CE 573: Structural Dynamics
HW#6 Supplemental Problems
Problem #1
Given
:
A popular method for limiting the effects of earthquakes on structures is to base
isolate
them;
that is, to put in supports underneath the structure that isolate the main part of the structure from the
ground. To understand why base isolation works so well, consider the following pair of structures
.
Structure (1) is unisolated, with
and
. Structure (2) is isolated using a
base slab having a total mass
and a series of rubber bearings having a total stiffness
. (The building properties for (2) are the same as (1).)
3000 kg
b
m
=
3
750
10
N/m
b
k
=
×
2000 kg
i
m
=
3
50
10
N/m
i
k
=
×
Required
:
(a) For Structure (1), estimate the maximum base shear of the building using the
pseudospectral acceleration design spectrum shown below.
(b) For Structure (2), estimate the maximum “base” shear of the building with respect to the isolator slab.
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 Fall '05
 Whalen
 Earthquake engineering, maximum base shear, design spectrum, Structural Dynamics HW, shear frame structure, shear frame model

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