Hello,
I am currently making some sensitivity runs on-bottom stability using AGA level 2 for a subsea pipeline , at 20 meter water depth.

However , I am getting a strange result which I can’t explain:

Taking a typical Case;

Current dominant case, with Spectral Peak Period (Tp) = 13.6s, AGA gives a high concrete coating requirement. While using Tp = 16s, AGA is gives a lesser concrete weight concrete.

I expected the concrete coating to reduce for a lesser Tp (which is the case for the wave dominant cases) but not the other way around.

Please can someone explain to me why i am requiring high concrete weight coating just by reducing Spectral Peak Period (Tp).