Sesimic Base Shear

[SteelPE]

Here is a very silly question:

When designing a foundation system on piles and caps, do you have to consider the weight of the foundation system and slab load (if used for storage) when calculating your seismic base shear? This base shear would only be used to check against the lateral load capacity of the foundation system (using the lateral resistance of all the piles or the passive resistance of the dirt against the exterior grade beam).

 

[vandede427]

I would say no, don't count them.


p.s. there's no silly question in engineering

 

[OHIOMatt]

I would say that it depends on the soil. I have designed pile supported structures were the existing soils had a high potential for liquefaction. This meant that the top third of the soil (based upon pile length) could not be used for lateral resistance. I ended up employing the use of battered piles and had to consider the weight of the foundations and a portion of the soil in the design.