Experimental and numerical investigation of integral/semi-integral bridge abutments for Texas conditions

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Date

2018-05-07

Authors

Walter, Jakob Richard

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Abstract

Integral abutment bridges (IAB), which are characterized by a lack of thermal expansion joints and bearings, expand into and contract away from retained backfill at the approaches. This behavior may lead to the development of increased lateral earth pressures or a long-term inward movement, as it has been observed in several structures. Additionally, it has been observed that repeated movements of IABs into and away from the adjacent soil because of annual and daily temperature fluctuations can lead to settlements in the approach roadways built on top of the retained fill. Yet, the possibly significant cost-effectiveness of the system has prompted the Texas Department of Transportation (TxDOT) to construct IAB and semi-integral abutment bridges (SIAB). The overall objective of the research is to investigate the geotechnical aspects relevant to the design of IAB/SIAB. The research project consists of four components: 1) a survey of state DOTs and Texas regarding IAB/SIAB design and construction, 2) an experimental program aimed to understand lateral earth pressure development and soil movement as a result of repeated movements, 3) a numerical component geared to predict soil response to repeated movements such as those in the experimental program, and 4) a field monitoring program involving instrumentation of three IAB/SIAB structures in the state of Texas. Surveys revealed that the anticipated approach to construct IAB/SIAB in Texas is viable. Furthermore, the compressible inclusion used by some states to prevent earth pressure ratcheting was proven to be successful in the laboratory and numerical components. Finally, the field monitoring program demonstrated two IAB/SIAB in Texas that have been performing well, and a third that has exhibited inadequate performance at the approach to bridge deck transition. In summary, the findings of the research have laid the foundation for development of design details to be presented to TxDOT for any future IAB/SIAB.

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