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Center for Accelerating Innovation

FHWA Home / OIPD / Accelerating Innovation / Accelerated Market Readiness (AMR) Projects / Bridge Technologies

Bridge Technologies

In-Situ Scour Testing Device (Erosion Resistance of Fine-Grained Cohesive Soils)

The photo depicts the typical In-Situ Scour Testing Device (ISTD) test setup in the field. The Advanced Linear Drive is shown mounted on top of the casings, which protrude from the auger section in the ground. The drill rig, used to auger the borehole for the test, is located behind the ISTD equipment. A series of flexible hoses attaches to the top of the device, where they connect to a 90-degree bend and then to the PVC piping mounted to the linear drive. The outlet PVC piping runs from the Advanced Linear Drive to a water tank shown in the foreground. A suction hose runs from the water tank back to the pump. A scaffold is assembled between the drill rig and the water tank to assist the technicians in setting up the device.

Challenge: Bridge scour is the leading cause of bridge failures in the U.S. Current methodologies for predicting scour depths around bridge foundations in the river or coastal environments employ empirical equations assuming stream beds with uniformly-graded, non-cohesive soils such as sand, which may result in overly conservative scour depth estimates. Most stream beds are composed of layers of sand, silt, clay or rock and every layer has its own soil erosion resistance. There is a need to assess the erodibility of such layers to improve the accuracy of the scour estimate.

Technology: The In-Situ Scour Testing Device is designed to determine the erodibility of soil layers consisting of fine-grained cohesive soils. The device consists of an erosion head that is placed inside a conventional drill casing that is used for standard subsurface geotechnical soil investigations. The erosion head measures the soil erosion rate resulting from flowing water that is pumped through the head at a constant flow rate and with a consistent gap between the soil and the head. By measuring erosion rates for the foundation soils the critical shear stress, which represents the erosion resistance of the soil layer, can be obtained. The result will be more cost-effective foundation designs, greater reliability and resiliency in bridge performance, and increased safety for the traveling public.

Activities Funded: Final development of the ISTD systems and 20 demonstration showcases

ISTD Field Tests - Status


Map of the United States showing the completed ISTD field tests. Demonstrations Completed: Arizona, California, Colorado, Illinois, Kansas, Kentucky, Maine, Michigan, Minnesota, Missouri, Nebraska, Nevada, North Carolina, Ohio, Texas, Vermont, Virginia.

Demonstrations Completed:

Arizona Maine Nevada
California Michigan Ohio
Colorado Minnesota Texas
Illinois Missouri Virginia
Kansas North Carolina Vermont
Kentucky Nebraska  

Four demonstrations planned in 2020. Locations pending.

Further Information: https://highways.dot.gov/laboratories/hydraulics-research-laboratory/hydraulics-laboratory-zones

Contact:

Veronica Ghelardi
FHWA, Hydraulic Engineer
Veronica.Ghelardi@dot.gov
720-963-3240

Daniel Alzamora
FHWA, Geotechnical Engineer
Daniel.Alzamora@dot.gov
720-963-3214


Electrically Isolated Tendons (EIT) to Monitor Post-Tensioning Tendons against Corrosion Attacks

The photo depicts a detail of two electrically isolated tendons and reinforcing bars before casting.

Need: Post-tensioning (PT) tendons provides the primary load carrying capacity in bridges and consequently there is great interest from owners to assess their in-service condition. However, inspection of a typical PT tendon is currently very difficult due to its multiple layers of encasement which typically include PT grout, PT duct, reinforcing steel and structural concrete.

Technology: EIT’s are a new non-destructive evaluation (NDE) technology that provides bridge owners with the highest level of corrosion protection and long-term monitoring on the PT tendon. The NDE readings can indicate that a PT system is puncture and damage free (fully encapsulated) which will provide bridge owners with a high level of assurance that the PT system, as installed, is highly protected against corrosion attack.

Activities Funded: demonstration showcases

  • First US installation of Electrically Isolated PT Tendons

Lehigh County, Pennsylvania completed the first U.S installation of electrically isolated PT tendons (EIT'S) to perform long-term monitoring of corrosion. Five EIT's total extending the full 542-foot length of the Coplay Northampton bridge were installed. Each EIT installed met the required electrical resistance threshold after installation, achieved full isolation, and is fully encapsulated and protected to the highest level possible. In addition to providing enhanced corrosion protection, the electrical isolation provides the opportunity to monitor each tendon's encapsulation quality and possible corrosion initiation through the bridges service life. The bridge is scheduled to open in the fall 2019. View article.

Contact:

Reggie Holt
FHWA Concrete Bridge Specialist
Reggie.Holt@dot.gov
202-366-4596


Full Depth Ultra High-Performance Concrete (UHPC) Waffle Bridge Deck Panels

The photo depicts a waffle bridge deck panel rotated to the vertical position by the casting bed to reduce the handling stresses on the piece.

Need: Bridge engineers are seeking new ways to build better bridges, reduce work zone travel delays, and improve repair techniques thereby reducing maintenance. Additionally, owners are challenged with replacing critical bridge components (particularly bridge decks) during limited or overnight road closure periods.

Technology: Precast panels manufactured from UHPC can provide significant durability improvements to bridge decks due to the high strength, extremely low permeability, and improved connection details inherent in the system. This technology results in reduced construction time for new and rehabilitated bridges, the ability to upgrade the load-carrying capacity of existing bridges, and improved durability of bridge decks. UHPC Connections for Prefabricated Bridge Elements and Systems was promoted in two rounds of the Every Day Counts Initiative.

Activities Funded: Coreslab Structures manufactured waffle bridge deck panels with UHPC and they were installed with field cast UHPC joints on a bridge in Wapello County, Iowa.

Further Information: https://www.fhwa.dot.gov/hfl/partnerships/bridgetech.cfm

Contact:

Ben Graybeal
FHWA Turner Fairbank Highway Research Center
Benjamin.Graybeal@dot.gov
202-493-3122

Mark Leonard
FHWA Resource Center
Mark.Leonard@dot.gov
720-963-3747


Bridge Bent System for Seismic Regions

The graphic illustrates an exploded view of the precast bridge bent concept - the girder superstructure, the cast-in place upper cap beam, the precast cap beam, and the precast column.

Need: Prefabricated bridge bents, also known as piers, have not been used in seismic regions because accepted methods of making connections that are both structurally robust and quick to assemble were not known and were not addressed in design specifications.

Technology: To construct precast elements in high seismic zones requires ductile detailing, which permits the structure to deform rather than to experience sudden unexpected brittle failure. The connections are made with a small number of large-diameter reinforcing bars that are grouted into larger-diameter ducts. This technology allows the main elements of bridge bents to be prefabricated on-site. The segments are then moved into place and assembled to form the bents, greatly reducing construction time and traffic delays.

Activities funded: Laboratory testing of column-to-spread footing connections and column-to-drilled shaft connections; development of design specifications; demonstration of the first U.S installation, Washington State, to use precast, segmental construction for bridge bents in a high seismic region. The design specifications developed under this project contributed to AASHTO’s 2018 publication of the first LRFD Guide Specifications for Accelerated Bridge Construction, which covers seismic design across the country.

Further Information: https://www.fhwa.dot.gov/hfl/partnerships/bridgetech.cfm

Contact:

Lee Marsh
Lee.Marsh@wsp.com
www.wsp.com


Composite Bridge Decking

The photo depicts how prefabricated deck panels were attached in a project by bolting from below with no penetrations on top. The panels measured 7.5 feet x 11 feet and weighed 17 pounds per square foot.

Need: Bridge owners expressed a need for a light-weight, solid-service deck. Solid-surface lightweight decks can alleviate weight restrictions on a bridge, save a historic bridge that has been compromised over time, or replace older light decks on bridges that cannot support a concrete one.

Technology: Composite materials such as fiber reinforced polymer (FRP) are ideal for bridge decks because of their high strength to weight ratio and resistance to corrosion.

Activities funded: Refinement of the materials and fabrication methods used to produce a FRP composite bridge deck developed by the University at Buffalo for New York State Department of Transportation and a demonstration installation in Allegany County, NY.

Further Information: https://www.fhwa.dot.gov/hfl/partnerships/bridgetech.cfm

Contact:

Jerome O'Connor, PE
Jerome.OConnor@bridgecomposites.com
607-725-0442

Page last modified on April 16, 2020
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000