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andfinallythefarmostrightpartofthefoundationthatupliftsu R
4m.Although
the situation is qualitatively similar with loose sand, uplifting is much less exten-
sive
(
u R
1m
)
.Theeffectivewidthofthefoundation,i.e.incontactwiththesoil,
19m.Andthedifferentialsettlementisabout2minbothcases.
(3) For the fault emerging (without SFSI) near the right edge of the foundation (S
isnow:b L =
b C
=
16m, or S
80), we see again diversion, diffusion, and a minor bifurcation
oftherupturepathforh
/
B
=
0
.
5%.Therightbranch(whichisthemostsignificant)
diverts slightly towards the footwall by about 2-4m, while the (barely noticeable)
left branch is diverted towards the hanging wall (
/
H
=
3m). But a clear significant
difference isnoted between theloose and dense sand cases:
The fault scarp that is formed near the right edge of the building is conspicuous
only with loose sand.
On dense sand, the middle part of the building loses contact with the bearing
soil, u C
11m, while the left and right part of it remain in contact, b L
2m
7m.
On loose sand, the response is quite favourable: not only is the dislocation
diverted by more than 4m and outcrops beyond the right edge of the struc-
ture, but full contact is maintained over the whole length of the soil-foundation
interface.
The distress of the foundation is thus significantly less with loose than with
dense sand. Also smaller on loose sand is the (rigid-body) rotation of the foun-
dation.
and b R
Such a good response of a building on loose soil on the “hanging wall” is reminiscent
ofseveralsuccessstoriesfromtheKocaeli1999earthquake,especiallyofthebuildingin
Denizerler across the entrance from the Ford factory, near Golcuk (see Anastasopoulos
and Gazetas, 2007).
(4) Although not shown here, the effect of an increase in the number of stories from 2
to5isquitebeneficialonloosesand,butalmostnegligibleondensesand.Themost
significant benefits are the decrease of foundation rotation (and of building tilting)
and the elimination of a large part of uplifting. As a consequence, the survival of a
“heavy” buildingontopofamajorfaultruptureinloosesoilseemsquitepossible,
in qualitative accord with numerous such success stories in several earthquakes.
2.3. NUMERICAL ANALYSIS AND RESULTS: DEEP FOUNDATIONS
Whereas piles are used for protecting structures by helping to keep total and differential
settlements small, their role in supporting structures straddling seismic faults is far from
clear. Scant (perhaps only circumstantial) evidence from recent earthquakes has impli-
catedthepilesinsomestructuraldamage—seeforexampletheanalysisofthedamageof
the pile-supported Attaturk Stadium in Denizerler during the Kocaeli Earthquake (Anas-
tasopoulosandGazetas,2007a,b).Systems“tied”tothedifferentblocksofthefaultmay
indeed be vulnerable. An interesting analogy has been brought to our attention by Pro-
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