Masters Theses

Date of Award

8-2002

Degree Type

Thesis

Degree Name

Master of Science

Major

Civil Engineering

Major Professor

Edwin G. Burdette

Committee Members

James H. Deatherage, David W. Goodpasture

Abstract

The Tennessee Department of Transportation has been designing and building jointless integral abutment bridges for many years. These bridges have a number of advantages, including their efficient design, increase in construction speed, durability, and their reduction in maintenance costs during the life of the bridge. A special consideration in jointless integral abutment bridges is the thermal force applied to the abutments and piles during cyclic temperature changes of the structure. In cooperation with TDOT, the University of Tennessee, Knoxville's Civil Engineering Department tested the lateral displacement capacity of four 14 inch square prestressed concrete piles driven in virgin clay soil. To replicate the rotational stiffness of an actual bridge, the testing setup utilized hold-down beams to provide the rotational restraint of the simulated abutment during lateral displacements. The research team utilized four different hold-down setups, each providing a different rotational stiffness. Equations for the theoretical rotational stiffness of each setup were derived to evaluate its rotational stiffness. These hold-down setups provided theoretical rotational stiffnesses both lower and higher than the calculated theoretical rotational stiffness in a typical bridge. Plots of P-Δ and M-Δ curves were used to compare different hold-down setups. The comparisons led to the conclusion that stiffer hold-down devices, as opposed to flexible hold-down devices, increase the slopes of the P-Δ and M-Δ curves. A stiffer hold-down device decreases the rotation verses displacement curves. The effect of leaving the pile's prestressing strands protruding in the abutment versus cutting them flush with the top of the pile was an important comparison. Abutments that lacked prestressing strands had larger cracks at the pile-abutment interface. Even though abutments that lacked prestressing strands did not behave as well as those which contained them, all abutments tested performed adequately to lateral displacements greater than the 1 inch maximum considered in designs by TDOT.

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