RR 21.03.00-3.1 Response Spectra per IBC 2018 / ASCE 7-16
Automatically generated response spectra loads per IBC 2018 / ASCE 7-16 are now available in STAAD.Pro.
The spectral acceleration data is now retrieved using the USGS dynamic web service (where as in older editions of the code this was extracted from text files made available from the USGS).
- Exceptions 1 in Clause 11.4.8 of ASCE 7-16 is implemented. In exception 1, for Site class E and Ss > 1.0, Fa value is taking the same for site class C. In this case, there is slight reduction in the seismic force generated.
- The exception of Clause 2 in 11.4.8 of ASCE 7-16 is not implemented in STAAD.Pro for response spectra.
- The vertical ground motion for seismic design as described in clause 11.9 is not implemented as the program cannot determine the vertical time period, Tv.
- ASCE 7-2016 Clause 18.104.22.168 stipulates that if the combined response for modal base shear, V, is less than that of the calculated base shear from the equivalent lateral force procedure, Vt, then the response spectra values should be scaled up by V/Vt. STAAD.Pro does not automatically check this nor increase the response quantities in this situation. You can check this by simply analyzing the static seismic load case and comparing the base shear values. The X, Y, or Z factors for the response spectrum can be then increased accordingly if required.