Design of Long Span Concrete Box Girder Bridges: Challenges and Solutions

Long span concrete box girder bridges first appeared in the 1950's. From the beginning, this bridge type was built segmentally using the balanced cantilever method of construction with form travelers and cast-in-place segments. After half a century of developments, concrete box girder bridges have a positive track record, are widely used, and have reached spans of up to 988 ft. These bridges present specific challenges to the designer that have to be addressed in the context of design codes, available materials, prevailing construction methods and project constraints. This paper describes current design trends for cross-section design, post tensioning layout and superstructure articulation. It also discusses the opportunities provided by high strength and lightweight concrete, and the impact of the new AASHTO LRFD code. The design of the Kanawha River Bridge in West Virginia is used to illustrate these topics. This river crossing, recently designed by T.Y. Lin International, will have a 760-foot main span, the longest concrete box girder span in the United States, and a total length of 2,975 ft.