DFI Journal - The Journal of the Deep Foundations Institute

Volume 13, Issue 1, January 2019
DOI: 10.1080/19375247.2019.1592893

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Estimating Capacity and Reliability of Existing Foundations for Evaluation of Reuse (RESEARCH PAPER)

Andrew Z. Boeckmann, Ph.D., P.E.

Abstract


"Foundation reuse is a design alternative that has found favor among many owners and engineers as a means for satisfying financial, schedule, and various other constraints on superstructure replacement projects. Reusing foundations presents several significant design challenges, primarily assessing the condition and capacity of the existing foundation system. Using results from a field research study of two bridges in Missouri, this paper presents several techniques for predicting axial capacity of existing foundations, ranging from simply assuming the original design value to performing load tests of the existing foundations, with several methods of intermediate design effort. The reliability of each prediction method is evaluated, with the reliability analyses explicitly considering known loading of the existing structure. Results from the capacity assessment indicate the capacity from original design plans is conservative, and in some cases grossly conservative. Results of the study are useful for improving capacity estimates of existing foundations, for demonstrating techniques for estimating the reliability of existing foundations, and for providing methods of reducing over-conservatism in foundation reuse design."

Keywords:
foundation reuse, unknown foundations, driven piles, geophysical methods, foundation load test, pile extraction, pile capacity, reliability