Hi there,
I notice that the article on AS3600-2018 load history gives the equations its using from the code to calculate the Basic Autogenous Shrinkage Strain & Basic Drying Shrinkage Strain.
The equation for basic drying shrinkage strain = 3.1.7.2(5), which is correct.
The equation for Basic Autogenous Shrinkage Strain = 3.1.7.2(3), however AS3600 defines this as the Final autogenous shrinkage strain. From what i can see, AS3600 doesn't define a basic autogenous shrinkage strain, but perhaps equation 3.1.7.2(2) is most correct.
In which case, is RAM simply labelling the equation name wrong, or is it using the wrong equation?
You are correct that AS 3600 does not define a basic autogenous shrinkage strain. RAM Concept uses generic labeling that is used for all design codes. This means that in some cases a "most correct" equation must be fit to a generic menu option that is labeled slightly different than what is found in the design code.
For AS 3600-2018, the Final Autogenous Strain that is defined in Equation 3.1.7.2(3) should be entered as the Basic Autogenous Shrinkage Strain in RAM Concept. For each load history step, RAM Concept will automatically apply Equation 3.1.7.2(2) to calculate the contribution of autogenous shrinkage using the time duration defined with the load history.
Hi Karl, thanks for confirming.
How does RAM consider the time in days after setting for the shrinkage strain? Equation 3.1.7.2(2) and 3.1.7.2(4) have a time component (which might be used at 30years), however there doesn't seem to be an input for this now?
Equations 3.1.7.2(2) and 3.1.7.2(4) have a time component and can be calculated for any time duration (not just at 30 years). RAM Concept uses the time durations defined with each load history step (Criteria - Load History) to calculate a differential shrinkage strain at each step. For autogenous shrinkage, the setting time is assumed to coincide total age t=0. For drying shrinkage, commencement of drying is assumed to start after the cure duration specified in Criteria - Calc Options - Load History/ECR tab.