Seismic isolated structure

We are analyzing seismic isolated structure for accelerogram loading using time-history step analysis and have some questions about that:

  1. Which options for Sofiload ACCE should be used to apply accelerations only on foundation nodes (unisolated part of structure), instead of all nodes of the model?
  2. Is it possible to model sliding isolation pendulum devices (Maurer SIP) by Spring Elements? The main equation for lateral force is F=W/R∙D ± μW, so force F depends on both axial load W and displacement D. We haven’t found this option in Sofimsha SPRI documentation.
  3. What is preferable Ase STEP options and iteration method to reach convergence of nonlinear time-history analysis for earthquake, having sliding isolation pendulum, dampers and friction springs?