In a Dynamic Analysis when defining a seismic load cases and using the command "SPECTRUM" does one use the site specific "Seismic Response Coefficient" Cs based on S1 and Ss accelerations derived from ASCE 7?
For example, if I calculated a Cs = 0.065 (ASCE 7 12.8-2) would the input line be as follows:
SPECTRUM SRSS X 0.065 Y 0 Z 0 ACC SCALE 32.2 DAMP 0.05
Thus, this would be a Seismic Load Case for the X-Direction based on spectral acceleration. Then a load case for each direction in x, y and z, using Cs, would be added to the seismic load case. Is this the correct approach?
Thank you for any input.
The Cs value that you are referring to, is used when computing base shear as per the Equivalent Lateral Force method and is not used in a response spectrum analysis. For response spectrum analysis, you may refer to the section 12.9 of ASCE7-05. The factor that you use for X ( or Y or Z ) while defining a spectrum loading is referred to as a direction factor and is used to factor the input spectrum data.
You will also find lot of good information on response spectrum analysis at
communities.bentley.com/.../2044.staad-pro-response-spectrum-faq.aspx
Thank you Sye. I'm still trying to understand what parameters are entered into STAAD for Dynamic Analysis that pertain to site specific data? Some input must reflect SDS or SD1 correct?