Peak Ground acceleration

[KenStructural]

Does anyone here has an idea with regards to the relationship between Peak Ground Acceleration (PGA) and Short period mapped spectral acceleration Ss per IBC requirement, and the relationship between PGA and UBC zoning, what specific section on IBC and UBC, Thank you,

 

[Bagman2524]

IBC has a short period spectral response Swhich is at 0.2 sec; and a 1 second spectral response S[1]. These are further subdivided into design and maximum values
S[DS]; S[D1] and maximum values S[MS] and S[M1]. IBC doesn't use the term Peak Ground Acceleraion. The S[M]values would be the equivalent. As far as a relationship between the two, IBC has maps for both the 0.2 sec and 1 sec spectral response. The relationship can be determined by comparing the maps for each.

 

[JLNJ]

It sticks in my mind that the Sds values are the traditional peak ground acceleration numbers x 2.5, or the PGA is 0.40 x Sds.

I'm not sure if this is exact or an approximation.

 

[OldPaperMaker]

KenStructural,
In ASCE7-10 go to Chapter 21, sections 21.4 & 21.5 explains where those terms come from.

As far as the relationship between the old UBC seismic zones and the S sub s and S sub 1 from the Risk-Targeted contour intervals you are on your own there.

 

[Hokie93]

JLNJ is correct. The spectral amplification factor is equal to 2.5 for a structure with 5% damping. This factor (2.5) is used in IBC and ASCE 7 but it isn't readily apparent. It does show up, or more correctly the inverse of the factor (0.4) shows up, in Equation 13.3-1 in ASCE 7-05 and ASCE 7-10.

 

[KenStructural]

Guys,

Thanks for the input, how about for UBC is there any relationship between PGA and Ca/Cv,

 

[KenStructural]

is table 16-1 (Seismic zone factor)from 1-4 refers to peak ground acceleration?i cant find any relationship between PCG to Ca and Cv,
thanks