further developments of eurocodes and geotechnical issues 1... · further developments of eurocodes...

Further Developments of EurocodesFurther Developments of Eurocodes

And Geotechnical IssuesAnd Geotechnical Issues

Jean-Armand CalgaroChairman of CEN/TC250Chairman of CEN/TC250

2nd International Workshop on Evaluation of Eurocode 7, Pavia, Italy, April 2010

10 Eurocodes – 58 Parts – 5320 pagesEN 1990

109 pagesEN 1995

269 pages

EN 1991783

EN 1996276 pages783 pages

EN 1992469 pages

276 pagesEN 1997

371 pages469 pagesEN 1993

1470 pages

EN 1998686 pages

1999EN 1994334 pages

EN 1999553 pages


Development of the present generation of EurocodesDevelopment of the present generation of Eurocodes


EC1 EC1 -- ActionsActions EC2 EC2 --ConcreteConcrete

EC3 EC3 --SteelSteelSteelSteel

EC4 EC4 -- CompositeCompositeEC5 EC5 -- TimberTimber

EC6 EC6 -- MasonryMasonry

EN 1990 Basis EN 1990 Basis

EC7EC7-- Geotechnical Geotechnical designdesign

EC8 EC8 --EarthquakesEarthquakes990 as s990 as s

of Structural of Structural designdesign

EC9 EC9 --AluminiumAluminium


EN 1990EN 1990

Structural safety, serviceability and EN 1990EN 1990 durability, combinations of actions

EN 1991EN 1991 Actions on structures

EN 1992EN 1992 EN 1993 EN 1994EN 1993 EN 1994 Design and detailingEN 1995 EN 1996 EN 1999EN 1995 EN 1996 EN 1999

EN 1998EN 1998EN 1997EN 1997 Geotechnical and Seismic design


IMPLEMENTATIONIMPLEMENTATIONOF THE EN OF THE EN EN 199nEN 199n--pp

Ch iCh i EUROCODESEUROCODESMain textMain text

NormativeNormative

ChoicesChoicesNationally Nationally

DeterminedDetermined

OPE

AnnexesAnnexes

InformativeInformative

Parameters (NDPs)Parameters (NDPs)

DecisionsDecisions

EUR

O

InformativeInformativeAnnexesAnnexes

DecisionsDecisions

TransformationTransformationinto a Nationalinto a National

National AnnexNational Annex(National Standard)(National Standard)ST

ATE

StandardStandard(«(« NSNS » EN 199n» EN 199n--p)p)

ProjectProjectEMB

ER S

Project Project specificationspecificationM

E


PROMOTION / EDUCATIONPROMOTION / EDUCATION

Next StepsNext StepsMAINTENANCEMAINTENANCE

N x S pN x S pHARMONIZATION (NDPs)HARMONIZATION (NDPs)

Evolution of the Eurocodes :Evolution of the Eurocodes :

FURTHER DEVELOPMENTFURTHER DEVELOPMENT

Evolution of the Eurocodes :Evolution of the Eurocodes :Preparation of the new generation of Preparation of the new generation of EurocodesEurocodes

FURTHER DEVELOPMENTFURTHER DEVELOPMENT

Development of scientific and technical Development of scientific and technical reports for :reports for :-- for new Eurocode Parts,for new Eurocode Parts,-- for new Eurocodes ENsfor new Eurocodes ENs


New Materials and/or Techniques New Materials and/or Techniques

•• Existing StructuresExisting Structures

•• Structural GlassStructural Glass

•• FRPFRP

•• Membrane StructuresMembrane Structures

•• RobustnessRobustness


FROM THE CPD TO THE FUTURE CONSTRUCTION FROM THE CPD TO THE FUTURE CONSTRUCTION PRODUCTS REGULATIONPRODUCTS REGULATIONPRODUCTS REGULATIONPRODUCTS REGULATION

ANNEX IANNEX I

Basic works requirementsBasic works requirements

ConstructionConstruction worksworks asas aa wholewhole andand inin theirtheir separateseparatepartsparts mustmust bebe fitfit forfor theirtheir intendedintended useuse..

SubjectSubject toto normalnormal maintenance,maintenance, basicbasic worksworksrequirementsrequirements mustmust bebe satisfiedsatisfied forfor anan economicallyeconomically

blbl kiki liflifreasonablereasonable workingworking lifelife..


Basic works requirements

1. Mechanical resistance and stability

2. Safety in case of fire

3 Hygiene health and the environment3. Hygiene, health and the environment

4. Safety in use

5. Protection against noise

6 Energy economy and heat retention6. Energy economy and heat retention

7. Sustainable use of natural resources


7. Sustainable use of natural resources

Th t ti k t b d i d b ilt dThe construction works must be designed, built anddemolished in such a way that the use of naturalresources is sustainable and ensure the following:resources is sustainable and ensure the following:

(a) recyclability of the construction works, their materialsand parts after demolition;and parts after demolition;

(b) durability of the construction works;

(c) use of environmentally compatible raw and secondary materials in the construction works.


The limit state conceptThe limit state concept


General Principles of Structural General Principles of Structural General Principles of Structural General Principles of Structural ReliabilityReliability

in the Eurocodesin the Eurocodes


Overview of reliability methods


The semiThe semi--probabilitic format for the verification of probabilitic format for the verification of construction worksconstruction works

The semiThe semi--probabilistic approach is based on rules, probabilistic approach is based on rules, partially deterministic that introduce safety at thepartially deterministic that introduce safety at the

construction worksconstruction works

partially deterministic, that introduce safety at the partially deterministic, that introduce safety at the following levels :following levels :•• Selection of appropriate representative values of theSelection of appropriate representative values of theSelection of appropriate representative values of the Selection of appropriate representative values of the various random parameters (actions and resistances)various random parameters (actions and resistances)•• Application of partial factors to these parametersApplication of partial factors to these parameters•• Introduction of safety margins, more or less appearent, Introduction of safety margins, more or less appearent, in the various models (models of actions, action effects in the various models (models of actions, action effects and resistances)and resistances)and resistances).and resistances).


THE BASIC MODEL WITH TWO VARIABLESTHE BASIC MODEL WITH TWO VARIABLES

EE Effect of actions Effect of actions (for example, bending moment)(for example, bending moment)RR Resistance Resistance Z = RZ = R--EE Safety marginSafety marginZ Z ≤≤ 00 Condition of failureCondition of failurerr e = 0e = 0 LimitLimit state functionstate functionr r –– e = 0e = 0 LimitLimit--state functionstate function

ppff = P(Z = P(Z ≤ ≤ 0)0) Probability of failureProbability of failure

ffE,RE,R(e,r)(e,r) Joint probability density of E and RJoint probability density of E and R

∫∫ d df )(Probability of failureProbability of failure ∫∫=fD REf dedrrefp ),(,


Calculation of the probability of failureCalculation of the probability of failure


Reliability approachReliability approach

Assumptions :Assumptions :

R, E follow Normal laws characterised by (µR, E follow Normal laws characterised by (µRR,, σσRR))R, E follow Normal laws characterised by (µR, E follow Normal laws characterised by (µRR, , σσRR))and (µand (µEE, , σσEE))

⇒⇒ Z = RZ = R –– E follows a Normal law of characteristics :E follows a Normal law of characteristics :⇒⇒ Z = R Z = R E follows a Normal law of characteristics :E follows a Normal law of characteristics :22; REZERZ σσσμμμ +=−=

2⎞⎛

∫∞−

−=Φ

x t

dtex 2

2

21)(π⎟⎟

⎠

⎞⎜⎜⎝

⎛ −Φ=

z

zµzzF

σ)(

Standard Normal lawStandard Normal law⎠⎝


Central Central A first approach of safety A first approach of safety

safety factorsafety factor

μ

E

R

μμγ =


Coefficients of Coefficients of variationvariationvariationvariation

EE

RR VV σσ

==ER μμ

kE

RRRk

EEEk

kµRkµE

σσ

−=

+=

«« Characteristic Characteristic safety factorsafety factor »»

RRRRRkk Vk

Vkkk

ER

+−

×=+−

==11γσμγ

EEEEEk VkkE ++ 1σμ


)( βΦ )( β−Φ=fp

22ER μμβ −

=22ER σσ

β+

2nd International Workshop on Evaluation of Eurocode 7, Pavia,

Italy, April 2010

Central safety factorCentral safety factorE

R

μμγ =

Coefficients of variationCoefficients of variationE

EE

R

RR VV

μσ

μσ

==

)(1 βγμμβ fER −−R li bilit i dR li bilit i d )(122222

βγγ

γσσμμβ f

VV REER

ER =⇒+

=+

=

Characteristic safety factorCharacteristic safety factor RRRRRk VkkR −×=

−===

1γσμγ

Reliability indexReliability index

Characteristic safety factorCharacteristic safety factorEEEEEk

k VkkE +×=

+===

1γ

σμγ

Partial factor designPartial factor designkMF

kkF

RE γγγγ ≤×⇒≤ggkMF

MkF E γγγ

γγ ≤×⇒≤

kMFMFk γγγγγγγβ ≤×→→→ /),(


E

Eσ P Design P Design

PointPointBoundary between safety Boundary between safety

and failure domainsand failure domainsPointPoint and failure domainsand failure domains

ββE

dEσ γγFF

CCdd βEEmk kEE σ+

=DDff Reliability indexReliability index

CCmm

ββγγFFCCkk

kd

RR =

EE σσ

E

mEσ

γγMM R

MdR

γ

EE γ=

DDss

RdRR

mRσ

kFd EE γ=

R

RσR

d

σ

RRmk kRRσ

σσ

−= k

kFREγ ≤

RR σσ

MkF E

γγ ≤


A tentative applicationϕtanVSliding limit state :

γϕtanVH ≤

Where :Where :

H = horizontal component of resultant forces

V = vertical component of resultant forcesV = vertical component of resultant forces

ϕ = internal friction angle

f t f tγ= safety factor

Safety margin : HVZ −= ϕtan

V, H and tanϕ are assumed independant and following a Normal law.


HVZ μμμμ ϕ −×= tan

Where VV and Vtanϕ are the coefficients of variation of V and tanϕ. Adopting

22tan

222tan

2tan

222tan

2HVVVHVZ σσμσμσσσσσ ϕϕϕϕ +++=+=

ϕμλμμ tan×= VH

Where VV and Vtanϕ are the coefficients of variation of V and tanϕ. Adopting the notation :

The reliability index is :

2222222222222

tan 1HV

Z

Z

VVVVV λ

λ

σσμσμσσ

μμμσμ

β ϕ

+++

−=

+++

−×==

tantantantantan HVVHVVVZ VVVVV λσσμσμσσ ϕϕϕϕϕ ++++++


With :

20,015,01,0 tan === HV VVV ϕ

11 λ

425,31,0

1

425,31,0

122 +

−=

+

−≅

γ

γ

λ

λβ

With λγ 1

=

Assuming :

0608162,1)(2,135,1

≅⇒≅⇒

=== HdHd

pHULSH

βμγγμ

06,08,1 ≅⇒≅⇒ fpβ


A few basic conclusions :

1) Probability of failure in geotechnical design, with safety factors usually adopted, turns out to be higher than for structures, which contradicts experience.

2) The basic random variables in geotechnical design are of a very different nature than the basic random variables in structural design.

3) I t t l b th ff t f ti i f tt d th th3) In a structural member, the effect of actions is far more scattered than the resistance. In a bridge foundation, for example, the effect of actions, mainly due to permanent loads, is far less scatterred than the bearing capacity of ground The two types of problems are very differentcapacity of ground. The two types of problems are very different.

4) A probabilistic approach of geotechnical problems is not useless. It is necessary to compare the reliability levels in geotechnical design and in structural design, and to give the right interpretation of observed differences.


Personal conclusions : three dreamsPersonal conclusions : three dreams1) The future Eurocode 7 should be enough developed to

id th d t d ft ti l iavoid the need to draft national accompanying standards

2) A background document would be very useful to explain why the reliability levels obtained by using the usual safety factors are in general acceptableusual safety factors are in general acceptable

3) Try to harmonize the reliability levels corresponding to the 3 geotechnical approaches defined in EN 1990the 3 geotechnical approaches defined in EN 1990


The Eurocodes : finally a nice meal, even the i l f blrestaurant is not always comfortable

Thank you for your attention2nd International Workshop on Evaluation of Eurocode 7, Pavia, Italy, April 2010

Thank you for your attention

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