1 / 27

Analysis of Test Slab Failure Data

Detailed analysis of CC2 rigid test item performance and failure, comparing with historical tests, effects of test variables, and correlation with SCI and coverages. Includes MRC, MRS, MRG test results, structural condition monitoring, Micro PAVER computations, and regression data. Evaluation of design factors, material properties, and ongoing efforts to refine failure models and base stiffness compensation.

abrianna
Download Presentation

Analysis of Test Slab Failure Data

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Analysis of Test Slab Failure Data David R. BrillFAA Airport Technology R&D Branch, AAR-410William J. Hughes Technical Center, Atlantic City, NJ Airport Pavement Working Group MeetingSheraton Atlantic City Convention Center HotelFebruary 2, 2005 1

  2. Objectives • Quantify CC2 rigid test item performance and failure using the SCI concept. • Relate to historical rigid full-scale tests (Lockbourne, Sharonville, MWHGL etc.). • Compare with current failure model. • Analyze effects of test variables: • Support type (stabilized base vs. conventional). • 4-wheel vs. 6-wheel. • Traffic on outside lane. 2

  3. CC2 Test Item Layout 3

  4. Construction Cycle 2 – Trafficking MRC North South • MRC trafficking stopped on June 24, 2004 (north side after 12,675 passes and south side after 5,402 passes. • A total of 96 cracks were detected and 20 cores taken.

  5. MRG After 31,020 Passes Construction Cycle 2:Trafficking Test Item MRG 5

  6. MRG After 31,020 Passes 6

  7. MRS After 30,996 Passes Construction Cycle 2:Trafficking Test Item MRS 7

  8. MRS After 30,996 Passes 8

  9. CC2 Test Items - Results • Full-scale traffic testing began on 4/27/04. • Trafficking ended 12/10/04. • Passes completed: • Top-down cracking has not been eliminated, but bottom-up longitudinal cracks have occurred in the lane receiving loading from both lines of tires. 9

  10. Performance Monitoring • Visual Distress Surveys. • ASTM D 5340-93 and FAA AC 150/5380-6. • Daily up to 10,000 passes. Weekly after 10,000 passes. • Embedded Sensors. • Responses monitored for early indication of cracking. • Nondestructive Tests. • HWD every 15 wanders (990 passes) up to 10,000 passes. Every 30 wanders after 10,000 passes. • Destructive Testing. • Cores to investigate origin of cracks. 10

  11. Structural Condition Index (SCI) • Rollings (1988) • SCI is structural component of rigid PCI. • Only load related distress types are considered (e.g., L/T/D cracks, corner breaks, shattered slab). • SCI is always equal to or higher than PCI for the same pavement feature. • Joint and corner spalling was excluded from the SCI computation for CC2 test items. 11

  12. Micro PAVER Computations • Record structural distresses based on visual surveys. • Treat each test item (north side or south side) as a sample unit. • Follow ASTM procedures for counting distresses and assigning severity levels. 12

  13. MRS North - Shattered Slab MRG North - Corner Spall MRG South - Longitudinal Crack Intersecting Corner Break MRS North - Long. & Diag. Cracks CC2 Test Item Distresses 13

  14. SCI Versus Coverage Analysis • Plot SCI as a function of applied coverages. • P/C ratio is computed from wander pattern. • All slabs in sample unit versus inside traffic lane only. • Obtain linear regression of SCI versus log(C). • Intercept with SCI=100 line yields CO (cov. to 1st crack). • Intercept with SCI=0 line yields CF (cov. to full failure). • New rigid design concerned with coverages to SCI=80. • Lower portions of failure curve (below SCI = 80) are important for overlay designs. 14

  15. Test Item MRC - SCI versus Coverages (All Distresses) PRELIMINARY DATA 15

  16. Test Item MRC - SCI versus Coverages (Center Traffic Lane Distresses Only) PRELIMINARY DATA 16

  17. Test Item MRS - SCI versus Coverage(Center Traffic Lane Distresses Only) PRELIMINARY DATA 17

  18. Test Item MRG - SCI versus Coverage(Center Traffic Lane Distresses Only) SCI = -247.03 log(C) + 941.57R2 = 0.9636 SCI = -246.96 log(C) + 935.11R2 = 0.9647 PRELIMINARY DATA 18

  19. CC2 Test Strip - SCI versus Coverage(S Slab Distresses Only) PRELIMINARY DATA C SLABS S SLABS 19

  20. Summary of SCI vs. Coverage 20

  21. Regression Data for SCI vs. Log of Coverages (preliminary) 21

  22. Design Factor vs. Coverages • Design Factor (DF) = ratio of concrete flexural strength to maximum calculated bending stress. • LEDFAA model based on Rollings (1988) regression: • DF = 0.5234 + 0.3920 log (CO) coverages to onset of cracking • DF = 0.2967 + 0.3881 log (CF) coverages to full failure (SCI 0) • Recompute design factors for all test items using FEDFAA (3D-FEM) edge stress. • Evaluate parameters including 7 new NAPTF data points. • Preliminary analysis - design factors subject to change as we continue to characterize the material properties. 22

  23. Recalculate Design Factors(Historic Full-Scale Test Data) Original Regression Recalculated Using FEDFAA Edge Stress 23

  24. Design Factor vs. Coverages (Coverages to Complete Failure, SCI=0) PRELIMINARY DATA 24

  25. Design Factor vs. Coverages (Coverages to Onset of Failure, SCI=100 -) PRELIMINARY DATA 25

  26. Current Efforts • Finalize material characterization (e.g., concrete strength, subgrade properties) for design factor computation. • Finalize “best fit” parameters for FAARFIELD rigid failure model from full-scale test data. • Re-evaluate current base stiffness compensation model considering: • full-scale test results showing straight-line trend. • improved ability of 3D-FEM model to give accurate stresses for stabilized base structures. 26

  27. Questions? 27

More Related