From the FHWA Innovator
Ultra-high performance concrete (UHPC) can be used to create the simple, strong, long-lasting connections needed for successful construction using prefabricated bridge elements (PBEs).
Prefabricated bridge elements are structural components of a bridge that are built offsite then brought, ready to erect, to the project location. Prefabricated bridge elements not only shorten onsite construction time—minimizing traffic impacts and increasing traveler and worker safety—but also offer superior durability.
The durability of prefabricated spans, and how quickly they can be constructed, relies on the connections between the elements. Field-cast UHPC has emerged as a solution for creating connections between prefabricated concrete components with more robust long-term performance than conventional PBE connection designs.
UHPC is a steel fiber-reinforced, portland cement-based, advanced composite material that delivers performance far exceeding conventional concrete. As UHPC performance exceeds that normally predicted from a field-cast connection, it allows the behavior of the joined prefabricated components to surpass that of conventional construction.
Compared to many solutions in current use, UHPC allows for small, simple-to-construct connections that require less volume of field-cast concrete and do not require post-tensioning. The mechanical properties of UHPC also allow for redesign of common connection details in ways that promote both ease and speed of construction. This makes using prefabricated bridge elements simpler and more effective.
- Speed. The mechanical properties of UHPC allow for redesign of common connection details in ways that promote both ease and speed of construction.
- Simplicity. UHPC connections are inherently less congested, simplifying fabrication and assembly.
- Performance. Field-cast UHPC between prefabricated bridge elements results in robust connections that can provide better long-term performance than connections constructed by conventional methods.
State of the Practice
Technical advancements and policy developments related to UHPC are enabling implementation of prefabricated bridge elements for accelerated bridge construction on a national basis. These deployments are demonstrating the constructability, field performance, and robustness of these systems in bridge inventories across the country.
New York, Pennsylvania, and New Jersey have done work to develop standards for using UHPC PBE connections. The Federal Highway Administration (FHWA) published design and construction guidance for UHPC connections in 2014. In addition, U.S. production of the steel fiber reinforcement commonly used in making UHPC began in 2013, creating more opportunities for use on federally funded transportation projects under FHWA’s Buy America requirements.
The third round of Every Day Counts (EDC-3) focused on demonstrating the advantages UHPC offers as an option for connecting prefabricated bridge elements, and this effort is continuing under EDC-4. The EDC implementation team is providing technical assistance and training, including peer exchanges, webinars, and workshops.