Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 1

Design of steel and composite bridges

Highway bridges

Joël Raoul

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 2

Main selected features

• General presentation and scope of EC3 and

EC4 related to steel and composite bridges

• Materials

• Structural analysis

• Cross-section analysis at ULS and SLS

• Treatment of instabilities

• Fatigue

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 3

application

s

Partie

2

bridges

Partie

7.1

pylons

Partie

7.2

chimneys

Partie 6

Cranes

Partie

4.2

tanks

Partie

4.3

Pipelines

Partie

5

piling

Partie

1.1 General rules

Partie

1.2 fire

Partie

1.3 sheetings

Partie

1.4 Stainless steel

Partie

1.5 Plated

elements

Partie

1.6 shells

Partie

1.7

Plated elements

loaded transv.

Partie

1.8 joints

Partie

1.9 Fatigue

Partie

1.10 Brittle

fracture

Partie

1.11 cables

Partie

4.1

Silos

generic

rules

Partie

1.12

S500 to S690

Eurocode 3 : steel structures

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 4

EN 1994 : composite steel-concrete structures

EN 1994-2 general rules and bridges (self-sufficient)

CONCRETE PART

EN 1992-2

STEEL PART

EN 1993-2

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 5

Scope of EN1993-2

All steel bridges (in general with an orthotropic deck) and the

steel part of composite bridges

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 6

Scope of EN1994-2

Composite bridges

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 7

Girder bridges

Economy : two-girder

bridges even for 2X2 lanes

due to robustness rules

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 8

Box girders

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 9

Composite members

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 10

Tension members (tie of bowstring arch)

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 11

Composite plates

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 12

Filler beam decks

In the transversal direction In the longitudinal direction

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 13

Materials

Concrete :

Between C20 and C60 for composite bridges (C 90 for concrete bridges)

Steel :

up to S460 for steel and composite bridges (S 500 to S 700 in a separate part 1-12 for steel bridges)

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 14

Choice of material :

avoid brittle behaviour

HOAN BRIDGE 2000

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 15

• An overlooked defect is assumed during execution : e.g. : a = 2.2 mm for tf=80 mm

• It grows acc. to fracture mechanics laws (assuming fatigue is governing the design)

• Up to the critical defect depending on Charpy energy at service temperature

• Over a period depending on the inspection periodicity

NOTE: fabrication rules and

quality plan are given in EN 1090 They are assumed to be met when using EN 1993

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 16

EN

10

02

5

grade quality

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 17

Structural analysis

Elastic

Plastic (buildings, bridges in accidental situations)

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 18

Classes of steel cross-sections

Cl.1

Cl.2 Cl.3

Cl.4

Mpl

Mel

1 3 6

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 19

Class of

flanges

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 20

Global analysis of composite bridges:

two aspects are considered

Cracking of concrete on

support

Mel,Rd

Mpl,Rd

Class 1

Non linear behaviour at

mid span

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 21

Modular ratio used in a composite section

L 0 L tn n . 1

a0

cm

En

E t 0t t creep coefficient given by EC2 :

and

Value of t0 : t0 = 1 day for shrinkage

t0 = a mean value in case of concrete cast in several stages

SIMPLE CALCULATIONS

L is given by : Permanent loads

shrinkage

Imposed deformations

1,1

0,55

1,5

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 22

Plate buckling and shear lag

Effectivep width

(plate buckling)

effectives width

(shear lag)

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 23

Effectives width of concrete slab (ULS and SLS)

b1 b1 b2

be1 be2 beff b0

eei i

Lb min( ; b )

8

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 24

1.2

0.083056

1.4 x( )

1 x( )

elu 1.4 x( )

1.0 x x

0 0.2 0.4 0.6 0.8 10

0.2

0.4

0.6

0.8

1

1.2beta élastique en fonction du raidissage

bo/Le

bet

a (a

lpha0

,x)

b0/Le 1/50

Shear lag at ULS:

3 alternatives, black

one recommended

Shear lag at SLS:

elastic (red line)

Effectives width of stiffened plates

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 25

Composite cross-section verification at ULS (M>0)

PNA

ENA

Elastic resistance

(for class 1, 2, 3)

plastic resistance

(for classes 1/2)

0,85 fck/gc fck/gc

fy/gM fy/gM

compression

traction

NOTE : gM is 1.0 (recommended for resistance formulae)

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 26

Verification at SLS

• Limitation of stresses for steel and composite bridges

– As in EN1992-2 and EN1993-2 (fy in the steel part)

• Limitation of crack widths for composite bridges

– As in EN1992-2 with tension stiffening (wk=0.3mm in

general)

– Using a simplified method

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 27

expérimental behaviour mechanical model

M

V

P

Aeff

equilibrium

1

2

tan

tan

=0

1 2=-cr

Treatment of instabilities

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 28

Principle of verification

)( f

Test /theory

(mechanical

model)

calibration

uRk PP PRd=PRk/gM

NOTE : gM is 1.1 (recommended for « stability » formulae)

cr

u

cr = critical loading / ULS loading

= ultimate loading (without instability)/ ULS loading u

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 29

Plate buckling of stiffened plates in EC3

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 30

Fatigue verification in EC3

Calculation of DE,2 under a fatigue loading • Influence of the type of influence line • Influence of the type of traffic • Influence of the number of lanes

P = 480kN

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 31

verification

partial factor for

loading= 1,0

Category of

detail

Dc =80

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 32

Orthotropic decks : recommended detailing

Deck plate thickness in the carriage way

in the heavy vehicle lane

t ≥ 14 mm for asphalt layer ≥ 70 mm

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 33

1st bridge entirely

designed to EC4 in

Avignon

4500 t

© SETRA

© SETRA

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 34

Outstanding composite bridges

Max span 144 m: Verrières viaduct (composite box-girder bridge)

Surface > 20000 m²: Vézère viaduct

© SETRA

© SETRA © SETRA

Max S460 thickness 120 mm: Guarrigue viaduct

Seminar ‘Bridge Design with Eurocodes’ – JRC Ispra, 1-2 October 2012 35

SOME INNOVATIONS / ECONOMY ISSUES

• Enormous scientific work • Simplicity of calculations • Robustness (fatigue + brittle fracture) • Full exploitation of the materials (postcritical range) • Steels up to S690 • Hybrid girders • Harmonization of the format and the reliability of all

the instability formulae • Treatment of stiffened plates • Design of orthotropic decks