As a pilecap gets thinner, it is less 'rigid' and the loading on pile clusters changes. Is there software available that analyses groups of piles and accommodates less than rigid pilecaps?
Any finite element software (SAP, ETABS, RAM Elements, etc) would accurately capture a non-rigid load distribution to piles using thick plate elements for the cap and springs (or pins if you want to view them as nonyielding) for piles.