Eurocodes application consequences on high speed railways design

Philippe RAMONDENC - SNCF

Chef du Département des Ouvrages d’Art

The European Commission decided to propose a single regulation for civil structures, in order to open the European construction market to architects, design offices as well as construction companies. The main objectives of such as standardization consists in improving performances, promoting innovations and optimizing costs.

Therefore, the railway structures, particularly viaducts and rail bridges, must be designed and built according to this new regulation, called Eurocodes, as required by the national authorities.

Eurocodes application consequences on high speed railways design

Eurocodes application consequences on high speed railways design

Among these Eurocodes it is necessary to quote two significant parts:

the appendix A2 of Eurocode 0 (EN1990)Eurocode 1 part 2 (EN 1991-2)

These two documents are meant to establish the loads to be taken into account for the design of railway bridges as serviceability or ultimate limit states.

Eurocodes application consequences on high speed railways design

Traditionally, the ultimate limit states correspond to the strength checks of the materials used :

The maximum total stresses should not exceed the values for the yield strength

The elastic instabilities should be controlled

Joints should not be slipping

The cracking should be controlled

Eurocodes application consequences on high speed railways design

One of the ultimate limit states is particular the fatigue limit state.

From now, Eurocodes allow its being rigorously taken into account

γff . λ.ø.Δσuic < Δσ c,t

γMF

Eurocodes application consequences on high speed railways design

The fundamental contribution of Eurocodes is taking into account the serviceability limit states which translate the aptitude of the structure to allow high speed railway circulation.

The bridges are deformable structures; they must ensure the continuity of the rail platform in order to permit the passage with the same conditions of safety and comfort for all circulation velocities of the trains below the Velocity Crossing Limit that have been defined.

Eurocodes application consequences on high speed railways design

Serviceability limit states

Track stability (sleepers/ballast)

Ballast acceleration

Ballast decompression (at the track’s ends)

TGV Atlantique simple rameVitesse du train v=70.30 km/h

Eurocodes application consequences on high speed railways design

Serviceability limit states

Track continuity

Rail stresses (depending on the functional diagram)

Eurocodes application consequences on high speed railways design

Serviceability limit states

Passengers’ comfort

deck’s deflection

Eurocodes application consequences on high speed railways design

Serviceability limit states

Wheel to rail contact Twist

Horizontal and vertical angulations

Deck’s acceleration

Rail

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θ2

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essi

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d’un

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Δθ

Eurocodes application consequences on high speed railways design

Serviceability limit states

These serviceability limit states are only considered if the bridge’s deformations are reversible

They involve the materials serviceability limit states

No plasticity

No post critical state

Eurocodes application consequences on high speed railways design

One of the new significant elements of Eurocodes is the complete taking into account of the bridge’s dynamic behaviour under various railway circulations (as fast crossing bridge circulation, or as inducing resonance circulation).In particular, it results from it:

a dynamic analysis procedure

the development of dynamic high speed load models allowing to make the necessary checks

Eurocodes application consequences on high speed railways design

Eurocodes application consequences on high speed railways design

Flow chart for determining whether a dynamic analysis is required

Eurocodes application consequences on high speed railways design

High speed load model (HSLM)

Eurocodes grant the engineers a synthetic document which displays, in a didactic form, all design rules for the high speed railways particularly taking into account two issues, neglected so far:

The track stability and continuity

The passengers comfort

Eurocodes application consequences on high speed railways design