CONTRIBUTION OF VISCOELASTICITY IN THE DYNAMIC SIMULATION OF HWD TESTS FOR FLEXIBLE PAVEMENT ASSESSMENT

Transcription

1 AUN2014 : Airports in Urban Networks Apr 2014 CNIT - Paris la Défense (France) CONTRIBUTION OF VISCOELASTICITY IN THE DYNAMIC SIMULATION OF HWD TESTS FOR FLEXIBLE PAVEMENT ASSESSMENT BROUTIN Michael, PhD (presenting)*, STAC, France KTARI Rahma, Limoges University, France PICOUX Benoît, PhD, Limoges University, France NEJI Jamel, PhD ENIT, Tunisia PETIT Chrstophe, PhD, Limoges University, France * [email protected] STS N

2 Outline of the presentation Background Principle of pavement testing using HWD STAC s advanced dynamic analysis method Refinements of the method: introduction of viscoelasticity in bituminous materials Modelling and resolution Operational implementation STS N BROUTIN Michael, PhD AUN2014 Paris avril

3 Outline of the presentation Background Principle of pavement testing using HWD STAC s advanced dynamic analysis method Refinements of the method: introduction of viscoelasticity in bituminous materials Modelling and resolution Operational implementation STS N BROUTIN Michael, PhD AUN2014 Paris avril

4 Principle of HWD Typicalrawdata Geophones Measuring Data analysis positions principle Towing vehicle Main beam Drop height H 0 Load plate Extension beam G 8 Mass M 0 G 9 G 7 G 6 G 5 G 4 G 3 G 2 G 1 G Buffers 1 G 8b Useful part (flexible pavements) Useful part (rigid pavements) G 2 G 3 G 4 Geophones Joints (rigid pavements) Load plate; Force sensor and geophone G 1 at centre. G 5 G 6 G 7 G 8 G 9 r Moving direction G 4b G 6b pavement Geophone GGeophone 1 G 2 G 3 G 4 G 5 G 1 G 6 G 72 GG 8 3 G 9 G 4 G 10 G 5 G 11 GG 6 12 G 713 G 817 G 9 G 18 d [cm] 0 d [cm] BROUTIN Michael, PhD AUN2014 Paris avril

5 HWD principle A three step process 1 -Backcalculation of the parameters of the chosen mechanical pavement modeling 2 - Critical stresses/strains calculation under real traffic linked to the rational design method 3 -Pavement residual life and/or pavement bearing capacity (Single wheel load or PCN) determination development of rational PCN; cannot be disconnected to thoughts about rational ACN (ICAO/PSG matter) BROUTIN Michael, PhD AUN2014 Paris avril

6 Outline of the presentation Background Principle of pavement testing using HWD STAC s advanced dynamic analysis method Refinements of the method: introduction of viscoelasticity in bituminous materials Modelling and resolution Operational implementation STS N BROUTIN Michael, PhD AUN2014 Paris avril

7 STAC s dynamical method Multilayered elastic modelling Modelling improved(vs pseudo-static methods) FEM modelling Complex shape of force signal (double peak) taken into account External action: force history (measured by HWD force sensor) Inertia Leffects u r =0 u r =0 H Structure under study p(t) p(t) G G G Load 7 G 8 G Modelling closer to 1 real G G 3 4 G phenomenon Surface AC plate Base AC Damping UGA Subgrade Nevertheless u z bituminous material modelling =0 can be refined Mesh has been optimized (width (L) and fineness) Viscoelastic behavior BROUTIN Michael, PhD AUN2014 Paris avril

8 Outline of the presentation Background Principle of pavement testing using HWD STAC s advanced dynamic analysis method Refinements of the method: introduction of viscoelasticity in bituminous materials Modelling and resolution Operational implementation STS N BROUTIN Michael, PhD AUN2014 Paris avril

9 Viscoelasticity consideration Huet & Sayegh rheological model [Sayegh,1965] 7 parameters Backcalculation too complex Simplified Huet model 3 parameters STS N BROUTIN Michael, PhD AUN2014 Paris avril

10 Viscoelasticity consideration Adjustment of the viscoelastic parameters Using complex moduli results from laboratory tests performed on the STAC s instrumented test facility bituminous materials (BBA+GB) Fitting on the HWD signal frequency range (1-80Hz) STS N BROUTIN Michael, PhD AUN2014 Paris avril

11 Viscoelasticity consideration Fitting on the GB: HWD frequency range Results: Material BBA 0/ ,623 0,343 GB 0/ ,733 0,339 STS N BROUTIN Michael, PhD AUN2014 Paris avril

12 Numerical resolution In the frequency domain 1-FFT on the force signal 2- Resolution of the complex problem 3-Inverse FFT to find time domain solution STS N BROUTIN Michael, PhD AUN2014 Paris avril

13 Numerical resolution deflection[m] attenuation(%) E E E E y = x + 25 R² = E E E-04 - FA+RAY -3.50E FA+RAY With viscoelasticity +VISQ -4.00E-04 (5.00) -4.50E-04 R(m) R[m] Without viscoelasticity Deflections attenuation is linear with the distance to load center STS N BROUTIN Michael, PhD AUN2014 Paris avril

14 Outline of the presentation Background Principle of pavement testing using HWD STAC s advanced dynamic analysis method Refinements of the method: introduction of viscoelasticity in bituminous materials Modelling and resolution Operational implementation STS N BROUTIN Michael, PhD AUN2014 Paris avril

15 Implementation Viscoelastic direct calculation timeconsuming Approximate method is advocated : define on the base of a sensibility study (as a function of material, temperature, layer thicknesses), corrections to be applied to deflections for the dynamical method to be used STS N BROUTIN Michael, PhD AUN2014 Paris avril

16 Thank you for attention STS N BROUTIN Michael, PhD AUN2014 Paris avril