MULTIPLE LOAD LEVEL FWD DATA ANALYSIS BY SYSTEM STIFFNESS METHOD

The paper firstly introduces a pavement system that is designed to fail by fatigue failure, i.e. cracking induced by repeated stress below the maximum strength of the material and the number of load repetitions (number of axle loading ) a pavement system can carry determines its service life. The number of repeated axle loadings to failure is an inverse function of the induced stress. Hence, the deflection of the pavement system is an indicator of the expected pavement life. This office has been collecting falling weight deflectometer ( FWD ) data at single load levels for layer backcalculation. The FWD is capable of applying multiple load levels during a single testing procedure. Tayabji ( Tayabji, et al, 1998 ) suggested that multiple load level FWD test results can be used to detect and quantify voids beneath continuously reinforced concrete ( CRC ) pavement. Our interest is in verifying whether this approach is also true for jointed concrete pavements ( JCP ). Preliminary data indicated that multiple load level FWD data may reveal stiffness of the pavement system, therefore multiple load level FWD data were collected from both rigid and flexible pavements. Temperature data at various depths of the pavement system were also collected. Data collected were analyzed using different approaches to determine whether multiple load test results produce additional information about pavement system layer propertics. Results indicate that there is merit to performing multiple load FWD testing.