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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
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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
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INTRODUCTION
3
Brittlefailure
Fatigue
Thermo-mechanical
model
Ongoing work on:
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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
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THERMO-MECHANICAL MODELLING
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Thermo-mechanicalmodelling
Strains calculation
due to:
-Mechanical loading
- Thermal gradient
STAC’s instrumentedtest facility
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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
THERMO-MECHANICAL MODELLING
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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
THERMO-MECHANICAL MODELLING
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)
THERMO-MECHANICAL MODELLING
Michael BROUTIN – French Civil Aviation Technical Center
Los Angeles, June 9-12, 2013
Presents all classical pavement types : flexible, rigid dowelled or not, shoulders
S1
S2
S3
(Flexible)
(Shoulders)
S2
S1
(Rigid)
(Maneuvering area)
THERMO-MECHANICAL MODELLING
Michael BROUTIN – French Civil Aviation Technical Center
Los Angeles, June 9-12, 2013
▪ 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
THERMO-MECHANICAL MODELLING
Michael BROUTIN – French Civil Aviation Technical Center
Los Angeles, June 9-12, 2013
▪ 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
Michael BROUTIN – French Civil Aviation Technical Center
Los Angeles, June 9-12, 2013
▪ 2 instrumented slab quarters: 1 with dowel bars, and 1 without
PR1
PR2
Instrumentation – rigid pavement
Slab central axis
Slab edge
Tensile strain sensors(base of the slab)
Vertical displacementsensors
Horizontal displacement sensors
Michael BROUTIN – French Civil Aviation Technical Center
Los Angeles, June 9-12, 2013
▪ V and H sensors
➢LVDT
➢Measurement range: resp. ±10mm et ±5mm ,
➢Measurement uncertainty: resp. 0,7% or 10µm and 0,5% or 5µm
Instrumentation – rigid pavement
Michael BROUTIN – French Civil Aviation Technical Center
Los Angeles, June 9-12, 2013
▪ E sensors
➢Designed and manufactured especially for this experiment
➢Geometry optimized
➢Measurement range: 0-3000µm/m. Evaluated uncertainty : 3-4%
Instrumentation – rigid pavement
In situ validation tool: STAC’s test facility
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BRITTLE FAILURE
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Brittle failure
Main strains/stresses: calculation: FE
model
In-situ case studies and/or
SPIDER
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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
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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
Etude des phénomènes de rupture
fragile
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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
Etude des phénomènes de rupture
fragile
2 APPLICATIONS
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Same study possible with the rotation
Remark: Possible to combine translation + rotation
Modèle
Thermomécanique
Etude des phénomènes de rupture
fragile
2 APPLICATIONS
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VALIDATION
Using :
• Real slab failure (related to real trafic)
• NAPTF CC8 data (STAC/FAA students exchange
Summer 2018)
Modèle
Thermomécanique
Etude des phénomènes de rupture
fragile
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DAMAGE LAWS
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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
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➢ Dynamical HWD loading
Measurements
Modeling
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Example – Mechanical resultsModèle
Thermomécanique
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Modèle
Thermomécanique
Example – Thermal results
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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).
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Modèle
Thermomécanique
Etude des phénomènes
de rupture fragile
Développement de
modèles d’endommag
ement
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UTILISATION DU SPIDER-AÉRO DU
STACModèle
Thermomécanique
Etude des phénomènes
de rupture fragile
Développement de
modèles d’endommag
ement
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Thank you