Research Interests
- Structural Health Monitoring
- Nondestructive Evaluation
- Guided ultrasonic waves
- Acoustic Emission
- Rail monitoring
Activity
Monitoring the neutral temperature of continuous welded rails
Rail neutral temperature (RNT) is the temperature at which the average longitudinal stress at a given section of a continuous welded rail (CWR) is zero. When the temperature of the rail is below (or above) the RNT, longitudinal tension (or compression) is developed. When extreme compression overcomes track resistance, permanent track deformation due to buckling may occur. Current methods to determine axial stress are partly disruptive. Therefore, minimally invasive nondestructive evaluation methods able to determine longitudinal stress and RNT are highly desirable. In this article, a wayside system able to estimate the RNT and then the longitudinal stress in CWR is presented. The system triggers and measures low-frequency vibrations whose power spectral densities (PSD) are calculated and then utilized as the input data of a one-dimensional convolutional neural network (1DCNN), which extracts and relates the PSDs to the RNT. The wayside system was tested at a controlled facility with known RNT and at two revenue service lines. The 1DCNN was trained with data collected during three field visits and 11 days of testing at two control facilities. The same network was then used to estimate blindly the RNT of three revenue service lines. The results of the blind tests showed some promising outcomes although some discordant results warrant for more tests and better improvements of the setup and the CNN.
Bridge Load Rating
The US transportation infrastructure counts more than 620,000 bridges, which the National Bridge Inventory (NBI) categorizes as Good, Fair, and Poor based on the current condition. The rapid aging of this infrastructure is reflected in the number of bridges rated as ‘Fair’, which in 2018surpassed those rated as ‘Good’, whereas over 46,000 are rated as ‘Poor’. The maximum live load a bridge can safely carry is determined through a load rating analysis (LRA). Load ratings are customarily underpinned by simplified structural analysis that can be conveniently performed by engineering staff, but also lead to overconservative load ratings that may result in unnecessary lane restrictions, speed limits, weight postings, and even closures. Our group is working on developing new strategies to perform more accurate LRA to avoid overly conservative estimations.
