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Bouckovalas (1998). It is reminded that, in its present status, this method requires sys-
tematic verification with respect to one basic assumption which may distort analytical
predictions significantly: the simplified modeling of the liquefaction-induced shearing
resistance degradation in terms of an equivalent degraded friction angle
tan
−
1
ϕ
=
)γ
.Further-
more,ananalyticalcomputationoftheexcessporepressureratio
U
,whichwilltakeinto
account the existence of the structure,needs tobeestablished.
γ
∗
=
(
[
(
1
−
U
)
tan
ϕ
o
]
oranequivalentreducedeffectiveunitweight
1
−
U
So far, our effort to obtain experimental evidence for a quantitative evaluation of the
above methodology was not successful. The main reason is that, with a few exceptions
(e.g.Yasuda,2004),allcentrifugeandshakingtableexperimentsretrievedfromthelitera-
turedidnotproceedbeyondtheevaluationofearthquake-inducedsettlementsandexcess
porepressuresinthefoundationsoil.Inotherwords,itwasnotpossibletofindwelldoc-
umented experiments where the footing was driven to a static bearing capacity failure,
immediately after theend of shaking, while the subsoil was stillat a liquefied state.
Hence, wereliedonthenumericalevaluationofthepost-shakingbearingcapacity, using
the fully coupled, effective stress, solution algorithm presented in the previous chapter.
Morespecifically,Figures11.12and11.13comparetheanalyticallyandnumericallypre-
dictedvariationofdegradationfactor
ζ
againsttheexcessporepressureratio
U
.Thefirst
figurereferstoproblemparameters
(
N
,
a
max
,
T
,
q
,
Z
liq
)
whichshouldhaveonlyanindi-
rect effect on the
-
U
relation, through the excess pore pressure ratio
U
, while the sec-
ond figure refers to the remaining parameters (
H
ζ
/
B
,
C
u
and
D
r
) which are analytically
Fig. 11.12. Comparison between numerical and analytical predictions ofthe bearing
capacity factor
ζ
for various combinations of seismic motion characteristics
(
a
max
,
T
,
N
)
, foundation loads
(
q
)
and thickness of liquefied subsoil
(
Z
liq
)
