Search for: All records

The long-term monitoring of transportation infrastructure assets at a lower cost and with short mobilization time is of significant interest to both state and federal transportation agencies in the U.S. Because of the significant improvement in spatial and temporal resolution of synthetic aperture radar (SAR) remote sensing systems and a notable reduction in the cost of data acquisition, SAR has now become a viable method to provide economic and rapid condition assessment of transportation assets. A research study was developed and performed to comprehensively perform the inspection and characterization of a pavement surface based on the amplitude of backscattering of an X-band radar. In situ characterization of the test site was first performed using traditional inertial profilers and aerial photogrammetry with unmanned aerial vehicle (UAV) surveys. The results from these in situ methods were compared with the corrected amplitude of the SAR data, which indicated that the distribution of surface roughness values computed from the inertial profiler, UAV, and SAR exhibited similar probability densities at various segmental lengths considered in this study. This suggested that the problematic areas that are evident during in situ characterization can be delineated and quantified based on the normalized radar cross section of the pavement surface. Overall, the outcome of this research exhibits the potential of SAR for future transportation asset management undertakings, and the systematic framework developed as a part of this research could be of significant interest to engineers and transportation practitioners. 

Bridges play a key role in supporting the transportation network in the United States. The 2021 infrastructure report card prepared by ASCE highlighted that more than 40% of bridges in the U.S. are over 50 years old. Some of these bridges are classified as structurally deficient, even though they are safe to travel. To address these challenges, highway agencies are exploring innovative technologies to conduct inspections and realize benefits in relation to access, cost, and safety. Federal and state DOTs have conducted several studies on the application of uncrewed aerial vehicles (UAVs) for bridge health monitoring. This study identified the existing knowledge gap in performing 360° inspection of bridges. In this current research, UAVs were demonstrated for conducting 360° inspections of three different bridges in Alaska. The locations of the aerial images during the inspections were also pictographically represented to provide a holistic idea for the highway agencies and practitioners. Three-dimensional models representing the actual conditions of the bridge were generated and used for comparing the bridge condition assessments with traditional inspection reports. Infrared imagery was also collected to identify the effect of thermal loading in assessing the conditions of the bridge elements. The applicability and recommendation scale for the use of UAVs for different bridge inspections was provided. The approach demonstrated in this study is expected to result in more than 90% savings in storage requirements and contribute to an increase in the applications of UAVs for conducting 360° bridge inspections across the U.S. 

Airports facilitate the fastest mode of transportation and connect local communities and businesses with national and international destinations. The American Society of Civil Engineers (ASCE) 2021 infrastructure report card rated the aviation infrastructure category with a D+. This highlights the need for frequent monitoring and performing timely preservation techniques to ensure the optimal performance of the asset. The Texas Department of Transportation (TxDOT) periodically inspects the regional airports in Texas through visual surveys and estimates the pavement condition index (PCI) for each airport on a network scale. These ratings are used to assess the need for rehabilitation in a timely manner. In this study, an attempt was made to use an unmanned aerial vehicle (UAV) mounted with an optical camera to inspect and evaluate the condition of various airport assets. Several observations were outlined to conduct a safe inspection of airport assets using UAVs. A comparison of PCI values, grouped into three categories, obtained from traditional and aerial inspections was made to understand the feasibility of using this new technology for airport asset management. It was observed that both inspections classified most of the airport assets similarly. The traditional inspection was observed to be quicker as it requires inspection of only sampled units, however, UAV data processing takes a relatively long time to offer a comprehensive digital footprint and immersive visualization experience of the whole airport assets. Overall, UAVs are identified to have a great potential as a data collection tool supplementary to the current traditional practices. 

Stabilization of sulfate-rich expansive subgrade soils is a persistent cause of concern for transportation infrastructure engineers and practitioners. The application of traditional calcium-based stabilizers is generally not recommended for treating such soils because of the formation of deleterious reaction products such as ettringite. Sulfate-induced heaving causes severe structural damage to pavements and accounts for enormous expenditure from routine maintenance and rehabilitation activities. A research study was undertaken to evaluate the feasibility of using a metakaolin-based geopolymer (GP) for the treatment of sulfate-rich expansive soil. Laboratory studies were conducted on natural soil and artificially sulfate-rich soils, when treated with either lime or GP, to evaluate and compare the improvements in the engineering properties, including unconfined compressive strength, swelling and shrinkage, and resilient moduli characteristics over different curing periods. Microstructural studies, such as field emission scanning electron microscopy and X-ray diffraction, were performed on treated soils to detect the formation of reaction products. The engineering studies indicate that GP treatment enhanced strength and resilient moduli while suppressing ettringite formation and the associated swell–shrink potential of the treated soils. The microstructural studies showed that GP gels contribute to the improvement of these engineering properties through the formation of a uniform geopolymer matrix. In addition, the absence of a calcium source suppressed the formation of ettringite in the GP-treated soils. Overall, the findings indicate that GPs could be used as a potential alternative to existing traditional stabilizers for treating sulfate-rich expansive soils.