on the verge of “failure” · on the verge of “failure ... concept:bridge pier foundation part...
TRANSCRIPT
Georges Gazetas
École Polytechnique Nationale d’ Athènes
on the Verge of “Failure”
7 th COULOMB Lecture, Paris 26 June 2009
Seismic Soil–Foundation
Interaction
Topics of Presentation
PART 1
(a) Why Going to the Limit and “Beyond”
in Seismic Foundation Analysis / Design
(b) Conventional versus New Design
Concept: Bridge Pier Foundation
PART 2
The Causes of Overturning
of Buildings in Adapazari (1999)
Seismic Foundation Practice
• Analysis in terms of FORCESFORCES
• Safety through SAFETY FACTORSSAFETY FACTORS
AnalysisAnalysis––Design in terms ofDesign in terms of
DISPLACEMENTS, DISPLACEMENTS, ROTATIONSROTATIONS
“ Performance–Based Design ”
But now TIME has come for CHANGE :
Current Seismic Approach :
“Capacity” Design
(α) Plastic Deformation Allowed Only in
the (Super)Structure
(b) NO “Plastic Hinging” Below Ground:
• Piles, Cap, Footings : Structurally Elastic
• NO Mobilization of Bearing Capacity Failure Mechanisms
• NO Slippage , LIMITED Uplift
Why we need to consider Soil–Foundation Nonlinearity + Inelasticity:
Records in last 20 years: have revealed very strong seismic shaking
Examples:
1994 Northridge : 0.98 g , 1.40m/s
1995 Kobe : 0.85 g , 1.50m/s
1986 San Salvador : 0.75 g , 0.84m/s
and SA values reaching 2 g
Foundation Foundation ““Plastic HingingPlastic Hinging””:: UNAVOIDABLEUNAVOIDABLE
(a)11
(b) Retrofitting Existing/Damaged Structures
Usually Impossible
to Accomplish Elastically
(even if very conservative design required)
Must Consider Inelastic Action in
Soil + Foundation
N small
M very large
Shear Wall
Existing Retrofitted
M
N
M
Uplifting, Nonlinearity:
Significantly affect
the sharing of lateral force
among shear-wall and
frames
Retrofitted
Shear Wall
M
N
(c) Need : Determine Collapse Motion
• for Insurance Purposes
( special projects demanding estimate of
LOSS in worst case )
• for Compatibility
with Structural Design
( Push-over analysis, ductility–based design )
Can we moveCan we move BeyondBeyond
this Conventional this Conventional
““CapacityCapacity”” DesignDesign ?
Major Contribution of Alain Pecker (1998)
“Capacity design principles for shallow
foundations in seismic areas”
Previous Research /Applications
• Pecker (1998): Capacity Design for Foundations
•Paolluci (1998): Inelastic-soil SSI
• FEMA 356 (2000): Rehabilitation Code
• Kutter et al (2001): Centrifuge Experiments
•Martin & Lam (2000): Retrofit of Bridges
• El Naggar et al (2000): Elasto-plastic Winkler
• Pecker et al (2009): Inelastic Macro-element
Factors of SafetyFactors of Safety
•• StaticStatic : FS > 1
• SeismicSeismic :: min FS (t) < 1t
ExternalExternal Force P >> Pu
δ
P
PuElastoElasto--Plastic Plastic Systems :Systems :
(a) if SSTTAATT IICC :: FailureFailure
P
sσ
R
PPP
(b) ii ff SEISMICSEISMIC ::Inelastic
Deformations
(only)
Thanks to the Nature of
Seismic Excitation
K I N E M A T I K I N E M A T I CC
C Y C L I CC Y C L I C
A
m As
ACPu m=
Elastic Response : As < ACP m
u
As
mAC
A
Plastic Response: As = AC PS = Pu
AC
P m
u
Pu m=
Unloading: 0< AS < AC
A
m As P m
u
ACPu m=
Unloading: As = - AC
A
mAC P m
u
ACPu m=
AA
umax
AA >> AC max AS (structure) =AC
umax > uelast
BButut NONO FFailureailure
ACPu m =
AS
(α) Sliding (symmetric, asymmetric)
(b) Uplifting , Overturning
in Geotechnical Engineering
the implications of
Dynamic Safety FactorDynamic Safety Factor
FSFS < 11 :
(c) Bearing Capacity “Failure” ??
N. Newmark:
1965 Rankine Lecture
Ambraseys & Sarma 1967
Seed et al 1967
Richards & Elms 1979
Pecker 1998
Whitman 1964
Current Seismic Codes
• (Gravity) Retaining walls
• Embankments / Natural Slopes
Designed (indirectly) forinelastic deformation ∆ ~ 10–30 cm :
ADESIGN = 1/2 A
W
WADES∆
W
WADES
∆
A(t)
AC = µgSymmetric
sliding
D
Asymmetric
sliding
D
A (t)
AC= µ g cosβ – g sinβ
LefLef kadakada 20032003
D(t)
[m]
-0.2
-0.1
0
0.1
3 6 9 12 15
0.14 m-1
-0.5
0
3 6 9 12 15
1 m
-5
-2.5
0
2.5
5 0.42 g
A(t)
[m/s2]
-5
-2.5
0
2.5
5
AC/A=0.1
0.42 g
V(t)
[m/s]
-0.4
-0.2
0
0.2
0.4
-0.4
-0.2
0
0.2
0.4
Effect of ExcitationEffect of Excitation FrequencyFrequency
Dmax : cm
0
5
10
15
20
25
30
0 1 2 3 4
µ / α = 0.1
µ / α = 0.2
µ / α = 0.4
µ / α = 0.6
µ / α = 0.8
Frequency : Hz
“Factor of Safety”
Rigid Block on a Rigid Base
mAc
mg
Uplifting
Acceleration
Ac = (b/h) gg
Toppling
(under Static Conditions)
θc
b
h
Rocking of Slender Block on Rigid Base
(undergoing a one-cycle sinusoidal shaking)
f ( Hz )0 1 2 3
OVERTURNING
SAFE
AAAA ( g )
4
3
2
11,10 g
= 0,25
bh = 4 b
Static Failure ΑΑΑΑ > 0,25 g
Seismic Failure (with f = 2 Hz ) ΑΑΑΑ > 1,10 g
h A
SPLB
-0.4
0.0
0.4
0 2 4 6 8 10t : s
α : g
Duzce
-0.4
0.0
0.4
0 2 4 6 8 10t : s
α : g
Overturning οf a Slender Tombstone
in the Athens Earthquake : 7 - 9 - 99
0.35 g
0.35 g
Two Hypothetical Base Excitations :
A : g
A : g
Düzce
Overturning οf Tombstone
2 h = 1.27 m , 2 b = 0.20 m , h / b = 6.35 , Ac ≈ 0.16 g
Overturning οf Tombstone
2 h = 1.27 m , 2 b = 0.20 m , h / b = 6.35 , Ac ≈ 0.16 g
SPLB - 0.85 g
-1
-0.5
0
0.5
1
0 2 4 6 8 10
α : g
-0.4
-0.2
0
0.2
0.4
0 2 4 6 8 10θ
: rad
0.85 g
0.84 g
Scaling of the Records needed
to Overturn the Tombstone
Overturning οf Tombstone
2 h = 1.27 m , 2 b = 0.20 m , h / b = 6.35 , Ac ≈ 0.16 g
-0.4
-0.2
0
0.2
0.4
0 2 4 6 8 10
θ : r
ad
0.85 g
0.84 gSPLB - 0.85 g
-1
-0.5
0
0.5
1
0 2 4 6 8 10
α : g
Scaling of the Records needed
to Overturn the Tombstone overturning
at A ≈ 5.3 AC
-0.4
-0.2
0
0.2
0.4
0 2 4 6 8 10
t : s
θ : r
ad0.27 g
0.26 goverturning
at A ≈ 1.7 AC
Duzce - 0.27 g
-1
-0.5
0
0.5
1
0 2 4 6 8 10
t : s
α : g
Düzce
Consequences
(α) Sliding (symmetric, asymmetric)
(b) Uplifting , Overturning
(c) Bearing Capacity “Failure”
Dynamic Safety FactorDynamic Safety Factor
FSFS << 11 :
Simple Model of Bridge Pier
N
B = 6m
Νu≈ 4000 kN
T = 1.5 sec
Su = 130 kPa
Inertial Force
Hs = 20m
h = 12m
Modelling with Finite ElementsModelling with Finite Elements
Beam
Elements
Interface
Elements
Soil and Column: Inelastic
Quadrilateral Solid
Plane–Strain
Elements
Viscous
Boundary
ρVS , ρVS
at x = 20 B
22BB
εpl
σmax
σ
σy0
0
σyσy0
σy0
a a’
S
S1
S3
S2
σmax√23
Limit
surface
Yield
surface
0adev
σy0√ 23
Limiting location
of a
af+ σy0
Nonlinear, Von-Mises Yielding,
Isotropic/Kinematic Hardening ,
Associative Flow Rule
Constitutive Cyclic Model for Soil
1-D Representation 3-D Representation
γ
tt
Calibration against G – γ curves
ττ
soil
Ishibashi & Zhang
0
0.2
0.4
0.6
0.8
1
0.0001 0.001 0.01 0.1 1 10
G/GG/G00
γγ (%)(%)(%)(%)(%)(%)(%)(%)
PI= 30σ0 = 100 kPa
0
10000
20000
30000
40000
50000
60000
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
Reinforced Concrete
d = 3m
C30C30
S400 :100 Ø32Ø13/8.
M : kNm
Curvature : 1/m
Simple Model of Bridge Pier
N
B = 6m
Νu≈ 4000 kN
T = 1.5 sec
Su = 130 kPa
Inertial Force
Hs = 20m
h = 12m
0
1000
2000
3000
4000
0 500 1000 1500 2000 2500
MMultult
N = 1000 kN
zcθθ
Ultimate Vertical LoadΝult
1900 kNmMMulultt
NN
Mu ≈ 1900 kN m
zcθ
N ≈ ¼ Νu
Pseudo–Static Analysis
(constant Ν = 1000 kN)
contact
Qu = Mu / h
1 250 kPa 410 kPa2
570 kPa
3
790 kPa
4
0
0.5
1
1.5
2
2.5
3
0 0.05 0.1 0.15 0.2 0.25
tilt-angle [rad]
mom
ent
[MN
m]
1
2
3
4
(π + 2) Su ≈ 670kPa
6 840
-0.3
0.2
t : sec
A(t) : g
00 2
1
2
4 6
3
4T : sec
R / A
Ricker Wavelet : fo= 0.5Hz and A = 0.30 g
A
0.6 A0.6 A
Pseudo – Static Analysis:
Determine the Yield AccelerationDetermine the Yield Acceleration
AAcc
((i.e., the maximum possible i.e., the maximum possible
acceleration of the massacceleration of the mass))
h = 12m
N = 1000 kN
mAc
Mu ≈ 1900 kN m
Mu = mAch
Ac= 1900 / [(1000 :g ) x 12 ] = 0.16 g
-0.4
0
0.4
-0.4
0
0.4
Excitation: Ricker Wavelet
2 s
0.30 g
0.50 g
free field
rock
Seismic Analysis
Excitation
M N = 1000 kN
Pseudo–Static Failure : M = MuCritical Acceleration : Ac = 0.16 g
Seismic (“Apparent”)
Safety Factor :
Ac /A = 0.16 / 0.50 = 0.32 << 1
Will there be Failure ??
2.2 s
0.4 g
Contours of Plastic Strains
Maximum Acceleration :
0.50 g
Base Excitation :
Ricker TE = 2 sec, PGA = 0.30 g
h = 12 m
M [kNm]
-3000
-1500
0
1500
3000
-0.15 -0.1 -0.05 0 0.05 0.1 0.15
tilt-angle [rad]θ [rad]
h = 12m
terminalterminal
Mzcθ
N = 1000 kN
-0.2
-0.1
0
0.1
0.2
-0.2 -0.1 0 0.1 0.2
zc [m]
θ [rad]
h = 12mM
zcθ
N = 1000 kN
Topics of Presentation
PART 1
(a) Why Going to the Limit and “Beyond”
in Seismic Foundation Analysis / Design
(b) Conventional versus New Design
Concept: Bridge Pier Foundation
PART 2
The Causes of Overturning
of Buildings in Adapazari (1999)
To demonstrate the feasibility of
designing a foundation to
undergo large deformations ,
beyond the conventional wisdom
a Comparative Example:
h = 12m
Stiff Clay
Su = 150 kPa
25m
B = 11 m
mdeck= 1200 t
d = 3 m
B = 7 m
ConventionalDesign
ExploredNew Concept
Pseudo-Static Safety Factors
for a Seismic Coefficient CS = Rd /q = 0.30
Β = 7m FSV = 2.8
FSE = 0.5 < 1
e > B/3
Β = 11m FSV = 5.8
FSE = 2.0
e < B/3
0
0.5
1
1.5
2
2.5
0 1 2 3
Kalamata, 1986
0.27 g
Takatori (Kobe, 1995)0.62 g
Lefkada, 1973
0.52 g
Τ : sec
R: g
ξ = 0.05
uθ
Aff
β
θ
utotuStr
wdyn
Am
BAΕ
Low-Intensity Shaking:
Kalamata Kalamata 19861986
RESULTSRESULTS for the for the RESPONSERESPONSE of the:of the:
((aa)) FOUNDATIONFOUNDATION
((bb)) STRUCTURE STRUCTURE –– FOUNDATION FOUNDATION
SystemSystem
M : MNm
w :m
-0.08
-0.06
-0.04
-0.02
0
-0.01 -0.005 0 0.005 0.01
-100000
-50000
0
50000
100000Β = 7m
-100000
-50000
50000
-0.08
-0.06
-0.04
-0.02
0
-0.01 -0.005 0 0.005 0.01
Β = 11m
-50
-100
100
50
0
FOUNDATION FOUNDATION (( M – θ andand w – θ ))
θ : rad θ : rad
≈ + 2 cm
≈ + 4 cm
-0.2
-0.1
0
0.1
0.2
0 5 10 15 0 5 10 15
u : m
t : sec
Β = 7m
t : sec
utotuθ u
Str
max uStr= 0.10 m
Β = 11m
max uStr= 0.02 m
STRUCTURESTRUCTURE + FOUNDATIONFOUNDATION
uθ uStr utotversus time
RESULTSRESULTS for the for the RESPONSERESPONSE of the:of the:
((aa)) FOUNDATIONFOUNDATION
((bb)) STRUCTURE STRUCTURE –– FOUNDATION FOUNDATION
SystemSystem
Very Strong Shaking:
Takatori Takatori ( ( Kobe Kobe 19951995 ))
0
0.5
1
1.5
2
2.5
0 1 2 3
Takatori (Kobe, 1995)0.62 g
Τ : sec
R: g
0.75TB=7
1.1TB=11
M :
MNm
w:m
-0.04 -0.02 0 0.02 0.04
-0.04 -0.02 0 0.02 0.04-0.3
-0.2
-0.1
0
-0.04 -0.02 0 0.02 0.04
Β = 7mΒ = 11m
-50
-100
100
50
0
θ : rad θ : rad
FOUNDATION FOUNDATION (( M – θ andand w – θ ))
≈ + 20
≈ + 8 cm
-2.5
-1.5
-0.5
0.5
1.5
2.5
0 5 10 15 20 25
-2.5
-1.5
-0.5
0.5
1.5
2.5
0 5 10 15 20 25
u : m
Β = 11m Β = 7m
utotuθ u
Str
t : sec t : sec
Collapse
STRUCTURESTRUCTURE + FOUNDATIONFOUNDATION
uθ uStr utotversus time
Β = 11m Β = 7 m
Comparison of the two Foundation Schemes
Takatori (Kobe, 1995)
Β = 11m Β = 7 m
The Final Stage
0
0.5
1
1.5
2
2.5
0 1 2 3
Takatori (Kobe, 1995)0.62 g
Τ : sec
R: g
1.7TB=7
2.1TB=11
Conventional Solution:
“Capacity” Design
Soil
Plastification
New Concept: Beyond “Capacity”
Design
Plastic “hinging”
ConclusionConclusion
The Main Conclusions
of Part 1
(α) The Dynamic behaviour of
inelastic soil–foundation systems
differs from the
Pseudo-Static response.
Sometimes dramatically
(β) New Design Approach (“Philosophy”) : Plastification
not only in the structure
but also :
at the soil–footing interface
(sliding, detachment+uplifting)
in the supporting soil
(bearing–capacity mechanism)
• Detachment–Uplifting
• Sliding at the Interface
• Mobilisation of
“Bearing–Capacity”
Mechanisms
(c) The following should NOT be a priori “forbidden” modes
FIN
Partie 1
The Overturning of Buildings The Overturning of Buildings
inin Adapazari Adapazari
1999 Izmit [Kocaeli] Earthquake
“ Even theEven the most refined theories
((before they before they can be establishedcan be established))
must be must be VALIDATED byby
COMPARISONS against the against the
REALITY that these theories that these theories
describedescribe …… ””
Istanbul Izmit Adapazari Düzce
Gölcük SapanzaYalova
Avcilar12
November Μ
= 7.2
17 August Μ = 7.5
The Geography of the The Geography of the 19991999 EarthquakesEarthquakes
ADAPAZARI : 17 – 8 – 1999
(α) Seismology; Damage distribution
(b) Soil: the disputed role of fines
(c) Soil: wave propagation analysis
(d) Seismic Analysis of Building Response
Explanation of Toppling, Settlement
12
2326
21
25
12 9
46
PGA PGA (( %% gg ))
Izmit Izmit (( KocaeliKocaeli )) 1717––88––9999
32
YPT
41
SKR
37
DUZ
41 = 0,41 g ≈≈≈≈ 4,1 m/s2
1 km
SKR
River
% ofHeavy
StructuralDamage
PLAN of
ADAPAZARI
Sagario
< 5 %
10 – 20
30 – 50
≥ 50 %
Adapazari
3 km
bedrock
1 km
Anatolian Fault
Sapanca
SW NE
SKR
Sandy SiltAlternating :
Sandy Clay
Typical Soil Profile:
Very Soft/Loose Soils
Small total thickness
of any liquefiable layers
CH / MH
Fill
SM / ML
ML
CH
ML
SM / CL
ML
CH / MH
SP / ML
CH / SM
20 400 0
qc
4
8
12
16
20
24
0.1 0.40
fs : MPa
0 5 10
Rf : %
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30
.
0 2 4 6
Building Width [m ] Number of Stories
Mean
Settlement
[ cm ]
Attempts for Empirical Correlations
by other researchers: Yasuda et al, 2002
80 80
3
H / B
Overturning
00
1 2
2
4
6
Hθ
Β
θo
D [mm]
0
10
20
30
40
50
60
70
80
90
100
0,001 0,01 0,1 1 10
Adapazari
Niigata
Dagupan
Kobe
Fines Sand Gravel% Passing
0
10
20
30
10 20 30 40 50
PI
LL
The fine-grained soils
of Adapazari
SSrr or or SSu u ??
++∆∆uu
M Q
NN
SSrr
εεαα
((σσ11 –– σσ33 )) / / 22
00
SSrr ≈≈ 0.090.09 σσvv
Reinforcement for Reinforcement for
Mat FoundationMat Foundation
-0.5
-0.25
0
0.25
0.5
0 5 10 15 20
t : sec
The Sakarya Record
t : sec
A : g
0.41 g
0
1
2
0 20 40 60 80 100
u : m
-80
0
80
0 20 40 60 80 100
0.41 g-0.5
-0.25
0
0.25
0.5
0 20 40 60 80 100
81 cm/s
0.41 g
2.16md : m
A : g
V : cm /s
t : s
Teverler (Appartment Building)
0
10
20
30
40
50
60
0 100 200 300 400 500
Soil Response : Teverler
Vs : m /s
-0.5
-0.25
0
0.25
0.5
0 4 8 12
0.25 g
Excitation : SKR
-0.5
-0.25
0
0.25
0.5
0.41 g
-0.5
-0.25
0
0.25
0.5
0 4 8 12
0.23 g
Without Pore pressure rise
0.16 g
With Pore pressure rise
-0.5
-0.25
0
0.25
0.5
0 4 8 12
-0.5
-0.25
0
0.25
0.5
-0.5
-0.25
0
0.25
0.5
0.31 g
0.25 g
0.20 g
Possible Ground Motions
1D Equivalent Linear 1D Inelastic Analysis
BWGG
Excitation : SKR
0
10
20
30
40
50
0 100 200 300
Vs : m/s
Dep
th :
mNonlinear Dynamic SFSI Analysis
0
5
10
Fill
Clayey Sand
Sandy Silt
Gravely Silty Sand
Silty
Sand
W.T.
φ = 25ο c = 1 kPa
τ /σv > 0.15 : φres = 3o
φ = 25ο c = 2 kPa
φ = 28ο c = 5 kPa
φ = 30ο c = 5 kPa
P = 275 kN
MQ
0
200
400
600
0 50 100 150
M:kNm
Q : kN
he= (2/3)H
AC = 0.13 g
M = Q he
Deformation Scaling Deformation Scaling = = x 3
t = 17 s
t = 8 s
t = 4 s
This is a Critical Moment
for our Approach:
it predicts Non-Overturning
when in REALITY the building
Overturned !
Many Plausible Causes
(1) Actual Base Motion Stronger
missing NS comp. : “Fault Normal” (FN),
used EW comp. : “Fault Parallel” (FP) :
FN > FP
(2) Soil at D > 20m : Detrimental Roledue to larger soil amplification
(3) 2-D and 3-D wave focusingdue to irregular bedrock geometry
But what about
Out–of–Phase Response of
Adjacent Buildings,
and hence IMPACT Forces ??
Did this Play any ROLE in
Adapazari ??
(4 )
NO Sign of IMPACT between the NO Sign of IMPACT between the 22 buildingsbuildings
impact region
Impact Velocity very small
Insignificant Damage to the Insignificant Damage to the ““HostHost”” BuildingsBuildings
Now what about
the very Presence of Adjacent
Buildings ?
(5 )
MMultult+ >> MM ult
- : due to greater
confinement of the soil
Reversal of Plastic Rotation : Reversal of Plastic Rotation :
inhibitedinhibited
Analysis of 2 Buildings
Buildings Buildings 22 ,, 33
Deformation Scaling : Deformation Scaling : x 3
1Building
2Buildings
t = 4 s t = 4 s
t = 8 s t = 8 s
t = 17 s
v = 17 cm/sv = 12 cm/s
t = 17 s
Let us further explore Let us further explore
this possible role this possible role
by replacing the adjacent building
by its Vertical Pressure
2 Buildings Side by Side
t = 4 s
t = 8 s
v = 17 cm/sv = 12 cm/s
t = 17 s
Teverlelr+Equivalent Load
for the 2ndBuilding
t = 4 s
t = 8 s
t = 17 s
v = 10 cm/s
Any EVIDENCE ??
The Role of the Adjacent Building :
One–Directional Accumulation of Tilt
NO Reversal of PLASTIC Deformation,
Asymmetric Yielding
Here is a
Mechanical
Analogue
0 0.2 0.4 0.6 0.8 1.0
1000
100
10
1
0.1
α / α
∆(cm)
αmax
αmax
∆
∆
0 0.2 0.4 0.6 0.8 1.0
1000
100
10
1
0.1
α / α
∆(cm)
0 0.2 0.4 0.6 0.8 1.0
1000
100
10
1
0.1
α / α
∆(cm)
αmax
αmax
∆
∆
One-Directional vs. Two-DirectionalSLIPPAGE
∆
(cm)
AC /Amax
∆
(cm)
“Lonely” Buildings
did not fail
Buildings surrounded by others
did not fail
… even if they were very
slender !
Any EVIDENCE ??Here is some ( further)evidence :
3
H / B
Overturning
00
1 2
2
4
6
Hθ
Β
θo
Aspect
Ratio
H/B ≈ 3
25 m
15 m
77 77 77 7755 55
11 22 33 44 55 66
2–D Seismic Response of Adapazari
Buildings : Buildings : 11, , 22 + + 33, , 44 + + 55 ++ 66
Deformation ScaleDeformation Scale : : xx 33
11 22 + + 33 44 + + 55 ++ 66
Buildings : Buildings : 44 + + 55 ++ 66
44 66
55
CONCLUSION:
The MAIN CAUSES of FAILURES
1. Large Overturning Moment+ Very Soft Soils :
Bearing Capacity Failure
Lateral Soil Displacement
(squeezing out)
Volumetric Compression
2. Large Periods (T ≥≥≥≥ 2 sec)
of ground oscillation with
A ≈≈≈≈ 0.20 g— 0.30 g
But causes But causes ((11)) and and ((22)) areare
(at least in some of the cases)
notnot sufficientsufficient
to explain the overturning even to explain the overturning even
of very slender buildingsof very slender buildings
3. A key culprit appears to be
the PRESENCE of ADJACENT
Buildings !One–Directional Accumulation of Tilt
- as with downward sliding on INCLINED plane,
- in contrast to the symmetric sliding
on HORIZONTAL plane.
Ioannis Anastasopoulos
Nikos Gerolymos
Marios Apostolou
Marianna Loli
Evangelia Garini
This presentation was possible only
thanks to my co-workers at NTUA:
Merci Beaucoup
Pour votre attention
F I N