French last research on rigid pavement: towards rational ... · Michael BROUTIN –French Civil Aviation Technical Center Los Angeles, June 9-12, 2013 V and H sensors LVDT Measurement

www.stac.aviation-civile.gouv.fr

Direction générale de l’Aviation civile - Service technique de l’Aviation civile 1

XIV Seminario ALACPA de

Pavimentos Aeroportuarios,

Quito, May 27-June 1

French last research on rigid

pavement: towards rational

design and assessment

Michaël Broutin

Amir Sadoun

French civil Aviation technical Center


Direction générale de l’Aviation civile - Service technique de l’Aviation civile

INTRODUCTIONRigid pavement present a complex behavior : superimposition

of:

• Brittle failure phenomena

• Fatigue behaviour

• Stress/strain condition due to thermal gradients

• Load transfer between slab to be taken into account as a

function of the transfer system (dowels, sinsusoïdal joints, ..).

Positive gradient, bottom-up cracking Negative gradient, top-down cracking



INTRODUCTION

3

Brittlefailure

Fatigue

Thermo-mechanical

model

Ongoing work on:



INTRODUCTION

4

Thermo-mechanicalmodelling

Brittle failure

Fatigue model

STAC’s

instrumented

test facility

Main strains/stresses: calculation : FE

model

In-situ case studiesand/or SPIDER

Concrete and transfer system

fatigue :FE model + fatigue law

SPIDER

Strains

calculation due

to:

-mechanical

loading

- Thermal

gradient



THERMO-MECHANICAL MODELLING

5

Thermo-mechanicalmodelling

Strains calculation

due to:

-Mechanical loading

- Thermal gradient

STAC’s instrumentedtest facility



Modèle

Thermomécanique

➢ Computation of the stresses/strains related to:

• A mechanical external load :

• Dynamical HWD loading

• Real Aircraft traffic

• A thermal loading: temperature gradient in the concrete slab (according to depth)

➢ FE modelling




Modèle

Thermomécanique

➢ Validation from test surveys performed on the STAC’s instrumented test facility; unique full-scale experimental test site in Europe for airfield pavement study


Michael BROUTIN – French Civil Aviation Technical Center

Los Angeles, June 9-12, 2013

Opportunities offered by the test facility:

▪ Improvement of the pavement behavior modelingunder heavy loading

➢ Reference structures with well-known layer thicknesses+ material characterization data available

➢ Strains data in the pavement available, throughembedded sensors

▪ Pavement testing devices and methods assessment

➢ Reference test site; crossed tests possible

▪ Pavement testing devices in-situ verification

➢ Dynamical precision weighing scales -> F(t)

➢ Deep anchors -> di(t)




Presents all classical pavement types : flexible, rigid dowelled or not, shoulders

S1

S2

S3

(Flexible)

(Shoulders)

S2

S1

(Rigid)

(Maneuvering area)




▪ Rigid pavement

➢Designed according to PCA method

➢Reference traffic = 10 HWD loads (300kN ; Ø45cm load plate) per day during 20 years;

➢2 designs ; Non dowelled: 33cm slab;dowelled : 26cm

Concrete slab, class 6, Rt = 3,25MPa : 30 cm

Lean concrete, Rt = 3MPa : 15 cm

GNT B : 30cm

Subgrade including a 70 cm GNT2 0/31,5, type A capping layer

Reaction modulus (Kmoy

≈ 50MN/m3)

Theoretical structure




▪ Rigid pavement

➢Mechanical sensors: one-off measurements of:

- The vertical displacements on the loaded slab and the next ones, for the study of the load transfers: V type

- the horizontal displacements at the slab edge center, for the joint opening measurement, under the effect of the temperature : H type

- tensile strains, at the bottom of the concrete slab: E type

Simultaneous data acquisition for all sensors (up to 2400Hz) possible

➢Temperature monitoring within the bituminous materials : continuous low- rate data acquisition (1 mes / 10min)

Instrumentation – rigid pavement



▪ 2 instrumented slab quarters: 1 with dowel bars, and 1 without

PR1

PR2


Slab central axis

Slab edge

Tensile strain sensors(base of the slab)

Vertical displacementsensors

Horizontal displacement sensors



▪ V and H sensors

➢LVDT

➢Measurement range: resp. ±10mm et ±5mm ,

➢Measurement uncertainty: resp. 0,7% or 10µm and 0,5% or 5µm




▪ E sensors

➢Designed and manufactured especially for this experiment

➢Geometry optimized

➢Measurement range: 0-3000µm/m. Evaluated uncertainty : 3-4%


In situ validation tool: STAC’s test facility



BRITTLE FAILURE

16

Brittle failure

Main strains/stresses: calculation: FE

model

In-situ case studies and/or

SPIDER



BRITTLE FAILURE PHENOMENA :

MAIN STRESS STUDY

Numerical approach Matlab/Cesar-LCPC codeincluding PNC module and TCNL.

Matlab HIM

FE modelling

PNC module

Modèle

Thermomécanique

Etude des phénomènes de rupture

fragile



2 APPLICATIONS

1. Single calculation: main stress at the bottom of the slab

for a specific landing gear position

Example for a 4 wheel gear

Modèle

Thermomécanique


fragile



2. Iterative process: For a given landing gear and slab

thickness, determination of the critical position and

associated stress.

Example: A350-900 with apositive temperature gradient

Modèle

Thermomécanique


fragile

2 APPLICATIONS



Same study possible with the rotation

Remark: Possible to combine translation + rotation

Modèle

Thermomécanique


fragile

2 APPLICATIONS



VALIDATION

Using :

• Real slab failure (related to real trafic)

• NAPTF CC8 data (STAC/FAA students exchange

Summer 2018)

Modèle

Thermomécanique


fragile



DAMAGE LAWS

22

Fatigue model

Concrete and transfer system

fatigue: FE model + fatigue

law

SPIDER

Mechanical modeling: FreeFEM++

➢ Center, edge or corner loading for an isolated single slab

Concrete slab; h1 = 30 cm

Lean concrete; h2 = 15 cm

Untreated graded aggregate;

h3 = 30 cm

Subgrade

➢ Extension to 9-slabs panel case: on progress

- with various transfer system



➢ Dynamical HWD loading

Measurements

Modeling



Example – Mechanical resultsModèle

Thermomécanique



Modèle

Thermomécanique

Example – Thermal results



NEXT CHALLENGE: DAMAGE LAWS

VALIDATION

➢ Towards a STAC’s airfield APT? Would be a unique device in

Europe

➢ Feasability study achieved.

➢ Project name: SPIDER AERO (System for Pavement

Investigation for Design Expertise and Reinforcement).

27

Modèle

Thermomécanique

Etude des phénomènes

de rupture fragile

Développement de

modèles d’endommag

ement



UTILISATION DU SPIDER-AÉRO DU

STACModèle

Thermomécanique

Etude des phénomènes

de rupture fragile

Développement de

modèles d’endommag

ement







Thank you

Documents

French last research on rigid pavement: towards rational ... · Michael BROUTIN –French Civil Aviation Technical Center Los Angeles, June 9-12, 2013 V and H sensors LVDT Measurement