Structural Steel Issues & Answers
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Weld Quality Audit & Fitness-For-Service Analysis Verify Safety Margins

The Issue

During structural steel erection, ambiguities and differences in the interpretation of the American Welding Society (AWS) D1.1 visual inspection guidelines raised issues concerning the integrity of inspections performed on weldments. Consequently, the fitness-for-service of the overall steel construction was questioned. Subsequent construction (e.g., fireproofing, interior framing, ductwork, mechanical subassemblies, etc.) limited access to some of the regions of interest. Therefore, a comprehensive reinspection was not practical due to accessibility and/or significant construction delay concerns.


The Answer

A visual weld quality audit was initially performed on a statistically-based random sampling of the moment-resisting connection weldments. Using this sampling plan, nonconformances expected to be present throughout the structure were identified and characterized with a high degree of certainty. The visual acceptance criteria of AWS D1.1 were augmented by criteria developed by the Nuclear Construction Issues Group for reinspection of existing statically-loaded steel structures.1 Not unexpectedly, some nonconformances were noted during this audit. A fitness-for-service evaluation was then performed to disposition nonconformances noted during the inspection.

A generic approach was taken for dispositioning since it was assumed that nonconformances discovered during the random sampling inspection might be present in other areas of the structure that were not part of the inspection sample. While minimizing construction delays and unnecessary repairs, this inspection program and evaluation showed, with a high degree of confidence, that the structure had sufficient safety margins to tolerate the nonconformances during severe design basis seismic events. 1Nuclear Construction Issues Group, "Visual Weld Acceptance Criteria," Electric Power Research Institute Report EPRI NP-5380, Volumes 1-3, September 1987.

Servicies Offered

Problem Solving (welding, engineering, stress analysis, flaw acceptance, fitness-for-service)

  • Failure and Root Cause Analysis Design, Fabrication, and Erection Oversight Services Inspection Reviews/Audits
  • Dispute Resolution Technical Support

Facilities, Technologies, Software
Personnel Experienced in Welding Engineering, Metallurgy, Applied Mechanics, and Expert Testimony

  • Finite Element Stress Analysis Tools Capable of Analytically Predicting Applied, Residual, and Restraint Stresses Fracture Mechanics and Plastic Instability Models for a Wide Variety of Flaws and Design Details
  • Complete Metallurgical Laboratory, Including Mechanical Testing Equipment

Recent Experience

  • USC Norris Cancer Center Building -- Root Cause Analysis and Dispute Resolution Santa Clara Valley Medical Center -- Root Cause Analysis/Design and Fabrication Review Yerba Buena/Sony Entertainment Center -- Flaw Acceptance/Fitness-For-Service Review/ Construction Oversight Services
  • U.C. Davis Medical Center -- Weld Procedure Specification Review

Structural Steel Issues & Answers is a periodic newsletter designed to provide you with timely information about important issues affecting all aspects of the structural steel industry. 

For more information, contact Geoff Egan or Mike Cronin at (408) 745-7000 or 408-745-7000.

 

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