NCAT Test Track Prediction

Transcription

1 NCAT Test Track Prediction % Cracking Measured O FW AW C RW R % Damage Predicted

2 Stress Sweep Rutting (SSR) Test Y. Richard Kim Jimmy D. Clark Distinguished University Professor Alumni Distinguished Graduate Professor NC State University Asphalt Mixture and Construction ETG Meeting Bozeman, MT September 21, 2017

3 Pavement Factors Affecting Rutting Relatively easy to change in laboratory tests Vertical Stress Horizontal Stress Load Time Temperature

4 Research Objectives Need a mechanistic permanent deformation model that can account for the effects of temperature, loading time, and stress state and can be integrated in FlexPAVE TM seamlessly Need an efficient test method for the model characterization

5 Time-Temperature Superposition Time (loading rate) and temperature are interchangeable. Create a continuous mastercurve by horizontally shifting data from different temperatures E* (MPa) E-08 1.E-06 1.E-04 1.E-02 1.E+00 1.E+02 1.E+04 1.E+06 1.E+08 Reduced Frequency (Hz) C 10.6 C 35.0 C 53.5 C Mastercurve Shift Factor, a T Shift Factor y = x x R 2 = Temperature( C) 35.0 Shift function 54.0

6 Time-Temperature Superposition with Growing Damage Time-temp. shift factor from E* test y = x x R 2 = σ t/a T Repeated creep and recovery test at 40º and 55ºC Shift Factor Shift function 2.0% Temperature( C) Viscoplastic Strain 1.5% 1.0% 0.5% 140kPa-827kPa 55 C VT (1) 140kPa-827kPa 55 C VT (2) 140kPa-827kPa 40 C VT (1) 140kPa-827kPa 40 C VT (2) 0.0% Cumulative Loading Time (sec)

7 Time-Stress Superposition Time (loading rate) and stress are interchangeable (Schapery 1969, glass-reinforced phenolic resin). Create a continuous mastercurve by horizontally shifting data measured at different stress levels Creep Compliance Mastercurve Creep Compliance (J/MPa -1 ) 59.4MPa 55.5MPa 48.5MPa 48.5MPa 31.0MPa Creep Compliance (J/MPa -1 ) 31.0MPa 48.5MPa 59.4MPa 55.5MPa 48.5MPa Time (sec) Log Time (sec) Jazouli et al. (2005). Application of Time-Stress Equivalence to Nonlinear Creep of Polycarbonate. Polymer Testing, Vol. 24, No. 4.

8 Verification of Time-Temp. Superposition Load Time Shifting FHWA ALF Control 90 psi After Shifting Reference: 0.1s-54 C 2.0% 2.0% Permanent Strain (%): FHWA 1.6% 1.2% 0.8% 0.4% 1.6s-54C 0.4s-54C 0.1s-54C 1.6s-40C 0.1s-40C Permanent Strain (%): FHWA 1.6% 1.2% 0.8% 0.4% 0.0% 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 Physical Cycles (N) 0.0% 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 Effective Cycles (N)

9 Verification of Time-Stress Superposition Stress Shifting After load time shifting, horizontally shift the permanent deformation vs. number of loading cycles to construct a mastercurve. After Load Time Shifting Mastercurve at 90 psi 2.0% 2.0% Permanent Strain (%): FHWA 1.6% 1.2% 0.8% 0.4% 90 psi 150 psi 120 psi Permanent Strain (%): FHWA 1.6% 1.2% 0.8% 0.4% 0.0% 1.E-02 1.E+00 1.E+02 1.E+04 1.E+06 Effective Cycles (N) 0.0% 1.E-02 1.E+00 1.E+02 1.E+04 1.E+06 Effective Cycles (N)

10 Shift Model for Rutting ε N vp red = ε N 0 red ( N + N ) I red p1 β ξ p σ v = A N 1 Pa a = a + a Total ξ p σ a = p log( ξ ) + p ξ p 1 p 2 v d1 a = d log( σ / P ) + d σ v 1 v a 2 Load Time SF (a ξp ) 2 Reduced Load Time SF E E E E E E E+01 Reduced Load Time (Sec) Total SF (a total ) Total SF (100 psi) Stress SF (a σd ) 2 Vertical Stress SF Vertical Stress (=dev+con) T H T L 70 psi 100 psi 130 psi E E E E E E E+01 Reduced Load Time (Sec)

11 Repeated Load Permanent Deformation Test or Confining Pressure 10 psi Temperature Control

12 Triaxial Stress Sweep (TSS) Test Reference Test (T H ) 0.4s x 600 cycles or more 2.5% Permanent Strain (%) 2.0% 1.5% 1.0% 0.5% 0.0% Cycles (N) 100 psi sec (1) Stress Sweep Test at T H, T I, T L 0.4s x 200 cycles for each loading block Permanent Strain 1.60% 1.20% 0.80% 0.40% NY9.5B-47C NY9.5B-37C NY9.5B-17C 0.00% Cycles (N)

13 TSS Calibration Procedure Reference Test (T H ) Permanent Strain 2.0% 1.6% 1.2% 0.8% 0.4% 0.0% (a) 47 C TRLPD: 0.4sec-100 psi Cycles Permanent Strain 1.6% 1.2% 0.8% 0.4% 0.0% 70 psi 100 psi 130 psi (b) 47 C 37 C 17 C Cycles SS test (T H,T I,T L ) Reduced Load Time Shift Factor Load Time SF (aξp) (d) Total SF (atotal) (c) 17 C 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 Reduced Load Time (sec) 37 C 47 C 70 psi 100 psi 130 psi 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 Reduced Load Time (sec) Stress SF (aσd) (e) Total Shift Factor Vertical Stress (psi) Vertical Stress Shift Factor

14 Permanent Strain: Random 2.5% 2.0% 1.5% 1.0% 0.5% 0.0% Model Verification Random Loading Test Predicted Measured Deviator (psi) Cycles (N) 0 Measured Predicted Loading history Testing Time (sec)

15 FlexMAT TM -Rutting Determines shift model coefficients from AMPT data files and generates input files for FlexPAVE TM

16 Export Data to FlexPAVETM

17 FlexPAVE TM Program for Pavement Performance Prediction Three dimensional layered viscoelastic analysis for moving loads and thermal stresses Fatigue performance analysis based on Viscoelastic Continuum Damage (VECD) Model Rutting performance analysis based on the shift model Support for multiple axle and multiple wheel loading Integrated with EICM software to capture temperature variation for thermal stress analysis and material properties Integrated GUI that includes pre and post processors

18 Material Properties Input in FlexPAVE TM

19 Shift Model in FlexPAVE TM T 1, t p,1, σ v,1 T i, t p,i, σ v,i T N, t p,n, σ v,n ε vp = ( N + N ( T, ξ, σ )) RD ε0 N ( T, ξ, σ ) red p v I red p v N = ε vp, i i= 1 h i β

20 Rutting Prediction by TSS/FlexPAVE TM FHWA ALF Rut Depth (mm) (a) Field Performance (AC Only) Rut Depth (mm) (b) LVECD FlexPAVE (AC TM (AC Only) Only) Control CR-TB SBS Pavement Sections (ALF) 0 Control CR-TB SBS Pavement Sections (ALF)

21 NCAT Test Track

22 Simplification of TSS to SSR Test Method TSS SSR Reference 1 (T H ) - TSS Temp. 3 (T H, T I, and T L ) 2 (T H and T L ) Pulse Time (s) Rest Period (s) 10 (T H ), 1.6 (T I ) 1.6 (T L ) 3.6 (T H ) 1.6 (T L ) Deviator Stress (psi) 70, 100, 130 (T H and T L ) 100, 70, 130 (T H ) 70, 100, 130 (T L ) SSR Number of Samples 8 4 Displacement Measurement Testing Time incl. Pre-conditioning On-specimen LVDTs 16 hrs for 8 TSS tests Actuator 6 hrs for 4 SSR tests

23 Shift Factors between TSS and SSR Total SF-TSS Total SF-SSR Reduced Load Time SF Vertical Stress SF

24 Effects of Simplifications on Rut Depths Predicted by FlexPAVE TM 4 in. RS9.5B 10 in. Aggregate Base 700 AADTT 40 kn wheel load Raleigh, NC 6.0 Actuator Displacement vs. LVDT 10 Temperature, Reversed Loading Block, and Rest Periods Rut Depth (cm) Rut Depth Comparison (RS9.5B) (1) LVDTs (2) X head (3) Corrected X head Total Rut Depth (mm) TSS S-TSS S-TSS S-TSS Time (Month) Time (Months)

25 Stress Sweep Rutting (SSR) Test Axial compression cyclic test under 10 psi confining pressure using UTS037 in AMPT 100 mm dia., 150 mm tall specimen cut and cored from 150 mm dia., 180 mm tall gyratory sample Use actuator displacement (i.e., no on-specimen LVDT) Test temperature: T H, T L Loading time: 0.4 sec. Rest period: 3.6 sec. for T H, 1.6 sec. for T L Deviator stress: 100, 70, 130 psi for T H and 70, 100, 130 psi for T L Two samples for each temperature for a total of four samples in one day

26 Test Temperatures T H = DD 15 log (H + 45) where T H = high test temperature, C (maximum 54 C), DD = Degree-Days >10 C ( 1000) from LTPPBind v 3.1, and H = depth of layer, mm (0 for surface layer). T L = T aaa. PP + 5 where T L = low test temperature, C, and T avg. PG = average of high and low climatic PG temperatures, C.

27 SSR Test Setup

28 Mechanistic Rutting Prediction Structure Traffic Climate Rutting Prediction

29 ALF Prediction Using SSR/Flex Programs

30 Draft AASHTO SSR Specification

31 Thank you! Questions?