Thermal Behavior of IDOT Integral Abutment Bridges and Proposed Design Modifications

Abstract

The Illinois Department of Transportation (IDOT) has increasingly constructed integral abutment bridges (IABs) over the past few decades, similar to those in many other states. Because the length and skew limitations currently employed by IDOT have not necessarily been based on rigorous engineering analyses, an extensive 3- D parametric study has been performed, complemented by installation of field monitoring equipment on two recently constructed bridges, to potentially expand the use of IABs in Illinois. Some notable findings from this study include: (1) IAB configuration with extreme skew (> 60°) can perform well with proper detailing; (2) H-pile webs oriented parallel to the longitudinal axis of the bridge, regardless of skew, substantially reduces weak-axis bending; (3) compacted backfill reduces pile stresses; (4) live loads affect thermally induced pile stresses; (5) longer intermediate spans tend to increase pile stresses; and (6) time-dependent behaviors, such as concrete shrinkage, may significantly influence maximum pile stresses. Based on these findings, a more rigorously developed set of recommendations for maximum IAB lengths and skews in Illinois are proposed.