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Design of concrete sleepers

November 22nd 2012

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SCOPE

• State of the Art

• New European Standard EN 13230 Part 6 “Concrete

sleepers – Design”

• SPENNCON means for concrete sleeper design

• “Smart sleepers” with cast-in sensors

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Sleepers design – State of the Art

There is existing documentation for the design of Concrete sleepers

Best known are:

UIC leaflet 713 R dated November 2004 « Design of monoblock concrete

sleepers »

AREMA Chapter 30 « Ties »

There is a general agreement among European experts that these calculation methods:

Are efficient for determining bending moments at rail seat section

Are not efficient for determining bending moments at centre section

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New European Standard EN 13230 Part 6 “Concrete sleepers – Design

New European Standard EN 13230 Part 6 « Concrete sleepers - Design » will be submitted for final vote from all European, Standard bodies in 2013

Standard provides 2 ways for designing concrete sleepers:

Experimental method from successful experience in tracks

Theoretical method with the use of finite elements calculation

In addition, both methods can be mixed

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New European Standard EN 13230 Part 6 “Concrete sleepers – Design

Levels of bending

moments in the sleeper

Effect of wheel load to the

sleeper

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New European Standard EN 13230 Part 6 “Concrete sleepers – Design

Steps for the

experimental method

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New European Standard EN 13230 Part 6 “Concrete sleepers – Design

Steps for the

theoretical method

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New European Standard EN 13230 Part 6 “Concrete sleepers – Design

Design model using

the elastic beam

on elastic foundation

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SPENNCON means for concrete sleeper design

First step is to check that:

geometry of the sleeper + position/quantity of prestressing

tendons + manufacturing process

will fulfill required bending moments

For this purpose, Excel sheet at SPENNCON for:

Calculation of losses according to Eurocode 2 for prestressing,

concrete shrinkage, etc

Takes into account:

– Position of each prestressing tendon

– Concrete strength

– Manufacturing process

– Etc

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SPENNCON means for concrete sleeper design

Second step in to check homogeneity of the prestress inside the

concrete sleeper

For this purpose, Finite Element tool at SPENNCON for:

Calculation run on the CAO 3D model

Help for the design

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New “Smart sleepers” with cast-in sensors

New European Standard « Concrete sleepers and bearers – Design » with many European Railway Administrations Accurate knowledge for sleeper « real » bending moments at rail

seat

Little knowledge for sleeper « real » bending moments at centre section

Little knowledge for bearers « real » bending moments

Proposal from CONSOLIS Rail Branch is to measure « real » bending moments in track with the use of dedicated

sleepers/bearers

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New “Smart sleepers” with cast-in sensors

• State of the art is to use strain gauges for the measurement of

stresses in the concrete sleepers.

• Strain gauges are glued on the lateral surface of the sleepers

• Durability of gauges is reduced

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“Smart sleepers” with cast-in sensors

• System is to use standard sleepers with sensors embedded in the concrete

• Why a fiber optical sensor (rather than a strain gauge)

Cast into the concrete

Insensible to electromagnetic perturbation

Dynamic measures up to 15kHz

Long sensor

Vertical sensors for load measurement Horizontal sensors for bending moment

measurement

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“Smart” sleepers with cast-in sensors

• Goal: provide to our clients a tool for better understanding of the

track behaviour

Utilization for R&D programs

– Provides measured values for the coefficients proposed in the EN standard

13230-6 “Concrete sleepers and bearers – Design”

• Wheel load distribution on sleepers

• Effect of speed on sleepers

• Effect of rail pad stiffness on sleepers

• Measurement of bending moments in bearers

– Measure the effect of USP, Soft rail fastening, etc

– Measure the effect of temperature on resilient materials (Rail pads, USP, etc)

– Measure the influence of maintenance operation (rail grinding, ballast

tamping…)

Utilization for track monitoring with measurement of the sleeper

bearing irregularities on ballast

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Thanks for your attention