The terms bridge and span are used interchangeably; however, to avoid confusion and misunderstanding, technicians and construction personnel draw a distinction between the two.
A bridge is made up of one or more spans. A span is a segment of a bridge that crosses from one substructure unit to the next, from abutment to abutment, from abutment to pier, from pier to pier, or from pier to abutment.
Span length refers to either the length of any individual span within the structure or to the total bridge length. In most cases, span lengths are considered as the distance between center lines of bearing from one substructure unit to the next.
Simple and continuous spans
In addition to the basic bridge design (girder, arched, trussed, suspension, etc.) a bridge may be further classified as a simple span, a continuous span, or a combination simple, continuous span. The classification is based on the arrangement of the bridge’s structural members.
A span with structural members that cross from one substructure unit to the next substructure unit is a simple span. The simple span has fixed bearings on one end and expansion bearings on the other end. Any bridge that is supported by abutments alone is a simple span. An individual span within a bridge that extends from an abutment to a pier or a pier to another pier is also a simple span. Occasionally bridges are constructed as a series of simple spans.
A continuous span is a bridge or bridge segment with structural members that cross over one or more substructure units without a break. The structural members may have to be spliced to obtain the necessary length; however, they are still considered one-piece members. Continuous spans are typically anchored to the substructure by a number of expansion bearings and a single fixed bearing. Many bridges have both simple and continuous spans.