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Recent traffic trends and permit issuance show significant mobility demands in the energy sectors across the nation. The increase in the axle loads and frequency of operations of over-weight (OW) trucks resulted in severe damage to transportation infrastructures. Traditionally, the damage imparted by OW vehicles has been quantified by means of the equivalent axle load factors (EALFs) concept. However, because of the nature of assumptions in the development of damage equivalency factors, the field distresses substantially deviate from the prediction models. Therefore, this study aimed to bridge this gap by developing a mechanistic framework to determine damage equivalency factors tailored toward the specific characteristics of OW vehicles operating in the OW corridors, while considering the environmental conditions and the unique features of transportation facilities in the network. To achieve this objective, initially, the authors devised a plan to collect traffic information using portable weigh-in-motion devices at two intervals for 10 representative sites in the energy corridors of Eagle Ford Shale region. Subsequently, a series of nondestructive tests were conducted in the field to determine the material properties of the pavement layers for further numerical simulations. This information was further incorporated into a 3D finite element system to calculate critical input parameters in the modified damage factor models. The proposed mechanistic approach confirmed that the modified damage factors were substantially higher compared with traditional industry-standard values. Further investigation of environmental factors and pavement profiles in this study underscored the significance of these components for accurate assessment of the damage equivalency factors.

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This paper describes work towards the development of a Lamb wave scanning method for the detection of defects in thin plates. The approach requires the generation of an ultrasonic S o -Mode Lamb wave using an incident transmitter excited with a tone burst centered at a near non-dispersive frequency. A pair of receiving transducers, with a fixed relative separation, remotely scans line sections of the thin plate. The global position of the receiver pair is moved to cover a large plate area. The arrival time information coming from incident and reflected waves contain information associated with the location of reflection surfaces or potential flaws. The cross-correlation between the excitation signal and the receivers' waveforms is obtained and subsequently demodulated using a quadrature amplitude method in order to facilitate the determination of arrival times. Distances from the source, to the reflection surface and to the receivers are found from the arrival times of the reflected waves and the Lamb wave phase velocity. The distances and the source and receiver locations are incorporated in an elliptical solution to find coordinates of the reflection points. In a line scanning the set of predicted reflection points define the extent of the defect. The Lamb wave scanning approach is tested using 1.6 mm-thick Aluminum plates with notches of various lengths and orientations from 0, 22.5 and 45 degrees with respect to the far edge of the plates. The results are summarized with defect maps that compare favorably to the actual notch locations.