Transportation Research Board 2002 Annual Meeting Presentations from Workshop on Plan of Action for Scour Critical Bridges

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Slide 1

Changes to FHWA's NBI Coding Guide (Items 60 and 113)

Plan of Action Workshop
January 16, 2002
Jorge E. Pagán-Ortiz
Senior Hydraulics Engineer
(e-mail:jorge.pagan@fhwa.dot.gov)

Federal Highway Administration
Office of Bridge Technology
Washington, D.C.

Slide 2

Implementation

• Revisions implemented by April 27, 2001, memorandum (Mr. James D. Cooper)
• Coordinated with National Bridge Inventory Steering Committee

Slide 3

Goal

• Provide new guidance for coding bridges over waterways for:
  • Observed and assessed scour condition
  • Scour and stream instability countermeasures
  
  

Slide 4 - 5

Objectives

• Make coding of Items 60 (Substructure) and 113 (Scour Critical) consistent when a rating of 2 or below is determined for Item 113
• Expand description of Item 113 codes 1, 2, 3, 4, 5, 7, 8, T and U
• Encourage bridge owners to develop a plan of action for:
  • Scour critical bridges (codes 1-3)
  • Bridges coded "7" and "U"
  • Improve communication between the engineer and inspector
  
  

Slide 6

Highlights of Changes to Item 60

• Description changed to emphasize that rating factor given to Item 60 should be consistent with the one given to Item 113 when:
  • Rating factor of 2 or below is determined for Item 113.
  
  

Slide 7 - 8

Highlights of Changes to Item 113

• Description changed to emphasize that:
  • Rating factor of 2 or below requires revising Item 60 and other affected items (load ratings and superstructure rating)
  • Plan of action should be developed for each scour critical bridge
  • Coding is based on an engineering evaluation, which includes consultation of NBIS field inspection findings
  
  
• Refers to FHWA's Hydraulic Engineering Circulars 18 and 23 for guidance on scour and countermeasures.

Slide 9

Specific Changes to Rating Factors (Codes U and T)

• Code "U" - plan of action should be developed to reduce the risk of failure during and immediately after a flood event.
• Code "T" - tidal bridges should be monitored until an evaluation is performed

Slide 10

Code 8

• Expanded guidance for a bridge foundation determined to be stable:
  • Assessment --bridge foundations on rock formations determined to resist scour within the service life of the bridge
  • Calculations
  • Installation of properly designed countermeasures
  
  

Slide 11

Code 7

• Countermeasures installed to mitigate an existing scour problem and to reduce the risk of bridge failure during a flood event
• Instructions in a Plan of Action have been implemented to reduce risk to users from a bridge failure during or immediately after a flood event

Slide 12

Code 5

• Foundation determined to be stable for the assessed or calculated scour condition
• Scour within the limits of footings or piles based on an assessment, calculation or installation of properly designed countermeasures

Slide 13

Code 4

• Bridge foundation stable for the assessed or calculated scour condition

Slide 14

Code 3 (Scour Critical)

• Bridge foundation unstable for the assessed or calculated scour condition

Slide 15

Code 2 (Scour Critical)

• Field review indicates that extensive scour has occurred at bridge foundations, which are determined to be unstableby:
  • Comparison of calculated and observed scour during bridge inspection
  • Engineering evaluation of the observed scour condition reported by the bridge inspector in Item 60
  
  

Slide 16

Code 1 (Scour Critical)

• Field review indicates that failure of bridge foundations is imminent based on:
  • Comparison of calculated and observed scour during bridge inspection
  • Engineering evaluation of the observed scour condition reported by the bridge inspector in Item 60
  
  

Slide 17

Current Status (04/15/01)

Slide 18

Scour Evaluation Status

Slide 19

Scour Evaluation Summary

• Evaluations Completed:  361,260 (92.4%)
• Evaluations Needed:        29,672 ( 7.6%)
• Evaluations Total:          390,932 (100.0%)

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