U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
Full-depth, precast, UHPC waffle deck panels with longitudinal and transverse ribs and a viable set of connections suitable for field implementation were developed for this HfL project. Following a successful laboratory validation of the full-scale unit, which consisted of two panels and recommended connections, the waffle deck was installed successfully on a replacement bridge in Wapello County, Iowa. The subsequent load testing confirmed the desirable performance of the UHPC waffle deck bridge. The project described in this report was undertaken as a follow-up study to broaden the applications of UHPC waffle deck panels to new bridges as well as deck replacement projects.
To make the broader applications of UHPC waffle deck panels feasible, this report was formulated as a guide to provide technical and practical information necessary to allow bridge owners to consider the use of UHPC waffle slabs for a wide variety of bridges. Using a series of simple and detailed finite element analysis models, every effort was taken to improve efficiency of design while ensuring safety, integrated versatility, and simplified design calculations.
This study serves as a guide for complete design, fabrication, and installation of UHPC waffle deck panels with mild steel reinforcement. The conclusions drawn from the development of this design guide, as well as construction and performance of the waffle deck panels in the laboratory and field, are summarized in this section.
The waffle deck panel should be designed to act compositely with the supporting bridge girders under traffic loads. For broader application of the precast deck panel in different bridge types with variable girder spacing, several deck panel configurations with variable transverse and longitudinal rib spacing were developed and evaluated under traffic loads. A maximum girder spacing of 10 ft was considered while arriving at panel and reinforcement details. AASHTO HL 93 truck loading was used to estimate the demand on the waffle deck panel.
A set of connections suitable for UHPC waffle panels were tested as part of this HfL project and proved satisfactory. While these connections can be used readily, additional connections established especially for full-depth precast panels have been identified as acceptable, as discussed in chapter 3.
While using these connections, it is recommended that all voids in the field be filled with in situ UHPC. With this modification, a designer may take advantage of increased compressive and bond strengths associated with UHPC and simplify the reinforcement details within the connections.
If a connection is expected to experience negative moments (e.g., top of a pier), it is recommended that the connection design include some precompression, such as that due to localized post-tensioning, to keep the connection from experiencing any tensile stresses.
Using traditional procedures combined with those recommended in this report, full-depth, precast UHPC waffle deck panels can be used effectively for replacing deteriorated bridge decks. Regardless of the use of steel or concrete girders in existing bridges, old decks should be removed using locally approved methods along with the appropriate guidance provided in chapter 4. The selection of the waffle panels and connections can follow the recommendations in chapters 2 and 3.
It is important make sure that the precaster has appropriate training from the UHPC producer for fabrication of the UHPC waffle deck panels and the ability to mix large volumes of UHPC and thermally cure the panel decks. In addition, it is advisable to have the UHPC manufacturer on-site with the contractor when casting the UHPC fill connections in the field, to ensure the expected product quality is achieved.
It is important to engage the supplier of the UHPC in the early stages of project design so that quality control with mixing and placing of UHPC can be satisfied adequately in the precast plant and the field. While an overlay can be used on a UHPC waffle deck, it can also be omitted by integrating a suitable riding surface on the top surface of the panel during construction.