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Concise Eurocode 2 for Bridges

Owen BrookerBEng CEng MICE MIStructE

Senior Structural Engineer

• Introduction to the Eurocodes• Eurocode• Eurocode 1• Eurocode 2

· Materials· Flexure· Shear

• When?• Resources• What next?

• BS EN 1990 (EC0) : Basis of structural design

• BS EN 1991 (EC1) : Actions on Structures

• BS EN 1992 (EC2) : Design of concrete structures

• BS EN 1993 (EC3) : Design of steel structures

• BS EN 1994 (EC4) : Design of composite structures

• BS EN 1995 (EC5) : Design of timber structures

• BS EN 1996 (EC6) : Design of masonry structures

• BS EN 1997 (EC7) : Geotechnical design

• BS EN 1998 (EC8) : Design of structures for earthquake resistance

• BS EN 1999 (EC9) : Design of aluminium structures

The Eurocodes

• BS EN 1990 (EC0): Basis of structural design

• BS EN 1991 (EC1): Actions on Structures

• BS EN 1992 (EC2): Design of concrete structures• BS EN 1993 (EC3): Design of steel structures

• BS EN 1994 (EC4): Design of composite structures

• BS EN 1995 (EC5): Design of timber structures

• BS EN 1996 (EC6): Design of masonry structures

• BS EN 1997 (EC7): Geotechnical design• BS EN 1998 (EC8): Design of structures for earthquake resistance

• BS EN 1999 (EC9): Design of aluminium structures

The Eurocodes

Eurocodes will be used in:

• EU countries

• EFTA Countries

• Malaysia

• Singapore

• Vietnam

• South Africa

• Others?

Introducing Eurocodes presents some challenges…

• 58 Parts to Eurocodes plus National Annexes

• Culture shock / steep learning curve

• New symbols and terminology

• Affects all materials

• Confusion over timescales

• Costs:

◦ Training

◦ Resources

Challenges

• Most of Europe using the same basic design codes:◦ Increased market for UK consultants◦ Increased market for UK manufacturers◦ Reduced costs for companies working in several European

markets◦ Reduced risk of confusion when using proprietary products ◦ Reduce software development costs

• Technically advanced codes

• Logical, organised to avoid conflicts between codes

• Eurocode 2 is less restrictive than current codes

• Eurocode 2 is more extensive than current codes

• Economy?

Opportunities

BS EN 1990 BASIS OF STRUCTURAL

DESIGN

BS EN 1991 ACTIONS ON STRUCTURES

BS EN 1992DESIGN OF CONCRETE

STRUCTURESPart 1-1: General Rules for

StructuresPart 1-2: Structural Fire Design

BS EN 1992Part 2:

Bridges

BS EN 1992Part 3:

Liquid Ret. Structures

BS EN 1994Design of

Comp. Struct.

BS EN 13369Pre-cast Concrete

BS EN 1997GEOTECHNICAL

DESIGN

BS EN 1998SEISMIC DESIGN

BS EN 13670Execution of Structures

BS 8500Specifying Concrete

BS 4449Reinforcing

Steels

BS EN 10080Reinforcing

Steels

Eurocode 2 Relationships

Each Eurocode Contains:

a. National front cover

b. National forward

c. CEN front cover

d. Main text and annexes (which must be as produced by CEN)

e. Annexes - can by normative and/or informative

f. National Annex (NA).

Format of the Eurocodes

National Annex

The National Annex provides:

• Values of Nationally Determined Parameters (NDPs) (NDPs have been allowed for reasons of safety, economy and durability)

• The decision where main text allows alternatives

• The choice to adopt informative annexes

• Non-contradictory complementary information (NCCI)

• The Eurocodes contain Principles (P) which comprise:

◦ General statements and definitions for which there is no alternative, as well as:

◦ Requirements and analytical models for which no alternative is permitted

• They also contain Application Rules, which are generally rules which comply with the Principles

• The Eurocodes also use a comma (,) as the decimal marker

Features of the Eurocodes

Eurocode

Design values of actions, ultimate limit state – persistent and transient design situations

Comb’tion expression reference

Permanent actions Leading variable action

Accompanying variable actions

Unfavourable Favourable Main(if any) Others

Eqn (6.10) γG,j,sup Gk,j,sup γG,j,inf Gk,j,inf γQ,1 Qk,1 γQ,i Ψ0,i Qk,i

Concrete self weight γG,sup = 1.35 γG,inf = 0.95Steel self weight γG,sup = 1.20 γG,inf = 0.95Super-imposed dead γG,sup = 1.20 γG,inf = 0.95Road surfacing γG,sup = 1.20 γG,inf = 0.95Weight of soi γG,sup = 1.35 γG,inf = 0.95Creep and shrinkage γG,sup = 1.35 γG,inf = 0.00

Eurocode

Design values of actions, ultimate limit state – persistent and transient design situations

Comb’tion expression reference

Permanent actions Leading variable action

Accompanying variable actions

Unfavourable Favourable Main(if any) Others

Eqn (6.10) γG,j,sup Gk,j,sup γG,j,inf Gk,j,inf γQ,1 Qk,1 γQ,i Ψ0,i Qk,i

Road traffic actions γQ = 1.35 (0 where favourable)Pedestrian actions γQ = 1.35 (0 where favourable)Rail traffic actions γQ = 1.45 (0 where favourable)Wind actions (F&E) γQ = 1.50 (0 where favourable)Wind actions (H&R) γQ = 1.65 (0 where favourable)Thermal actions (F&E) γQ = 1.50 (0 where favourable)Thermal actions (H&R) γQ = 1.65 (0 where favourable)

F&E - footbridge & execution, H&R - highway & rail structures

Serviceability Limit States

Characteristic combination (Normally used for irreversible limit states)

Gk,j + Qk,1 + Σψ0,I⋅Qk,I

Frequent combination (Normally used for reversible limit states)

Gk,j + ψ1,1⋅Qk,1 + Σ ψ2,I⋅Qk,I

Quasi-permanent combination (Normally used for long term effects and appearance of the structure)

Gk,j + Σ ψ2,I⋅Qk,I

Eurocode

Eurocode

Eurocode: Annex A2

• Revised National Annex due out now

Eurocode 1 has ten parts:

• 1991-1-1 Densities, self-weight and imposed loads• 1991-1-2 Actions on structures exposed to fire• 1991-1-3 Snow loads• 1991-1-4 Wind actions• 1991-1-5 Thermal actions• 1991-1-6 Actions during execution• 1991-1-7 Accidental actions due to impact and explosions• 1991-2 Traffic loads on bridges• 1991-3 Actions induced by cranes and machinery • 1991-4 Actions in silos and tanks

Eurocode 1

Eurocode 1 Part 1-1: Densities, self-weight and imposed loads

• Bulk density of mass concrete is 24 kN/m3

• Bulk density of reinforced concrete is 25 kN/m3

• This represents 1.84% reinforcement

• Add 1 kN/m3 for wet concrete

Eurocode 1

• Code deals with phenomenon, rather than element types

• Design is based on characteristic cylinder strength

• Does not contain derived formulae (e.g. only the details of the stress block is given, not the flexural design formulae)

• Unit of stress in MPa

• One thousandth is represented by ‰

• Plain or mild steel not covered

• High strength, up to C70/85 covered for bridges

Eurocode 2/BS 5400 Compared

Materials

Concrete Properties (Table 3.1)

Strength classes for concrete

fck (MPa) 12 16 20 25 30 35 40 45 50 55 60 70 80 90

fck,cube(MPa) 15 20 25 30 37 45 50 55 60 67 75 85 95 105

fcm (MPa) = fck+ 8(MPa) 20 24 28 33 38 43 48 53 58 63 68 78 88 98

fctm (MPa)

= 0.30 fck(2/3) ≤C50/60= 2.12 In(1+(fcm/10))

> C50/60 1.6 1.9 2.2 2.6 2.9 3.2 3.5 3.8 4.1 4.2 4.4 4.6 4.8 5.0

Ecm (GPa) = 22[(fcm)/10] 0.3 27 29 30 31 33 34 35 36 37 38 39 41 42 44

εc3 (‰) See BS EN 1992-1-1 1.75 1.8 1.9 2.0 2.2 2.3

εcu3 (‰) See BS EN 1992-1-1 3.5 3.1 2.9 2.7 2.6 2.6

fck = Concrete cylinder strengthfck,cube = Concrete cube strength fcm = Mean concrete strength fctm = Mean concrete tensile strength Ecm = Mean value of elastic modulus

Product form Bars and de-coiled rods Wire Fabrics Class

A

B

C

A

B

C

Characteristic yield strength fyk or f0,2k (MPa)

400 to 600

k = (ft/fy)k

≥1,05

≥1,08

≥1,15 <1,35

≥1,05

≥1,08

≥1,15 <1,35

Characteristic strain at maximum force, εuk (%)

≥2,5

≥5,0

≥7,5

≥2,5

≥5,0

≥7,5

Fatigue stress range

(N = 2 x 106) (MPa) with an upper limit of 0.6fyk

150

100

cold worked seismichot rolled

• In UK NA max. char yield strength, fyk, = 600 MPa• BS 4449 and 4483 have adopted 500 MPa

Reinforcement properties (Annex C)

Extract BS 8666

A

B

C

UK NA (Part 2) requires Class B or C reinforcement to be used

Flexure

For grades of concrete up to C50/60, εcu= 0.0035η = 1λ = 0.8fcd = αcc fck/ γc = 0.85 fck/1.5 = 0.57 fck

fyd = fyk/1.15 = 435 MPa

Simplified Stress Block

Eurocode 2/BS Compared

Strut inclination method

θcotswsRd, ywdfz

sAV =

θθναtancot

1maxRd, +

= cdwcw fzbV

21.8° < θ < 45°

Latest publication dates Dec 08

Reference Title Publication dateCode NA

Eurocode Basis of Structural Design Jul 02 Dec 04

Eurocode 1 Pt 1–1 Densities, self-weight and imposed loads Jul 02 Dec 05Eurocode 1 Pt 1–2 Actions on structures exposed to fire Nov 02 Apr 07Eurocode 1 Pt 1–3 Snow loads Jul 03 Dec 05Eurocode 1 Pt 1–4 Wind actions Apr 05 Oct 08a

Eurocode 1 Pt 1–5 Thermal actions Mar 04 Apr 07Eurocode 1 Pt 1–6 Actions during execution Dec 05 May 08Eurocode 1 Pt 1–7 Accidental actions due to impact and explosions Sep 06 Dec08a

Eurocode 1 Pt 2 Traffic loads on bridges Oct 03 May 08Eurocode 1 Pt 3 Actions induced by cranes and machinery Sep 06 Sep 09a

Eurocode 1 Pt 4 Actions in silos and tanks Jun 06 Oct 09a

Eurocode 2 Pt 1–1 General rules and rules for buildings Dec 04 Dec 05Eurocode 2 Pt 1–2 General rules- structural fire design Dec 04 Dec 05Eurocode 2 Pt 2 Bridges Dec 05 Dec 08Eurocode 2 Pt 3 Liquid-retaining and containment structures Jul 06 Oct 07

Eurocode 7 Pt 1 General rules Dec 04 Nov 07a

Eurocode 7 Pt 2 Ground investigation and testing Apr 07 Aug 09a British Standard Institution planned publication date Source: BSI

When will British Standards be withdrawn?

There will be a period of co-existence between our current codes and the Eurocodes:

• For a maximum of 3 years after the final part of a

‘package’ is made available to BSI by CEN or:

• Until March 2010 at the latest.

• (BS 8110 was withdrawn in May 2008)

What standards are still awaited for bridges?

Eurocode Annex 2 – National Annex Due: June 2009

Eurocode 7 Part 2 Ground Inv. & Testing - National Annex

Due: Aug 2009EN 13670 Execution standard

Due: Late 2009?

Corrigenda for parts 1 and 2 are available from:

Corrigenda

http://www.bsi-global.com/en/Standards-and-Publications/Industry-Sectors/Eurocodes-a/Eurocodes_Corrigenda/

NCCI (1)

Properties of concrete for use in Eurocode 2

Designer’s Guides

EN 1992-2

Text Books

TCC Courses

www.eurocode2.info

Keep up to date

Download:

• Column charts

• Derivations

• Worked examples

• How to… guides

• & more

The Concrete Centre Helpline

Provides a rapid response for all questions related to design and use of concrete

[email protected]

What next?

• Code maintenance• UK NA to be updated• Consensus on NDPs

• New Model Code - serviceability

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