Soil-Structure Interaction

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Main Question or Discussion Point

Stiff soil like tuff rock is said to be in resonance with short storey buildings (like 2 to 3 storey).. meaning during seismic movement the response in the short storey buildings would be greater. Is there any formula that can relate the two... like does stiff soil has the same frequency as short storey buildings when they shake??
 

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  • #2
davenn
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Stiff soil like tuff rock is said to be in resonance with short storey buildings (like 2 to 3 storey).. meaning during seismic movement the response in the short storey buildings would be greater. Is there any formula that can relate the two... like does stiff soil has the same frequency as short storey buildings when they shake??

Hi ya

I'm not going to personally give an answer when there is so much more professional info online
have a look at some of these links


https://www.researchgate.net/publication/237709756_Seismic_Response_at_Soft_Ground_Sites_Bay_of_Plenty

https://www.researchgate.net/publication/321036988_Experimental_Study_on_the_Seismic_Response_of_Subway_Station_in_Soft_Ground

https://www.ijser.org/researchpaper/Evaluation-of-seismic-response-of-a-building-with-soft-story.pdf

https://www.pwri.go.jp/eng/ujnr/joint/33/paper/61sato.pdf

https://pubs.usgs.gov/of/1996/ofr-96-0263/localeff.htm

http://users.ntua.gr/gbouck/downfiles/geot_earthquake_eng_Ch4-SITE-ADERS-10.pdf


There's just a small collection of dozens of sites


Dave
 
  • #3
Baluncore
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Is there any formula that can relate the two... like does stiff soil has the same frequency as short storey buildings when they shake??
For a specified seismic wave, the frequency spectrum of the vibration is the same, but the amplitude of oscillation is greater in slower rocks.

The foundations of small buildings do not need to be deep, so are often just the low velocity surface soil covered by a concrete slab. The foundations of tall buildings are dug well down below the low velocity weathered soil, onto deeper fast rock.

So small buildings tend to be shaken by greater amplitude waves than tall buildings. A tall building built on a low velocity rock, such as a volcanic tuff, will be shaken significantly more than if it were securely founded on a fast granite.
 
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For a specified seismic wave, the frequency spectrum of the vibration is the same, but the amplitude of oscillation is greater in slower rocks.

The foundations of small buildings do not need to be deep, so are often just the low velocity surface soil covered by a concrete slab. The foundations of tall buildings are dug well down below the low velocity weathered soil, onto deeper fast rock.

So small buildings tend to be shaken by greater amplitude waves than tall buildings. A tall building built on a low velocity rock, such as a volcanic tuff, will be shaken significantly more than if it were securely founded on a fast granite.

What physics principle why the amplitude of oscillation is greater in slower (you mean low velocity?) rock?
 
  • #5
Baluncore
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Fundamentally it comes down to the energy density of the wave propagating through the material. At half the velocity of propagation, there is twice the energy present per unit length of the propagation path. That implies a higher amplitude.
 

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