Spectrum Analysis in ANSYS 1

[july1983]

HI.. I want to do seismic spectrum analysis on composite frame structures, as I read in the structural guide of ANSYS ONLY linear behavior is valid in spectrum analysis. My first question is how can I include the nonlinear behavior in the spectrum analysis, and the second one the spectrum analysis is for single-DOF system, so in this case I can do this analysis for a frame with just a single floor? and the final question, If it is impossible to make the nonlinear spectrum seismic analysis, How can I input the seismic record ACCELERATIONS- FREQUENCIES to do Transient analysis? since in Transient analysis ANSYS take into account the nonlinear response.
PLEASE, I WANT TO DO THIS ANALYSIS IN A SHORT TIME IF ANY ONE HAS INFORMATIONS HELP ME