Design Aids of NU I Girders Bridges





Chapter 1 Introduction

Precast prestressed concrete girder bridges have become the most dominant bridge

system in the United States. In the early design stages, preliminary design becomes a vital first

step in designing an economical bridge. Within the state of Nebraska, the two standard precast

prestressed products used are Inverted Tee (IT) girders and University of Nebraska I girders

(NU-I). In the early 1990s, Nebraska Department of Roads (NDOR) developed design charts for

NU-I girders in order to assist in member selection and preliminary design. In 2004, design

charts were developed for IT girders. However, the NU-I girder charts have since become

obsolete because they were developed for low strength concrete (6 ksi) and 0.5 inch prestressing

strands. In addition, the charts were based off of American Association of State Highway and

Transportation Officials (AASHTO) standard specifications. Since then, NDOR has adopted

AASHTO Load and Resistance Factor Design (LRFD) specifications for superstructure design

and the Threaded Rod (TR) continuity systems in their standard practice. Therefore, the new

design charts are based on the latest AASHTO LRFD specifications for superstructure design

and NDOR Bridge Operations, Policies, and Procedures Manual (BOPP).



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