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Topic: Falling weight deflectometer

	Falling Weight Deflectometer
		The FWD (Falling Weight Deflectometer) is a non-destructive testing device that is used to complete structural testing for pavement rehabilitation projects, research, and pavement structure failure detection.
		The FWD is a device capable of applying dynamic loads to the pavement surface, similar in magnitude and duration to that of a single heavy moving wheel load.
		FWD generated data, combined with layer thickness, can be confidently used to obtain the "in-situ" resilient elastic module of a pavement structure.
	www.wsdot.wa.gov /biz/mats/pavement/fwd.htm (217 words)

	Patent 4116041: Apparatus for bearing capacity measurement with a falling weight deflectometer (Site not responding. Last check: 2007-11-04)
		A falling weight deflectometer operates with a falling weight, transmitting shock energy upon its fall to an intermediate weight and to a holder for a pressure plate engaging the ground.
		Between the falling weight and the intermediate weight is interposed a shock absorber of elastically yieldable material such as shock absorbing rubber, and a corresponding shock absorber is interposed between the intermediate weight and the holder.
		Thereafter, the falling weight is dropped and the shock force obtained is transmitted via the rubber shock absorbers 19, 21, intermediate weight 17 and the holder 18 to the pressure plate.
	www.freepatentsonline.com /4116041.html (2135 words)

	ATREL Research: Analysis of the Performance of New Pavement Mixes Using Falling Weight Deflectometer (Site not responding. Last check: 2007-11-04)
		The main objective of this project was to analyze the response of the different pavement layers to Falling Weight Deflectometer (FWD) loading with special emphasis on the hot-mix asphalt layers.
		The structural capacity of the 12 flexible pavement test sections was evaluated using a Falling Weight Deflectometer (FWD) as the pavement was constructed.
		The deflections obtained from the FWD testing were analyzed to estimate the "as-built" in-situ resilient modulus of each layer.
	cee.uiuc.edu /research/atrel/fwd.html (284 words)

	Abstracts (Site not responding. Last check: 2007-11-04)
		Use of Falling Weight Deflectometer (FWD) for the evaluation of pavements is gaining popularity in many countries, as it is possible to simulate the magnitude and duration of load applied by a fast moving vehicle on highways using this equipment.
		In this project FWD testing and analysis were used for a variety of functions - assessing the existing condition of the mainline pavement (a jointed reinforced concrete pavement), investigating the causes of premature distresses in the mainline pavement, and monitoring the effectiveness of slab undersealing at joint locations.
		FWD test results proved to be very useful during this investigation - both in evaluating the pavement condition and investigating the causes of the transverse cracking.
	www.rpug.org /2002/Abstracts.html (12536 words)

	July 2004 - Back to Basics
		A rolling wheel deflectometer, as its name suggests, is a device designed to measure and record pavement deflections at highway speeds, thus increasing productivity by an order of magnitude as compared to the falling weight deflectometer.
		When the rolling wheel deflectometer has moved forward, a distance equal to the sensor separation distance, the same three points on the pavement are again measured; but now using the second, third and fourth sensor.
		Falling weight deflectometer and rolling dynamic deflectometer data were collected over the same sections for comparison to the rolling wheel deflectometer data.
	www.asnt.org /publications/materialseval/basics/jul04basics/jul04basics.htm (3941 words)

	Applied Pavement Technology (Site not responding. Last check: 2007-11-04)
		APTech’s heavy-weight model falling weight deflectometer (FWD) is a specialized pavement testing device that allows the rapid and accurate characterization of the structural condition of all types of paved structures through non-destructive means.
		The heavy-weight model FWD is able to apply loads up to 55,000 pounds, thereby simulating loadings ranging from vehicular traffic on highways up to the heaviest aircraft on large commercial airports.
		One of the primary benefits of FWD testing is the ability to evaluate multiple locations in a short period of time without disturbing the pavement structure.
	www.pavementsolutions.com /engserv/fwd.asp (215 words)

	Dynatest® Falling Weight Deflectometer Test Systems - FWD / HWD -
		Dynatest, the original commercial developer of the Falling Weight Deflectometer (FWD) technology, is the world’s largest supplier of FWD equipment.
		The use of a Dynatest FWD enables the engineer to determine a deflection basin caused by a controlled load with accuracy and resolution superior to other existing test methods.
		The FWD produces a dynamic impulse load that simulates a moving wheel load, rather than a static, semi-static or vibratory load.
	www.dynatest.com /hardware/fwd_hwd.htm (504 words)

	IRC Network - Technology profiles diffused via the Automatic Matching Tool
		The deflectometer can be used in road building for estimating the compaction degree of road embankment, splinters ground and road covering, also for evaluating the bearing capacity of ground under the basement in house building.
		The deflectometer is a portable device with relatively small dimensions and mass and therefore easy to handle and use in places difficult to reach with other devices due to their bigger size.
		The deflectometer body represents the quadrate aluminium tube; in the upper part of the quadrate tube there is the electronic part with intuitively usable LCD (liquid crystal display) panel, the acceleration sensor and the holding magnet.
	www.ircnet.lu /matching/completerec.cfm?BBS_ID=10549&COMPANY=21291 (455 words)

	Number 2, 2001 of Nordic Road & Transport Research
		FWDs are now used to test the bearing capacity of roads as part of the routine evaluation of the road networks in many countries.
		The falling mass, the drop height, and the buffer system, are selected to simulate the stresses produced in a pavement structure similar to that of a heavy truck travelling at 60 km/h.
		A Contract Agreement for the “Implementation of Falling Weight Deflectometer Technology and Development of Analytical Pavement Design Project” was signed between the DOH, Thailand, and the DRD on 30th October 1998.
	www.vti.se /nordic/2-01mapp/drd.htm (1404 words)

	ACPA - Research Digest 2000 (Site not responding. Last check: 2007-11-04)
		Falling-weight deflectometers are often preferred over destructive methods of testing because they are much faster than destructive tests and do not entail the removal of pavement materials.
		Pavement properties are "back-calculated" from the observed dynamic response of the pavement surface to an impulse load (the falling weight).
		The disadvantage of the FWD method is that its results are often dependent on such factors as the particular model of tester used, the specific testing procedure, and the method of back-calculation.
	www.pavement.com /PavTech/Research/resdigest/2000/materials/m14.asp (319 words)

	Title page for ETD etd-04092003-162026
		Falling weight deflectometer (FWD) is currently used by most highway agencies to determine the structural condition of the highway network.
		In addition, the FWD measurements were used to establish a comparison between in-situ measured and computed stresses and strains in the pavement.
		The study also recommended further validation of FWD measurements using embedded instruments to calibrate analytical models and further analysis of deflection data so that optimum number of testing points can be determined to limit amount of testing performed for determination of deflection variability.
	scholar.lib.vt.edu /theses/available/etd-04092003-162026 (486 words)

	FHWA-SA-95-038
		The actual operation of the FWD during the calibration process is the responsibility of the FWD operator.
		FWD Manuals and typical spare parts should be in the tow vehicle as you may need them in case of unforeseen problems.
		Allow the FWD buffers to stabilize to the temperature of the calibration center prior to the calibration.
	www.tfhrc.gov /pavement/ltpp/fwdcal.htm (1166 words)

	TRB Annual Meeting Program (Site not responding. Last check: 2007-11-04)
		Falling weight deflectometer measurements were conducted on 12 sections at the Virginia Smart Road to quantify the variability within and between test sections.
		Analysis of the deflection measurements and temperature data resulted in the development of an exponential model for deflections versus temperature for all 12 sections.
		The COV ranged from as low as 7% to as high as 42% for the FWD loading plate center deflections.
	gulliver.trb.org /am/ip/paper_detail.asp?paperid=2312&p=yes&h= (304 words)

	Falling Weight Calculation (Site not responding. Last check: 2007-11-04)
		Falling (Heavy) Weight Deflectometer (FWD andHWD) - Falling Weight Deflectometer and Heavy Weight Deflectometer The Equipment...
		Falling Weight Deflectometer Testing/Evaluation -...impact, plate size and the development of improved back-calculation methods.
		Abatech - Analysis of falling weight deflector - ANALYSIS OF reliable method for performing back-calculation of...
	www.dailybodybuilding.com /falling-weight-calculation.html (709 words)

	Falling Weight Deflectometer, FWD, Pavement Evaluation
		The van integrated FWD equipment may be driven at normal driving pace and the clear and good view from the van while testing offers optimum road safety.
		The FWD unit is well protected in the van and leaves room for further equipment or even a small laboratory.
		The standard van-integrated FWD is supplied with personal computer, Windows FWD software, time history module, transport lock, DMI (Distance Meter Indicator) integrated in the software, three temperature sensors, four-split loading plate, 9 geophones and warning lights.
	www.mastrad.com /fwdvan.htm (363 words)

	Carl Bro (Site not responding. Last check: 2007-11-04)
		Falling weight deflectometers (FWD) were introduced at the end of the 1960s.
		They were developed and produced by, among others, the people behind the current state-of-the-art falling weight deflectometers from Carl Bro.
		PRI 2100 FWD are the tratitional falling weight deflectometer available in two verions and both versions are modular in design and can easily be upgraded from the trational 7-150 kN to 7-250 kN Heavy Weight Deflectometer (HWD) and from trailer to van:
	pavementconsult.carlbro.dk /fwd_products.php (509 words)

	LTPP Temperature Prediction and Correction Guide -- Glossary
		Datasets used in backcalculation are generally generated by falling weight deflectometers and dynamic deflectometers.
		A class of fl or dark-colored solid, semisolid or viscous cementitious substances, natural or manufactured, composed principally of high molecular weight hydrocarbons, of which asphalts, tars, pitches and asphaltites are typical.
		A device that measures the deformation response of a pavement due to a load generated by the arrest of a falling mass.
	www.ltpp.org /fwd_temp/gloss.htm (582 words)

	[No title]
		Measurement of pavement structural properties via the falling-weight deflectometer (FWD) is an accepted practice in highway pavement testing.
		Despite the increasing popularity of FWD devices, the FAA does not currently issue specifications for their use on airport pavements.
		Emphasis will be placed on verifying repeatability of FWD results, linearity of load impact, plate size and the development of improved back-calculation methods.
	www.airtech.tc.faa.gov /pavement/28ndt.asp?p=T (514 words)

	Falling Weight Deflectometer, FWD, Pavement Evaluation (Site not responding. Last check: 2007-11-04)
		The FWD produces a load pulse which simulates the effect of a moving wheel load in magnitude.
		The measured set of data (peak load, deflection values, distance from start point, air and surface temperatures) is displayed on the micro computer for direct visual inspection, and is printed out and stored on disk when accepted by the operator.
		Information about layer thicknesses and expected traffic load during the desired period combined with the FWD generated data enable calculation of the E-moduli of the pavement.
	www.petroleum-test.com /fwd.htm (293 words)

	dirfwd
		One method, which involves dividing the deflection 1828.8 mm (72 inches) away from the load plate by the deflection underneath the load plate, relates directly to the ratio between the pavement modulus and subgrade modulus for a two layer system.
		According to the construction plans, the pavement structure consisted of 177.8 mm (seven inches) of asphaltic concrete pavement, 330.2 mm (thirteen inches) of a flexible or granular base, and 152.4 mm (six inches) of lime treated subgrade.
		Results of the FWD data analysis for the eastbound lanes are shown in Table 9.
	home.flash.net /~awimsatt/dirfwd.htm (2558 words)

	4.3.1 Transportation / Geotechnical Methods
		The falling weight deflectometer is a nondestructive device that sends an impulse (with known magnitude and duration) to the pavement and/or base.
		For example, large deflectometers permit the evaluation of complete structural pavements, while lightweight deflectometers permit the evaluation of subsystems, such as bases and sub-bases.
		In-situ soil unit weight: the relative dielectric permittivity of the in-situ soil, the relative dielectric permittivity of the Proctor mold compacted soil, the Proctor mold compacted soil unit weight and the water content.
	www.cflhd.gov /AGM/engApplications/Pavements/43TransportGeotechMethods.htm (1158 words)

	Abstract Review Form
		Another assumption is that Falling Weight Deflectometer (FWD) testing at any single point should provide the same measured deflections and calculated parameters, such as layer moduli, if tested under equivalent loading and environmental conditions.
		Testing performed at a single location using an FWD while controlling as many of the possible variables provides a hypothesis to explain the variations between multiple tests detected in previous research.
		While the measured deflections can change significantly when performing multiple tests at a single point, the backcalculated parameters such as layer modulus and critical strains are not as variable and appear to be the same between multiple drops.
	webce.ent.ohiou.edu /orite/Conference/Orr,%20D.html (652 words)

	Falling Weight Deflectometer for Estimating Subgrade Elastic Moduli (Site not responding. Last check: 2007-11-04)
		Falling Weight Deflectometer for Estimating Subgrade Elastic Moduli
		In this study, 12 test sections with subgrade reflecting a range of soil types (fine- and coarse-grain soils) were tested.
		Falling weight deflector measurements were conducted directly on the prepared subgrade, followed by thin-wall Shelby tube samples from depths up to 1.5 m for laboratory M
	www.pubs.asce.org /WWWdisplay.cgi?0300121 (198 words)

	Pavement Design - Anders Lenngren (Site not responding. Last check: 2007-11-04)
		He has been involved in the development of methods for evaluating fast, non-contact devices as a means of assessing surface characteristic data as well as non-destructive structural bearing capacity.
		His doctoral work included validation of the use of back-calculation techniques in falling weight deflectometer data, currently the prime choice for pavement structural evaluation.
		It is towed behind a vehicle, which drives along the road and at regular intervals drops a weight onto the surface in such a way that the load is equivalent to a truck driving at 70 km an hour.
	www.chalmers.se /HyperText/Prof-E/Lenngren-E.html (1231 words)

	COST-Transport: Completed Actions: Use of Falling Weight Deflectometers in Pavement Evaluation
		The potential for using FWDs in evaluation at network level will also be assessed, and the final objective of the project will be to establish a preparatory basis for European standardisation in the field.
		COST 336 deals with issues surrounding the use of falling weight deflectometers for measuring the bearing capacity of road pavements.
		Use of FWDs is one of a number of technical areas selected by national government road research laboratories for addressing at European level.
	www.cordis.lu /cost-transport/src/cost-336.htm (618 words)

	Structural Evaluation of Airfield Rigid Pavements Using Falling Weight Deflectometer (Site not responding. Last check: 2007-11-04)
		By analyzing these FWD measurements with the finite element model, the usefulness of the FWD as a tool for measuring various important pavement properties is assessed.
		Based on the deflection basins measured by FWD, the resilient modulus of the foundation can be calculated, load transfer efficiency at joints of pavement can be determined, and the size of voids beneath the slab can be detected.
		Field measurements made at an in-service airfield pavement indicate that the FWD is a suitable device for the structural evaluation of jointed concrete airfield pavements.
	www.pubs.asce.org /WWWdisplay.cgi?9301590 (161 words)

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