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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)
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
Later…
Steady-State Loading Devices (Sinosoidal Loads)
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
Present…
Falling Weight Deflectometers or FWDs (Impact Load)
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
• 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…
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
FWD Data...
Deflection Basins
Load- & Deflection-Time
Histories
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
• 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:
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
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
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
California Traveling Deflectograph
Danish Deflectograph
MOVING PAVEMENT DEFLECTION TESTING
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
French Curviametre
British Pavement Deflection Data Logging
Lacroix Deflectograph
MOVING PAVEMENT DEFLECTION TESTING
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
MOVING PAVEMENT DEFLECTION TESTING
• 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)
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
Quest/Dynatest RWD
• Four sensors; 9 ft apart
• Optical triangulation to calculate changes in slope due to applied load
~9 kip load
< 20 mph
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
Quest/Dynatest RWD vs. FWD
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
Swedish RDT
8 to 14 kip load
< 55 mph
• Two arrays of laser sensors; each consisting of 20 sensors
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
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
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
Swedish RDT vs. FWD
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
Texas RDD8 to 12 kip static load
+ 3 to 5 kip dynamic load
< 3 mph
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
Texas RDDFull Runway
Section C
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
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
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
ARA RWD vs. FWDRWD vs. FWD
RWD vs. FWD vs. RDD
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
UK TSD
Danish HSD
UK TSD
11 kip load
< 50 mph
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
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
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
UK TSD vs. FWD
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
• 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…
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
• 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…
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
• 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…
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
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
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
• 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…
VI ALACPA Airport Pavements Seminar & IV FAA Workshop
Thank you! Questions?…
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