Articles

Development of Standardized Nebraska Family of UHPC Decked I-Beams

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Abstract

The state of Nebraska has begun an ambitious initiative to develop a standardized bridge superstructure system utilizing ultra-high-performance concrete in the precast concrete beams and in the cast-in-place closure pours between beams and over the supports. The initiative was motivated by recently made available structural design guidelines by the Federal Highway Administration (FHWA) and by the Precast Prestressed Concrete Institute (PCI), which followed over 25 years of intensive materials research and non-structural applications. Research has demonstrated that UHPC can be produced in available precasting facilities and can result in outstanding tensile properties due to use of steel fibers, and excellent durability due to the application of particle packing theory. Nebraska is in an environment of extreme temperatures during the year. Deicing chemicals and freeze-thaw cycles cause deck cracking which requires significant maintenance work. In addition, urban areas require rapid construction to minimize traffic disruption. The newly developed UHPC NUDIB (Nebraska University Decked I Beam) was designed to meet both the requirements of accelerated bridge construction (ABC) and deck durability. Further, due to the relatively high unit cost of the UHPC mix, effort was made to minimize the volume of concrete used without sacrificing stiffness. The result is an I beam shape that has a top flange whose width is nearly equal to the beam spacing. The gap between beams is only 8 inches and is filled with CIP UHPC. The web width is standardized at 4 in. The bottom flange is designed to be suitable for both segmental post-tensioning and full-length pretensioning. The top flange has a 2.5 in. skin and a total depth of 8 in., with the 5.5 in. difference occupied by thin ribs spaced at 24 in. The family of sizes has three depths: 54, 72, and 90 in. and variable flange width from 72 to 136 in. The expected spans range up to 200 feet. This paper explains the evolution of the cross-section shape. It details an innovative forming system for this relatively complex cross section shape. It provides a span chart and explains the various challenges faced and how they were resolved.

Keywords: UHPC decked I beam, forming system, accelerated bridge construction, segmental construction, standardized girders shape

How to Cite:

Barron, R., Jaber, F., Tadros, M. K. & Morcous, G., (2023) “Development of Standardized Nebraska Family of UHPC Decked I-Beams”, International Interactive Symposium on Ultra-High Performance Concrete 3(1): 37. doi: https://doi.org/10.21838/uhpc.16662

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