seismic design including soil-structure interaction ... · 2d plaxis analysis in time-domain 0.20 g...

Seismic Design including Soil-Structure

Interaction Effects Case Study: Metro Line

Stations and Twin Tunnels in Soft Ground

NYC, 14.11.2012

Christos VrettosChair of Soil Mechanics and Foundation Engineering

Thessaloniki Metro Line

Subsoil conditions

C. Vrettos, EERI Lecture, NYC, 14.11.2012

Top-to-down construction

Top-to-down construction- Examples -

Top-to-down construction- Project particularity -

- Single-cell structure with no central support- Seismic region- Inhomogeneous soft soil with artesian water- Depths down to -45 m

post grouting

micropiles

building


Depth 35m

Top-to-down constructionSintrivani Crossing

micropiles

Construction of diaphragm walls

Construction of diaphragm walls



Connection of wall to base slab

TBM-Excavation by EPB-Shield

Monitoring

Static analysis

-45.5

0.0

Singe cell structure


Excavation phase:diaphragm walls: Mwall = 3340 kNm/m

Static analysis- max. bending moments -

Static analysis- max. bending moments -

Final construction phase:walls Mwall = 1360 kNm/mbase slab Mslab = 1573 kNm/m

Seismic Design


-0.4g

0.4g

0 2 4 6 8 10-0.4g

0.4g

0 2 4 6 8 10

Seismic response of underground structures

[s] [s]

amax = 0.3 g amax = 0.28 g

Seismic design methods

Inertia Force

Ground Deformation

2D PLAXIS analysis in time-domain

0.20 g

0.30 g

Geff

Dam

ping

Frequency

Natural frequency of the system

Predominantfrequency of input motion


-40

-30

-20

-10

0

0 0.05 0.10 0.15 0.20

shear strain [%]

De

pth

[m

]

2D Analysis in time-domain- Free-field -

0.30 g

0.20 g

0.18 g

0.25 g

2D Analysis in time-domain- with tunnel -

0.20 g

0.16 g

Mmax = 565 kNm/m

0.20 g

0.29 g

Mmax = 283 kNm/m

x

0z

Hz

SBV

SV

Sectional forces due to ground deformation

c

VAEN 0

max 2

1

20

max c

AIEM


Soil-structure interaction

NSSI RNN maxmax,

MSSI RMM maxmax,

a

aN

KAE

KR

2

2

2

t

tM

KIE

KR

4

2

axial + transverse

dG

KK ta )43(

)1(16- St. John and Zahrah

GKK ta - AFPS/AFTES Guidelines

GKa 3- Clough and Penzien

Springs for soil-structure interaction

Racking of rectangular tunnel cross sections

sC

v

- Free-field seismic site response analysis (SHAKE,EERA), or

- Newmark approximation


ff

tunnelR

Hk

BGF

1

)1(4

Rsk

k )43(

H

Gks

Bk /

ff

tunnelR

Sectional forces in tunnel lining

Penzien (2000)

Racking of rectangular tunnel cross sections- Pseudo-coupled procedure -

Map of known earthquakes with M≥3.0 in central–northern Greece from 550 BC till 2007. Open circles: historical earth-quakes before 1911. High seismicity areas: Servomacedonian massif (yellow) and North Aegean Trough (blue).From Skarlatoudis et al. (2011).

Local seismicity

Result of a seismic hazard analysis

Results of a seismic hazard analysis

Results of a seismic hazard analysis

Tunnel project

at rock outcrop: PGA 0.273 g

1D Seismic site response analysis

Loma Prieta 1989 EQ recordat Palo Alto SLAC Lab, SGS Station 1601

5.0max '9500 vG [kPa]

1457.6103.1

8.0max

G

G8.0204.01

5.192

D [%]


at rock/soil interface: PGA 0.178 g



2D Seismic response analysis



EQ: Mwall,left = 2230 kNm/m ; Mwall,right = 2970 kNm/m

Static + EQ: max M = 6479 kNm/m ; min M = -5002 kNm/m


Bending moments at t = 10.20 s

Static + EQ: M = 6411 kNm/m ; min M = -2399 kNm/m


Wireframe distribution: envelope from all calculation steps;Solid lines: values due to the structure installation

2D Quasi-static response analysis


Quasi-static approach

Mwall = 1950 kNm/m

vs. Mwall = 2970 kNm/m from dynamic analysis

Quasi-static approach

N = 322 kN/mM = 39.8 kNm/m

Comparison

Partial factors for actions (EC7, DIN):Permanent: 1.35Temporary: 1.20Seismic: 1.00

Diaphragm wallsStatic: 4010 kNm/mSeismic peak: 2970 kNm/mQuasi-static: 1950 kNm/m

Tunnel lining:Static: 1460 kN/mSeismic peak: 402 kN/mQuasi-static: 322 kN/m


seismic design including soil-structure interaction ... · 2d plaxis analysis in time-domain 0.20 g...

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