Converting USGS seismic parameters to Canadian Code parameters

[Olafo1971]

I'm working on project in Haiti. I have been able to obtained the Ss and S1 which are equivalent to Sa(0.2) and Sa(1.0) respectively in the Canadian Building Code.
However, I need to obtain Sa(0.5) and S(2.0). Any idea on how to get these values from Ss and S1?

 

[TLHS]

Do you actually need them? What are you designing and what's its period? Until you start doing dynamic analysis, or things with larger periods you can usually get away with just the short period (0.2sec) values as they end up governing by a significant margin.

Also, those values aren't directly equivalent. Canadian and US tabulated values are calibrated to different site classifications (Canada tabulates/reports values for class C, US tabulates/reports values for class B). You have to compensate for that. Basically, if you have US values, you have to apply the factors necessary to get it to site class C. Then you have the Canadian equivalent values.

 

[Olafo1971]

Thanks for your reply TLHS.
I have checked and you are right. This is a two story 700m2 building and I'm using the Equivalent Static Force Procedure. The procedure includes a variable called Mv.
Mv depends of Sa(0.2)/Sa(2.0) but I don't have Sa(2.0). This is why I'm looking for those values.

 

[TLHS]

The US code uses fewer data points for their spectrum, so if you only have inputs from them you're a little stuck. If you have no source for a two second period, I would take half the one second period acceleration. This is in line with how ASCE builds their spectrum (higher period accelerations are the one second acceleration divided by the period, so in this case it would be divided by two). This also looks to be about right or conservative if you flip through the design values in the back of the NBCC for various locations.

Realistically, though, you still don't need any of that for low period structures. Mv is equal to one for anything with a period less than or equal to one second.

 

[cnorvell]

If you use the USGS seismic design application to obtain your S[sub]DS[/sub] and S[sub]D1[/sub] values, the "Design Maps Summary Report" that the application outputs shows the design response spectrum. If you need S[sub]a[/sub] values for periods of 0.5 s or 2.0 s, just read them off of the design response spectrum plot.