PGA for liquefaction analysis
PGA for liquefaction analysis
(OP)
What is the correct PGA for seismic analysis?
1. (Ss/2.5) x Fa as indicated in ASCE 7-02 and 7-05
or
2. Sa/2.5 as indicated in the 2009 NEHRP Seismic Provisions and IBC.
1. (Ss/2.5) x Fa as indicated in ASCE 7-02 and 7-05
or
2. Sa/2.5 as indicated in the 2009 NEHRP Seismic Provisions and IBC.





RE: PGA for liquefaction analysis
ASCE 7-05 will be applicible to 2006 IBC and 2009 NEHRP will be applicible to 2012 IBC.
RE: PGA for liquefaction analysis
RE: PGA for liquefaction analysis
RE: PGA for liquefaction analysis
RE: PGA for liquefaction analysis
It seems to me that the NEHRP incorrectly identifies the PGA (amplified for soil effects) for liquefaction as (SDS/2.5) because the SDS value includes the 2/3 seismic margin appropriate for structural design only.
Still unclear on appropriate value, but I've heard that Section 11.8.3 of ASCE/SEI 7-05 correctly identifies the PGA for liquefaction evaluation as (Ss/2.5), which would then be multiplied by the published site coeficient (Fa) to account for soil amplification effects.
RE: PGA for liquefaction analysis
I should have indicated the following in the initial posting for bullet item 2:
......
2. The IBC and 2009 NEHRP indicate peak ground acceleration to be used in liquefaction analysis as (SDS/2.5); which I assume would be Amax.
RE: PGA for liquefaction analysis
RE: PGA for liquefaction analysis