Analysis of test slab failure data
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Analysis of Test Slab Failure Data. David R. Brill FAA Airport Technology R&D Branch, AAR-410 William J. Hughes Technical Center, Atlantic City, NJ Airport Pavement Working Group Meeting Sheraton Atlantic City Convention Center Hotel February 2, 2005. Objectives.

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Analysis of Test Slab Failure Data

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Analysis of test slab failure data

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


Objectives

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


Cc2 test item layout

CC2 Test Item Layout

3


Analysis of test slab failure data

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.


Analysis of test slab failure data

MRG After 31,020 Passes

Construction Cycle 2:Trafficking Test Item MRG

5


Analysis of test slab failure data

MRG After 31,020 Passes

6


Analysis of test slab failure data

MRS After 30,996 Passes

Construction Cycle 2:Trafficking Test Item MRS

7


Analysis of test slab failure data

MRS After 30,996 Passes

8


Cc2 test items results

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


Performance monitoring

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


Structural condition index sci

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


Micro paver computations

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


Cc2 test item distresses

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


Sci versus coverage analysis

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


Test item mrc sci versus coverages all distresses

Test Item MRC - SCI versus Coverages (All Distresses)

PRELIMINARY DATA

15


Test item mrc sci versus coverages center traffic lane distresses only

Test Item MRC - SCI versus Coverages (Center Traffic Lane Distresses Only)

PRELIMINARY DATA

16


Test item mrs sci versus coverage center traffic lane distresses only

Test Item MRS - SCI versus Coverage(Center Traffic Lane Distresses Only)

PRELIMINARY DATA

17


Test item mrg sci versus coverage center traffic lane distresses only

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


Cc2 test strip sci versus coverage s slab distresses only

CC2 Test Strip - SCI versus Coverage(S Slab Distresses Only)

PRELIMINARY DATA

C SLABS

S SLABS

19


Summary of sci vs coverage

Summary of SCI vs. Coverage

20


Regression data for sci vs log of coverages preliminary

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

21


Design factor vs coverages

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


Recalculate design factors historic full scale test data

Recalculate Design Factors(Historic Full-Scale Test Data)

Original Regression

Recalculated Using FEDFAA Edge Stress

23


Design factor vs coverages coverages to complete failure sci 0

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

PRELIMINARY DATA

24


Design factor vs coverages coverages to onset of failure sci 100

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

PRELIMINARY DATA

25


Current efforts

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


Questions

Questions?

27


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