Long-Term Bridge Performance (LTBP) Program Protocols, Version 1

Chapter 1. Introduction

The Long-Term Bridge Performance (LTBP) Program is a long-term research effort, during which a large amount of data on bridge condition and bridge performance will be collected for different groups of bridges across the United States. The activities of the LTBP Program will concentrate on the types of bridges most heavily represented in the U.S. bridge population. Although the population of U.S. bridges is diverse, there are a few common bridge types that predominate and are likely to do so in the future. For example, multigirder bridges of steel, concrete, or prestressed concrete represent the most common bridge types, and focusing on their performance enables the LTBP Program to make the largest impact in the near- and mid-terms.

The specific data to be collected will support experiments designed to study various issues related to bridge performance for these common bridge types. Depending on the specific experiment, data will be collected using a combination of document review, detailed visual inspection, sampling and testing of materials, nondestructive evaluation (NDE) testing, finite element modeling, structural testing, and long-term monitoring. These data collection efforts are designed to allow a series of guiding questions to be answered from existing documentation, if possible, and from field data collection efforts if necessary.

At the program level, guiding questions were developed via consultations with key program stakeholders who helped identify several high-priority bridge performance issues.⁽¹⁾ The LTBP Program aims to address these guiding questions. However, on a per-bridge level, additional, more specific, guiding questions will be developed prior to data collection considering what is learned during the previsit activities.

To maximize the quality and usefulness of the data, it is imperative that evaluations, data collection, testing, and reporting be implemented in a consistent manner regardless of where, when, and by whom they are conducted. To meet this need, the data collection processes, the units of measure, and the level of accuracy should be as consistent as possible. Therefore, a set of protocols that support the objectives of the LTBP Program have been developed. These protocols provide a set of step-by-step instructions governing all aspects of data collection, including planning, designing experiments, gathering bridge documentation from State transportation departments, extracting data, visual inspection, material testing, NDE testing, live load testing, instrumentation, logistics, safety, data reduction and processing, data interpretation, reporting results, data storage, archiving, and importing into the LTBP Program Bridge Portal.

The LTBP Program protocols are for research purposes and intended primarily for use within the LTBP Program. The protocols have the following attributes:

• Quantitative in nature and avoid vague statements that may permit multiple interpretations.
  
  
• Mandatory language without unnecessary commentary that may cause confusion.
  
  
• Integrated through a robust structure that permits cross-referencing to avoid repetition.
  
  
• Reference existing and proven standards without repeating content, which would likely result in conflicts over time as the existing standards are updated.