Post-tension ing and splicing of precast/prestressed bridge beams to extend spans

摘要

This paper explores the status and techniques of post-tensioning and splicing precast concrete Ⅰ-beams in bridge applications. It will look at the current practices that have been used in the United States and comment on the advantages of these techniques. Representative projects are presented to demonstrate the application and success of specific methods used. To demonstrate the benefits of using post-tensioning and splicing to extend spans, multiple analysis of simple span post-tensioned Ⅰ-beams were performed varying such characteristics as beam spacing, beam sections, beam depth and concrete strength. Tables were then developed to compare the maximum span length of a prestressed Ⅰ-beam versus a one segment or a spliced three segment post-tensioned Ⅰ-beam. The lateral stability of the beam during fabrication, transportation and erection is also examined and discussed. These tables are intended to aid designers and owners in preliminary project studies to determine if post-tensioning can be beneficial to their situation. AASHTO Standard Specifications will be used as basic guidelines and specifications. In many cases, post-tensioning was found to extend the maximum span length of a typical 72-inch precast Ⅰ-beam more than 40 feet over conventional prestress.