll have to sign in to download it)

https://communities.bentley.com/oth...s/member_folders/m/jason_colemans_files/87861

 

[dik]

There are numerous methods of calculating long term deflection in concrete structures; I normally accommodate deflections with deflection space and lateral support of partitions, etc. that can accommodate movement. The space is achieved by a 'fudged' deflection calculation; due to uncertainty of loading (dead load can be pretty close) and early loading conditions which has a major impact, I don't have a lot of confidence in long term deflection calculation.

Dik

 

[rapt]

Get R I Gilberts latest book on it, Time Dependant Behaviour of Concrete Structures.

Shrinkage strain does not equate to stress in a member. Any stress due to it is due to restraint of shrinkage strain. Reinforcing internally will provide partial restraint. Connected elements may provide external restraint. But if there is no restraint, there is no stress unless the shrinkage strain is not linear..