This class includes all structures by which a roadway or railroad is carried across a space intervening between supports and all structures, such as gates, etc., whose operation is dependent upon the operation of the bridge (as in drawbridges). Included in this class are both construction techniques and methods for building a bridge, regardless of type.
There has been no attempt in this classification to separate lateral bracing. Sometimes, as in suspension bridges, the lateral bracing is more or less peculiar to the class of bridge structure. In some cases there appears to be no distinction in either structure or function between bracing intended to strengthen a bridge against wind pressure and that intended to support weight, and they have all been classified together. Except as provided for under ARCH and SUSPENSION bridges, support at the approaches (land to bridge transition) are generally considered to be a retaining wall-type structure.
