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Innovative precast concrete composite bridge systems
Abstract
This thesis covers the development and testing of new precast concrete bridge systems. It describes the implementation program of the Nebraska University I girders (NU Girders) in bridge design, the development and testing of a new girder/deck connecting system for composite action, and the development and full-scale testing of a new shallow precast concrete bridge system for short to medium spans. As part of implementing the NU girders, design charts, tables, and simplified equations are developed to help engineers in the preliminary selection of girder size for both pretensioned and post-tensioned girder bridges. For post-tensioned girders, a new haunched section is developed for use in spliced post-tensioned girder bridges. The new haunched section significantly increases the span capacity of the NU post-tensioned girders. A new girder to cast-in-place deck slab connecting system is developed. It facilitates future deck replacement with less expected damage to the girder's top flanges, yet provides sufficient strength for full composite action. The new system has an unbonded interface with formed shear keys protruding from the precast girders. Design criteria of the new system is presented. Extensive testing program of both push-off and beam specimens designed with the proposed system proved the applicability of the new system and its design procedure. Changes to both the ACI Code and the AASHTO LRFD Specifications horizontal shear design are proposed. The AASHTO Standard Specifications, which require all vertical shear reinforcement to be extended into the cast-in-place deck slabs, are found unnecessary for satisfaction of horizontal shear requirements, and significantly increase the effort required in deck slab replacement. As a result of this study, this requirement has been removed by the AASHTO Subcommittee on Bridges and Structures. A new shallow precast concrete beam system is developed for short to medium span bridges. The Inverted Tee (IT) System can span up to 85.0 ft (25.9 m) with a total structural depth of 28.5 in. (725 mm). The IT system is less expensive and faster to build than a cast-in-place conventionally reinforced slab bridge. A full-scale test of two ITs with CIP topping was conducted at the University of Nebraska Structures Lab. The test results confirmed that available design procedures are sufficient for the design of this new system. The Nebraska Department of Roads has adopted the new Inverted Tee System. Several bridges are in various stages of design in Nebraska, including a bridge near Syracuse, and two bridges in the Omaha area.
Subject Area
Civil engineering
Recommended Citation
Kamel, Mounir R, "Innovative precast concrete composite bridge systems" (1996). ETD collection for University of Nebraska-Lincoln. AAI9623625.
https://digitalcommons.unl.edu/dissertations/AAI9623625