s2 Ec8-Lisbon e Carvalho

EUROCODE 8Background and Applications

Dissemination of information for training Lisbon, 10-11 February 2011 1

Ground conditions and seismic actionGround conditions and seismic action

Eduardo C CarvalhoGAPRES SA

Ch i TC250/SC8Chairman TC250/SC8

Ground conditionsDissemination of information for training Lisbon 10-11 February 2011 2

Earthquake vibration at the surface is strongly influenced b th d l i d ditiby the underlying ground conditionsEN 1998-1 requires that appropriate investigations (in situ

i th l b t ) t b i d t i d tor in the laboratory) must be carried out in order to identify the ground conditions, with two main objectives:

allow the classification of the soil profile, in view of defining the ground motion appropriate to the site (i.e. g g (allowing the selection of the relevant spectral shape)

identify the possible occurrence of soil behaviour during an earthquake detrimental to the response of th t tthe structure


Five ground types:Five ground types:A - RockB Very dense sand or gravel or very stiff clayB - Very dense sand or gravel or very stiff clayC - Dense sand or gravel or stiff clayD - Loose to medium cohesionless soil or soft to

firm cohesive soilE - Surface alluvium layer C or D, 5 to 20 m thick,

over a much stiffer material

Ground conditions defined by shear wave velocities in the top2 special ground types S1 and S2 requiring special studies

Ground conditions defined by shear wave velocities in the top 30 m and also by indicative values for NSPT and cu


Table 3.1: Ground types

Ground type

Description of stratigraphic profile Parameters

vs,30 (m/s) NSPT (blows/30cm)

cu (kPa)

A Rock or other rock like geological 800A Rock or other rock-like geological formation, including at most 5 m of weaker material at the surface.

800 _ _

B Deposits of very dense sand, gravel, or very stiff clay, at least several tens of metres in thickness, characterised by a

360 800 50

250 , y

gradual increase of mechanical properties with depth.



Ground type


vs,30 (m/s) NSPT (blows/30cm)

cu (kPa)

C Deep deposits of dense or medium 180 360 15 50 70 250C Deep deposits of dense or medium-dense sand, gravel or stiff clay with thickness from several tens to many hundreds of metres

180 360 15 - 50 70 - 250

hundreds of metres.

D Deposits of loose-to-medium cohesionless soil (with or without some

180 15 70 (

soft cohesive layers), or of predominantly soft-to-firm cohesive soil.



Ground type


v (m/s) N c (kPa) vs,30 (m/s) NSPT(blows/30cm)

cu (kPa)

E A soil profile consisting of a surface alluvium layer with v values of type C

alluvium layer with vs values of type C or D and thickness varying between about 5 m and 20 m, underlain by stiffer material with v > 800 m/sstiffer material with vs > 800 m/s.

S1 Deposits consisting, or containing a layer at least 10 m thick, of soft l / ilt ith hi h l ti it i d

100 (indicative)

_ 10 - 20

clays/silts with a high plasticity index (PI 40) and high water content

( d c ve)

S2 Deposits of liquefiable soils, of p q ,sensitive clays, or any other soil profile not included in types A E or S1

Seismic zonationDissemination of information for training Lisbon 10-11 February 2011 7

Competence of National Authorities

Described by agR (reference peak ground l ti t A d)acceleration on type A ground)

Corresponds to the reference return period TCorresponds to the reference return period TNCR

agR modified by the Importance Factor I toagR modified by the Importance Factor I to become the design ground acceleration (on type A ground) ag = agR . I

Objective for the future updating of EN1998-1:European zonation map with spectral values for different

A ground) ag agR . Ip p p

hazard levels (e.g. 100, 500 and 2.500 years)

Seismic zonationDissemination of information for training Lisbon 10-11 February 2011 8

Attenuation relationshipsSeismic Hazard AnalysisAttenuation relationshipsSample law: Ambraseys et al. [1996]valid for:

Intraplate seismicit (E rope)320

M 5 0at

i

o

n

Intraplate seismicity (Europe) Rock sites 4.0 < M < 7.3 240

280Mag=5.0Mag=6.0Mag=6.5M 7 0n

d

a

c

c

e

l

e

r

a

3 km < R < 200 km

120

160

200 Mag=7.0

Spectral law:log SA [g] = c1 + c2M + c4 logR

e

p

e

a

k

g

r

o

u

T (s) C'1 C2 C4 h0 PGA -1.48 0.27 -0.92 3.50 0.250.10 -0.84 0.22 -0.95 4.50 0.27 40

80

120log SA [g] c1 c2M c4 logR-

r

e

f

e

r

e

n

c

e

0.20 -1.21 0.28 -0.92 4.20 0.270.30 -1.55 0.34 -0.93 4.20 0.300.40 -1.94 0.38 -0.89 3.60 0.310.50 -2.25 0.42 -0.91 3.30 0.321.00 -3.17 0.51 -0.89 4.30 0.321 50 -3 61 0 52 -0 82 3 00 0 31

010 100 1000

Distncia [km]

a

g

R

1.50 -3.61 0.52 -0.82 3.00 0.312.00 -3.79 0.50 -0.73 3.20 0.32

Distncia [km]

Spectral shapeDissemination of information for training Lisbon 10-11 February 2011 9

Effect of Magnitude on Response Spectra (Rock, 5% damping)

0.35

(

g

)

0.25

0.30

S

e

(

R = 30 km

0.15

0.20 Magnitude

56

0.05

0.10 6,57

0.000 0.5 1 1.5 2

Period T (s)Period T (s)


Effect of Magnitude on normalised shape (Rock, 5% damping)

3.00

/

a

g

2.00

2.50

S

e

/

Magnitude

5

R = 30 km

1.00

1.505

6

6,5

0.00

0.507

0 0.5 1 1.5 2

Period T (s)


Effect of Epicentral Distance on Response Spectra(Rock, 5% damping)

0 25

0.30

e

(

g

)

0.20

0.25

S

Distance (km)

M = 6

0.10

0.15 153050

0.05

50100

0.000 0.5 1 1.5 2

Period T (s)


Effect of Epicentral Distance on normalised shape(Rock, 5% damping)

2.50

a

g

2.00Se

/

a

Distance (km)M = 6

1.00

1.50 15

30

50

0.50

50

100

0.000 0.5 1 1.5 2

Period T (s)Period T (s)

Basic representation of the seismic action in Eurocode 8Dissemination of information for training Lisbon 10-11 February 2011 13

Elastic response spectrump p

Common shape for the ULS and DLS verificationsp

2 orthogonal independent horizontal components

Vertical spectrum shape different from the horizontal spectrum (common for all ground types)

Possible use of more than one spectral shape (to model different seismo-genetic mechanisms)

Account of topographical effects (EN 1998-5) and spatial

model different seismo genetic mechanisms)

variation of motion (EN1998-2) required in some special cases

Definition of the horizontal elastic response spectrumDissemination of information for training Lisbon 10-11 February 2011 14

Four branches

0 T TB Se (T) = ag . S . (1+T/TB . ( . 2,5 -1))TB T TC Se (T) = ag . S . . 2,5TC T TD Se (T) = ag . S . . 2,5 (TC /T)( ) g ( )TD T 4 s Se (T) = ag . S . . 2,5 (TC . TD /T 2)S (T) l ti tSe (T) elastic response spectrumag design ground acceleration on type A groundTB TC TD corner periods in the spectrum (NDPs)B C D p p ( )S soil factor (NDP) damping correction factor ( = 1 for 5% damping)

Additional information for T > 4 s in Informative Annex

Normalised elastic response spectrumDissemination of information for training Lisbon 10-11 February 2011 15

Standard shape

Control variables S, TB, TC, TD (NDPs)( ) ( 0,55) damping correction for 5 %Fixed variables Constant accelerationConstant acceleration, velocity & displacement spectral branches acceleration spectral amplification: 2,5

Normalised elastic response spectrumDissemination of information for training Lisbon 10-11 February 2011 16

Correction for damping 55,05/10 1 4

1.6o

r

1

1.2

1.4e

c

t

i

o

n

f

a

c

t

o

0.6

0.8

C

o

r

r

e

0

0.2

0.4

0 5 10 15 20 25 30

Viscous damping (%)

To be applied only to elastic spectra

Elastic response spectrumDissemination of information for training Lisbon 10-11 February 2011 17

Two types of (recommended) spectral shapesTwo types of (recommended) spectral shapes

Depending on the characteristics of the mostDepending on the characteristics of the most significant earthquake contributing to the local hazard:

Type 1 - High and moderate seismicity regions

local hazard:

yp g y g(Ms > 5,5 )

Type 2 - Low seismicity regions (Ms 5,5 );

Optional account of deep geology effects (NDP) for the definition

ype o se s c ty eg o s ( s 5,5 );near field earthquakesOptional account of deep geology effects (NDP) for the definition of the seismic action

Recommended elastic response spectraDissemination of information for training Lisbon 10-11 February 2011 18

Normalised shape for Type 1 and Type 2 seismic action (rock)

3.00

M it dR = 30 km

2.00

2.50

S

e

/

a

g

Magnitude

5

6

1.00

1.50 6,5

7

EN1998 1 type 1

0.00

0.50EN1998-1 type 1

EN1998-1 type 2

0 0.5 1 1.5 2

Period T (s)


Recommended parameters for the definition of th t f i d tthe response spectra for various ground types

Seismic action Type 1 Seismic action Type 2Seismic action Type 1 Seismic action Type 2

GroundType S TB (s) TC (s) TD (s) S TB (s) TC (s) TD (s)yp

A 1,0 0,15 0,4 2,0 1,0 0,05 0,25 1,2

B 1,2 0,15 0,5 2,0 1,35 0,05 0,25 1,2, , , , , , , ,

C 1,15 0,2 0,6 2,0 1,5 0,1 0,25 1,2

D 1,35 0,2 0,8 2,0 1,8 0,1 0,3 1,2D 1,35 0,2 0,8 2,0 1,8 0,1 0,3 1,2

E 1,4 0,15 0,5 2,0 1,6 0,05 0,25 1,2


4

g E D4

5

B

EC

D

S

e

/

a

g

3

S

e

/

a

g

AB

E DC

2

3A

B

1

2A

1

2

00 1 2 3 4T(s)

00 1 2 3 4

T(s)

Type 1 - Ms > 5,5 Type 2 - Ms 5,5


3

4

S

e

/

a

g

E D

C

2

3

A

B

1

00 1 2 3 4T (s)

Type 1 - Ms > 5,5


5

E

D

S

e

/

a

g

3

4B

CS

2

3A

1

00 1 2 3 4

T (s)

Type 2 - Ms 5,5T (s)

Definition of the vertical elastic response spectrumDissemination of information for training Lisbon 10-11 February 2011 23

Four branches

0 T TB Sve (T) = avg . (1+T/TB . ( . 3,0 -1))TB T TC Sve (T) = avg . . 3,0TC T TD Sve (T) = avg . . 3,0 (TC /T)( ) g ( )TD T 4 s Sve (T) = avg . . 3,0 (TC . TD /T 2)Sve (T) vertical elastic response spectrumavg vertical design ground acceleration on type A groundT T T i d i th t (NDP )TB TC TD corner periods in the spectrum (NDPs) damping correction factor ( = 1 for 5% damping)

Soil factor not influencing the vertical response spectrum

Definition of the vertical elastic response spectrumDissemination of information for training Lisbon 10-11 February 2011 24

Recommended parameters

Seismicaction avg/ag TB (s) TC (s) TD (s)

Recommended parameters3

a

g action

Type 1 0,90 0,05 0,15 1,02

2.5

S

v

e

/

a

EN1998-1Vertical Elastic

Type 2 0,45 0,05 0,15 1,0

1.5

2

1Type 1

Type 2

0

0.5Type 2

0 1 2 3Period T (s)

DisplacementsDissemination of information for training Lisbon 10-11 February 2011 25

DCgg TTSad 025,0Design ground displacementElastic displacement response spectrum in Informative Annex A of EN 1998-1Annex A of EN 1998 1

Soil TE(s)

TF(s)(s) (s)

A 4,5 10,0

B 5 0 10 0B 5,0 10,0

C 6,0 10,0

D 6,0 10,0

E 6,0 10,0

Design spectrum for elastic analysisDissemination of information for training Lisbon 10-11 February 2011 26

Derived from the elastic spectrum

0 T TB Sd (T) = ag . S . (2/3+T/TB . (2,5/q -2/3))TB T TC Sd (T) = ag . S . 2,5/qTC T TD Sd (T) = ag . S . 2,5/q . (TC /T)( ) g , q ( )

. agTD T 4 s Sd (T) = ag . S . 2,5/q . (TC . TD /T 2 )( ) g , q ( )

. agSd (T) design spectrum( ) g pq behaviour factor lower bound factor (NDP recommended value: 0,2)

Specific rules for vertical action: q 1,5

Design spectrum for elastic analysisDissemination of information for training Lisbon 10-11 February 2011 27

Derived from the elastic spectrum but:

Correction factor for damping not included

Values of the behaviour factor q already account forValues of the behaviour factor q already account for the influence of the viscous damping being different from 5%

The behaviour factor q is an approximation of the ratio of

from 5%

the seismic forces that the structure would experience if its response was completely elastic with 5% viscous damping to the seismic forces that may be used in thedamping, to the seismic forces that may be used in the design, with a conventional elastic analysis model, still ensuring a satisfactory response of the structure.

Design spectra for elastic analysisDissemination of information for training Lisbon 10-11 February 2011 28

2.5Sd

2.0

d (cm/s2)

EN1998 1

1.5

EN1998-1Soil C

Behaviour factor

1.0

1,5

2

3

Behaviour factor

0.5

3

4,5

0.00 0.5 1 1.5 2 2.5 3

T (s)

Alternative representations of the seismic actionDissemination of information for training Lisbon 10-11 February 2011 29

Time history representation (essentially for NLTime history representation (essentially for NL analysis purposes)

Three simultaneously acting accelerograms

Artificial accelerogramsMatch the elastic response spectrum for 5% dampingDuration compatible with Magnitude (Ts 10 s)Minimum number of accelerograms: 3

Recorded or simulated accelerogramsScaled to ag . SScaled to ag . SMatch the elastic response spectrum for 5% damping

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