Seismic Load for Underground structure
Seismic Load for Underground structure
(OP)
This sounds silly but Is there a seismic load for structure below the ground level? I.e. a 3m x 3m x 2m block foundation and embedded 1.5m below the soil. My colleagues calculate the seismic force as a factor (0.1~0.4) of the foundation weight using Table 18-I-C of UBC 94; I think this is wrong. In my opinion, think there is no seismic load for portion of structure below ground level. Please correct me.






RE: Seismic Load for Underground structure
Regards,

Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: Seismic Load for Underground structure
The lateral support for the structure however is guite a bit better than for one above ground.
RE: Seismic Load for Underground structure
RE: Seismic Load for Underground structure
RE: Seismic Load for Underground structure
RE: Seismic Load for Underground structure
You must transfer lateral and vertical load via a path into the ground. Unless the concrete block is keyed into rock, how does it transfer lateral load to the surrounding soil? In my opinion - in one or two means or a combination thereof. first is the passive pressure of the earth on the footing and the second is the friction at the base of the footing. If the ground moves independently of the foundation you can't use the passive pressure and you're left with friction. Since the frition is acting at the base of the concrete block why isn't the inertial force of the block considered? It should be.
If the friction is found to be insufficient then you should use anchors or something similar to provide a positive connection into the soil.
Regards,

Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: Seismic Load for Underground structure
RE: Seismic Load for Underground structure
RE: Seismic Load for Underground structure
You can also model the interaction behavior of soil and structure but the results would be much dependent of some unknown soil factors :( !
in your case, if the soil around the foundation are adequately compacted, I guess that there would be no need to worry about the earthquake load on the foundation.