You can find lot of details on this specific topic at section 5.32.10.1.8 of the Technical Reference Manual. The section is titled Response Spectrum Specification per IBC 2012.
Also there are a bunch of training videos that you would be able to access from the Bentley Learn Server learn.bentley.com/.../Public
When you get there, click on Find Training and enter STAAD.Pro as the product name and you will get a list of training videos.
Out of these there are a couple which specifically deals with response spectrum analysis.
Also there are a bunch of training videos that you would be able to access from the Bentley Learn Server learn.bentley.com/.../Public
When you get there, click on Find Training and enter STAAD.Pro as the product name and you will get a list of training videos.
Out of these there are a couple which specifically deals with response spectrum analysis.