ABSTRACT
ABSTRACT: An integral bridge is one in which the continuous deck and the abutments are integrated to form a rigid frame structure. The abutments are generally supported on a single row of steel H-piles to provide the required flexibility for accommodating the longitudinal bridge movements due to temperature variations. In lieu of expansion joints at the bridge ends, such movements result in imposition of cyclic lateral displacements on the abutments, backfill and the steel H-piles. The magnitude of these cyclic displacements is a function of the level of temperature variation, type of the superstructure material and the length of the bridge. Many transportation agencies tend to push up the length limits of integral bridges to increase their range of application so as to eliminate the maintenance problems concerned with expansion joints in conventional bridges. Thus, the thermal-induced cyclic displacements in the components of such long integral bridges will become larger as well. Consequently, the piles may experience cyclic lateral deformations beyond their elastic limit. This may lead to a reduction in the service life of the bridge due to low-cycle fatigue effects in the piles. To minimize such detrimental effects, the lengths of integral bridges should be limited. Currently, rational guidelines to determine the maximum length of integral bridges do not exist. In general, state departments of transportation utilize in-house specifications that provide length limits for integral bridges based on the past performance of existing integral bridges. Therefore, a rational methodology is required to determine the maximum length limits for integral bridges.
