Does SFA account for the moments due to horizontal shears in foundation design ?
Yes it can do that. If the horizontal shears in your STAAD Foundation Advanced (SFA) model are not at the base of the mat but is at a certain height from the base ( like if they are acting at the top of a pedestal ) then you can have the software account for the additional moments due to these horizontal shears by specifying a non-zero value for Pedestal height, input within the Foundation Plan > Pedestal And Anchor Bolt page. In that case the software would calculate the moment arm = pedestal height + mat thickness and multiply the horizontal shear by that moment arm to calculate the additional moment at the base.
If you do not have a pedestal, the shears are assumed to act at the top of the mat and moment arm = mat thickness. The horizontal shear is multiplied by this moment arm to calculate the additional moment at the base.
NOTE: In older versions of the product like STAAD Foundation which are deprecated ( like version 05.03.00.34 and prior ) the behavior was different. Horizontal shears were always assumed to act at the base of the mat unless pedestal height was specified. When pedestal height was specified, the moment arm was calculated as = pedestal height. The mat thickness was not included in the moment arm calculation. STAAD Foundation has been replaced by STAAD Foundation Advanced and we recommend all users to use STAAD Foundation Advanced.