Oasys SIREN

Oasys SIREN

Bedrock

Soil Surface

Output motion

F

= F

Input motion

Displacement

Response spectrum

The use of SIREN in the Seismic Design of Stonecutters Bridge

Jack Pappin

Site Response

Liquefaction

Foundation Design

Bedrock

?

Site Response

Mexico City ground conditions

Ground conditions

SIREN - input parameters

• Soil profile

• Density

• Small strain shear modulus G0 g

• G/G with shear strain amplitude

• Input time history – selected to match target bedrock outcrop response from the seismic hazard assessment

Geophysical methods for G0

Down hole insitu test

G0 = VS2

Down hole shear wave testing

Time

Sig

nal

s re

ceiv

ed b

y o

rth

og

on

al s

enso

rs

Shear wave arrival through the ground

Reverse polarity signals generated by hitting beam from opposite directions

P waves or S waves travelling through casing or grout column

Interpretation of Down-hole Seismic Survey

Gsec

G0

1

010.0001 0.001 0.01 0.1 10

Cyclic shear strain (%)

15

0

3050

100PI = 200

OCR = 1 - 15

Variation of G/G0 with shear strain amplitude

Bedrock

Soil Surface

Output motion

F

= F

Input motion

Displacement

Oasys SIREN

CalculatedSite response effects

120 year Velocity Response Spectrum - 5% damping

0.001

0.010

0.100

1.000

0.01 0.10 1.00 10.00

Period (sec)

Ve

loc

ity

(m

/s)

Serviceability

2400 year Velocity Response Spectrum - 5% damping

0.001

0.010

0.100

1.000

0.01 0.10 1.00 10.00

Period (sec)

Ve

loc

ity

(m

/s)

CalculatedSite response effects

Ultimate

6000 year Velocity Response Spectrum - 5% damping

0.001

0.010

0.100

1.000

0.01 0.10 1.00 10.00

Period (sec)

Ve

loc

ity

(m

/s)

CalculatedSite response effects

Structural IntegrityLimit State - SILS

Liquefaction

Philippines 1989

Liquefaction

Philippines 1989

Liquefaction

Standard method of assessing the likelihood

500 10 20 30

0.2

40

0.1

0.3

0.4

0.5

Corrected SPT N value (N1)

Ave

rage

pea

k sh

ear

stre

ss /

vert

ical

effe

ctiv

e st

ress Percent fines (%)

35 15 <5

No Liquefaction

Liquefaction

0

Note: figure applies for a magnitude 7.5 earthquake

FromSIREN

Liquefaction

Predicted likelihood of liquefaction

0

5

10

15

20

25

30

35

40

45

50

0.00 0.10 0.20 0.30 0.40 0.50

CRRM=7.5

De

pth

CRRM=7.5

CSRM

Liquefaction

0

5

10

15

20

25

30

35

40

45

50

0.00 0.10 0.20 0.30 0.40 0.50

CRRM=7.5

De

pth

CRRM=7.5

CSRM

No Liquefaction

0

5

10

15

20

25

30

35

40

45

50

0.00 0.10 0.20 0.30 0.40 0.50

CRRM=7.5

De

pth

CRRM=7.5

CSRM

No Liquefaction

Serviceability SILSUltimate

Bedrock

CDG

Alluvium

Fill

500 250

Bending Moment (kNM)

0 5 10 15

Horizontal displacement (mm)

Soil displacement from SIREN

Pile displacement

100 : 30combination rule

Foundation design - Lateral Loads on Piles

Large Diameter Bored Piles Pile Caps

Pile group modelling

.0 100.0 200.0 300.0

X [m]Scale x 1:1395 y 1:1395

-40.00

-30.00

-20.00

-10.00

.0

10.00

20.00

Y [m

]

Cumulative Graphical Output

Scale factor: 1

et-r11 Event 1 Run 2 Increment 1 18:13 11-06-04

-50.00 50.00 150.0 250.0

X [m]Scale x 1:1627 y 1:1627

-40.00

-30.00

-20.00

-10.00

.0

10.00

Y [m

]

Soil Profile

PilesInterface elements

Free field soil lateral

displacement

Acceleration

Bending moments induced in piles

Cumulative Total Stress Component: y

Interval: 20 Scale factor: 0.1

et-r11 Event 1 Run 2 Increment 1 18:13 11-06-04

< 2020 - 4040 - 6060 - 8080 - 100100 - 120

-50.00 50.00 150.0 250.0

X [m]Scale x 1:500 y 1:500

-40.00

-30.00

-20.00

-10.00

.0

10.00

Y [m

]