Date of Award

5-2005

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Thomas C. Sandford

Second Committee Member

William G. Davids

Third Committee Member

Dana N. Humphrey

Abstract

Although the advantages of integral abutment bridges are widely know, design practices and assumptions vary extensively. Currently, pile supported integral abutments are limited to locations where the depth of overburden can provide fixed support conditions. In Maine, there are often cases where the depth to bedrock prohibits integral abutment bridges from being used. The objective of this research is to expand the use of pile-supported integral abutment bridges to sites where the depth to bedrock is considered shallow, less than 4 m (1 3 ft) from the ground surface. Phase I of the project has been completed (DeLano, 2004), producing preliminary design guidelines for pile supported integral abutment bridges with overburden depth less than that required to develop fixity. The objective of Phase 1 of this two-part research project is to finalize the design and construction guidelines by monitoring the performance of a constructed, skewed integral abutment bridge on shallow bedrock. Three tasks within the first part of Phase 1 include instrumentation installation, construction monitoring, and construction and initial behavior interpretation. The Coplin Plantation, ME site offered a unique opportunity to investigate possible differences in short and long pile behaviors. One abutment has a depth of overburden sufficient to achieve pile fixity, while the other abutment has insufficient overburden to achieve pile fixity. This allowed for the unique comparison of pile behavior for deep and shallow bedrock conditions at the same bridge. Instrumentation of the bridge included measurements of pile and abutment movements, pile strains, soil and pore pressures, and temperatures. The sequence and procedure of construction was analyzed to assess its effects on stresses in the pilings. Upon completion, the bridge was subjected to a comprehensive live load test to assess the effects of truck loads on the structure. Observations made during both the construction sequence and live load testing generally agree with those made during Phase 1 of this study. The stresses in the short piles were found to be no more severe than the stresses in the long piles. The longer piles were found to be fixed at some depth, while the shorter piles did not develop fixity. The large skew of the bridge did have an effect on the stresses in the piles. The near-obtuse piles saw a larger percentage of the loads. Large thermally induced loads were not included in this study but will be examined in further research. Monitoring of the bridge will continue for a full year from the completion of construction. This data will be used to provide calibration data for finite element models developed by other UMaine researchers and to assess any limitations of the preliminary design guidelines. A final design guideline will be developed for all anticipated conditions in Maine.

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