If SAP2000 reads external files then covert the current time histories using say, excel, and save as a file that is read by the program, txt, prn, etc.  If not then you are likely to enter the points one by one (tedious) and the program may have a limit on the data points.

SAP gives some built-in UBC spectra under Define menu>Response spectrum functions. Using that same menu, you can create your own functions Period vs acceleration using whatever units you wish

Dear Sirs:

Hi and thanks for your answers, but I still ignore how to generate automatic seismic load in SAP2000, can anyone help me?

Thans a lot!

Hi Odco,
You cannot generate seismic loads automatically in SAP2000, it has to be calculated manualy using the applicable building code. One help which i mostly take from SAP2000 is to find the time period, and then checking it out with the applicable code provision. Usually they are quite comparable. The automatic generation of seismic loads by the UBC can be done for buildings in ETABS. Probably this automatic generation capabilty is not there in SAP2K as it is a general purpose program. Any way the required loads calculation can very easily be done using Excel or other spread sheets available.
smanzur