1. As per Caesar help documents ,the ZPA entry in the Control Parameter input is only used with the Reg. Guide 1.60 shock spectra and the UBC shock spectra. If I am not using those pre-defined spectra, the ZPA input is not used.

Does this mean that the ZPA parameter automatically will be inactive if i am using some site specific response spectrum or response spectrum as per code IS1893 Part I & IV .

2.As a rule the modal ground acceleration taken from the response spectrum(site specific) is first divided by ratio R/I*g [ by {R/(Z/2)I*g} in case of IS1893 code specific response spectra] before using in response spectrum analysis .
As per IS 1893 , R= Response reduction factor to take into account the redundancy and ductility of structure , I=Importance factor assigned to structure as per category ,g = Gravitational acceleration , Z =Zone factor

As per my understanding this factor can be consider by Providing the value of factor R/I*g or {R/(Z/2)I*g} in the Spectrum load case tab . In this case the value of ZPA will be 1 .

Please respond !

Please help me to get the answer of above questions !