How can I model friction supports in STAAD.Pro
There is no direct way to model friction supports in STAAD.Pro as of now.
However here are some points for you to consider. As long as the lateral force that is trying to cause sliding, is less than the resisting static friction, you may always consider the friction supports as lateral supports providing full lateral restraint. Static Friction (F) is calculated by multiplying the vertical load (W) by the coefficient of friction. So F= Coeff of Friction x W
Start by modeling the friction supports as full lateral restraints ( FIXED, PINNED or FIXED BUT supports as the case may be ). For any applied load, check the Static Check ( from the Postprocessing Mode > Reactions > Statics Check Results table). The Load Fy would give you the total vertical load for the case (mentioned as W above). Multiply that by the coefficient of friction to get friction force F. As long as the lateral force ( Fx or Fy from the Statics Check Results table ) is less than F, you may simply consider the friction supports as supports offering full lateral restraint.
If the Fx or Fz is greater than F, your structure is going to slide and you need to stabilize it by adding additional lateral supports.