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Title:Modification of IDOT Integral Abutment Design Limitations and Details
Author(s):Olson, Scott M.; Long, James H.; Hansen, James R.; Renekis, Dzuigas; LaFave, James M.
Subject(s):integral abutment bridges (IABs), pile embedment, concrete girders, steel girders
Abstract:The use of integral abutment bridges (IABs) is growing rapidly in the U.S., primarily because of lower maintenance costs compared to conventional bridges. However, current length and skew limitations employed by IDOT are not based on rigorous engineering analysis. To potentially expand the use of IABs in Illinois, the project team performed extensive 2-D and 3-D analyses to examine a wide range of IAB parameters in addition to length and skew. The numerical analyses yielded the following findings when the bridge structures were subjected to extreme thermal loading: (1) The presence of the backfill and development of full passive pressures against the abutment backwall have a negligible effect on the pile foundation performance. (2) The use of wingwalls that are parallel to the bridge deck (rather than parallel to the abutment backwall) has little effect on the abutment or pile foundation performance, and does not significantly reduce backfill settlement when the backfill is uncompacted. In addition, use of uncompacted backfill reduces the vertical support of the approach slab and results in greater stresses and moments in the approach slab. (3) Soil type (when the soil is reasonably competent) has only a secondary effect on the abutment and pile foundation performance. (4) Use of steel vs. concrete girders (within the limited number of girder types and sizes considered) also has only a secondary effect on the abutment and pile foundation performance. (5) Acceptable IAB length and skew combinations that induce stresses in the foundation piles that do not exceed the pile yield stress are summarized in the report. Several moment-reducing options are available to increase these limitations, including: (a) predrilling pile locations to 8 feet, (b) reducing pile embedment into the pile cap to 6 inches (creating a hinge at the pile/pile cap interface), and (c) incorporating a mechanical hinge such as that used by the Virginia DOT at the cold joint between the pile cap and the abutment. (6) Instrumenting and monitorning one or more IABs in Illinois is essential to validate the numerical modeling described in this report, and to potentially investigate the effectiveness of one or more moment-reducing options.
Issue Date:2009-08
Series/Report:ICT-09-054 UILU-ENG-2009-2035
Genre:Technical Report
Publication Status:published or submitted for publication
Peer Reviewed:not peer reviewed
Rights Information:No restrictions. This document is available to the public through the National Technical Information Service, Springfield, Virginia 22161
Date Available in IDEALS:2013-11-07

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