The U.S. National Highway System (NHS) – the federally managed bridge and road network that moves American people and goods – has suffered from decades of insufficient maintenance and heavy use. Lack of funds, increasing traffic loads, and environmental exposure have encouraged rapid bridge deterioration in an already aging system. In 2016, nearly 40% of the nation’s bridges were over 50 years old and 9.1% were rated “structurally deficient.” To properly prioritize maintenance, repairs, and reconstruction, the Federal Highway Administration (FHWA) has implemented the National Highway Performance Plan (NHPP), which requires states to design and implement management strategies for their NHS assets.
To fulfill Montana’s NHPP requirements, two WTI employees, Senior Research Engineer Damon Fick and Researcher Matt Bell, have developed a bridge assessment program for the Montana Department of Transportation (MDT) using three decades of inspection and deterioration data. By performing a time-based statistical analysis on these data Bell and Fick were able to create graphical deterioration projections – or Deterioration Curves – for bridges across the state. These were then adjusted to better reflect the deterioration observed in MDT’s real-world observations. “These bridge deterioration curves guide maintenance planning and decision-making at both the project and network level,” noted Bell. “By reflecting what we see in the real world, MDT can use the curves to appropriately allocate money for future work and make sure maintenance is happening at the right time.
While the deterioration curves indicate the general deterioration rate of bridges across Montana, Bell and Fick will identify specific deterioration variables (deicers, precipitation, traffic volume, etc.) in their next MDT project. “Faster or slower deterioration rates in different Montana districts may be related to maintenance practices, as much as, or in combination with, environmental conditions,” said Bell. “For example, bridges that permit heavy truck loads may experience faster deterioration. If we understand the specific impact, MDT can improve truck permitting and preemptively identify maintenance activities and building specifications. Continually improving the accuracy of the deterioration curves will support the decision-making process for our colleagues at MDT.”
The Montana Department of Transportation (MDT) has found concrete-filled steel tube (CFST) piles connected at the top by a concrete pile cap to be a very cost-effective support system for short and medium span bridges. This type of system offers low initial cost, short construction time, low maintenance requirements, and a long service life. While the gravity load performance of these systems is well understood, their strength and ductility under extreme lateral loads (e.g., seismic events) is more difficult to reliably predict using conventional design procedures.
MDT has sponsored previous WTI research to investigate the performance of these systems under extreme lateral loads and to develop appropriate analysis/design procedures. The primary objective of this research, led by Michael Berry, is to further validate/improve MDT’s CFST to concrete pile cap connection design/analysis methodologies, and to ensure the efficacy of these methodologies for a wide variety of potential design configurations. This research has important potential benefits for evaluating and enhancing bridge performance during earthquakes and other seismic events.
Additional information is available on the project page of the WTI website.
Ultra-high performance concrete (UHPC) has mechanical and durability properties that far exceed those of conventional concrete. However, using UHPC in conventional concrete applications has been cost prohibitive, with commercially available/proprietary mixes costing approximately 30 times more than conventional concrete. Previous WTI research resulted in nonproprietary UHPC mixes made with materials readily available in Montana. These mixes are significantly less expensive than commercially available UHPC mixes, thus opening the door for their use in construction projects in the state. The Montana Department of Transportation (MDT) Bridge Bureau is interested in using UHPC in field-cast joints between precast concrete deck panels. The use of UHPC in this application will reduce development lengths, and subsequently reduce the requisite spacing between the decks and improve the overall performance of the bridge. Through this project, P.I. Michael Berry will build on the non-proprietary Phase I UHPC research he recently completed for MDT and focus on ensuring the successful application of this material in these field-cast joints.
If these mixes are viable for this application, Montana could take advantage of the cost savings of the non-proprietary mixes and ultimately improve the performance and durability of bridges. More information on this Phase II project is available here.
The Montana Department of Transportation has released the final reports for two projects by WTI researchers:
“Evaluation of Effectiveness and Cost-Benefits of Woolen Roadside Reclamation Products.” This research project developed three types of products for study: woolen erosion control blankets (ECBs), wool incorporated into wood fiber compost, and wool incorporated into silt fence. The project, supported by Montana Department of Transportation (MDT) and the Center for Environmentally Sustainable Transportation in Cold Climates, compared the wool products’ performance to roadside reclamation products commonly used for revegetating cut slopes. Rob Ament(P.I.) and Eli Cuelhoserved on the research team. The final report and project summary are available on the MDT website. Additional information and all of the reports related to this project are available on the WTI website.
“Feasibility of Non-Proprietary Ultra-High Performance Concrete (UHPC) for Use in Highway Bridges in Montana.” Ultra-high performance concrete (UHPC) has mechanical and durability properties that far exceed those of conventional concrete. However, using UHPC in conventional concrete applications has been cost prohibitive, costing 20 times that of conventional concrete. The overall objective of the Phase I research was to develop and characterize economical non-proprietary UHPC mixes made with materials readily available in Montana. The research was led by Michael Berry. The final report and project summary are available on the MDT website and additional project information is available on the WTI website.
The Montana Department of Transportation has released the final report for “Investigation of Prefabricated Steel Truss/Bridge Deck Systems,” a WTI and MSU Civil Engineering project led by Damon Fick, Tyler Kuehl, Michael Berry, and Jerry Stephens. The study evaluated a prototype of a welded steel truss constructed with an integral concrete deck, which has been proposed as a potential alternative for accelerated bridge construction (ABC) projects in Montana. Steel truss bridges are relatively light weight compared with plate girder systems, which makes them a desirable alternative for both material savings and constructability. The full report and a summary report are available on the MDT website. Additional project information is available on the WTI website.