behavior of massive earth retaining walls …se.sze.hu/images/ngb_se005_4/2_massive earth retaining...

BEHAVIOR OF MASSIVE EARTH RETAINING WALLS UNDER EARTHQUAKE SHAKING Comparisons to EC-8 Provisions

U N I V E R S I T Y O F P A T R A SD E P A R T M E N T O F C I V I L E N G I N E E R I N G

L a b o r a t o r y o f G e o t e c h n i c a l E n g i n e e r i n g

Győr, October 2015

Prof. G. AthanasopoulosV. Kitsis, MSc

V. Vlachakis, MScProf. A. Athanasopoulos – Zekkos

MASSIVE EARTH RETAINING WALLS

Free standing Components ofinfrastructure works

1. INTRODUCTION

An earth retaining structure may be:1) yielding (translation/rotation is allowed)2) non-yielding (restrained against movement)

1. INTRODUCTION

BackfillWall

Pstatic

PEarthquake

Pinertia

Components of thrust:1)Static earth pressure, Pstatic

2)Dynamic earth pressure(increment), Pearthquake

3)Wall inertia, Pinertia

Design of the wall(must know):1)Magnitude of each component & point of application2)Phase differences

2. YIELDING RETAINING WALLS

Harmonic excitationf = 3Hz, ag= 0.05g, 0.10g, 0.15g, 0.20g, 0.30g, 0.40g, 0.70g

Two cases were analyzed

Time histories of recorded earthquakes: a) Erzincan, Turkey, earthquake,(1992) & b) Loma Prieta, USA, earthquake (1989)


Numerical models of gravity wallsValidated through comparisons to centrifuge results by Nakamura (2006)

Athanasopoulos – Zekkos et al. 2013, Soil Dynamics and Earthquake Engineering 55, 59 -70


Seismic response of backfill

The computed horizontal acceleration at point A is used as the meanbackfill acceleration.

Α


Seismic response of backfill for H = 4m



Seismic response of backfill for H = 7.5m

Distribution of computed peak active earth pressures along theheight of retaining walls and comparison with the M-O method.


≈1/2≈1/2

Dyn. Increm. EC-8, Part 5,§ 7.3.2.3

Dyn. Increm. EC-8, Part 5,§ 7.3.2.3PNum ≈ PM-O

EC-8, Part 5, Annex E.4

Phase difference between seismic thrust and wall inertia

The phase difference is described by the ratio Δσ /Δσmax

where:Δσmax: maximum value of seismic increment of soil pressure at

the middle of the wallΔσ: value of seismic increment at the instant of maximum

wall inertia


Normalized value of dynamic earth thrust (compared to its maximum value)acting at the instant of maximum wall inertia (Η = 4.0m)

Backfill acceleration (g)


Backfill acceleration (g)


Normalized value of dynamic earth thrust (compared to its maximum value)acting at the instant of maximum wall inertia (Η = 7.5m)

EC-8 Provisions

The numerical analyses indicate that the wall design could be based on a much reduced (r = 1.67 to 5) seismic increment, especially for

strong ground motions.


Type of retaining structure r 1/r

Free gravity walls that can accept a displacement up to dr = 300aS (mm) 2 0.5

Free gravity walls that can accept a displacement up to dr = 200aS (mm) 1.5 0.67

Flexural reinforced concrete walls, anchored or braced walls, reinforced concrete walls founded on vertical

piles, restrained basement walls and bridge abutments1 1

3. ΑΡΙΘΜΗΤΙΚΗ ΠΡΟΣΟΜΟΙΩΣΗ

Υλικό επίχωσης E, v, γ, φ Tοίχος αντιστήριξης

Ε, ν, γ Η

ag

Συνθήκες πάκτωσης

Simplified model of non-yielding retaining wall

3. ΑΝΕΝΔΟΤΟΙ ΤΟΙΧΟΙ ΕΔΑΦΙΚΗΣ ΑΝΤΙΣΤΗΡΙΞΗΣ3. NON-YIELDING RETAINING WALLS

Retaining wall

Backfill

Fixity conditions

Numerical model of non-yielding massive wall3. ΑΡΙΘΜΗΤΙΚΗ ΠΡΟΣΟΜΟΙΩΣΗ

Finite element mesh for wall height Η=4.0m


(v.2012.01)

4. ΑΠΟΤΕΛΕΣΜΑΤΑ ΠΑΡΑΜΕΤΡΙΚΩΝ ΑΝΑΛΥΣΕΩΝ3. ΑΝΕΝΔΟΤΟΙ ΤΟΙΧΟΙ ΕΔΑΦΙΚΗΣ ΑΝΤΙΣΤΗΡΙΞΗΣ3. NON-YIELDING RETAINING WALLS

Seismic response of backfill for H = 4m

Input acceleration (g)


Input acceleration (g)

Seismic response of backfill for H = 7.5m

4. ΑΠΟΤΕΛΕΣΜΑΤΑ ΠΑΡΑΜΕΤΡΙΚΩΝ ΑΝΑΛΥΣΕΩΝ

115.2kN/m199kN/m


Distribution of earth pressure (total, static, dynamicincrement) along the height of the wall and valuesof computed dynamic increment from PLAXIS andWood’s equation.

0.53, (EC-8, Part 5, Annex E.9, = 1/2)

Pnum(Dyn.inc.) ≈ ΔPd(αSγH2)(EC-8, Part 5, Annex E.9)


0.0

0.2

0.4

0.6

0.8

1.0

0 50 100 150 200 250 300

H=7.5m, φ=35ο, ah=0.5g

PLAXIS (total pressure) static pressure

PLAXIS (dynamic increment) Wood (dynamic increment)

σh (kN/m2)

h/H 773kN/m 708.75kN/m

Distribution of earth pressure (total, static, dynamicincrement) along the height of the wall and valuesof computed dynamic increment from PLAXIS andWood’s equation.


0.52, (EC-8, Part 5, Annex E.9, = 1/2)

Pnum(Dyn.inc.) ≈ ΔPd(αSγH2)(EC-8, Part 5, Annex E.9)


Normalized value of dynamic earth thrust (compared to its maximumvalue) acting at the instant of maximum wall inertia (Η = 4.0m)


Normalized value of dynamic earth thrust (compared to its maximumvalue) acting at the instant of maximum wall inertia (Η = 7.5m)

EC-8 Provisions3. NON-YIELDING RETAINING WALLS

The numerical analyses indicate that the wall design could be based on the maximum value (r ≈ 1) of seismic increment,

especially for strong ground motions.

Type of retaining structure r 1/r

Free gravity walls that can accept a displacement up to dr = 300aS (mm) 2 0.5

Free gravity walls that can accept a displacement up to dr = 200aS (mm) 1.5 0.67

Flexural reinforced concrete walls, anchored or braced walls, reinforced concrete walls founded on vertical

piles, restrained basement walls and bridge abutments1 1

Comparison of the behavior of non-yielding and yielding retaining walls


Non-yielding retaining walls

3. ΑΝΕΝΔΟΤΟΙ ΤΟΙΧΟΙ ΕΔΑΦΙΚΗΣ ΑΝΤΙΣΤΗΡΙΞΗΣ

Yielding retaining walls

3. NON-YIELDING RETAINING WALLS

4. CEPHALONIA EARTHQUAKES 2014


Mw6.003/02/2014

Mw6.126/01/2014

0.76g (2nd)

(ARG2)PGA=0.43g (1st)PGA=0.27g (2nd)

(LXRB)PGA=0.54g (1st)PGA=0.68g (2nd)

(1st)

(2nd )


Cemeteries

4. ΑΝΤΙΚΕΙΜΕΝΟ ΠΕΡΑΙΤΕΡΩ ΕΡΕΥΝΑΣ4. CEPHALONIA EARTHQUAKES 2014

The reconnaissance performed by the UPATRAS team provided information regarding the behavior of earth retaining structures.


1st Case study

• CONCRETE CANTILEVER RETAINING WALL

• Height: (varies from 0.6m to 2.5m)

• Measured horizontal displacement: 12cm

• Stem tilt: 2.5°


4. ΑΝΤΙΚΕΙΜΕΝΟ ΠΕΡΑΙΤΕΡΩ ΕΡΕΥΝΑΣ

2nd Case study

• CONCRETE GRAVITY RETAINING WALL

• Height: (varies from 3.2m to 3.9m)

• Measured horizontal displacement: 4cm

• Measured vertical displacement: 7cm

• Crack opening in the retained roadway (extending to a length of 150m)


4. ΑΝΤΙΚΕΙΜΕΝΟ ΠΕΡΑΙΤΕΡΩ ΕΡΕΥΝΑΣ

3rd Case study

• MASONRY GRAVITY RETAINING WALL (flanked by concrete walls)

• Height: 3.3m

• Horizontal displacement: 21cm

• Vertical displacement: 20cm

• Cracks opening in the church’s front yard supported by the wall (extendingto a length of about 24m).


Thank you !!Köszönöm !!

behavior of massive earth retaining walls …se.sze.hu/images/ngb_se005_4/2_massive earth retaining...

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