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Publication Number:  FHWA-HRT-13-101    Date:  November 2013
Publication Number: FHWA-HRT-13-101
Date: November 2013

 

Characterization of Bridge Foundations Workshop Report

INTRODUCTION

In 2013, FHWA proposed a new research program for the characterization of bridge foundations. To narrow the focus and develop a research roadmap for the program, a workshop on "Characterization of Bridge Foundations" was held in Arlington, VA, from April 30 to May 1, 2013, to solicit key stakeholder input. This report presents an overview, and documents the results and conclusions of the workshop. The invitation-only workshop consisted of 1.5 days of meetings to solicit key stakeholder input for the development of a research program on the characterization of bridge foundations. This research program will be led by the FHWA Turner-Fairbank Highway Research Center (TFHRC).

The workshop opened with plenary sessions to provide the participants with the national perspective, and summaries of geotechnical and hydraulic hazards and changes in service loads and foundations reuse. The plenary sessions were followed by breakout sessions to discuss these issues. The final session consisted of discussions among the participants to evaluate the results of the workshop and determine what follow-up activities are necessary to capitalize on the workshop results. The workshop agenda is shown in appendix A, and a list of workshop attendees is provided in appendix B. This document is intended to summarize the results of the workshop and frame them in the larger perspective of developing and implementing the CBF program.

BACKGROUND

The transportation system in the United States includes over 600,000 bridges for grade separations, interchange configurations, and stream crossings.(1) The operation and functionality of the highway system depends on the performance of these structures. As of December 2012, the National Bridge Inventory (NBI) included 607,380 structures (bridges and culverts) with a span greater than 20 ft (6 m).(1) Of those structures, 36,076 bridges over waterways (riverine and tidal) are identified as having unknown foundation characteristics. Additionally, there are a number of bridges over land with unknown foundation characteristics, which are not documented in the NBI database

In 2013, FHWA proposed a renewed effort for the development of a multiyear strategic research plan to address the "unknown foundation" problem. The unknown foundation has been associated with the population of existing bridges over waterways that cannot be evaluated for hydraulic vulnerability related to scour. The primary interest of unknown foundation investigation is determination of the bottom depth of the foundation (pile tip elevation). However, there are other engineering risks besides scour, as described in appendix C.

On January 16, 2013, a multidisciplinary task force met during the Transportation Research Board (TRB) annual meeting. The 14-member task force was comprised of FHWA and State transportation department stakeholders who were selected based on their recognized expertise in the areas of unknown foundation and foundation assessment issues. During the meeting, the task force members brainstormed on steps needed to move forward with a multiyear strategic research plan for unknown foundations. The consensus of the taskforce and FHWA management was to broaden the scope of the research program from "unknown foundation" to "foundation characterization" in order to incorporate multi-hazard issues, including changes in service loads and foundation reuse. Appendix C provides more detail on multi-hazards associated with the unknown foundation problem, including previous FHWA/Department of Transportation initiatives to address this problem.

The objective of the CBF program is to develop and/or evaluate new and existing technologies and methodologies for characterizing existing bridge foundations for the determination of unknown geometry, material properties, integrity, and load carrying capacity. Many foundation characterization/reuse decisions will likely be made in the framework of life-cycle cost and risk management analysis.

 

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