earthquake design
earthquake design
(OP)
when designing a structure for earthquake, would the earthquake forces be higher at the top of the structure or at the base? or would the earthquake loads be dependent of the dead loads on the specific floor? thanks






RE: earthquake design
TTFN
RE: earthquake design
RE: earthquake design
RE: earthquake design
The seismic design using international codes and standards can be done using an equivalent static method or dynamic analysis.
The equivalent static method calculates seismic forces, which is normally higher on the top and reduces as you go down the structure.
HTH
RE: earthquake design
It should also be noted that the above assumes a linear elastic relationship. Large displacements don't always imply large forces!
Regards
RE: earthquake design
RE: earthquake design
TTFN
RE: earthquake design
If I remember right there are two separate kinds of seismic waves that are generated, "S" and "P". The "S" wave is horizontal or a shear wave that moves the base of the building back and forth. The "P" wave has a vertical component like a water wave, and in thick gravels produces ground waves which are apparently very disconcerting to see. I did a search on "Seismic Forces" and found this site, based in California, that provides free information.
http://www.atcouncil.org/
roger
RE: earthquake design
Yes, there are those 2 waves. Yes, the foundation must be designed to withstand the seismic load expected in that location. Otherwise the seismic effect will not get into the building but the foundation will just stand there and let the earth wiggle under it!!
FL Wright claims to have designed his Tokyo Hotel that way. It may have been an accident but that is the way the building sitting on long piles, reacted.
And why not create a new thread here, called Seismic, or Seismicity??
Evank
RE: earthquake design
RE: earthquake design
Yes you are right. Frank Wright was on goo so put his stiff buildings on piles and let the goo vibrate around them under their stiff cap. I wonder if he really expected that.
But to the origianl question--surely the foundation has to be designed to accept and handle the seismic ground motion. Since the earth will move it must lean on the footings as it moves so they should not skid around nor break up unless you are designing a floating building. Which can be done.
EvanK
RE: earthquake design
If you have more mass and rigidity in one point that in another point. The point with more mass and rigidity absorb more energy and have to have the capacity to send these energu to others poinst of the structure.
A hand rules: soil rigid lihe rock or similar flexible ( beams and columns) structure, soil flexible like clay rigid strcuture like tube, shear wall and so on.
RE: earthquake design
RE: earthquake design
Yes the foundation has to be designed to accept the lateral load. Usually this is done through bending in deep foundations, or friction in spread footings.
RE: earthquake design
RE: earthquake design