Geoscience Reference
In-Depth Information
The EUROSEISTEST project (Pitilakis et al., 2005) provided a reference site and struc-
ture for the NEMISREF studies of site effects. The heavily instrumented test site of
EUROSEISTEST is established in the epicentral area of the Thessaloniki 1978 earth-
quake (
M
s
5), 30km northeast from Thessaloniki, an active graben with an annual
extension rate of a few millimetres. The soft-loose soils at the surface have shear wave
velocity
V
s
<
=
6
.
160m/s.
The EUROSEISTEST research infrastructure includes two instrumented reinforced con-
crete model structures (scale 1:3), with surface foundations, in the centre of the valley:
afive-storeyreinforcedconcretebuildingwithinfillmasonrywallsandapierbridgewith
deck. Forced vibration tests, short and long distance deep blast tests and pull-out tests
have been performed, and a few records of small real earthquakes are also available.
The single degree of freedom sway frame model of the EUROSEISTEST structure used
in the shaking table tests is shown in Figure 6.8. The model sits on the surface of a
bed of Hostun sand in a shear stack (Crewe et al., 1995) with dimensions: 1.19m long,
0.55m wide and 0.81m deep. The shear stack (or laminar box) is constructed from a
series of rectangular aluminium box section rings. Each ring is separated from the rings
aboveandbelowbyneopreneblocksinsuchawaythattheboxhashighflexibilitywhen
shaken in its long direction and can, as far as possible, permit the sand mass to deform
as if it were an infinite free field. When empty the shear stack has a resonant frequency
ofabout7.7Hzwith3%damping.Whenfilledwithdrysand,pluviatedtoavoidratioof
about0.76(relativedensityabout70%)theresonantfrequencyisabout26.5Hzwith8%
damping.
The model ontheshearstackwasshaken ontheBristol6-axisshakingtablewhichhasa
3
3m working platform controlled by eight 50kN actuators (Crewe, 1998). The tests
described here were all controlled to generate purely unidirectional horizontal shaking
alongthelongaxisoftheshearstack.ExperienceatBristolhasshownthatthedistribution
ofmassontheshakingtableinalmostanymodelmeansthatthereisaseriouslikelihood
×
Fig. 6.8. Model singledegree offreedom structure: dimensions inmm
