Dear reader we were discussing about seismic site classification according to IBC. In previous part we have discussed about all site classification; of which some clarification is required:
In defining site classification we depend on v̅S, N̅, and s̄u where
v̅S= Shear wave velocity of soil at site (ft/s)
N̅= Resistance against standard penetration
s̄u= Undrained shear strength of corresponding soil (psf)
Though site class E is defined based on shear wave velocity, standard penetration resistance and undrained shear strength, if any profile with more than 10 feet of soil having the following characteristics should also be treated as site class E:
So shear strength, resistance against standard penetration and shear wave velocity are required to classify site according to IBC. In some class like E and F plasticity index, moisture content, organic content are important though these properties are relatively simple to determine.
In some cases, when we have no sufficient details about site soil, it is recommended to define site as site class D. But we can assume this only when geotechnical data or building officials ensure that site do not fall in the class of E/F.
When a site cannot be classified as Class F, this site can be taken as site class E under following conditions: