Research News

Best Practices of Using Shotcrete for Wall Fascia and Slope Stabilization, Phase I Study

Shotcrete, concrete applied pneumatically at high velocity, has become attractive because of its potential for saving cost and construction time when used to replace cast-in-place (CIP) concrete for retaining walls and slope stabilization. However, it also has potential drawbacks that raise concerns about its durability. This project was a first-phase effort in determining the best practices for using shotcrete for wall fascia built with soil nails and soldier piles. With the increasing desire of highway agencies to use shotcrete to save time and money, such information will be helpful to them in achieving the best structural quality and durability.

Snow Removal Performance Metrics

This project sought to identify effective performance metrics for snow and ice maintenance operations. The project team gathered information from published literature and surveyed the winter road maintenance operations community. They analyzed the information with a focus on performance measures for snow/ice maintenance operations, their temporal evolution and effectiveness, costs of gathering and analyzing the performance data, and methods of communicating the level of success inside the organization and beyond.

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Preliminary Study to Develop Standard Acceptance Tests for Pervious Concrete

The growing popularity of pervious concrete pavement applications, desired for their role in stormwater management and runoff control, has increased the need for development of quality control and quality-evaluation test procedures that are suited specifically for pervious concrete rather than for traditional concrete. This brief study took preliminary steps toward developing appropriate quality control and quality-evaluation test procedures by identifying suitable specimen sizes for testing, proper methods of casting and compacting specimens at the job site, the compatibility of fresh and hardened physical properties, and proper curing methods for compressive strength testing.

Numerical Evaluation of Forces on Piled Bridge Foundations in Laterally Spreading Soil

For seismically active areas, designers must consider how bridge foundations will respond to ground liquefaction, particularly lateral spreading of the soil. Current design procedures generally rely on simplified analytical methods based on a two-dimensional description of the site geometry. However, numerous bridges affected by lateral spreading during past earthquakes have displayed three-dimensional soil deformation that cannot be captured in a two-dimensional analysis, and an analysis that assumes 2-D conditions may be overly conservative, leading to unnecessarily expensive design solutions. The objectives of this research were to identify and quantify the mechanisms that may result in potential reductions in the bridge foundation demands that develop during lateral spreading by considering the 3-D geometry of the bridge site.

Liquefaction-Induced Downdrag on Drilled Shafts

This study developed an analytical method that can account for the liquefaction-caused settlement of deep foundations, in particular a structure’s drilled shafts. During and following liquefaction caused by an earthquake, sandy soil layers shrink in volume and settle. Depending on the site conditions, the changes in forces that result from liquefaction-induced soil settlement and downdrag can significantly affect the performance of drilled shafts, even damaging the structure. The new analytical method, based on the neutral plane method, proved successful in application to a case study of downdrag observed during the February 2010 8.8-magnitude earthquake in Maule, Chile.

Shear Design Expressions for Concrete-Filled Steel Tubes and Reinforced Concrete-Filled Tube Components

Concrete-filled steel tubes (CFSTs) and reinforced concrete-filled steel tubes (RCFSTs) are increasingly used in transportation structures as piers, piles, caissons, or other foundation components. CFSTs combine steel and concrete to create efficient and economical composite structural members. Because currently accepted methods for calculating the shear capacity of CFSTs and RCFTs are adapted from shear strength equations used for structural steel or reinforced concrete components, they likely significantly underestimate the shear capacity of the composite section, potentially increasing undesirable conservatism and cost. This research used integrated experimental testing methods, combined with high-resolution analytical models, to investigate the shear capacity of CFST and RCFST members and to develop an improved and more accurate shear strength expression. The resulting new expression provides a total CFST shear strength of 2 times that produced by WSDOT’s currently used expression and is proposed for implementation in WSDOT’s Bridge Design Manual.

Digital Roadway Interactive Visualization and Evaluation Network Applications to WSDOT Operational Data Usage

Researchers made improvements to the data fusion techniques and database design of an online system called the WSDOT Digital Roadway Interactive Visualization and Evaluation Network (DRIVE Net). DRIVE Net is a region-wide, web-based transportation decision support system that, using digital roadway maps as its base, provides layers for integrating and analyzing roadway data from a variety of sources and serves as a practical tool for visualizing historical observations in both space and time. With its ability to support complex analytics and decision-making for a large-scale transportation network, the system is expected to be of great practical use for both traffic engineers and researchers.

Assessment of Lube Oil Management and Self-Cleaning Oil Filter Feasibility in WSF Vessels

To help Washington State Ferries investigate the use of a self-cleaning oil filtration system, researchers from Washington State University tested such a system on one ferry vessel, looking specifically at filtration effectiveness, environmental impacts, and costs. Results of filtration effectiveness showed little difference between the standard paper cartridge filtration system currently in wide use and the self-cleaning system. A life cycle environmental impact assessment revealed that although impacts from oil and filter use would be less, the additional diesel fuel consumed by that system would outweigh any benefits in many impact categories. Finally, a life cycle cost analysis suggested that the standard system would outperform the self-cleaning system in terms of whole life cost (unless the oil lifetime could be increased by more than three-fold), primarily because the self-cleaning system used additional fuel. The researchers’ overall assessment was that if expected costs and environmental impacts are major decision points, a suitable alternative system would need to consume less diesel fuel to be viable.

Underwater Noise Reduction of Marine Pile Driving Using a Double Pile: Vashon Ferry Terminal Test

Impact driving steel piles through the water—for example, for ferry docks—produces extremely high underwater sound levels that can harm aquatic wildlife. Previous research has shown that without containing the noise, larger steel pipe piles cannot be installed with impact hammers without exceeding underwater noise thresholds established to protect critical species. To address this problem, a series of research projects for the Washington State Department of Transportation has developed a double-walled pile to decrease the total amount of noise. This project conducted a full-scale test of the double-walled pile technology at Vashon Island, Washington, with encouraging results.

Recommendations for Extending Asphalt Pavement Surface Life within Washington State

This study identified and evaluated hot mix asphalt (HMA) mix design and construction techniques that have potential for improving pavement surface life in Washington state. HMA pavement performance in Washington state varies across the state’s three broad climatic zones. In Western Washington, the average surface life of WSDOT pavements is 16.7 years. In Eastern Washington, the average surface life of WSDOT pavements is 10.9 years, and in the mountain passes, it is as low as 5 years. In addition, WSDOT pavements generally tend to fail first by cracking. However, rutting plays a more substantial role as traffic levels increase. The researchers evaluated and prioritized the application of 17 construction techniques to improve pavement life for Washington’s different climate zones and traffic conditions.

Washington State Transportation Center