Shrinkage strain in Ram concept according to AS3600

The following comes from an old email exchange I had with the lead developer, but I think it still applies here: 

AS 3600 breaks down total shrinkage into autogenous shrinkage and drying shrinkage, whereas Concept only has a single value for shrinkage that represents the combination.  I think it is most important to get the final ultimate shrinkage calculated and input correctly.

RAM Concept’s assumption is that no shrinkage occurs during the moist cure duration period, after which shrinkage strains start occurring according to the ACI 209 equation 2-9.  The term in the AS 3600 standard that is most analogous to the end of Concept’s moist cure duration period is “commencement of drying”.

Be aware that the input moist cure duration value will have the most significant effect in very short term deflection calculations.  Because of the sensitivity of short-term deflection deflections (in real concrete behavior, in addition to the calculations) short-term deflection results should be used with extreme caution.

My recommendation for AS-3600 would be to set the moist cure duration to be the time elapsed since casting to the commencement of drying.  The time dependent part of Figure 3.1.7.2 should not be included in the shrinkage strain calculated, but the final (30 year) value should be included for k1.

Thank you Seth, would you mind give a hand calculation example.

I added some notes on determining the shrinkage strain to our wiki on Load History Parameters and AS 3600. Please review and let us know if this answers your question.

Load History Parameters and AS 3600

Karl.

For shrinkage strain, if the time dependent factor k1 is accounted for automatically by RAMConcept.

Why is it used the Shrinkage example and included in step 3?

Also Step 4 should say 'Step 1 and 3'.

Thanks

The final 30-year shrinkage strain including all adjustments is the shrinkage value that should be input into RAM Concept. k1 is a function of time and the thickness of the section. The time-dependent part is taken care of automatically by the program through the ACI 209 model and the input duration for each load history step. The adjustment for the section thickness, however, needs be accounted for in the input ultimate shrinkage strain.

Thank you for pointing out the typo with the step 4 reference. That is corrected now.