Broad Definition of VI (ref Spencer)

1. 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.”

2. 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

4. 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)

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

6. 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)

7. 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

8. 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.

9. 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

10. 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

11. Size of Defects • Tape measure • Ruler • Micrometer • Crack width gauge

12. 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 - 2-7 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