Performance of Deflection Measurement Equipment and Data Interpretation in France Jean-Michel SIMONIN 1 , Jean-Luc GEFFARD 1 , Pierre HORNYCH 1 1 LUNAM Université, IFSTTAR, Route de Bouaye, CS4, F-44344 Bouguenais Cedex France Phone: +33 2 40 84 58 29, Fax: +332 40 84 59 94 email: jean-michel.simonin@ifsttar.fr, jean-luc.geffard@ifsttar.fr, pierre.hornych@ifsttar.fr Abstract In France several systems are used to measure pavement deflections: the curviameter, the Falling Weight deflectometer (FWD), and several types of deflectographs. These devices use different measurement principles and sensors (geophones or rotary coder) and have different operating speeds (static to 18 km/h). They also differ by their level of performance, and domain of use. The paper presents a comparison of the metrological performance of these different devices. Then, a sensitivity analysis is performed, to evaluate the influence of measurement frequency and temperature on deflection measurements, and correction methods to take into account these parameters, for determination of bituminous layer moduli are proposed. . Finally recommendations are proposed concerning deflection measurement in two different contexts: network monitoring and pavement reinforcement studies Keywords: Pavement monitoring, Deflection, Temperature correction, Non Destructive Technique, Metrological Performance 1. Introduction Pavement deflection, which represents the vertical displacement of the pavement under a known load, is one of the main parameters used for structural evaluation of pavements, and back-calculation of pavement layer moduli. In France, the deflectograph has been the first apparatus developed by the French road laboratories in the years 1960 for the measurement of pavement deflections. Successively, several improved versions have been developed. The FWD was developed at the same period in other countries. More recently, the research center of public works (CEBTP: Centre d’Expérimentation pour le Bâtiment et les Travaux Publics) has developed the idea of the Curviameter. Although deflection measurements are relatively standard for pavement monitoring, improving the quality of the measurements, and the interpretation of the test results is still an important issue. After describing the different devices, and discussing their accuracy, the paper proposes different approaches for improving deflection data analysis:  Corrections for taking into account temperature and loading frequency variations  Examples of analysis of deflection measurement results to detect different pavement deterioration mechanisms such as layer debonding or vertical cracks. 2. Presentation of deflection measurement methods A load applied on a pavement, induces a vertical displacement of the pavement surface. The shape of the deformed pavement surface is called the deflection bowl. The main parameters determined form the deflection bowl are the maximum deflection (maximum vertical displacement) under the center of the load, and the radius of curvature, defined as the radius of the circle that fits best the deflection bowl, at the point of maximum deflection. International Symposium Non-Destructive Testing in Civil Engineering (NDT-CE) September 15 - 17, 2015, Berlin, Germany More Info at Open Access Database www.ndt.net/?id=18284