INFORMATION AND RECOMMENDATIONS FOR IMPROVED QUALITY ALUMINUM SIGN STRUCTURES

A QUESTIONNAIRE SURVEY REVEALED THAT THE PRIMARY CAUSE OF THE FAILURES IN ALUMINUM OVERHEAD SIGN TRUSSES IS DUE TO ACCELERATED FATIGUE RESULTING FROM THE AEOLIAN EFFECT. MODERATE OR LOW VELOCITY WINDS PASSING AROUND THE TUBES CREATE HARMONIC VIBRATIONS WHICH MAY CAUSE FATIGUE WELD FAILURES. FORCING CAMBER INTO TRUSSES, MISALIGNMENT OF FLANGES, POOR FABRICATION TECHNIQUES AND PRACTICES, UNDERSIZE TUBE SECTIONS, IMPROPER SELNDERNESS RATIOS, METHODS, OF SHIPMENT, AND FAULTY ERECTION PROCEDURES ALL CONTRIBUTE TO WELD FAILURES. MOUNTING OF THE SIGN PRIOR TO ERECTION OF THE TRUSS; INSTALLATION OF SIGNS AND ATTACHMENTS WITHIN EIGHT HOURS OF TRUSS ERECTION; USE OF TRUSS DAMPERS; ARE SOME SOLUTIONS TO THE PROBLEM. BASIC RULES IN THE FABRICATION AND WELDING OF ALUMINUM SHOULD BE FOLLOWED. TUBES SHOULD BE MILLED TO THE REQUIRED RADII WITH THE MAXIMUM GAP AT ANY POINT NOT GREATER THAN 0.0125 INCH. ALL AREAS OF WELDING MUST BE BRUSHED WITH STAINLESS STELEL BRUSHES IMMEDIATELY PRIOR TO MAKING THE WELDS. WELDING WIRES SHOULD BE MICROSCOPICALLY CLEANDED AND REMAINING SPOOLS MUST BE SEALED IN POLYTHYLENE BAGS. FORCED FITS MUST BE AVOIDED AND ONLY DOWN HAND WELDING IS RECOMMENDED. ALL WELD CRATERS MUST BE ELIMINATED AND WHERE POSSIBLE, WELDS SHOULD CARRY THROUGH TIGHT WITHOUT STOPPING. THE SUPERVISION OF ERECTION CREWS IS IMPORTANT. STRICT ADHERENECE TO SPECIFICATION REQUIREMENTS OF ALUMINUM FABRICATION IS EMPHASIZED.

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  • Accession Number: 00210018
  • Record Type: Publication
  • Files: TRIS
  • Created Date: May 15 1974 12:00AM