ATHENS WORKSHOP / EC 8–3 : 2005 and nGCSI : 2012APRIL 12, 2013

MAIN DIFFERENCES BETWEEN THE TWO CODESM. CHRONOPOULOS, LRC/NTUA/GR

EARTHQUAKE PLANNING AND PROTECTION ORGANIZATION

(E.P.P.O.)

COUNCIL OF EUROPE

EUROPEAN CENTRE ΟΝ PREVENTION

AND FORΕCASTING OF EARTHQUAKES

(E.C.P.F.E.)

CODE for STRUCTURAL INTERVENTIONS (2012)

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TEAM FOR DEVELOPMENT OF CODE OF INTERVENTIONS ON REINFORCED CONCRETE BUILDINGS HARMONIZATION TEAM OF CODE OF INTERVENTIONS TO EUROCODES

ENGLISH TEMPORARY VERSION

CODE OF STRUCTURAL INTERVENTIONS 2012

FINAL HARMONIZED TEXT

AUGUST 2012

• Assessment and Retrofitting of existing structures for non-seismic actions is not yet covered by the relevant material-dependent Euro-Codes (or existing National Codes).

• The “framework” of the EC 8-3 (and the nGCSI) was specifically developed because :

For many older structures, seismic resistance was not considered during the original design/construction, whereas non-seismic actions were catered for, at least by means of “traditional” construction rules.

Seismic hazard evaluations in accordance with present knowledge may indicate the need for retrofitting programmes and campaings (“active” or “passive”).

Damage caused by earthquakes may create the need for major and costly structural interventions

(repair/strengthening), not to mention other consequences.

DESIGN OF BUILDINGS FOR EARTHQUAKE RESISTANCEASSESSMENT AND RETROFITTING or STRUCTURAL (ASSESSMENT AND) INTERVENTIONS

• The EC8-3 : 2005Main Body/Six (short) Chapters / approx. 30 pages, and Informative Annex A for RC Structures / approx. 20 pages.

• The nGCSI : 2012, for RC Structures (only), Final Harmonized Text

Main Body and (Normative) Commentary / Eleven Chapters / approx. 350 pages. A new Chapter (no. 12) on Structural Additions or/and Changes of Use. Retrofitting = Str. Interventions, Repair or/and Strengthening

THE RATIONALISM OF THE nGCSI : 2012, ITS CONTENTS

1. SCOPE-FIELD OF APPLICATION-OBLIGATIONS AND RESPONSIBILITIES2. BASIC PRINCIPLES, CRITERIA AND PROCEDURES3. INVESTIGATION AND DOCUMENTATION OF THE EXISTING BUILDING4. BASIC DATA, ASSESSMENT AND REDESIGN

+ Four (4) Appendices (normative)5. ANALYSIS, BEFORE AND AFTER THE INTERVENTIONS6. BASIC BEHAVIOUR MODELS7. THE BEHAVIOUR OF EXISTING OR NEW RC ELEMENTS + INFILLS

+ Four (4) Appendices (normative)

8. DESIGN OF INTERVENTIONS9. SAFETY VERIFICATIONS10.REQUIRED CONTENTS OF THE DESIGN FILE, ASSESSMENT AND REDESIGN11.CONSTRUCTION-QUALITY ASSURANCE-MAINTENANCE

NOTE 1

The definition of the LS of NC given in EC 8-3 is different than that given in EC 8-1.

Thus, the LS of NC is closer to the actual collapse and corresponds to the fullest exploitation of the deformation capacity of the structural elements.

NCEC 8-1 SDEC 8-3

NOTE 2

• Distinction between “ductile” or “brittle” structural elements and mechanisms, i.e. deformation or strength controlled ones.

See additional details and rules given by the nGCSI(μ 2 , μφ 3).

• Distinction between “primary” (P) or “secondary” (S) seismic structural elements, using more or less conservative estimates of their capacities.

EC’s : S/P+S 15%nGCSI : S/P+S 25% .

EC8-3 / STATE OF DAMAGE IN THE STRUCTURE

Three (3) LIMIT STATES (LS’s), namelyNear Collapse (NC), Significant Damage (SD) and Damage Limitation (DL).

The National Authorities decide whether all three LS’s shall be checked, or two of them, or just one of them.

NC : Pe = 2% in Lt = 50 years, Tr = 2.475 years

SD: Pe = 10% in Lt = 50 years, Tr = 475 years

DL: Pe = 20% in Lt = 50 years, Tr = 225 years

_______________________________________________________ nGCSI : DIFFERENCES …

nGCSI / TARGET BEHAVIOURPERFORMANCE LEVEL, SEISMIC ACTION

IMPORTANCE : I / All, II / All but C2, III and IV / A1, A2, B1

EQPL

A/LD B/SD C/NC

10% / 50 yearsA1 B1 C1

100%

50% / 50 yearsA2 B2 C2

60%

Since existing structures (old ones, damaged or not) :(i) reflect the state of knowledge at the time of their construction, (ii) possibly contain hidden gross errors and problems, and (iii) may have been submitted to previous actions (accidental or not) with unknown effects, structural evaluation/assessment, structural intervention and redesign (if needed) are typically subjected to a different and a more complex degree of uncertainly than the design of new structures.

Therefore, different sets of partial safety and structural safety factors are required, as well as different analysis, dimensioning and verification procedures, depending (among others) on the completeness and reliability of the information available.

INVESTIGATION / DOCUMENTATION

EC8-3 / Capacities of ductile or brittle structural elements

• In general, mean value properties of the existing materials are used, as directly obtained from in-situ tests and from the additional sources of information, appropriately divided by the confidence factor (CF), accounting for the knowledge level (KL) attained.

• Especially for brittle primary seismic elements, their strengths shall be based on material strengths divided by appropriate partial safety factors (γm), taking into account that the γm values of the EC 8-1 are meant for the design of new buildings.

nGCSI : DRL and a full set of mod. γf and γm, as well as of γSd and γRd.

Mat. properties : fm or fm – S.

EC8-3 / KNOWLEDGE LEVEL (KL), CONFIDENCE FACTOR (CF)

Regarding the RC structural system, its components and its elements, for choosing the allowable type of analysis and the appropriate confidence factor values ...

Factors determining the appropriate knowledge level :1) GEOMETRY

From original outline construction drawings with sample visual survey or from full survey

2) DETAILS See Table3) MATERIALS See Table

____________________________________________________________

KL1 : Limited Knowledge CF = 1,35

KL2 : Normal Knowledge CF = 1,20

KL3 : Full (?) Knowledge CF = 1,00

KL DETAILS MATERIALS ANALYSIS CF

1SIMULATED design

+lim. in-situ inspection

DEFAULT values+

lim. in-situ testingLINEAR 1,35

2

Original design+

lim. in-situ inspection

Original design+

lim. in-situ testing ALL 1,20

Extended in-situ inspection/testing

3

Original design+

lim. in-situ inspection

Original design+

lim. in-situ testingALL 1,00

Comprehensive in situ inspection/testing

… outline or detailed dwgs, visual, full, limited, extended, comprehensive

MIN. REQUIREMENTS FOR INSPECTION (OF DETAILS) AND TESTING (OF MATERIALS)FOR EACH TYPE OF PRIMARY RC ELEMENT (BEAM, COLUMN, WALL)

Non-destructive combined with destructive testing …

Cross-checks should be made between the datacollected from different sources to minimize uncertainties.

LEVELDETAILS, PERCENTAGE

OF ELEMENTSMATERIAL SAMPLES

PER FLOOR

Limited 20 1

Extended 50 2

Comprehensive 80 3

EC8-3 / THE q – APPROACH

Generally, not suitable for cheching the LS of NC.

For RC structures of any type :

• SD q 1,5 • NC q’ 4/3 . q 2,0 .

Higher values may be adopted if suitably justified with reference to the local and global available ductility (and overstrength …).

____________________________________________________________

nGCSI : A lot of provisions, rules, etc.

The m – approach …

Table 4.1 : Values of q*/q΄ ratio depending on the target

Performance level Immediate use

after the earthquake

(Α)

Life protection

(Β)

Collapse prevention

(Γ)

0,6 with

1.0<q*<1.5

1.0

1.4

Table C 4.4 : Values of behaviour factor q΄ for performance level B (life protection)

Standards applied

for design (and construction)

Favourable presence or absence of infill

walls (1)

Generally unfavourable

presence of infill walls (1)

Substantial damage in primary elements

Substantial damage in primary elements

No Yes No Yes 1995<… 3.0 2.3 2.3 1.7

1985<…<1995(2) 2.3 1.7 1.7 1.3 …<1985 1.7 1.3 1.3 1.1

(1) On the role and effect of infill walls see §5.9 και §7.4. (2) For buildings of this period, the values of the Table are valid provided

that the check for non-formation of plastic hinges in column ends is made according to §9.3.3 (by satisfying ΣΜRc ≥1,3ΣΜRb).

For torsionally sensitive structures, or for those with at least 50% of the mass concentrated in the upper 1/3 of their height (inverted pendula), the values of the Table are multiplied by 2/3 but can not be lower than 1.0.

THE INFILLED RC FRAMES (OR QUASI-FRAMES)

Existing or even new/added infills …

• EC’s …

• nGCSI A lot of provisions, rules, etc.See a specific presentation.

nGCSI : 2012

• ASPECTS OF MODELLING AND ANALYSISSee the presentation by A. Kappos

• BEHAVIOUR OF EXISTING OR NEW ELEMENTS (RC, infills)See the presentation by M. Fardis

• BEHAVIOUR OF REPAIRED/STRENGTHENED ELEMENTS (RC, infills)See the presentation by S. Dritsos and T. Tassios

• FINAL CHECKS/SAFETY VERIFICATIONSSee the presentation by M. Fardis