Eurocode Conference 2023 Bisch Eurocode 8

Philippe Bisch
EUROCODE Conference I Berlin I 24 May 2023

DIBt 1 of 16
Contents
1. Eurocode 8 in the frame of the Eurocode set
2. Organisation and concepts of EN1998
3. New features in Eurocode 8
DIBt EUROCODE Conference I Berlin I 24 May 2023 2 of 16

Eurocode 8 in the frame of the Eurocode set
Consequence classes
1st GENERATION 2nd GENERATION
IMPORTANCE CLASSES CONSEQUENCE CLASSES (EC0)
PART 1 PART 2
I I CC1
II II CC2
III CC3a
III
IV CC3b

Seismic situation & limit states
 Homogenisation of Limit States definition through all parts with
better consistency with EN1990 (ULS and SLS)
 Verification of Operational (OP) limit state
1st GENERATION 2nd GENERATION
PARTS 1 & 2 PART 3 Limit state
NEAR COLLAPSE NEAR COLLAPSE (NC)
ULS
NO COLLAPSE SIGNIFICANT DAMAGE SIGNIFICANT DAMAGE (SD)
DAMAGE LIMITATION DAMAGE LIMITATION DAMAGE LIMITATION (DL)
SLS
OPERABILITY (OP)
 At least one ULS verification is mandatory (safety of the structure)

 Choice of SLS to be verified is up to the NA or the contract
Reduction of NDPs
Case of Eurocode 8 (evaluation)
1st generation 2nd generation
EC8-1 general 18 13
/EC8-1-1
EC8-1 materials 39 18
/EC8-1-2
EC8-2 29 5
EC8-3 8 8
EC8-4+6 10+7 3
EC8-5 4 8
TOTAL 115 55

Organisation and concepts of EN1998
Restructuration of EN 1998 in three levels
EN1998-1-1 EN1998-5
GENERAL
Seismic action Geotechnics
RULES
& general rules
DESIGN OF
NEW EN1998-1-2 EN1998-2 EN1998-4&6
STRUCTURES Buildings Bridges Other structures
ASSESSMENT
OF EXISTING EN1998-3
STRUCTURES Buildings & bridges

Performance requirements
Objectives to be met with an appropriate degree of reliability:
 human lives are protected
 damage is limited
 facilities important for civil protection remain operational
Design verification principles for new structures:
 verification of SD limit state mandatory
 ensure deformation capacity and cumulative energy dissipation capacity
 avoid brittle failure or the premature formation of unstable mechanisms

Safety choices for buildings (NDPs)
Return periods in years
Limit state Consequence class
(LS) CC1 CC2 CC3-a CC3-b
NC 800 1600 2500 5000 10% of exceedance in 50y
SD 250 475 800 1600
DL 50 60 60 100
Performance factors
Limit Consequence class (IC)
state (LS) CC1 CC2 CC3-a CC3-b
NC 1,2 1,5 1,8 2,2
SD 0,8 1 1,2 1,5
DL 0,4 0,5 0,5 0,6
Global safety choice: seismicity index
• Seismicity index
Seismic action
Sd = δ Fα FT Sα,475
Can depend on the Consequence Class of the structure (NDP)
• Ranges of Sδ values for seismic action classes

New definition of elastic spectrum
Stiff structures
Flexible structures

New definition of ductility classes
Sα map
Linear elastic design, force approach (q = 1)

D
C Overstrength capacity (q = 1,5)
1
D
Overstrength capacity, local deformation
C
capacity and local energy dissipation capacity
2
D
Ability of the structure to form a global plastic
C
mechanism at SD limit state
3

Principle of design in the post-elastic domain
Ensure controlled post-elastic behaviour of the entire structure
 Locate plastic zones in areas chosen for a good global behaviour
 Eliminate possible brittle failures and instabilities
➯ Capacity design
Improve ductility of plastic zones (capability of plastic deformation)

➯ Size of sections and geometry
➯ Detailing
➯ Two necessary compromises:

 between strength and ductility
 cost versus risk
Ease of use and flexibility
 DC2 simpler than DCM
 DC3 intermediate to DCM and DCH, simpler than DCH
 Existing rules more detailed for easier practice
 Simpler approach for choice of partial factors
 But important additional content which makes access less direct
 Eurocode 8 not for very low seismicity

 Simpler rules may be adopted in case of low seismicity (national
choice)
 Many openings to NCCI for local production (eg masonry)
 Removal of most of ”shall”
 Extensive use of “may”
New features in EN 1998
Key changes to EN 1998
 Homogenisation of seismic zones definition
 Simplification of the global safety choice (for Members)
through seismic action classes (NDP)
 Resistance partial factors γRd unified based on a single
fractile of the resistance distribution - gives a consistent
way to derive the partial factors (NDP)
 Better definition of site classification introducing the depth
of the bedrock formation
 Redefinition of the elastic response spectrum using two
parameters instead of ag
 Spatial model of the seismic action
 Better control of drift and 2nd order effects
New content included in scope of EN 1998
 Verification of Operational (OP) limit state
 Development of the displacement-based approach and
verification rules
 Structures equipped with antiseismic devices
 Soil structure interaction
 Ancillary elements and floor response spectra
 Flat slab systems (buildings)
 Infilled frames and claddings (buildings)
 Aluminium structures in part 1-2 (buildings)
 Bridges in part 3 (existing structures)
 Timber structures in part 2 (bridges) and part 3
(assessment of existing structures)
Presented by
BISCH Philippe
Chairman of CEN/TC 250/SC 8
DIBt 16 of 16

Eurocode Conference 2023 Bisch Eurocode 8

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Philippe Bisch

EUROCODE Conference I Berlin I 24 May 2023

DIBt EUROCODE Conference I Berlin I 24 May 2023 2 of 16

DIBt EUROCODE Conference I Berlin I 24 May 2023 3 of 16

 At least one ULS verification is mandatory (safety of the structure)

DIBt EUROCODE Conference I Berlin I 24 May 2023 5 of 16

DIBt EUROCODE Conference I Berlin I 24 May 2023 6 of 16

Design verification principles for new structures:

 verification of SD limit state mandatory

 ensure deformation capacity and cumulative energy dissipation capacity

 avoid brittle failure or the premature formation of unstable mechanisms

Can depend on the Consequence Class of the structure (NDP)

• Ranges of Sδ values for seismic action classes

DIBt EUROCODE Conference I Berlin I 24 May 2023 9 of 16

DIBt EUROCODE Conference I Berlin I 24 May 2023 10 of 16

Linear elastic design, force approach (q = 1)

DIBt EUROCODE Conference I Berlin I 24 May 2023 11 of 16

Improve ductility of plastic zones (capability of plastic deformation)

➯ Two necessary compromises:

 Eurocode 8 not for very low seismicity

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