A Guide to Concrete Performance

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A Guide to Concrete Performance

• Dr. Bryan Magee

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Law Courts, Bordeaux
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Canary Wharf, London
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The Millau Viaduct, France
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My living room
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Scope

• Properties in the design process
• Options for modifying properties
• How properties can be measured
• How each property is determined in EC2
• How values may be used in design

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Structural design

• Compressive strength

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Structural design

• Compressive strength
• Tensile and flexural strength
• Modulus of elasticity
• Bond strength
• Creep shrinkage
• Coefficient of thermal expansion
• Thermal conductivity
• Specific heat
• Fire resistance

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• BS EN 1992-1-1, Table 3.1

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Concrete performance
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Portland cement
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Portland cement
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Cement hydration

• Calcium
• Silica
• Water

Cement grain 20µm
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Cement hydration

• Calcium
• Silica
• Water

• Calcium Silica - Hydrate
• Calcium hydroxide Ca(OH)2

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Cement hydration
CH
C-S-H
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Voids
0.001µm
Voids within C-S-H
CH
0.01µm
CH
Capillary voids
0.1µm
CH
CH
1.0µm
10µm
CH
CH
100µm
CH
1mm
Entrapped voids
CH
10mm
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BS 8500
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Cement Additions

• Portland cement (20µm)
• GGBS (lt20µm)
• Fly ash (10 µm)
• Silica fume (0.1µm)

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Cement Additions

• Portland cement (20µm)
• GGBS (lt20µm)
• Fly ash (10 µm)
• Silica fume (0.1µm)

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Cement Additions
2,000,000 SF grains 1 PC grain

• Portland cement (20µm)
• GGBS (lt20µm)
• Fly ash (10 µm)
• Silica fume (0.1µm)

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Cement Additions
SiO2
SF
FA
GBS
PC
L
CaO
Al2O3
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Cement Additions
CEM I
CEM II
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Cement Additions
CEM I
CEM II
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Cement Additions
CEM I
CEM V
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Aggregate
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Aggregate
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Aggregate
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Aggregate
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Aggregate
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Aggregate
China clay stent
Blastfurnace slag
Recycled concrete
Lead shot
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Aggregate
Flaky
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Aggregate
Elongated
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Aggregate properties

• Shape / size (63µm - 40mm)
• Surface texture
• Strength
• Density (1200-5000 kg/m3)
• Porosity
• Drying shrinkage
• Creep
• Thermal expansion

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Aggregate properties

• Stiffness
• Self weight
• Thermal insulation
• Noise insulation
• Fire resistance

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Aggregate grading
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Admixtures

• Permitted by BS 8500 (not mandatory)
• Widely used (e.g. water reducers)
• Do not prohibit their use!

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Admixtures
Flocculation
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Admixtures
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Fibres

• Steel
• Hook end / crimped
• Length 12.5 63.5 mm
• Diameter 0.45 - 1.0 mm
• Dosage 20 - 157 kg/m3
• Synthetic
• Length 40 50 mm
• Aspect ratio 80 - 90
• Dosage 2 10 kg/m3

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Fibres
ASTM C1018-97 (third point bending test)
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Compressive strength

• Column design
• Stress distribution
• Shear capacity
• Reinforcement design

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Burj Dubai
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Tensile strength

• Cracking
• Shear / punching shear
• Bond and anchorage
• Deflection calculations
• Reinforcement design
• Fibre / un-reinforced sections

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Tensile strength
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Tensile strength
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Tensile strength
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Tensile strength
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Tensile strength
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Modulus of elasticity

• Deflection calculations
• Pre- or post-tensioned elements
• Column shortening
• Restrained movements

Key Bank Tower, Cleveland (50GPa)
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Modulus of elasticity
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Modulus of elasticity
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Modulus of elasticity
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Modulus of elasticity
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Modulus of elasticity
Aggregate volume 5 increase
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Modulus of elasticity
CEM I
CEM IIIA
CEM IIIB
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Conclusions
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www.concretecentre.com
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End

• Many thanks for your attention

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Using Concrete Properties in Design to Eurocode
2

• Mungo Stacy

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Agenda

• Introductions and objectives for the day
• Overview of the Eurocodes and accompanying
  documents
• Overview of Eurocode 2
• Properties of concrete in Eurocode 2
• Outline of design process
• Summary and conclusions

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Establish Urgency

• The implementation of the structural eurocodes
  is the biggest change to codified structural
  design ever experienced in the UK
• IStructE report to ODPM

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Embracing Change
If you dont like change,
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Embracing Change
If you dont like change, youre going to like
irrelevance even less Gen Eric Shinseki
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• I feel about globalisation a lot like I feel
  about the dawn. Generally speaking, I think it
  is a good thing that the sun comes up each
  morningbut even if I didnt much care for the
  dawn there isnt much I could do about it
• Thomas Friedman, The Lexus and the Olive Tree

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PBs role in Eurocodes

• Managing Contractor for Implementation of
  Eurocodes Phase 2 for the Highways Agency
• Development of National Annexes
• Development of Eurocodes-aligned DMRB, BSi PDs
• Studies and implementation strategy
• BSi Committee Membership
• Strategic advice to structure owners
• Training development

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Objectives for this evening

• Explain the structure of the Eurocodes
• Explain the role of relevant documents, including
  NA, PDs, Product and Execution Standards
• Provide an overview of the Eurocodes relevant to
  concrete design
• Discuss how concrete properties are determined in
  the Eurocodes
• Discuss how designs can be optimised

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Euro-speak

• What is a National Annex?

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Euro-speak

• What is a Nationally Determined Parameter?

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Agenda

• Introductions and objectives for the day
• Overview of the Eurocodes and accompanying
  documents
• Overview of Eurocode 2
• Properties of concrete in Eurocode 2
• Outline of design process
• Summary and conclusions

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Introduction to Eurocodes

• What are the Eurocodes?
• How the Eurocodes relate to the overall suite of
  DC standards
• Why are we changing?
• Eurocodes required for concrete design
• Supporting documents
• National Annexes
• BSi Published Documents
• Timescales

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What are the Eurocodes?

• Structural Eurocodes
• 10 standards in 58 parts for the design of
  structures inc. buildings, bridges, chimneys,
  masts and towers, dams etc.
• For bridge design, about 24 parts are needed
• Eurocodes are not yet appropriate for assessments
• Product Standards (specification of construction
  products)
• Execution Standards (construction requirements,
  workmanship)
• Test Standards

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Design and construction suite of standards
Structural Eurocodes
Product standards (national)
Product standards (european)
Testing standards
Execution standards
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Why are we changing?

• Public Procurement Directive
• Common technical specifications
• Construction Products Directive
• Compliance of building and civil engineering
  works with the Essential Requirements on
  mechanical resistance and stability
• Framework for drawing up harmonised technical
  specifications

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Do we have to?

• Mandatory for formulating public procurement
  specifications in EU
• Authorities in EU must accept solutions in
  accordance with Eurocodes
• Authorities in EU must accept solutions if they
  are equivalent to Eurocodes (onus is on designer
  to prove equivalence)
• Will become preferred method of satisfying
  building regulations in UK

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The structural eurocodes

• EN 1990 Eurocode Basis of structural design
• EN 1991 Eurocode 1 Actions on structures
• EN 1992 Eurocode 2 Design of concrete structures
• EN 1993 Eurocode 3 Design of steel structures
• EN 1994 Eurocode 4 Design of composite
  structures
• EN 1995 Eurocode 5 Design of timber structures
• EN 1996 Eurocode 6 Design of masonry structures
• EN 1997 Eurocode 7 Geotechnical design
• EN 1998 Eurocode 8 Design for earthquake
  resistance
• EN 1999 Eurocode 9 Design of aluminium structures

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How they fit together
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Eurocodes required for concrete design
EN1990
EN1991
Limit states, combination and partial factors
Actions, inc. load groups, application etc.
Design
Design approach, partial factors, foundations,
earth pressures etc.
Analysis and section design, partial factors
EN1992
EN1997
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Eurocodes required for concrete design
BASIS OF STRUCTURAL DESIGN
EN 1990 Basis of structural design Annex A1
Application for buildings Annex A2 Application
for bridges Annex An Application for other
structure types
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Eurocodes required for concrete design
ACTIONS
EN 1991-1-1 Densities, self weight and imposed
loads EN 1991-1-2 Actions due to fire EN
1991-1-3 Snow loads EN 1991-1-4 Wind loads EN
1991-1-5 Thermal loads EN 1991-1-6 Actions
during execution EN 1991-1-7 Accidental
actions EN 1991-2 Traffic loads on bridges
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Eurocodes required for concrete design
CONCRETE
EN 1992-1-1 General rules and rules for
buildings EN 1992-1-2 Structural fire design EN
1992-2 Bridges EN 1992-3 Liquid retaining and
containing structures
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Eurocodes required for concrete design
GEOTECHNICAL
EN 1997-1 Geotechnical Design
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Design and construction suite of standards
Concrete design to Eurocode 2
EN 1992-1-1 General rules and rules for
buildings EN 1991-1-2 Structural fire design EN
1992-2 Bridges EN 1992-3 Liquid retaining and
containing structures
Product standards (national)
Other related structural eurocodes
EN 1990 Basis of structural design (1 part
Annex) EN 1991 Actions on structures (8
parts) EN 1997 Geotechnical design (1 part) EN
1998 Design for earthquake resistance (1 part)
Product standards (european)
Testing standards
Execution standards
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National Annexes

• Each Eurocode Part has a National Annex which
  must be used in conjunction with the Eurocode
  Part
• National Annex can only contain parameters left
  open for national choice (Nationally Determined
  Parameters or NDPs)
• Values and/or classes where alternatives are
  given in EN
• Country specific data (e.g. snow maps)
• Procedure to be used when Eurocode contains
  alternatives

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National Annexes
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National Annexes
EN1992-1-1 Clause 3.1.1 (2)P
UK National Annex to EN1992-1-1 NDP for Clause
3.1.2 (2)P
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BSi Published Documents

• PDs contain referenced Non-Contradictory
  Complementary Information (NCCI) in the form of
• Background to the National Annexes
• Additional guidance and expansion on Eurocodes
• Residual non-conflicting information from current
  British Standards
• PDs are NOT standards, but may be made mandatory
  by authorities

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Planned Published Documents
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Design and construction suite of standards
BS EN 197 Specifying cement
BSi PDs
EN 13791 Testing concrete
National Annexes
BS EN 13369 Pre-cast concrete
Concrete design to Eurocode 2
BS EN 206 Specifying concrete
EN 12390 Testing hardened concrete
BS 8500 Specifying concrete
EN 1992 (4 parts)
Other related structural eurocodes
BS EN 10080 Reinforcing steels
BS 4449 Reinforcing steels
EN 1990 (2 parts) EN 1991 (8 parts) EN 1997 (1
part) EN 1998 (1 part)
EN 15630 Test methods for steel reinft. and
prestress
BS EN 10138 Prestressing steel
EN 13670 Execution of Structures
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When will it happen?
2006
2007
2008
2009
2010
Eurocode Publication
All Eurocodes published
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When will it happen?
2006
2007
2008
2009
2010
Eurocode Publication
All Eurocodes published
National Annex Publication
All NAs published
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When will it happen?
2006
2007
2008
2009
2010
Eurocode Publication
All Eurocodes published
National Annex Publication
All NAs published
All British Standards withdrawn
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When will it happen?
2006
2007
2008
2009
2010
Eurocode Publication
All Eurocodes published
National Annex Publication
All NAs published
All British Standards withdrawn
Where are we now 56 Eurocode parts, 19 NAs
published
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When will it happen?
2006
2007
2008
2009
2010
Eurocode Publication
All Eurocodes published
National Annex Publication
All NAs published
All British Standards withdrawn
Where are we now 56 Eurocode parts, 19 NAs
published
August 08 (approx.) All NAs published for
non-special structures
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When will it happen?
2006
2007
2008
2009
2010
Eurocode Publication
All Eurocodes published
National Annex Publication
All NAs published
Coexistence
All British Standards withdrawn
Where are we now 56 Eurocode parts, 19 NAs
published
August 08 (approx.) All NAs published for
non-special structures
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Agenda

• Introductions and objectives for the day
• Overview of the Eurocodes and accompanying
  documents
• Overview of Eurocode 2
• Properties of concrete in Eurocode 2
• Outline of design process
• Summary and conclusions

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Eurocode 2 design of concrete structures

• EN1992-1-1 - contents
• Eurocode terminology
• Eurocode design approach
• Analysis options, stress blocks, formulae
• Significant changes to concrete design
• Shear, strut and tie

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EN1992 Design of Concrete Structures Contents

• 1 General
• Basis of Design
• Materials
• Durability
• Structural Analysis
• Ultimate Limit States
• Serviceability Limit states
• Detailing of Reinforcement and Prestressing
• Detailing of Members and Particular Rules
• Additional Rules for Precast Concrete Structures
• Cont.

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EN1992 Design of Concrete Structures Contents

• 11 Lightweight Aggregate Concrete Structures
• 12 Plain and Lightly Reinforced Concrete
  Structures
• Design for Execution Stages
• Annexes A - Q

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Eurocode English

• Use of English in Eurocodes is careful to
  facilitate exact translation into other
  languages. As such there is new terminology,
  e.g.
• Load lt-gt Action
• Load case lt-gt Combination of actions
  appropriate to limit state
• Construction lt-gt Execution
• Design check lt-gt Verification
• Strength lt-gt Resistance
• and many more new terms.

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Subscripts

• Extensive use of subscripts
• Ed design effect
• MEd, NEd, VEd (Moment, Axial force, Shear)
• Rd design resistance
• MRd (Design moment resistance)
• Verification generally expressed as
• MEd/MRd1,0

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Concrete Design

• Uses cylinder strength ( ? 0.8fcu)
• More rooted in plasticity theory
• Consistent approach for reinforced and
  prestressed concrete
• Based on behaviour not element
• Greater coverage of non-linear analysis and time
  dependent effects

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Analysis options

• Linear elastic analysis
• Linear elastic analysis with limited
  re-distribution
• Plastic analysis
• Non-linear analysis

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Stress Blocks
Stress
Strain
0.8x
x
Bi-linear
Rectangular
Parabolic - rectangular

• (for fck lt 50 MPa)

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Reinforcement
Rising branch with strain limit check
kfyd
k (ft/fy)k
fyd fyk/gs
Horizontal branch with No strain limit check
eud
euk
Two alternative stress-strain relationships
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Design Formulae

• BS8110 Design Formulae

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Shear

• Shear resistance can be greater or less than
  BS5400-4 values
• Variable-angled truss used for shear-reinforced
  sections
• Vc and Vs not added
• Possibility of flatter truss angle means more
  links can contribute to capacity

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Variable Angle Truss Model
Web Compression Strut
Compression Chord
a
q
Tension Chord
Reinforcement (stirrups)
21.8 q 45
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Observations on usability

• More documentation
• Scatter of key information
• Principles are clear application not always
  easily understood
• More academic in style
• Large number of possible load combinations
• Less prescriptive require a greater
  understanding of engineering principles

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Agenda

• Introductions and objectives for the day
• Overview of the Eurocodes and accompanying
  documents
• Overview of Eurocode 2
• Properties of concrete in Eurocode 2
• Outline of design process
• Summary and conclusions

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Properties of Concrete for use in Eurocode 2

• Compressive strength
• Tensile strength
• Bond strength
• Modulus of elasticity
• Tensile strain capacity
• Creep

• Shrinkage
• Thermal expansion
• Thermal conductivity
• Specific heat
• Fire resistance
• Adiabatic temperature rise
• Durability

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Properties of Concrete for use in Eurocode 2

• Compressive strength
• Tensile strength
• Bond strength
• Modulus of elasticity
• Tensile strain capacity
• Creep

• Shrinkage
• Thermal expansion
• Thermal conductivity
• Specific heat
• Fire resistance
• Adiabatic temperature rise
• Durability

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Properties of Concrete for use in Eurocode 2

• Compressive strength
• Tensile strength
• Bond strength
• Modulus of elasticity
• Tensile strain capacity
• Creep

• Shrinkage
• Thermal expansion
• Thermal conductivity
• Specific heat
• Fire resistance
• Adiabatic temperature rise
• Durability

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Compressive strength

• UK practice

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Compressive strength

• Eurocodes

• UK practice

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Compressive strength
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Compressive strength
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Compressive strength

• Relationship between product standards and design
  standards

BS EN 1992 Design of concrete structures
BS 8500 Specifying concrete (UK)
BS EN 206 Specifying concrete
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Compressive strength

• BS8110
• fcd 0.67 fcu / gm

Fig. 3.3
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Compressive strength

• EN 1992-1-1
• fcd acc fck / gc

EC2 3.15

• acc
• Takes account of long term effects under
  sustained load
• Recommended value 1
• NA modifies acc to 0,85 for flexure and axial
  loading (see PD6687 for background)

EC2 3.15

• gc
• Recommended value 1,5

EC2 Table 2.1N
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Compressive strength

• EN 1992-1-1
• fcd acc fck / gc

EC2 3.15
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Compressive strength
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Characteristic / mean compressive strength

• Characteristic strength fck
• Basis of design calculations and specification
• Target mean strength fcm
• Serviceability checks and to establish mix design
• Defined relationship in EC2

EC2 Table 3.1
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Reinforcement (ULS)

• Historic UK practice (e.g. BS8110 pre 1997)
• Reinforcement gm 1.05
• fy 460 N/mm2
• European practice (e.g. EN1992-1-1)
• Reinforcement gS 1,15
• fyk 500 N/mm2

Table 3.1 (Note 1)
EC2 Table 2.1N BS4449 Table 4
BS EN 1992 Design of concrete structures
BS 4449 Specifying reinforcement (UK)
BS EN 10080 Specifying reinforcement
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Reinforcement (ULS)

• Historic UK practice (e.g. BS8110 pre 1997)
• Reinforcement design stress
• Eurocode (e.g. EN1992-1-1)
• Reinforcement design stress

fy / gm 438 N/mm2
Figure 2.2
Figure 3.8
fyd fyk / gS 435 N/mm2
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Compressive strength

• Development with time
• Expressions given for strength development with
  time
• Coefficient s depends on cement type
• Strength development after 28 days not to be used
  to justify non-conformance

EC2 3.1
EC2 3.2
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Compressive strength
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Properties of Concrete for use in Eurocode 2

• Shrinkage
• Thermal expansion
• Thermal conductivity
• Specific heat
• Fire resistance
• Adiabatic temperature rise
• Durability

• Compressive strength
• Tensile strength
• Bond strength
• Modulus of elasticity
• Tensile strain capacity
• Creep

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Tensile strength

• Used for
• considerations of cracking, shear, punching
  shear, bond, anchorage
• evaluation of cracking moment for prestressed
  elements
• crack width control for restrained early-age
  thermal contraction
• moment-curvature diagrams and deflection
  calculations
• unreinforced concrete sections

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Tensile strength

• Minimum reinforcement area

EC2 7.1
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Tensile strength

• Crack width control

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Tensile strength

• fctd design tensile strength

EC2 3.16
fctk characteristic tensile strength. Related
to fck (characteristic compressive strength) or
fcm (mean compressive strength) depending on
strength
EC2 Table 3.1
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Tensile strength

• fctm,fl - flexural tensile strength
• May be higher that fctm axial tensile strength
• EC2 7.4.3 (4) allows deflection calculations
  using fctm,fl provided no axial tensile stresses
  (e.g. due to shrinkage or thermal effects)
• Opportunity for designers to specify higher
  values than shown in Table 3.1 if justified

EC2 3.23
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Properties of Concrete for use in Eurocode 2

• Shrinkage
• Thermal expansion
• Thermal conductivity
• Specific heat
• Fire resistance
• Adiabatic temperature rise
• Durability

• Compressive strength
• Tensile strength
• Bond strength
• Modulus of elasticity
• Tensile strain capacity
• Creep

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Bond strength

• Used to
• establish anchor and lap lengths
• calculate crack spacing / crack width

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Bond strength
fbd ultimate bond stress
EC2 8.2
Uses fctd design concrete tensile strength
h1 related to quality of bond condition h2
related to bar diameter
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Bond strength
EC2 Figure 8.2
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Bond strength

• Anchorage length

EC2 8.3
ssd design stress in bar
a1 effect of form of bars (bend / hook /
straight) a2 effect of minimum cover a3
confinement by tranverse reinforcement a4
influence of welded transverse bars a5 pressure
transverse to splitting plane
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Properties of Concrete for use in Eurocode 2

• Compressive strength
• Tensile strength
• Bond strength
• Modulus of elasticity
• Tensile strain capacity
• Creep

• Shrinkage
• Thermal expansion
• Thermal conductivity
• Specific heat
• Fire resistance
• Adiabatic temperature rise
• Durability

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Modulus of elasticity
146
Modulus of elasticity

• BS8110
• E 5.5 fcu / gm 0.5

Fig. 2.1
147
Modulus of elasticity

• EN1992-1-1
• Recognises strong dependency on concrete
  composition, especially aggregates
• Gives indicative values for different aggregate
  types
• Recommends specific assessment for sensitive
  structures
• Retains relationship to (mean) compressive
  strength

148
Modulus of elasticity

• Table 3.1 gives indicative values for Ecm
• Reduce by 10 for limestone, 30 for sandstone
• Increase by 20 for basalt

EC2 3.1.3
149
Modulus of elasticity
150
Modulus of elasticity

• SLS calculations
• use Ecm
• ULS calculations
• use Ecd Ecm / gcE, gcE 1,2
• Long term modified by creep
• use Ec,eff Ecm / (1f), f 1-3

EC2 5.20
EC2 7.20
151
Properties of Concrete for use in Eurocode 2

• Compressive strength
• Tensile strength
• Bond strength
• Modulus of elasticity
• Tensile strain capacity
• Creep

• Shrinkage
• Thermal expansion
• Thermal conductivity
• Specific heat
• Fire resistance
• Adiabatic temperature rise
• Durability

152
Durability

• Exposure classes
• X0 no risk of reinforcement corrosion or attack
• XC corrosion induced by carbonation
• XD chlorides other than seawater
• XS chlorides from seawater
• XF freeze/thaw cycles
• XA chemical attach

BS EN 1992 Design of concrete structures
BS 8500 Specifying concrete (UK)
BS EN 206 Specifying concrete
153
Durability
154
Durability
EC2 4.1

• cmin - minimum concrete cover in order to ensure
• safe transmission of bond forces
• protection of steel against corrosion
• adequate fire resistance
• Dcdev allowance for deviation, recommended 10mm

EC2 4.4.1.3
155
Durability
EC2 4.4.1.2 NA Table NA.2-NA.3

• Cover requirements

156
Agenda

• Introductions and objectives for the day
• Overview of the Eurocodes and accompanying
  documents
• Overview of Eurocode 2
• Properties of concrete in Eurocode 2
• Outline of design process
• Summary and conclusions

157
Outline of design process

• Action combinations EN1990
• Eq 6.10
• Actions EN1991
• Verifications EN1992
• May need supporting guidance on how to apply
  principals (NCCI)

158
Combinations of actions EN1990
From EN1990 Eq. 6.10
Ed E Sj1gG,jGk,j gpP gQ,1Qk,1
Sigt1gQ,i y0,i Qk,i
159
Actions EN1991

• EN1991-1-1 Typical material densities, floor
  loading categories
• EN1991-2 Traffic loads on bridges (notional
  lanes, load models 1-4

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Verifications EN1992
Ed Rd
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BS 5400 verification
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BS EN 1990 verification (STR)
163
Agenda

• Introductions and objectives for the day
• Overview of the Eurocodes and accompanying
  documents
• Overview of Eurocode 2
• Properties of concrete in Eurocode 2
• Outline of design process
• Summary and conclusions

164
Summary and conclusions

• Reviewed structure of the Eurocodes
• Role of related documents, including NA, PDs,
  Product and Execution Standards
• Overview of the Eurocodes relevant to concrete
  design
• Looked at selected concrete properties - how they
  are determined and used
• Overview of overall design process
• Confidence in use of Eurocodes

165
Summary and conclusions

• Majority of Eurocodes are now published
• Many guidance documents for concrete design are
  available
• Eurocodes offer opportunities to optimise
  concrete designs
• Start designing concrete structures to Eurocode 2