Explain the difference between the option ‘Age’ which appears under both ‘Composite Section’ and ‘Construction Stage’.

Now, for the composite section, we need two different age of loading for the members because when the girder start taking the load it might have a different age than when the slab start taking the load. Therefore they will have different creep coefficients that need to be taken care of in the losses and secondary effects.

So, we need to define the age of loading for the slab and girder and that can be done only by having a separate input in the "Composite Section for Construction stage". Now, as it is mentioned in the online manual as well all the inputs we provide in the Composite section for the construction stage supersede the inputs for the Construction Stage. Therefore for composite sections, for having the different creep values for slab and girder, we need to define their respective age of loadings separately.