| Applies To | |||
| Product(s): | STAAD.Pro | ||
| Version(s): | All | ||
| Environment: | N/A | ||
| Area: | Analysis | ||
| Subarea: | Response Spectrum Analysis | ||
| Original Author: | Bentley Technical Support Group | ||
I am doing a response spectrum analysis and getting an error "No unsupported masses entered ...". What is the problem ?
There are 3 things you need to check
1. You have not defined any seismic masses as part of your seismic load case. You need to add these as loads and the software internally converts these to masses. You may refer to section 5.32.10.1.1 of the Technical Reference Manual for details. There is an example 11 provided with the software which can also be referred to.
2. You may have included Self weight as part of the seismic mass definition but the density of the material you have used may have been set to 0.
3. All nodes in your model are restrained from vibrating due to supports. You may need to generate additional nodes so that there are some free masses in your structure that can vibrate.
Although the question is specifically related to Response Spectrum but the same is applicable for other forms of dynamic analysis like Modal Calculation or Time History as well.