From “Building Bridges Better – Ultra-high performance concrete creates strong, long-lasting connections,” Federal Highway Administration Center for Accelerating Innovations’ Innovator, Issue 67 … The use of ultra-high performance concrete (UHPC) to make better field-cast connections between prefabricated bridge elements (PBEs) is advancing across the United States. Transportation agencies have used the steel fiber-reinforced, portland cement-based composite material on 100-plus projects since the nation’s first bridge incorporating UHPC was completed in Iowa in 2006. Half of those structures were built after the Federal Highway Administration began encouraging deployment of UHPC connections for PBEs through Every Day Counts (EDC) in 2015.
|Since a 2006 Iowa premier, ultra-high performance concrete has been specified for connections on more than 100 bridges incorporating precast elements. Positive field outcomes have compelled federal and state transportation officials to acknowledge UHPC connections’ more recent role in advancing the use of precast for accelerated bridge construction. PHOTOS: Hennepin County, Minnesota|
“We’re promoting UHPC to help make prefabricated bridge element connections simpler, stronger, and more durable,” says FHWA Resource Center Structural Engineer Mark Leonard, co-leader of the EDC-4 (round four) UHPC team. As a result, 14 states and the U.S. Virgin Islands have expressed interest in using UHPC connections and are learning more about the material. Nineteen states, Federal Lands Highway, and Washington, D.C., are demonstrating and assessing the use of UHPC connections in bridge-building processes. Georgia, New Jersey, Pennsylvania, and Rhode Island have made UHPC connections a standard practice on bridge projects with PBEs.
WHY UHPC CONNECTIONS?
UHPC exhibits performance far exceeding that of conventional concrete. “The way I like to explain UHPC is that it is a combination of lots of advancements that have occurred in the field of concrete,” says FHWA Office of Infrastructure Research and Development Bridge Engineering Research Team Leader Ben Graybeal, EDC-4 UHPC team co-leader. “We know that using it for connections between prefabricated elements works very well.”
PBEs—structural components built offsite and moved to the project location for installation—shorten onsite construction time, enhance safety, and offer superior durability. Field-cast UHPC creates connections between PBEs that use less concrete for the connections and provide better long-term performance than typical connection designs. UHPC’s mechanical properties allow for redesign of common connection details in ways that promote ease and speed of construction, making PBE connections simpler and more effective.
Transportation agencies are exploring various uses of UHPC to improve bridge projects. The Delaware Department of Transportation, for example, completed the nation’s second bridge deck overlay using UHPC on the Blackbird Station Road project in New Castle County. The project showed the material’s suitability to connection details that make PBEs simpler and more effective for accelerated bridge construction.
DelDOT also used UHPC to connect the adjacent box girders on the structure, which received Accelerated Innovation Deployment Demonstration funds. The Illinois Department of Transportation is using prefabricated deck panels with UHPC connections on an AID Demonstration project to reconstruct the Campground Road Bridge over Interstate 57 in Jefferson County. The bridge will have increased load-carrying capacity and enhance safety by providing a wider roadway and more clearance over the interstate.
The Iowa Department of Transportation is the lead state on a pooled fund research project to develop a UHPC structural design guide. In late 2017, the agency published new standards for adjacent box girders, including material and construction specifications for UHPC. The New Mexico Department of Transportation is monitoring the performance of a UHPC girder bridge and designing another four projects that will use the material for connecting PBEs. NMDOT is also conducting research on UHPC bridge deck overlays and applying State Transportation Innovation Council Incentive funds to develop an overlay mix design using local materials for UHPC to integrate into specifications.