Having Doubt in STAAD Seismic Analysis for New Zealand Project

Currently Working on Pipe rack Design for the New Zealand site. And I want to do Seismic analysis for the pipe rack. I have seen the seismic code list which is available in software. New Zealand Seismic code is not available in code list then how we can analyse seismic design. Could you please suggest proper way of doing seismic analysis as per New Zealand code?