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Using Fiber-optic Sensor Technology to Measure Strains Under the Asphalt Layer of a Flexible Pavement Structure
Elfino, Mohamed K.
Stephen R. Sharp
Stephen R. Sharp
Year: 2006
VTRC No.: 07-R5
Abstract: In this study, a flexible pavement system was instrumented using fiber-optic strain sensors (FOSS). The purpose of this study was to demonstrate the feasibility of a FOSS installation, monitor the long-term strains under repeated traffic loading, and compare the measured strains with the calculated ones from multi-layer elastic (MLE) analysis. MLE analysis was performed before and after FOSS installation to monitor strains during and after construction. Insitu strains during construction under the hot-mix asphalt (HMA) delivery truck, paver operations, and roller operations were compared to the results of theoretical MLE analysis. In addition, in-situ strains after construction under dump truck and falling weight deflectometer (FWD) loadings at multiple load levels were compared to the results of theoretical and in-situ MLE analysis. The in-situ strain under construction was at least 50 fold that obtained with MLE analysis. The FOSS were sensitive enough to collect strain measurements during construction at very high construction temperatures and moisture conditions. Further, the MLE analysis results were very close to the measured deflection under dump truck and FWD loadings. The results show that MLE analysis can be used to validate and calculate the strains in asphalt pavement sections. Long-term performance monitoring is continuing, and the study will be repeated after FOSS placement in new HMA pavement sections. Understanding the behavior of asphalt pavement under repeated traffic loads can result in an optimized design, thus reducing the rehabilitation costs associated with premature failures or the higher costs associated with conservative asphalt pavement designs. The in-situ strains can be used to calibrate mechanistic-empirical pavement design guide (MEPDG) performance models for local conditions so that measurements can better predict the life of pavement layers and the layers that will need replacement. The installation of FOSS at selected pavement sites that represent the typical pavement designs across the state would allow for the development of accurate statewide mechanistic-empirical performance models, which would lead to more cost-effective pavement rehabilitation decisions.