th Load models for slab track - RailTech.com | … models are important for slab track design...

Load models for slab track

Pierre-Etienne Gautier, SYSTRA

January 26th, 2016

Introduction and motivation

Slab track systems widely developed so far as technological specific systems also developed in collaborative projects (e.g.Capacity4rail),In the same time, specific standardization work carried out prEN_14362-

1(2015) and prEN_14362-2(2015)Load models are important for slab track design correct specification may involve significant differences in the slab system design,

dimensions, and internal characteristics.

significant savings in the overall system costs may be expected from tailored loadmodels.

This paper focuses on: A review of current international practices in slab track design,Main current trends as they appear in published material as well as in

standards ,Review of current status prEN_14362-1(2015) and prEN_14362-2(2015)

17/11/2015 Rail Tech 2016 / LOAD MODELS FOR SLAB TRACKS- PE Gautier

Contents

1. Review of current practice

2. prEN_16432_1&2(2015)

3. Discussion

4. Conclusion and outlook

Review of international practices in terms of loads fordesign

Design principles

Rail Tech 2016 / LOAD MODELS FOR SLAB TRACKS- PE Gautier

Types of loads:Eurocodes 1-2 (EN 1991-2:2003) generally followed in Europe:

Ultimate and service limit state calculations

UIC LM 71 ( 4 x 250 kN axles 1.6 m distant + 80 kN distributed verticalload)

Longitudinal forces, Centrifugal and Lateral Y= 100kN (yawmovements)

Multiplicative coefficient for dynamical forces =1.43

Fatigue calculation, Dynamic amplification calculation

17/11/2015

Design principles


Temperature :

Thermal dilatation for continuous slabs or jointed >reinforcement ratio around 0.8 to 0.9%, cracks width limitedto 0.2mm to 0.5 mm

Thermal gradients (35°C, 50°/m Germany, 70°/m in China,Liu 2011)

Subgrade settlements:

J Slab Sinus with max displacement = 20mm

Imposed displacement (China, Liu,2011)

17/11/2015

Design principles


Overall procedure: ultimate and service limit statecalculations

Eurocode : combination of loads ( ultimate and limit states)

Fatigue for 100 years,LM 71, dynamic amplification included, lateral loads neglected

Japan :

wheel tread = 3*static, 1.45* static for fatigue, lateral basedon Y/Q

China :

coefficient 3 when train load only is considered, 1.5 incombination loadings (Liu, 2011)

17/11/2015

prEN_14362-1(2015) and prEN_14362-2(2015) principles

Railway traffic loading: vertical

General : static , dynamic and exceptional loads(derailment), including vehicles running duringconstruction,

Vertical loads: LM 71 in general (deemed to representEU vehicles up to 250 kN axle load, but open to precisespec (real vehicles allowed for self contained railways))

Unless otherwise specified (alignment definition) loadvariation inner/outer wheel 25 %, kq = 1,25

Dynamic load : kdx( Load model 71) , with kd=1.5

Rail Tech 2016 / LOAD MODELS FOR SLAB TRACKS- PE Gautier17/11/2015

Railway traffic loading: vertical

Factor 1,5 set against limit of 5m/s2 vertical acceleration

Alternatively dynamic vehicle response simulation may beused using:Track quality with coefficient of variation limited to 10%

Confidence level limited to 99,7%

PSD for vehicle response

Models describing vehicle track interaction in accordance withEN 13231-3

Models for slab systems structural characteristics (avoidresonance and unacceptable groundborne vibration)


Railway traffic loading: lateral

In combination with vertical loads

Static and quasi static guiding loads (coherent with EN14363)-Prudhomme

Yl is the sum of lateral guidance forces acting on the rail in kN;k1=1 for all vehiclesQ vertical static wheel load in NExceptional lateral loads:on a single wheel (derailment criterion )Longitudinal loads according to EN 1991-2 2003Eddy current brake provision (vertical attractive force, longitudinal,

heating (<6K))


3

210.1

QkYl

QYls .2.1

General design principles for subsystem design: prEN 16432-2:2015

General dimensioning schemes providedDimensioning principles for all subsytemsRails , fastenings (EN 13481-5) , slabs , supporting layers

For elements like frames, application of “generalprinciples” , e.g. EurocodesEN 1992 seriesDesign of standard elements by analytical toolsFinite Element Models esp. non standard validated by

calculations by simple methods on reference casesSystem integration studies include limit state , FMEA,

RAMS


Analysis and discussion


prEN_14362-1(2015) and prEN_14362-2(2015)more in line with homologation limits for vehicles default values for limit loads in agreement with

Eurocode

Simplified calculation procedure for subsystems

FEM calculations allowed for subsystems

FEM model “validation” with respect to simplifiedprocedure



Relevance of default loadsSpecific loads allowed

Remark: UIC 518 tests for TGV at 360 km/h

Vertical forces below 150 kN, 3 m wheelbase…

Lateral forces below 40 kN


Analysis and discussionfocus on dynamical models and transition zones


Dynamical models :

Successive use of MBS for train- trackinteraction followed by FEM

Full coupling model tested (Blanco-Lorenzo et al.2011)

Successive models OK with appropriatetuning of track receptance

Specific coupled models in vertical forstochastic response (Zhang et al. 2012)

Transitions zones are still a significantproblem

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Conclusions

Conclusions and outlook

Various international practice and experience in slab trackdesign criteria especially for load models

Towards a general design process and criteria (prEN_14362-1(2015) and prEN_14362-2(2015) )

Load models are important, also depending on the systemcharacteristics (thermal, train loads,…)

Reference classical models for loads confirmed in pr. EN,although somehow over dimensioning?

Use of specific load models allowed with validation in “simplereference cases”, process described in prEN

Towards a reliability based explicit approach?

17/11/2015 Rail Tech 2016 / LOAD MODELS FOR SLAB TRACKS- PE Gautier

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