00802452

Component

https://doi.org/10.3141/1716-02

http://scholar.google.com...nson&publication_year=2000

More than 400 falling weight deflectometer (FWD) devices are presently in use throughout the world, and deflection reading accuracy is very important. Deflections are measured in microns, or hundredths of a mil, and even very small errors in the deflection readings can have a profound effect on the results of backcalculation. One question that has somehow escaped scrutiny is the one alluded to in the title to this paper--exactly where along the deflection basin are the FWD deflection sensors positioned? This is an extremely important issue for proper definition of the deflection basin as a function of distance from the center of the loading plate. A review of the FWD load-deflection data in the Long Term Pavement Performance (LTPP) study found that in at least 7% of some 4 million lines of FWD deflection data in the National Information Management System (NIMS) database, the sensors were not positioned as reported. This problem is not limited to LTPP and NIMS, and it occurs all too frequently on FWDs everywhere. How sensor positioning errors influence backcalculated moduli, even if all other facets of the FWD data are 100% correct, is described. Examples of the errors found in NIMS are also presented--real-life illustrations of what can go wrong and how much influence these errors can have on pavement analysis. A method of scanning for sensor positioning errors without carrying out backcalculation is presented. By use of the suggested transform, sensor positioning errors are clearly evident when suspect data are compared with correct data along the same, or other, pavement sections.

This paper appears in Transportation Research Record No. 1716, Pavement Assessment and Testing.

English

p. 10-19

2000

Transportation Research Record

0309066956

Figures (5) ; References (4) ; Tables (3)

Accuracy; Backcalculation; Deflection tests; Errors; Falling weight deflectometers; Modulus of elasticity; Positioning; Sensors

Long-Term Pavement Performance Program; National information Management System

Data and Information Technology; Highways; Pavements; I23: Properties of Road Surfaces

TRIS, TRB, ATRI

Nov 6 2000 12:00AM

• ACCELERATED PAVEMENT TESTING OF RUTTING PERFORMANCE OF TWO CALTRANS OVERLAY STRATEGIES
• BACKCALCULATION OF THERMALLY DEFORMED CONCRETE PAVEMENTS
• CURVILINEAR BEHAVIOR OF BASE LAYER MODULI FROM DEFLECTION AND SEISMIC METHODS
• DYNAMIC INTERPRETATION OF FALLING WEIGHT DEFLECTOMETER TEST RESULTS: SPECTRAL ELEMENT METHOD
• EFFECT OF MOISTURE ON MODULUS VALUES OF BASE AND SUBGRADE MATERIALS
• ESTIMATING SUBGRADE STIFFNESS AND BEDROCK DEPTH: COMBINED FALLING WEIGHT DEFLECTOMETER AND SIMPLIFIED SPECTRAL ANALYSIS OF SURFACE WAVES MEASUREMENTS
• EVALUATING MEASURED TIRE CONTACT STRESSES TO PREDICT PAVEMENT RESPONSE AND PERFORMANCE
• EVALUATING RUNWAY PAVEMENTS AT SEATTLE-TACOMA INTERNATIONAL AIRPORT: CONTINUOUS DEFLECTION PROFILES MEASURED WITH THE ROLLING DYNAMIC DEFLECTOMETER
• PERFORMANCE OF SUPERPAVE MIXTURES UNDER ACCELERATED LOAD TESTING
• PERFORMANCE PREDICTION OF LOUISIANA ACCELERATED LOADING FACILITY TEST SECTIONS
• RUTTING OF THIN PAVEMENTS: FULL-SCALE STUDY
• SUPER-ACCELERATED TESTING OF FLEXIBLE PAVEMENT WITH STATIONARY DYNAMIC DEFLECTOMETER
• TEMPERATURE CORRECTION ON FALLING WEIGHT DEFLECTOMETER MEASUREMENTS
• TRUCK TRAVEL TIME AROUND WEIGH STATIONS: EFFECTS OF WEIGH IN MOTION AND AUTOMATIC VEHICLE IDENTIFICATION SYSTEMS
• USING A ROAD SURFACE ANALYZER TO EXPLAIN NOISE CHARACTERISTICS OF PORTLAND CEMENT CONCRETE PAVEMENT SURFACE TEXTURE
• USING TRANSVERSE PROFILE DATA TO COMPUTE PLASTIC DEFORMATION PARAMETERS FOR ASPHALT CONCRETE PAVEMENTS