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BACKCALCULATION OF AIRFIELD PAVEMENT STRUCTURES BASED ON WAVE PROPAGATION THEORY

BACKCALCULATION OF AIRFIELD PAVEMENT STRUCTURES BASED ON WAVE PROPAGATION THEORY. Kunihito MATSUI (Tokyo Denki University) Yoshiaki OZAWA (Century-techno Inc.) Kazuya TAKEHARA (Tokyo Denki University). 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22. CONTENTS.

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BACKCALCULATION OF AIRFIELD PAVEMENT STRUCTURES BASED ON WAVE PROPAGATION THEORY

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  1. BACKCALCULATION OF AIRFIELD PAVEMENT STRUCTURES BASED ON WAVE PROPAGATION THEORY Kunihito MATSUI(Tokyo Denki University) Yoshiaki OZAWA (Century-techno Inc.) Kazuya TAKEHARA (Tokyo Denki University) 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  2. CONTENTS • Brief description of wave propagation equations • Time domain backcalculation procedure • Pavement sections FWD tests were conducted • Backcalculation results • Comparison of measured and computed deflections • Complex modulus • Strain responses after backcalculation 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  3. Pavement model Impulse Definition of stresses in the axisymmetric coordinate 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  4. Wave propagation expression by FEM Mass matrix Damping matrix Stiffness matrix Force vector A typical damping model Stiffness proportional damping Density proportional damping 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  5. Wave Propagation in Viscoelastic Media (1a) (1b) Density c Density proportional damping 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  6. Strain-displacement relationship , , , (2a) (2b) (2c) (2c) 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  7. Stress-strain relationship for Voigt Model (3) 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  8. Boundary Conditions at Surface (4) where 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  9. Matching measured and computed deflections 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  10. Pavement of FWD test site (1) (*) (2) (3) (4) 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  11. 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  12. Backcalculation results 1 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  13. Backcalculation results 2 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  14. Backcalculation results 3 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  15. Backcalculation results 4 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  16. Backcalculated Layer Damping(MPa s) 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  17. Complex modulus Magnitude of complex modulus Complex modulus varies with frequency 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  18. Magnitude of complex modulus (Section 3 : Loading area) 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  19. Computed and measured deflections (Section 1) 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  20. Horizontal strain at loading and no loading area (Section 2)(at bottom of As stabilized layer) 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  21. Vertical strains at loading and no loading area (Section 2)(At the top of subgrade) 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  22. Conclusions • PCC modulus is about 24,500 MPa, Econocrete modulus about 13,000 MPa. • Soft subgrade modulus runs from 90 MPa to 120 MPa. • Stiff subrade modulus is from 300 MPa to 380 MPa. • Damping coefficients are roughly less than 1 % of layer moduli in magnitude. 2010 FAA Technology Transfer Conference, Atlantic City, NJ, USA April 19-22

  23. Other observations • When subgrade strength is low, layer moduli of upper layers reduce after repeated loading. When subgrade strength is high, layer moduli of upper layers increase and subgrade modulus reduces after repeated loading. Is it because of densification of upper layers when subgrade is stiff? • Advantage of analytical solution is that responses (displacements, stresses and strains) can be easily computed anywhere.

  24. Thank you for your attention

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