OVERVIEW

A superstructure can be thought of as the conduit which carries a roadway over a crossing. Like any other bridge component, the superstructure is comprised of many elements. In the bridge design profession, no other component elicits so much discussion, and even downright controversy, as to the type of elements to be utilized in construction. The structural and geometric complexities of the superstructure component make it one of the most challenging design problems in a bridge engineering project.

In this section we will examine the various types of superstructures and the different elements which comprise them. While it would be impossible to cover every permutation of superstructure types that are in use, this section will attempt to provide the reader with fundamentals behind several of the common superstructure configurations presently being used in highway networks around the world.

3.1 SUPERSTRUCTURE TYPES

The type of superstructure chosen for a bridge can be based on a variety of factors ranging from maintenance considerations to personal preference. Specifically, some of the commonly used criteria in selecting the type of superstructure to be used are:

• Material function and availability

• Construction cost

• Speed of construction and constructability

• Design complexity

• Maintenance costs and life expectancy

• Environmental concerns

• Aesthetics

Where there are no steadfast rules governing which of the factors listed above is more important than the other, one certainty is that the use of superstructure types varies geographically. Due to the way highway systems like the U.S. Interstate develop, bridges tend to come into an...