Earthquake Engineering Research - HKU Libraries - The University ...

438
The effectiveness of the seismic isolation system in multi-story buildings has been well proved and
realized. However, until recently few research efforts have been directed toward the application of
seismic isolation system in spatial structures.
The most commonly used seismic isolation device for multi-story buildings is a combination of
laminated rubber isolators to elongate the natural period apart from the dominant period of earthquakes
and dampers to absorb vibration energies (AD, 2001). Kato et al (1998) attempted to apply such an
isolation system in spatial structures and confirmed its effectiveness analytically in reducing seismic
response of a 300m span dome. However, the dynamic properties of laminated rubber isolator is
known to vary depending on many factors, such as the weight of super-structure, strain level,
temperature and so on. It is generally difficult to elongate the natural period of commonly used seismic
isolation devices sufficiently long to be applied to spatial structures with light weight and relatively
long natural period (typically 1 second or so). In order to lengthen the natural period of the isolator
without a restriction on the mass of super-structure or mechanical properties of the materials of device,
Kawaguchi and Tatemichi (2000) proposed the "paddle isolator", a kind of rocking pendulum, and
realized the isolator with a natural period up to 4 seconds.
In the present paper, the use of a seismic isolation system with sliding mechanism is proposed for
large-span spatial structures. Such an isolation system can be realized, e.g. by an elastic sliding device
composed of a laminated rubber isolator with Teflon sheet attached to the bottom and placed on
stainless plate, which is usually combined with commonly used laminated rubber isolators to give
restoring forces after sliding. In order to confirm its effectiveness in reducing the seismic response,
shaking" table tests are performed using a small-scale arch model. The test results are utilized to
validate the simulation method, which is then applied to investigate the seismic response of a 200m
span latticed dome supported by the base-isolation system. The effectiveness of the proposed seismic
isolation system is demonstrated to reduce the dome response under strong earthquake motions.
SHAKING TABLE TESTS FOR SMALL-SCALE ARCH MODEL
Test Model
In order to confirm the effectiveness of the
proposed seismic isolation system, shaking
table tests were performed using a
small-scale arch model composed of
polyvinyl chloride (PVC) sheet and a pair of
aluminum tie rods, as shown in Fig. 2.1. The
arch is hinge-supported along the bottom
sides on a pair of horizontal edge beams
which are roller-supported on a stainless
plate and connected through 4 springs to the
shaking table. A twin model of non-isolated
arch was also manufactured which is
hinge-supported directly on the bed of the
shaking table. The material and mechanical
properties of the model were selected such
that the fundamental natural period of the
model is close to that of this type of structure.
Roller:
Shaking tabl*
FIG. 2.1
TEST MODEL