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5 chapter one IntroductIon A central challenge for an aging U.S. infrastructure is managing aging bridges safely and cost- effectively. One appealing, sustainable option for many bridge replacement and rehabilitation efforts is the reuse of bridge foundations, which can result in time and cost savings as well as reduced mobility impacts. However, foundation reuse presents significant challenges, including uncertain- ties in foundation condition, remaining service life, and capacity. The goal of this study is to docu- ment current practices and guidelines used by various transportation agencies for the reuse of bridge foundations. objectIves This Synthesis has two objectives: (1) to document current practices and guidelines used by transpor- tation agencies for the reuse of bridge foundations, and (2) to identify challenges and gaps in infor- mation impeding foundation reuse. The objectives are achieved by collecting information regarding the following eight topics: 1. Extent and frequency of foundation reuse 2. Existing specifications, policies, and guidelines related to foundation reuse 3. Motivations for foundation reuse 4. Challenges for foundation reuse 5. Investigation methods and condition assessment of existing foundations 6. Methods for predicting capacity of existing foundations 7. Construction techniques used to facilitate foundation reuse 8. Post-reuse monitoring and analysis of performance. Methodology and outlIne The required information was gathered through a literature review, a survey of transportation agen- cies, and interviews with several agencies selected for case examples. These activities are summarized here, and the results for each presented in chapters two, three, and four, respectively. Conclusions are presented in chapter five. literature review References relevant to each of the objective topics were studied and are summarized in the chap- ter two literature review. The literature review begins by briefly introducing topics that provide necessary background and contextual information for foundation reuse. The topics include an overview of U.S. bridges near the end of their service life focusing on agency management and inspection practices as well as the history of foundation reuse. The literature review next pres- ents challenges for foundation reuse as identified by early U.S. experience. The middle sections of the literature review present technical topics: investigation and condition assessment methods, deterioration mechanisms, methods for predicting remaining service life, and construction tech- niques. The literature review closes with decision methods related to reuse and prominent exam- ples of reuse.
6 survey A survey was distributed electronically to 62 transportation agencies, including state transportation agencies for all 50 states, Puerto Rico, and the District of Columbia as well as ten Canadian prov- inces and territories. Forty-five of the 50 state departments of transportation (DOTs) responded to the survey, a response rate of 90% for the state agencies. In addition, responses were received from eight Canadian provinces (80%). The survey was distributed to agency geotechnical engineers; however, these individuals were encouraged to share the survey with bridge or structures colleagues. The first survey question asked if the respondentâs agency had experience with foundation reuse as explained in the Definitions section of this chapter. Respondents who indicated their agency does not have experience reusing foundations were asked three follow-up questions. Respondents who indicated their agency does have experience with foundation reuse were asked 22 follow-up questions. Chap- ter three summarizes the results of the survey, including general information on reuse experience, the frequency of reuse for various applications, foundation investigation methods related to reuse, service life of foundations, design issues, construction techniques, and performance monitoring. case examples Survey responses were reviewed to identify agencies with unique policies regarding foundation reuse, agencies that reuse foundations frequently, and agencies with experience on noteworthy foun- dation reuse projects. Additional investigation into the practices and experiences of these agencies was performed by conducting interviews with agency personnel and reviewing available agency documents. The agency interviews were also used to more closely examine agency practices related to bridge scour in the context of foundation reuse. Chapter four includes the results of each case example and a summary of lessons learned from the five case example agencies. defInItIons There is no consensus regarding what exactly constitutes reuse of a foundation. For the purposes of this Synthesis, foundation reuse refers to any agency action that changes the design load of the existing foundation. Examples of foundation reuse include bridge superstructure replacement, bridge widening, bridge repurposing, and retrofitting for seismic or other purposes. Reuse may include using the existing foundation as-is or it may include modifications such as the addition of piles or widening a footing. For the purposes of this Synthesis, in-kind bridge deck replacement is not con- sidered foundation reuse. Other definitions of foundation reuse beyond the one used in this Synthesis are possible (e.g., Foundation Reuse and Enhancement, Jalinoos et al. 2016). This Synthesis report frequently uses terms that (1) represent important concepts related to foun- dation reuse and (2) may be unfamiliar to readers. Some of the terms are defined on their first use in the report, and all are defined in the Glossary, which is presented immediately following the report.
