ATHENS WORKSHOP / EC 8–3 : 2005 and nGCSI : 2012 APRIL 12, 2013 MAIN DIFFERENCES BETWEEN THE TWO CODES M. CHRONOPOULOS, LRC/NTUA/ GR

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 RESISTANCE ASSESSMENT AND RETROFITTING or STRUCTURAL (ASSESSMENT AND) INTERVENTIONS The EC8-3 : 2005 Main 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 RESPONSIBILITIES 2.BASIC PRINCIPLES, CRITERIA AND PROCEDURES 3.INVESTIGATION AND DOCUMENTATION OF THE EXISTING BUILDING 4.BASIC DATA, ASSESSMENT AND REDESIGN + Four (4) Appendices (normative) 5.ANALYSIS, BEFORE AND AFTER THE INTERVENTIONS 6.BASIC BEHAVIOUR MODELS 7.THE BEHAVIOUR OF EXISTING OR NEW RC ELEMENTS + INFILLS + Four (4) Appendices (normative) 8.DESIGN OF INTERVENTIONS 9.SAFETY VERIFICATIONS 10.REQUIRED CONTENTS OF THE DESIGN FILE, ASSESSMENT AND REDESIGN 11.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. NC EC 8-1  SD EC 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, μ φ  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), namely Near 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:P e = 2% in L t = 50 years,T r = years SD:P e = 10% in L t = 50 years,T r = 475 years DL:P e = 20% in L t = 50 years,T r = 225 years _______________________________________________________ nGCSI : DIFFERENCES …

nGCSI / TARGET BEHAVIOUR PERFORMANCE LEVEL, SEISMIC ACTION IMPORTANCE : I / All, II / All but C2, III and IV / A1, A2, B1 EQ PL A/LDB/SDC/NC 10% / 50 years A1B1C1 100% 50% / 50 years A2B2C2 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 (γ m ), taking into account that the γ m values of the EC 8-1 are meant for the design of new buildings. nGCSI : DRL and a full set of mod. γ f and γ m, as well as of γ Sd and γ Rd. Mat. properties : f m or f m – 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)DETAILSSee Table 3)MATERIALSSee Table ____________________________________________________________ KL1:Limited KnowledgeCF = 1,35 KL2:Normal KnowledgeCF = 1,20 KL3:Full (?) Knowledge CF = 1,00

KLDETAILSMATERIALSANALYSISCF 1 SIMULATED design + lim. in-situ inspection DEFAULT values + lim. in-situ testing LINEAR1,35 2 Original design + lim. in-situ inspection Original design + lim. in-situ testing ALL1,20 Extended in-situ inspection/testing 3 Original design + lim. in-situ inspection Original design + lim. in-situ testing ALL1,00 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 data collected from different sources to minimize uncertainties. LEVEL DETAILS, PERCENTAGE OF ELEMENTS MATERIAL SAMPLES PER FLOOR Limited 201 Extended 502 Comprehensive803

EC8-3 / THE q – APPROACH Generally, not suitable for cheching the LS of NC. For RC structures of any type : SDq  1,5 NCq’  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 …

THE INFILLED RC FRAMES (OR QUASI-FRAMES) Existing or even new/added infills … EC’s… nGCSIA lot of provisions, rules, etc. See a specific presentation.

nGCSI : 2012 ASPECTS OF MODELLING AND ANALYSIS See 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 VERIFICATIONS See the presentation by M. Fardis