Broad Definition of VI (ref Spencer)

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Broad Definition of VI (ref Spencer)

• Visual Inspection . examination . by
• use of human sensory systems
• aided only by such mechanical enhancements to
  sensory input
• using looking, listening, feeling, smelling,
  shaking, and twisting
• observations are correlated with knowledge of
  structure and with descriptions and diagrams from
  service literature.

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Importance of Visual Inspection

• Visual Inspection is the most frequently used
  nondestructive evaluation technique
• using looking, listening, feeling, smelling,
  shaking, and twisting
• Standard by which all other non-destructive
  evaluation technologies may be compared
• No matter how sophisticated and elaborate the
  analysis and no matter how elegant the algorithms
  employed, in the final analysis, the recommended
  decisions are no better than the data upon which
  they are based.

3
Significance

• By far the most predominant non-destructive
  evaluation technique.
• Standard by which all other non-destructive
  evaluation technologies may be compared
• reliability of the Visual Inspection
• Jack hammer (forensic approach)
• Core cut
• Proforma Inspection sheets
• Crack gauge
• Camera
• Thermography
• Binoculars

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Visual Inspection - Issues
Reliability of Visual Inspection for Highway
Bridges. Volume I Final Report

• Inadequate identification of important structural
  aspects
• low or high condition ratings not used
• Results affected by
• Traffic
• Sight (vision, colour, light)
• Training, QA system (training with visual aids
  increased defects detected by 70)
• Perceived importance
• Ease of inspection (Accessibility, structure
  complexity, pressure/speed, environment, comfort)
• Inspectors consistent in themselves
• Large inconsistencies between inspectors.
• Significant variability assignment of Condition
  Ratings
• Significant variability in documentation
• Inaccuracies in delamination survey (only 25 of
  inspectors are within 5 of true value)

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AASHTO Types of Inspection

• Initial Inspection
• The first inspection completed on any new bridge.
  Goals
• (1)   to obtain all required Structure Inventory
  and Appraisal data
• (2)   to determine the baseline structural
  conditions and to identify current or potential
  problem areas.
• Routine Inspection
• A regularly scheduled inspection to
• Determine the physical and functional condition
  of a bridge
• Identify any changes since previous inspections
• Ensure that a bridge continues to satisfy all
  applicable serviceability requirements
• Must satisfy prescribed frequency and inspector
  qualifications requirements.
• Generally conducted from permanent access ways
• In-Depth Inspection
• A close-up, hands-on inspection of one or more
  members to
• identify deficiencies not normally detected
  during Routine Inspections.
• Generally completed at longer intervals than
  Routine Inspections
• May include the use of NDE techniques.
• Damage Inspection
• Completed to assess structural damage resulting
  from environmental or human actions.
• The scope is unique, with the general goal of
  assessing the need for further action.

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Visual Inspection - Issues
Reliability of Visual Inspection for Highway
Bridges. Volume I Final Report

• Inadequate identification of important structural
  aspects
• low or high condition ratings not used
• Results affected by
• Traffic
• Sight (vision, colour, light)
• Training, QA system (training with visual aids
  increased defects detected by 70)
• Perceived importance
• Ease of inspection (Accessibility, structure
  complexity, pressure/speed, environment, comfort)
• Inspectors consistent in themselves
• Large inconsistencies between inspectors.
• Significant variability assignment of Condition
  Ratings
• Significant variability in documentation
• Inaccuracies in delamination survey (only 25 of
  inspectors are within 5 of true value)

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CDOT program for VI enhancement

• A Quality Assurance (QA) inspector conducts
  unannounced evaluations of each inspectors work.
  The QA inspector performs the inspection without
  knowledge of previous inspection results in order
  to eliminate any bias. Differences between the
  two inspections are evaluated and a check on
  consistency is easily made
• Inspectors do not inspect the same structures
  each year. This ensures that inspections are not
  completed from within the same rut each time
• Most inspectors have 15 or more years of
  experience
• A minimum of 5 years of training is required to
  become a certified bridge inspector
• Quarterly meetings between all inspectors are
  held to discuss issues, identify discrepancies,
  and answer questions.
• A training program in which new inspectors work
  side-by-side with more experienced inspectors is
  required of all prospective inspectors
• Definitions have been clarified by CDOT to make
  them less ambiguous to the field inspector

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Purvis Two Parts VI Monitoring System

• QC is maintained within a single organization and
  consists of team members checking one anothers
  work. Inspectors review each others sketches or
  descriptions, and they check for consistency of
  descriptions and measurements.
• QA is performed by an independent, external third
  party. QA team members assess the quality of
  inspections previously completed and monitor
  activities to recommend changes to an established
  inspection program. The goal of QA is to ensure
  that inspections are performed in a manner
  consistent with established guidelines.
  Furthermore, QA serves to review a QC program and
  to offer suggested courses of action.

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Training Effect on Inspector Performance (ref
Chaney and Teel)

• Four groups each tested twice
• Test 1
• minimal information given to the inspectors.
• Test 2

Group 1 Group 2 Group 3 Group 4
Training No training 4hrs training Visual aids
provided Training visual aids
Defects detected 0 increase 32 increase 42
increase 71 increase
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Visual Inspection - How

• Record information
• Accuracy important
• Location
• Correct reference location
• Accurately marked on proforma
• Defect Type
• Use a standard system
• Simplified internal system recommended
• Avoid assumptions
• Description
• Make the extra effort to get up close
• Meaningful descriptions
• Photographs
• Size
• Subjective assessment not useful if uncontrolled
• Size does matter

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Size of Defects

• Tape measure
• Ruler
• Micrometer
• Crack width gauge

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Visual Inspection TrialsNon Destructive
Evaluation for Highway Bridges in the US
G.Washer. Int. Symp. On Non Destructive Testing
in Civil Engineering, Berlin 2003

• 49 practicing bridge inspectors
• 10 different inspection tasks
• Behaviour during inspection documented
• General condition rating used 0-9 scale
• Wide normal distribution of ratings for same
  bridge
• Seven Cracks in detail survey area

Superstructure - 2-7 Deck condition
- 3-7 Substructure - 4-7

• Correctly identified Not correctly identified
• 4 96
• Used Torch 86 38
• Inspector dist. to surf. 0.2m 2.7m
• ie Crack detection related to method

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