Unformatted text preview: 1.0 in all frequencies.
This indicates that the
horizontal F.I.M ∆ is always
less than the response Us of
the ground surface.
Two troughs are observed
around the first and the
second natural frequencies
of the surface stratum.
Because the foundation footing or the basement
possesses normally much higher rigidity than that of the
surrounding soil and the growth of the response of the
surface stratum is restrained, ∆ forms the troughs at
around the natural frequencies. The differences in the
horizontal F.I.M are small between both foundation types. The rotational F.I.M
becomes larger with
increase of frequency. Because the real part of the
rotational D.I.F for the pile
foundation is much larger
than that for the raft
foundation, the rotation
motion of the pile foundation
is more restrained and Θ of
the pile foundation becomes
smaller than the raft
foundation. 3.6 Response Characteristic
Resonance curves UT at the roof floors are shown with
increase of number of floor . Magnification factor (M.F)
denotes UT/2Eo , where Eo is the amplitude of the
incident SH wave. M.F for the n=5 building
on the raft foundation
have two resonance
peaks.
The lower resonance
frequency is 1.25 Hz
1.25Hz
which corresponds to the
2.25Hz
first natural frequency of
the surface stratum.
While the higher is 2.25Hz
corresponding the natural
frequency of the coupling
system of a building, a
foundation and ground.
With increase of the number of floors n, the natural
frequency of the coupling system becomes lower and
approaches to the first natural frequency of the surface
stratum 1.25 Hz. The natural frequency of
the coupling system
approaches to that of the
surface stratum, two
peaks converge...
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This note was uploaded on 03/14/2014 for the course CE 5680 taught by Professor Drgrd during the Summer '14 term at Indian Institute of Technology, Chennai.
 Summer '14
 DrGRD

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