Continuous Runway Load-Deflection Evaluation Methodology

During the Phase-I research we only spent 6 months (not 9 months) an air droppable rolling weight deflectormeter (ADRWD) was built and a conceptual demo at a small airport was successfully conducted. The Phase-II main objective is to refine the Phase-I design and build a lightweight working ADRWD prototype that can accurately measure the runway deflection and correctly evaluate the load carrying capacity of any runway to give a go or not go answer for a class of airplane. In order to realize this goal we have deeply analyzed those big RWDs and found that there are 7 serious problems must be overcome: (1) the measurement assumptions and calculating equations are questionable, (2) it is impossible to measure the deflection at the same point in the two-step and two-point procedure, (3) the two-step procedure will get large error from the truck vibration and pavement unevenness, (4) the two-point measurement cannot get the deflection basin, (5) the error from support beam bending should be simply removed, (6) the error from different sensor heights should be eliminated, (7) the effects of the dust, dirt and moisture to the sensor window should be prevented. The key of our new design to solve these problems is to put a sensor between the front tire and rear tire without deflection and put 3 sensors behind the rear tire with deflection and sample their data simultaneously then make average and subtraction to get the relative deflection basin and eliminate the errors from pavement unevenness, truck vibration, test not at exact point, and so on. In Phase-II, we will build and deliver 3 prototypes: (1) use high accuracy laser rangefinders with inclinometer, speed/distance encoder, GPS and ground marker to get the deflection profile, (2) add the thermal scanner and ground penetration radar to the above for layer analysis, (3) add a portable falling weight deflectometer to the system (1) for test verification at discrete points. Since there is no software can be adopted from existing RWD, two new software packages will be developed: (1) automatic high speed sensor operation and data collection software and ASIC, (2) backcalculation and runway load bearing capacity estimation equations and data analysis software to get a 3-D runway deflection and defects profile with ground marks as a function of space and time. In addition to the airport application, the portable ADRWD will be used for highways, gas stations and many other places; the technology related with laser rangefinder, IR, Radar, etc. will be used for railway defects inspection and missile defense and their prototypes will be built up in Phase-II as a part of commercial applications.