Fa and Fv values for site class F (site specific response spectrum)

[compe_ad]

ASCE 7-16 Section 21.4 specify that the design acceleration parameters should not be less than 80% of the values determined from section 11.4.3. Ss and S1 are not site specific and can be calculated from available maps. For calculating SDS and SD1, Fa and Fv are required which depends on the site class. And for site class F, these values are not provided in the table 11.4-1 and 11.4-2. How would we approach in this situation? Please provide reference as well. Thanks

 

[HTURKAK]

The determination of Site Class procedure should be with the following steps ;

1- Any site if satisfy one of the conditions is (at 20.3.1 Site Class F. ) the site shall be classified as Site Class F
- Soils vulnerable to potential failure or collapse under seismic loading, such as liquefiable soils ..
-Peat and/or highly organic clays [H > 10 ft (3 m)];
- Very high plasticity clays [H > 25 ft (7.6 m) with PI > 75]
- Very thick soft to medium stiff clays [H > 120 ft (37 m)] with su < 1,000 lb/ft2 (50 kPa)

2-Look to the preceding exceptions for each conditions if met,follow the procedure defined at exceptions. That is , no need to site specific study.

3- If the preceding exceptions are not met , a site response analysis shall be performed for sites determined to be Site Class F.(Section 21.1)
(For sites classified as Site Class F requiring site-specific analysis in accordance with Section 11.4.7, the design spectral response acceleration at any period shall not be less than 80% of Sa determined for Site Class E in accordance with Section 11.4.5.)






According to the grace of God which is given
unto me, as a wise masterbuilder, I have laid the foundation, and another buildeth thereon. . . .
I Corinthians 3:10