Fiber Reinforced Polymer Repair of Aluminum Overhead Sign Structures - Factsheet
Representatives from NY State DOT have performed on site demonstrations of the FRP repair procedure at NJ, PA, and IA DOTs. If your State DOT would like a demonstration, please contact contact Harry White of NY DOT.
Future demonstrations will be at CT DOT and Montreal.
Overhead Sign Structures (OSS) perform a valuable service to the traveling public. They support the signs that makes travel safer by informing the driver well before any action is required. However, these helpful structures can become a serious hazard if they are not properly maintained. The best insurance to preventing collapse is a comprehensive inspection program. NYSDOT has had a bridge inspection program for many years but never had a program to systematically inspect OSS. NYSDOT organized a sign inspection program in 2000. Inspectors took inventory of, and conducted hands-on inspections of all OSS. The results were startling: It was found that 10% of all signs had some form of structural damage. The most prevalent damage found included cracking of the joint between the internal trussing and the main chords. Some joints were totally severed. The cause of the cracks is difficult to determine and may be due to several factors. The lack of shop inspection during fabrication yielded some poor quality joint welds. Insufficient construction supervision may have induced some internal stresses into the OSS before the first sign was attached. Also, and possibly the greatest contributor, fatigue design was not a code requirement when the original truss designs were done in the 1960's.
An FRP manufacturer approached NYSDOT with a possible solution using GFRP to repair the cracked truss joints. NYSDOT and Utah DOT joined to form a Pooled Fund Research Program to study the feasibility of the FRP solution. Test samples of cracked joints were salvaged from existing OSS that had been taken out of service. These samples were then wrapped with FRP and sent to the University of Utah for tensile testing. The repair proved to be as strong as the fully welded connection. A second round of testing is being completed to determine the resistance of the FRP repair to cyclical loadings.