If no rail dilatation device is installed in the superstructure, the continuous welded rail remains stationary, in theory, under the influence of temperature change and allows the bridge structure to dilate freely. In practice, structural elements work closely together because the superstructure is fixed to the bridge. Dilating bridge structure attempts to drag the superstructure along but this latter withstands that force to some extent. As a result, relative displacement occurs between the bridge structure and superstructure allowing normal forces to develop in structural elements.

heat induced movement, steel bridge, no-clearance superstructure, dilatation, monitoring system