Connection Between Simple Span Precast Concrete Girders Made Continuous

Download or read book Connection Between Simple Span Precast Concrete Girders Made Continuous written by Angela Marie Mueller and published by . This book was released on 2002 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: Continuous precast/prestressed bridges are formed by placing the girders end to end and then pouring a slab and intermediate diaphragms. The girders carry the dead load of the structure as simple spans but are continuous for live loads. These connections provide sufficient negative moment continuity, however their effectiveness in providing positive moment continuity is questionable. Cracking has been observed in bridges of this type due largely to time dependent effects and this has raised questions regarding the bridges performance. The National Cooperative Highway Research Program (NCHRP) Project 12-53 was developed to study the effectiveness of the connections between precast/prestressed bridge girders made continuous. This thesis presents a portion of the experimental work for project 12-53. Six specimens, representing portions of full-scale bridges, were tested and fatigued to evaluate their performance after cracking has occurred. The loading procedure represents extreme loading events occurring after cracking at the diaphragm has occurred and the structure is subjected to normal traffic loads. Data from each specimen was analyzed and the results were compared for each connection type. The specimens were designed to evaluate the effect of the use of bent bars versus bent strands, embedment, and the addition of web bars and/or stirrups to a bent bar connection with regard to performance. It was found that all connection types would provide adequate negative moment continuity. Each detail provided differing levels of crack control; however cracking did not significantly affect the stiffness of the specimen. The best method for providing better crack control and a more efficient section is to embed the girder into the diaphragm. There is little difference between bent bar and bent strand connections and both seem to offer sufficient crack control. Additional stirrups in the diaphragm slightly increase the stiffness of the connection. The main advantage to adding stirrups would be the ductility that is added to the connection. The addition of web bars was very effective, but is not recommended. Although the addition increases the strength of the connection, it causes cracking of the ends of the girders and is difficult to construct.