Impact of Specialized Hauling Vehicles and Emergency Vehicles on Bridge Load Rating

The Federal Highway Administration (FHWA) mandated states to adopt specialized hauling vehicles (SHVs) and emergency vehicles (EVs) in 2013 and 2016, respectively, in the load rating of bridges. Both the AASHTO single-unit trucks (SUs) and EVs are specially configured so that they may result in high load effects and can adversely affect bridge load rating factors. This paper investigates the impacts of rating these vehicles on the states’ bridge load ratings. An extensive literature review of the states’ load rating policies is performed. To determine whether any state can possibly be exempted from the new load ratings for SUs and EVs for Interstate highway bridges, the load effects of various state legal vehicles are analyzed and compared with those of SUs and EVs. The results of the study indicate the inevitability of executing the new load rating analysis for SUs and EVs for the vast majority of states. Weigh-in-motion data are processed to screen the potential EV traffic fleeting on the highway, and the calibrated live load factors are proposed for EVs accordingly. The load effects are found to be smaller than those FHWA originally assigned, improving the rating factors. Lastly, this paper proposes a screening tool to help state agencies to convert the known rating factors to the rating factors of SUs and EVs so that the load rating work can be prioritized for the bridges that are vulnerable to SUs and EVs.

Rolling bearing performance rating parameters: Review and engineering assessment

The choice of a rolling bearing for a particular application relies on performance rating parameters as the static, the dynamic, and the fatigue limit load of bearings. The values of these parameters define the calculated performance of the bearing. Endurance testing of high-quality rolling bearings has been used for the development of rolling bearing performance standards like the ISO 281 and ISO 76 that are commonly used throughout the industry. However, standard test methods for the measurement and validation of load ratings of rolling bearings are not available in the standards. This leads to the undifferentiated use of the “status of the art” standardized performance to the very large variety of rolling bearing types and qualities that are produced today. The current paper revisits the origin, definition, and development of rolling bearing performance parameters. A numerical study for the determination process of bearing load ratings is carried out. The results are compared with standardized values and values quoted by bearing manufacturers. This provides an overview of the load rating practices that are in use. The limitations and possible improvements of the present methodology are discussed.

Steel Bridge Load Rating Impacts Owing to Autonomous Truck Platoons

Autonomous truck platoons are two or more trucks driving together as a single unit through the use of vehicle-to-vehicle communication technology. These platoons can automatically accelerate or brake together, allowing them to travel at closer distances. With the world moving towards a more environment-friendly approach to everyday decisions, it is not a surprise that the concept of truck platooning is gaining momentum, as it reduces CO2 emissions by lowering fuel consumption. However, studies need to be performed to confirm that existing bridges will be able to adequately support truck platoons. The scope of this research is to study the effects of truck platooning on steel girder bridges in the United States (US). A multi-dimensional parametric study was conducted, which evaluated a variety of bridge span configurations and span lengths. Load ratings (using three different methodologies) were calculated for each of these structures for a range of truck platoons (both the number of trucks within a platoon and spacing between trucks). For comparison, the American Association of State Highway Transportation Officials (AASHTO) design and legal load ratings were also calculated for each bridge and were used to quantify the adequacy of current bridges to carry truck platoons. The study was able to identify the potentially inadequate existing bridges based on the original design methodology, configuration, and span length. This information is intended to be valuable to bridge owners as an initial screening process along corridors that will be subjected to regular truck platoon traffic.

Evaluation of a Redesigned Personal Protective Equipment Gown

Background In healthcare, the goal of personal protective equipment (PPE) is to protect healthcare personnel (HCP) and patients from body fluids and infectious organisms via contact, droplet, or airborne transmission. The critical importance of using PPE properly is highlighted by 2 potentially fatal viral infections, severe acute respiratory syndrome–associated coronavirus and Ebola virus, where HCP became infected while caring for patients due to errors in the use of PPE. However, PPE in dealing with less dangerous, but highly infectious organisms is important as well. This work proposes a framework to test and evaluate PPE with a focus on gown design. Methods An observational study identified issues with potential for contamination related to gown use. After redesigning the existing gown, a high-fidelity patient simulator study with 40 HCP as participants evaluated the gown redesign using 2 commonly performed tasks. Variables of interest were nonadherence to procedural standards, use problems with the gown during task performance, and usability and cognitive task load ratings of the standard and redesigned gowns. Results While no differences were found in terms of nonadherence and use problems between the current and the redesigned gown, differences in usability and task load ratings suggested that the redesigned gown is perceived more favorably by HCP. Conclusions This work proposes a framework to guide the evaluation of PPE. The results suggest that the current design of the PPE gown can be improved in usability and user satisfaction. Although our data did not find an increase in adherence to protocol when using the redesigned gown, it is likely that higher usability and lower task load could result in higher adherence over longer periods of use.

Extending the Life of Historic Concrete Bridges

<p>Open-spandrel, concrete arch bridges were a common bridge design in the United States during the early 1900s. Many of these bridges are now urban landmarks and listed historic structures that local jurisdictions wish to rehabilitate, including widening the deck to more safely accommodate pedestrians and bicyclists. However, decades of exposure in harsh climates have led to advanced deterioration and reduced load ratings for most extant examples. Further complicating rehabilitation, the height, and arch-reliant behavior of these bridges make construction access, staging, and maintenance of traffic difficult. Drawing upon the authors’ experience with several bridges of this type, this paper discusses best practices and special considerations for investigating and rehabilitating historic concrete arch bridges to extend their life.</p>

Impact of Specialized Hauling Vehicles on Load Rating Older, Bridge-Class, Reinforced Concrete Box Culverts

This paper describes the comparison of load ratings associated with application of three live load models recognized by AASHTO—AASHTO legal loads, the notional rating load including single-unit specialized hauling vehicles (SHVs), and the HL-93 design tandem live load—versus load ratings associated with application of the typical HS-20 standard truck. The test bed for this study was a statistically representative sample of Texas’ older bridge-class reinforced concrete box culvert structures. Rating factors were determined using the load factor rating method with demands calculated from a production-simplified, calibrated, two-dimensional soil–structure interaction model using linear elastic constitutive models for both concrete and soil. The study was motivated in part by research which showed that SHVs create force effects significantly greater than those from the HS-20 truck (for bridges proper), and recent federal policy mandating that states load rate their bridges for SHVs. Findings from this study indicate the standard HS-20 truck, and not SHVs or other legal or design loads, is the critical model for most culvert load rating applications. In particular, operating rating factors calculated from both the AASHTO legal loads and SHV models tend to be higher than corresponding rating factors calculated using the HS-20 standard truck, most of the time. The response is explained primarily by considering the relatively short span length of culvert structures and the load-attenuating benefit of cover soil above the culvert top slab. More detailed exploration of rating variables suggests interactions between culvert geometry, cover soil thickness, and the various types of applied vehicle loads.