High performance concrete bridge stringer system

This dissertation presents two independent systems which can be implemented in the stringer bridges with high performance. They relate to the threaded rod bridge continuity system making precast girders continuous for deck weight and NUDECK precast bridge deck panel system. Prestressed concrete girder bridges are generally made continuous by adding longitudinal reinforcement in the deck over the pier. With this continuity method, the superstructure is continuous only for one-third of the total load. The pier diaphragm, which is normally cast prior to the deck, may experience distress because no negative moment resistance is available as the deck is being placed. An innovative threaded rod continuity system was introduced to make the precast girders continuous for deck weight, which results in reduced demand for prestress and for high strength concrete at release. The same girder size can span 10 to 15 percent longer than the conventional system. Bridge structural performance is significantly improved without causing cracking at the piers. The Clarks Viaduct in Nebraska is the first bridge in the United States implementing this system. Its completion shows this system is cost-effective and easy to construct without need for a specialty contractor. The second objective of this dissertation is to develop an efficient precast bridge deck panel system. Most of the deficiency in existing stringer-type bridges lies in deterioration of the bridge deck. Cast-in-place reinforced concrete decks experience cracking shortly after construction due to their large differential creep and shrinkage with the supporting beams, and due to the temperature drop they experience in the hydration cycle. The NUDECK (Nebraska University) system is a full-depth precast/prestressed concrete bridge deck panel system. The combination of high performance precast concrete, where little creep and shrinkage occur after the deck is made composite with the beams, and two-way prestressing assure of continued pre-compression of the deck during its life. Construction time is greatly cut and the traveling public is least inconvenienced. Implementation of this system in the design and construction of the Skyline Bridge (89 ft + 125 ft with a 25° skew) in Omaha, Nebraska is presented