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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