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1 1 BACKGROUND The quality of element-level bridge inspection data is critical for effective bridge management and to ensure the safety and serviceability of bridges. The objective of this research was to develop guidelines to improve the quality of element-level data collection for bridges on the National Highway System (NHS). Element-level data are collected according to the requirements provided in the AASHTO Manual for Bridge Element Inspection (MBEI)(AASHTO 2013). The collection of element-level data for NHS bridges became a requirement for all agencies in 2014 to meet the requirements of the âMoving Ahead for Progress in the 21st Century Act (MAP-21)â legislation. Prior to that time, element-level data was not required, although many bridge owners collected element-level data within their programs as part of their normal business practice. Required data to be collected and reported generally includes National Bridge Elements (NBEs) and certain Bridge Management Elements (MBEs) deemed to be necessary to analyze bridge condition on a national scale. Many agencies may collect additional element-level data to meet their needs for bridge management and data analysis, while other agencies may not use element-level data within their normal business practices. Some agencies have many years of experience in conducting element-level inspections, while other agencies are relatively new to this process. To meet the requirements in the MAP- 21 legislation and to ensure the safety and serviceability of bridges, bridge owners need guidelines that promote consistency in the collection of element-level data for bridges on the NHS. The collection of quality element-level data is important to support good asset management practices. For these reasons, guidelines that provide recommendations to improve consistency in element-level data collection are needed. The guidelines should also provide recommendations for establishing accuracy levels for element conditions and applicable defect quantities. The purpose of these recommendations is to support bridge management system deterioration forecasting and evaluation. To address these needs, the research developed and field-tested guidelines for improving the quality of element-level inspections. Field exercises using the developed guidelines were completed using state bridge inspection teams. The objective of this research was to develop guidelines to improve the quality of element-level data collection for the NHS bridges in reference to the AASHTO MBEI. 1.1 Element-Level Bridge Inspection Prior to the implementation of the National Bridge Inspection Standards (NBIS), bridge inspection practices in the U.S. varied significantly between bridge owners with only a few owners inspecting bridges on a regular basis. The inspections were typically performed as a result of observed deficiency or need. Bridge inspection transitioned from a function completed on an as-needed basis to a federal mandate following the collapse of the Silver Bridge on December 15, 1967 (NTSB 1970). Following this historic bridge collapse, the FHWA developed requirements for bridge inspection, first for bridges on the Federal- aid system, and later extended to all bridges on public roadways. Historically, the inspections have been completed on a component-level basis that rated three primary components of a bridge; the deck, superstructure, and substructure. Additional data on the characteristics and location of the structure were also recorded (FHWA 1995). The results of conventional component-level bridge inspections are used by bridge managers to identify maintenance needs from the safety perspective and to help make decisions regarding repair. A subjective condition rating scale ranging from 0 (Failed condition- out of service) to 9 (Excellent condition) is used to characterize the condition of bridge components relative to the as-built condition (FHWA 1995). The engineering aim of bridge inspection using a component-level approach is to manage bridges by maintenance action and to identify bridges requiring more detailed (in-depth) inspection. The modern day bridge element-level data collection began with FHWAâs Demonstration Project 71 in October 1989 (O'Connor 1989). This project was the beginning of the AASHTOWare Pontis Bridge
2 Management Software and required bridge inspection data to have more granularity than the NBIS categories of deck, superstructure, substructure, and culverts. The report concluded that for an effective bridge management system, additional information would be required to support the management function. The report sighted several states that had begun the process of adding sub-categories to the NBIS data, which inspectors would need to evaluate and record as part of a field inspection. The forerunner to the AASHTO Guide for Commonly Recognized (CoRe) Elements for Bridge Inspection, developed in 1993, was Pontis 2.0 (FHWA 1993). The users of this software were required to supplement the NBIS data with the condition of the bridge based on certain specific elements. In 1998, the FHWA formally adopted the CoRe elements, after the Subcommittee on Bridges and Structures (SCOBS) had defined the commonly recognized bridge elements utilizing common engineering language (AASHTO 1997). The CoRe guide was revised in 2002 and 2010 to address necessary changes in the way inspection data was recorded. During this period, the development of BRIDGIT was sponsored by NCHRP (NCHRP 1999). This system required the inspector to collect the condition of the structural members and the protective system of those members. The philosophy of member definitions and condition states was similar to the CoRe definitions (i.e., up to five condition states within each element type or group). By the year 2000, many states had moved to collecting at least some element-level data based on the CoRe guide, BRIDGIT, or agency-developed system. In 2010, work on the AASHTO Bridge Element Inspection Guide Manual was initiated by SCOBS (AASHTOâs Technical Committee 18, Bridge Management, Evaluation, and Rehabilitation) due to the shortfalls of the CoRe and BRIDGITâs element definitions. The international scan tour, âBridge Evaluation Quality Assurance in Europe,â found that many of the European nations had added additional granularity to their element inspection process, which provided them with additional information and data quality (Everett, Weykamp et al. 2008). In 2011, the Guide Manual for Bridge Element Inspection (GMBEI) was adopted in order to provide: ï· Improvements through changes in the measurement units of decks and slabs. ï· The development of wearing surface elements. ï· The standardization of the number of element states. ï· The development of protective coating elements. ï· The incorporation of expanded element Smart Flags (Defect Flags). ï· Defining the subjective engineering terms of ânarrow,â âsmall,â âlarge,â âsum,â etc. These improvements were made to better capture the condition of the elements by reconfiguring the element language to utilize multiple distress paths within the defined condition states. The multi-path distress language provides the means to incorporate possible defects within the overall condition assessment of the element. The defect elements also provide data for developing deterioration models that more explicitly consider the active deterioration mechanisms in a bridge. The AASHTO Manual for Bridge Element Inspection (MBEI), First Edition 2013 with the 2015 Interims, was the current edition for the element inspection process at the time this research was conducted (AASHTO 2013). The engineering aim of element-level inspection is to achieve consistent, data-driven systematic investment in preventive maintenance, rehabilitation, and capital investment along with the project level, network level, and bridge- level condition ratings. The administrative benefits of element-level inspections include better funding schemes and performance measures for asset management. The research documented herein is intended to improve the quality of element-level bridge inspection data to meet these needs.