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.”

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.

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

Visual Inspection - Issues 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)

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

AASHTO Types of InspectionInitial 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.

Special Inspection A Special Inspection is completed to monitor a known defect or condition.

Visual Inspection - Issues 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)

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

CDOT program for VI enhancement A Quality Assurance (QA) inspector conducts unannounced evaluations of each

inspector’s 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

Purvis Two Parts VI Monitoring System QC is maintained within a single organization and consists of

team members checking one another’s work. Inspectors “review each other’s 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.

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 1Group 2Group 3Group 4

TrainingNo training4hrs trainingVisual aids providedTraining & visual aids

Defects detected0% increase

32% increase42% increase71% increase

Visual Inspection - How Record information

Accuracy importantLocation

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

Size of Defects Tape measure Ruler Micrometer Crack width gauge

Visual Inspection Trials“Non 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 - 2-7Deck condition - 3-7Substructure - 4-7

Correctly identified Not correctly identified4% 96%

Used Torch 86% 38%Inspector dist. to surf. 0.2m 2.7m

ie Crack detection related to method