Field Measurements of Passive Pressures behind an Integral Abutment Bridge: Fid-Bau Portal

Field Measurements of Passive Pressures behind an Integral Abutment Bridge

Hassiotis, Sophia / Xiong, Kai

A bridge that is cast continuously with its abutments is known as an integral abutment bridge. A short stub-abutment supported on a pile-bent creates a flexible foundation that transfers the temperature and traffic-induced horizontal loading and eliminates the need for expansion bearings. Integral abutments are gaining wide acceptance by many states; however, a nationally accepted design methodology does not exist for their design and construction. Instead, each highway department depends on the experience of its engineers to develop adequate design criteria. By studying the response of such systems to horizontal loading, we may be able to extend the learned concepts to different structures and conditions. To study integral bridges, we instrumented a medium-length (300 ft) highway bridge in Trenton, New Jersey and have been observing the reaction of the bridge and its foundation to seasonal and daily thermal loadings. Design parameters of interest include the flexural behavior of the piles that support the abutment, the soil-pressure distribution behind the abutment, and the displacement and rotation of the superstructure during thermal loading. As such, we have gathered data every two hours for the past four years on displacement, rotation, strains, and pressures on the bridge and its foundation. In this paper, we will be sharing some of the data and will discuss relevant conclusions of our studies. In general, we have been witnessing an excellent correlation between temperature and displacement, expected behavior from the horizontally loaded piles, and a steady build-up of soil pressure behind the abutment. A short study of passive pressure build-up is also summarized.