The National Academies

NCHRP Synthesis 20-05/Topic 51-13 [New]

Load Rating of Bridges with Missing As-Built Plans
[ NCHRP 20-05 (Synthesis of Information Related to Highway Practices) ]

  Project Data
Funds: $45,000
Staff Responsibility: Tanya Zwahlen
Fiscal Year: 2019

Preliminary Scope

Lack of as-built information for older bridges is a problem that many state departments of transportation (DOTs) are facing across the nation. Analytical load-rating of bridges can only be successfully performed with complete information of the bridge’s as-built composition. When missing as-built information, the AASHTO Bridge Evaluation Manual allows the use of conservative assumptions, which often result in unreasonably low load postings with economic and logistical implications. There is no uniformity in the way different DOTs approach the problem of load rating the bridges with missing plans.

In a recent survey, the majority of surveyed states reported more than 100 bridges with missing plans in their inventory. In some of the surveyed states, bridges with missing as-built plans exceed 25% of the total bridge inventory. The methods used to obtain missing information vary significantly between different jurisdictions. Employed methods range from diagnostic and/or proof load testing, using engineering judgement, a range of non-destructive testing techniques to determine materials and geometrical properties, to utilizing conservative assumptions prescribed by AASHTO Bridge Evaluation Manual.

The objective of this synthesis is to document practices for load rating of bridges with missing as-built plans used by DOTs. Examples of condition-specific strategies for allowing a bridge rater to use the analytical load-rating for bridges for which information is missing or incomplete will be identified.

Information to be gathered includes but is not be limited to:

• Techniques used by DOTs for load rating of bridges with missing as-built plans focusing on field load testing methods as well as the range of non-destructive techniques for determination of unknown materials properties and missing geometrical information
• Categorization of load rating practices according to the bridge type
• Condition-specific strategies to allow a bridge rater to use the analytical load-rating for bridges in the state DOTs inventory for which information is missing or incomplete

Information will be collected through literature review, survey of DOTs, and follow-up interviews with selected agencies for the development of case examples. Information gaps and suggestions for research to address those gaps will be identified.

Information sources (Partial):
• NCHRP 20-05/Topic 50-12: Development and Use of As-Built Plans by State DOTs
• American Society of Civil Engineers (ASCE) publications (https://ascelibrary.org/)
• Transport Research International Documentation (TRID) (https://trid.trb.org/)
• National Transportation Library (https://ntl.bts.gov/)
• WorldCat (https://www.worldcat.org/)
• ScienceDirect (www.sciencedirect.com)

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