The AASHTO strategic plan in 2005 identified extending the service life of bridges and accelerating bridge construction as two of the grand challenges in bridge engineering. Previous studies have shown that using a prefabricated full-depth precast concrete deck system not only accelerated the bridge deck rehabilitation process but also extended its service life with reduced user delays and lower life-cycle costs. The recent use of ultra-high-performance concrete (UHPC) in the United States for bridge applications has proved efficient and economical because of its superior structural and durability characteristics. On the basis of the advantages of UHPC and precast systems, a design for a full-depth UHPC waffle deck panel system was developed. A full-scale, single-span, 60-ft long by 33-ft wide prototype bridge with full-depth prefabricated UHPC waffle deck panels has been planned as a replacement bridge in Wapello County, Iowa. In support of this project, structural performance and constructability of the UHPC waffle deck system and its critical connections were studied through an experimental program at Iowa State University. Two prefabricated, full-depth, UHPC waffle deck panels were connected to two 24-ft long precast prestressed girders, and the system was tested under service, fatigue, and ultimate loads. On the basis of the test observations and results and the experience gained from fabrication of deck panels and casting of UHPC infill joints (transverse and longitudinal), the prefabricated UHPC waffle deck system concept was found to be a viable option to achieve the goals of the AASHTO strategic plan.

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Deterioration of existing bridge decks, which usually originates with the deck cracking on the top surface, is a common problem in North America. It causes frequent repair of the decks to limit further damage resulting from water/chloride ingress. Superior engineering and durability properties facilitate the use of ultra-high performance concrete (UHPC) as an attractive alternative for a deck overlay, minimizing both deck deterioration and maintenance costs. Recently developed UHPC thixotropic mix designs, which are different from commonly used self-leveling UHPC, enable UHPC overlay to be used on decks with slopes and meet specific crowning requirements. The use of a UHPC thixotropic mix design with 3.25% of steel fibers was successfully evaluated under laboratory conditions by applying it on sloping deck surfaces with appropriate roughness between the normal concrete (NC) and UHPC. The feasibility of applying this technology in the field was then investigated on a small bridge for the first time in North America in May 2016. This paper presents the details about the laboratory evaluation, field implementation of UHPC overlay, and lessons learned from this first UHPC overlay project in North America.

Accelerated bridge construction techniques taking advantage of prefabricated bridge elements and high-performance materials are being used more frequently for bridge replacement projects. They result in minimal road closure times and traffic interruption and in the reconstruction of long-lasting highway bridges. Longitudinal closure pour connections are an important deck-level component for modular bridge elements that are heavily stressed by traffic loadings and environmental effects and whose durability is a concern. To address cracking and leakage issues in such connections, the strength and failure modes of the longitudinal ultrahigh-performance concrete (UHPC) closure pour connection between adjacent prefabricated deck units were evaluated. First, specimens with and without a longitudinal UHPC closure pour connection were fabricated, instrumented, and tested. Finite element (FE) models were established to improve understanding of the behavior of the specimens under the loading condition. In addition, strut-and-tie models (STMs) were developed on the basis of FE model predictions to estimate the strength of the specimens. The jointed specimens were found not to have any cracks or leakage at the early stage but had lower cracking loads than did the jointless specimens. The strength and ductility of the jointed specimens were comparable with those of the jointless specimens. On the basis of the FE models and STMs, the ultimate strength of the specimens was accurately predicted.

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