Design Alternatives of Liberty Memorial Bridge

摘要

As the second largest bridge prqject in North Dakota after Four Bears Bridge, Liberty Memorial Bridge is a new 2,369-foot long bridge with four traffic lanes crossing the Missouri River in Bismarck, ND. The total cost of the bridge is estimated to be $48 million. Designs and construction documents were developed for two alternatives - concrete and steel bridges. This paper summarizes the designs for both alternatives and makes comparisons between the two types of structures regarding aesthetics, structural characteristics, and construction costs. The steel alternative consists of four steel box girders supported on tall piers with six river spans. The longest span is 285 feet. The concrete alternative is a cast-in-place segmental bridge consisting of two concrete box girders supported on split-"Y"-shaped piers. The upper legs of each pier, connected with external PT tendons, are in a plane parallel to bridge centerline. This alternative has six river spans with a maximum span of 315 feet. The concrete alternative for this project did not have a cost advantage over the steel alternative for many reasons, including a unique pier design, the increase of concrete unit prices and construction staging challenges.