| 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 an analysis with response spectrum loads. I also need to define compression only springs to simulate soil support. How can I do this ?
Response Spectrum loading, due to it's very nature, does not lend itself to any iterative type analysis ( Tension/compression, Pdelta etc.). So the short answer to the question is, response spectrum loading cannot be used in conjunction with compression only springs.
However you may do a couple of things.
First option is to define the support springs without compression only attribute to analyze the response spectrum cases and other primary cases ( live load, equipment load etc.). Use PERFORM ANALYSIS and CHANGE after that. Subsequently re-define the support springs with compression only attribute followed by REPEAT LOADs to combine the primary cases. For combining the response spectrum cases with other loads, you still have to use LOAD COMBINATION. Once all REPEAT LOADs and LOAD COMBINATIONs ( for response spectrum combos only ) are defined, follow it up with another PERFORM ANALYSIS and CHANGE.
Other option is to use equivalent static seismic loads to represent seismic loads as opposed to using a response spectrum load in which case you would be able to use REPEAT LOADs and compression only springs to combine gravity+seismic loads. You may scale the equivalent static seismic loads by the ratio of the base shears ( equivalent static base shear/ response spectrum base shear).