Integral abutment bridges with skew angles

Traditionally, a system of expansion joints, roller supports, and other structural releases has been provided on long multiple-span highway bridges to permit thermal expansion and contraction. Flow of runoff water through open bridge deck joints or leaking sealed joints has been one of the major causes of extensive maintenance and costly rehabilitation work on bridges in general. This study focuses on integral abutment jointless bridges with skew angles. A three-dimensional non-linear finite element model is used to perform parametric study to investigate the effect of different parameters on the behavior of skewed, jointless steel girder bridges. Over 250 finite element bridge models were studied, and each model considered the complete bridge including the superstructure, substructure and soil. Another three-dimensional model that consisted of a pile and the surrounding soil was also used to study the effect of lateral displacement on load carrying capacity of piles in integral abutment bridges. The study also investigates designs and standards used by different departments of transportation and highway agencies in the United Stated and abroad and compares them to the ones used in the past. A survey questionnaire was mailed to all state departments of transportation and foreign agencies, and the responses were compared to an old survey that was conducted in 1987 by the University of Maryland. The results of the study are used to appraise current design practices and to make recommendations on design of skewed jointless bridges. It is concluded that piles in integral abutment bridges with skew angles need to be oriented with their strong axis parallel to the centerline of the bridge, and the use of pre-drilled holes is highly encouraged due to the reduction in pile stresses that occurs as shown in the three-dimensional finite element analysis. Limiting skew angles to 30° by many states appears to be a valid approach, since the finite element analysis results show that after 30° the rate of increase in stresses in piles becomes higher. It is also recommended that approach slabs sit directly on the abutment, and be tied to it with epoxy-coated dowels. Granular backfill material should always be used on the backside of abutments, and an acceptable drainage system should also be provided.