Study of Two-Span Continuous Tubular Flange Girder Demonstration Bridge

This report presents a study of a demonstration bridge designed with concrete-filled tubular flange girders (CFTFGs), conducted for the Pennsylvania Department of Transportation (PENNDOT). A CFTFG consists of a conventional web plate and bottom flange plate, with the top flange fabricated with a rectangular tube that is then filled with concrete. The main advantage of the CFTFG is an increased torsional stability that enables the number of diaphragms (or cross-frames) needed to brace the girders under construction loading conditions to be reduced. As a result, the time and cost of fabricating and erecting the bridge girder system can be reduced. The CFTFGs of the demonstration bridge are designed to be constructed as simple spans for dead loads, and are then made continuous for superimposed dead loads and live loads by adding continuity at the pier. This construction sequence reduces the design moments and shears for the interior-pier section of the girder and for the field splice at the pier. The bridge is also designed to be constructed with precast deck panels to promote accelerated construction. Design criteria for CFTFGs were developed in a format compatible with the 2000 PENNDOT Design Manual Part 4 (PENNDOT 2000) and the 2004 AASHTO LRFD Bridge Design Specifications (AASHTO 2004). A preliminary design of the CFTFGs for the two-span demonstration bridge was developed. In addition, preliminary designs of the field splice over the pier and of the precast concrete deck were developed. Finally, finite element analyses of the stability of the CFTFGs under critical construction loading conditions were conducted.