Could someone please confirm that scaling the Response Sectra Analysis generated in RAM Frame using the Indian Standard IS 1893:2016 code does not include an adjustment for the Zone Factor, Z? If this is the case, I would assume the scale factor should be what some call the direction factor = (Z/2)*(I/R)?
This scale factor was recommended for STAAD.Pro with Response Spectrum (https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/12317/is-1893-part-i-2002-response-spectrum-philosophy)
The current FAQ on this subject only mentions scaling by I/R which would apply to ASCE 7 for example (https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/4029/ram-frame---dynamic-analysis-faq).
I would also note that if this is the correct starting scale factor, I'm assuming an iterative approach needs to be taken using this factor on the first run, then comparing with the base shear from the equivalent static method (some would interpret this to mean using a dynamic analysis but with Ta fundamental period as used in equivalent static method) and adjusting the scale factor so that at least that base shear is maintained as a minimum (IS 1893:2016 7.7.3).
Thank you,
Dan
That all sounds correct to me. I will double check on the first point with one of my colleagues in India, but the scaling of the dynamic load case so not to exceed a threshold minimum is common to all the codes.
Answer Verified By: Daniel Slegh
I would like to add that in STAAD.Pro, we have -
(Z/2)*(I/R) can be used as direction factor or scale factor. Generally, we use that as direction factor.
If you provide a IS 1893 Seismic definition, STAAD.Pro can compare base shear obtained for RSA and static method.
Vb/VB will be computed by the program internally and all the response quantities from RSA will be multiplied by this ratio (Vb= RSA base shear, VB= static base shear)
Thank you for the info regarding STAAD implementation. At the moment we are using RAM but we intend to use STAAD also on certain projects; so we will use this. And I assume that you actually mean scaling by the ratio VB/Vb as response spectra base shear is often lower than the static base shear and needs to be scaled up to at least match the static base shear.
Ok, I think this is makings sense, but please do let me know if your colleagues familiar with Indian implementation in RAM would give any unique advice for our design. We will be using RAM for the analysis and then doing the code check/design in Advanced Concrete / RCDC.