SPECTRAL RESPONSE ANALYSIS: scale factor in ETABS

[OSE]

Dear all,

I am analyzing building by ETABS software. In seismic analysis, I am using UBC curve for spectral response analysis (SRA).

as far as I know with SRA: Generally, Seisemic Force F = m*Sd(T)*f where: m: mass; S: spectral function; f: factor;

I have ever used EUROCODE, in this code, showing equation of spectral function Sd(T)= ag*f(a,b,T). And when using ETABS for analysis, depending on choosing each Sd curve I have a scale factor. For example: if I choose S'=f(a,b,T), scale factor = f*ag;

from 1), I think when using UBC for analyzing, I have a solution as the same as above solution.

But in UBC,I only found the spectral curve, didn't find equation of spectral curve. So I am not sure about the scale factor in ETABS;

Could you kindly give me an explanation!

I look forward to hearing from you.

 

[edwin17th17]

not sure about etabs..

but for risa3d, we usually do STATIC seimic base shear.. then response spectra base shear reaction.. then scale down the dynamic base shear by the ratio on the load combination factor..

 

[OSE]

Thanks for your prompt reply.

Could you explane more detail about the way you have used with risa3d?

 

[edwin17th17]

it's been a while since i last used risa3d.. but if i remember it right, you just put something like i think sds and sdm (not sure).. anyway after i put that.. you just run response spectra (dynamic analysis) then get support reaction and ratio it to manual static base shear..

then scale down the res spec on the load combination using the ratio..

this scaling down of dynamic base shear is in the code..

the only thing that varies here is how you compute response spectra per software you use..