Past… MOVING PAVEMENT DEFLECTION TESTING: …alacpa.org/index_archivos/MovingPavementDeflection... MOVING PAVEMENT DEFLECTION TESTING: THE FUTURE? VI ALACPA Airport Pavements Seminar

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MOVING PAVEMENT MOVING PAVEMENT DEFLECTION TESTING: DEFLECTION TESTING:

THE FUTURE?THE FUTURE?

VI ALACPA Airport Pavements Seminar & IV FAA WorkshopSao Paulo, BrazilOctober 26, 2009

Gonzalo R. Rada, Ph.D., P.E. (Fugro Consultants, Inc.)

VI ALACPA Airport Pavements Seminar & IV FAA Workshop

Past…

Benkelman Beam

(Static Load)


Later…

Steady-State Loading Devices (Sinosoidal Loads)


Present…

Falling Weight Deflectometers or FWDs (Impact Load)


• Overall pavement structural capacity

• Layer elastic moduli • Void detection in PCC

pavements• Load transfer efficiency

determinations in PCC pavements

• Delineation of homogeneous sections

• Quality control / quality assurance

FWD Uses…


FWD Data...

Deflection Basins

Load- & Deflection-Time

Histories


• Boussinesq• Burmeister• MLET• Finite elements• Dynamic analysis

FWD Data Aanalysis...

Analysis as much a science as it is an art –engineering judgement required

Analysis Methods:


Other FWD Shortcomings…

• Stop-and-go operation– Not continuous

• Operation closures required– Cause disruptions – Can create safety hazard to personnel involved

in operation• Amount of testing (production rate) is less

than continuous operation– Affects operational costs


California Traveling Deflectograph

Danish Deflectograph

MOVING PAVEMENT DEFLECTION TESTING


French Curviametre

British Pavement Deflection Data Logging

Lacroix Deflectograph




• Quest/Dynatest Rolling Weight Deflectometer (RWD)

• Swedish Road Deflection Tester (RDT)

• Texas Rolling Dynamic Deflectometer (RDD)

• ARA Rolling Wheel Deflectometer (RWD)

• UK Traffic Speed Deflectometer (TSD)


Quest/Dynatest RWD

• Four sensors; 9 ft apart

• Optical triangulation to calculate changes in slope due to applied load

~9 kip load

< 20 mph


Quest/Dynatest RWD vs. FWD


Swedish RDT

8 to 14 kip load

< 55 mph

• Two arrays of laser sensors; each consisting of 20 sensors


Swedish RDT

• Method 1 – calculate area under transverse deflection profile • Distance measurements from outer sensors subtracted

from values measured by other sensors to obtain deflection profile

• Method 2 – calculate baseline values using the three sensors on either side of each wheel• Deflection at center of load wheel relative to pair of

sensors on each side of wheel is calculated


Swedish RDT vs. FWD


Texas RDD8 to 12 kip static load

+ 3 to 5 kip dynamic load

< 3 mph


Texas RDDFull Runway

Section C


ARA RWD9 kip load

< 65 mph

• Four triangulation lasers collect continuous deflection profiles

• Three measure unloaded pavement surface, while fourth one between rear axle dual tires measures deflected surface


ARA RWD vs. FWDRWD vs. FWD

RWD vs. FWD vs. RDD


UK TSD

Danish HSD

UK TSD

11 kip load

< 50 mph


Uses two sets of lasers based on Doppler technique to measure deflection velocity of road surface

Velocity of sensors with respect to road and their angle is measured with three accelerometers and three gyro sensors

UK TSD


UK TSD vs. FWD


• Quest/Dynatest RWD and Swedish RDT– Development funding cancelled– Commercialization activities not being carried out– Prototype no longer available

• Texas RDD– Slow operational speed– Extensively used for project level and forensic

studies for delineating weak spots and assessing load transfer efficiency of joints

– Provides up to four deflections values; most versatile device in terms of measuring deflection basins

Summary…


• ARA RWD and UK TSD– High speed data collection devices– Can detect variations in pavement

stiffness– Intended to complement/supplement

FWD at present– Intended for network-level evaluation of

highway flexible pavements– Being presently implemented in US and

UK

Summary…


• Identify potential applications of moving pavement deflection devices for airports– Pavement / layer structural evaluation– Construction QC / QA– Pavement management systems

• Establish device specifications for each potential pavement application

• Assess devices against specifications developed as function of pavement application– Quality data needed regardless of pavement

application, where quality defined in terms of accuracy and precision

– Assessment contingent upon review of actual raw (point-by-point not averages) data

Airport Needs…


Research Needs…Topic Subject

Establishing Precision of Each Device

Establishing Accuracy of Each Device

Equi

pmen

t-

Rel

ated

Defining Load applied to Pavement

Understanding Sources of differences in Deflections from moving devices and FWD

Exploring why Differences in Deflections between FWD and Moving Devices are not systematic

Mea

sure

men

t- R

elat

ed

Developing a Methodology for Calibration of Moving Devices

Establishing Sensitivity of Measured Deflections to Pavement Condition

Identifying Number and Locations of Deflection Points Necessary for a Specific Application

Establishing Other Pavement Parameters that Can Improve Reliability of a Specific Application A

pplic

atio

n-

Rel

ated

Defining Best Index that Relates Pavement Deflection to Pavement Condition


• Have come long way in structural evaluation of pavements using deflection data

• State-of-the-practice today is FWD and will likely remain so for foreseeable future

• Moving deflection testing devices will continue to evolve and will eventually be used for airport pavement applications

– Continuous operation– Reduce closure times / disruptions / safety hazard– Higher production rate / lower operational costs– Additional development needed

Conclusions…


Thank you! Questions?…

Documents

Past… MOVING PAVEMENT DEFLECTION TESTING: …alacpa.org/index_archivos/MovingPavementDeflection... MOVING PAVEMENT DEFLECTION TESTING: THE FUTURE? VI ALACPA Airport Pavements Seminar