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8
C
ONCLUSIONS
Starting from the first chapter this study describes all the development trial and all the improvements which have been made year by year on the Rolling Weight Deflectometer. The latest devices are much more accurate than the first ones, and this technology used on these devices is still being developed. From the first prototypes based on an automatization of the Benkelmann’s beam, which were able to test at 5 km/h, today we have developed device which can be towed up to 100 km/h while collecting useful and accurate data about the pavement. Looking at what we can use nowadays to collect data and information about the performance of a pavement we understood the reason of developing a device such as the RWD. While to collect functional data we can use devices which can operate up to 80 km/h, structural data are collected mainly with the Falling Weight Deflectometer, which is non-destructive and very accurate, but also slow and stationary, collecting data on discrete points. As a consequence, many road administrations do not collect any structural data, and the result is a wrong planning of the maintenance repairs. Starting from 1990 many companies tried to develop a new high-efficient testing device capable of performing measurements of the pavement bearing capacity at normal traffic speed. The target was a device which will facilitate pavement maintenance and rehabilitation strategies on a network level, providing data to better allocate funds and resources.
This study includes all the development process up to the production of the first new Dynatest RAPTOR. It contains all the test performed and all the results obtained with a prototype of the RAPTOR trailer, which has been built to carry out the same technology. A hundred kilometers of shadow testing between the RAPTOR prototype and the FWD have been used to validate the output of this new device. The repeatability of the RAPTOR output has been studied, as well as the comparability with the FWD data. The comparison has been made both with curvatures and deflections. The repeatability of the RAPTOR was evaluated and proved through a comparison between data coming from different runs of the prototype over the same pavement. Regarding the comparability with the FWD measurements, the matching between the output coming from the RAPTOR and the one from the FWD was very high. Comparability of the data collected was proved both in terms of curvatures and deflections. The RAPTOR was capable of identifying the same sections with a poor bearing capacity as the FWD. It was also capable to identify sections with very good structural
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behaviors as bridges, providing low curvature or deflection values along them. The results achieved are very encouraging despite the two devices compared are completely different. The FWD and the RAPTOR differ in geometry of the sensors, accuracy of the sensors and kind of load applied, therefore the response of the pavement to these two different devices will be different as well. Considering all these differences, the results are very promising. The research performed in this study supports the validity of the RAPTOR as a reliable device to be used in pavement management and work programming on a network level. It has proved that in its current state of development, the RAPTOR can offer a high repeatability for network-level data collection, both for curvatures or deflections. These data are comparable with the most used and widely accepted FWD. The RAPTOR can already be used as a screening device on a network level, used to identify sections with poor bearing capacity. Those sections can suddenly be further investigated using the FWD for a more accurate structural evaluation. Therefore the RAPTOR is not intended to replace the FWD, but to be a complementary equipment to reduce significantly the time needed for pavement analysis.
The accuracy of the RAPTOR measurements is expected to improve when the RAPTOR prototype will be replaced by the more advanced and sophisticated RAPTOR trailer which will be operational in the first part of 2018. The new RAPTOR trailer will have more sensors and more slots available for those, allowing different configurations of the laser sensors. It will also be possible to measure deflection in the rear part of the deflection. Due to a complex system of sensors the trailer will measure the load applied instantaneously by the wheels. Therefore the data collected will be normalized to a reference load. In addition, the new RAPTOR trailer will have an integrated calibration system, with a reference surface scanned by the sensors. Later on the new RAPTOR will be equipped with a LCMS system, so that a single device will be able to provide both functional and structural data. This means that the RAPTOR will bring pavement evaluation to a network level, allowing a consistent saving in time and therefore money required for pavement analysis.
All this will be possible soon, thanks to all the test which have been performed with the RAPTOR prototype, which are described in this thesis. These tests have helped defining an operative procedure for collecting and processing data. The software for data collection has been improved during these tests, as well as the post processing operations and the models used. This technology is still under development and has shown its promising capabilities. The Dynatest RAPTOR will be operative soon, and it will radically change the future of pavement analysis.
