The most common design concept for a road bridge traditionally consists of some type of super structure resting on an abutment at each end as shown in Figure ES.1. There may also be one or more intermediate piers but they are incidental to the focus of this report. Because of natural, seasonal variations in air temperature, the bridge superstructure will change in temperature and tend to change dimension in its longitudinal direction as shown in Figure ES.1.
However, the supporting abutments are relatively insensitive to air temperature so remain spatially fixed year 'round. To accommodate the seasonal relative movement between super structure and abutments and prevent temperature-induced stresses from developing within the superstructure, the traditional solution has been to provide expansion joints and bearings at each end of the superstructure as shown in Figure ES.1. These joints and bearings typically must accommodate movements of the order of several tens of millimetres (one inch).
Although the design shown in Figure ES.1 works well in concept, experience indicates that the expansion joint/bearing detail can be a significant post-construction maintenance item and thus expense during the in-service life of a bridge. Therefore, the concept was developed to physically and structurally connect the superstructure and abutments as shown in Figure ES.2 to create what is referred to as an integral-abutment bridge (IAB). In doing so, the troublesome and costly expansion joint/bearing detail is eliminated. IABs have been used for roads since at least the early 1930s in the U.S.A. However, they have seen more extensive use worldwide in recent years because of their economy of construction in a wide range of conditions. Over the years and in different countries IABs have also been called integral bridges, integral bridge abutments, jointless
