BEHAVIOR OF ABUTMENT PILES IN AN INTEGRAL ABUTMENT IN RESPONSE TO BRIDGE MOVEMENTS

A field study of the behavior of abutment piles for a bridge that has integral abutments, piers, concrete box girders, concrete deck, and six 75-ft spans is discussed. To compensate for anticipated thermal movements, two unique features were built into the bridge. Expansion joint material was placed between the back side of the abutment and the soil backfill, and compressible material was placed on the webs of the abutment piles to create low soil resistance to pile movement. Over a one-year period, monthly readings were taken of bridge length (by using steel tape), gap between soil backfill and back side of abutment, openings in the expansion joints on the concrete approach slabs, vertical elevation of abutments and piers, slope indicator readings on the four corner abutment piles, and temperatures of concrete deck and air. A formula involving air temperatures was developed to estimate the maximum change in bridge length due to thermal changes. The changes in bridge length agree with changes measured from steel tape and expansion joint openings. The study concluded that these changes did not result in equal abutment movements at each end of the bridge, and the maximum abutment movement resulted in stresses at the top of the piles sufficient to initiate a yield stress in the steel but not sufficient to form a plastic hinge. An analytic model was used to predict stresses in the abutment piles due to movements of the abutments. (Author)