| Applies To | |||
| Product(s): | STAAD.Pro | ||
| Version(s): | All | ||
| Environment: | N/A | ||
| Area: | Analysis | ||
| Subarea: | Response Spectrum Analysis | ||
| Original Author: | Sye Chakraborty Bentley Technical Support Group | ||
This is a question dealing with response spectrum analysis. I know that if a force is applied in the response spectrum load case, it will be converted to a mass that will in turn affect the modal response. My question is, will that input force still be applied as a static force in the analysis? Or, would I have to apply the force in a different load case to account for it?
Response spectrum analysis is a dynamic analysis based on ground motion spectral acceleration. The acceleration usually varies with the period. Since there is no direct input for masses, what you are entering as forces are weights, and STAAD extracts masses from those weights. Hence, the same weight value should be entered in all 3 global directions for general space structures in order to get the natural modes and frequencies correctly.
However this weight input or mass input is going to be used for the seismic load case only and one still needs to define the dead and the live loads separately.
If static loading results needs to be combined with spectrum results, then load combinations maybe used.