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Title: Guidelines for the Installation, Inspection, Maintenance and Repair of Structural Supports for Highway Signs, Luminaries, and
Author: Federal Highway Administration US DOT
Source: US Department of Transportation
Publication year 2002
Document number: 2002136
Number of pages: 145
Abstract:
1.0 Introduction
This document provides guidance for the installation, inspection, maintenance, and repair of structural supports for highway signs, luminaries and traffic signals. The
primary purpose is to provide owners with information that can assist them in managing their inventory, identifying potential problem areas, and ensuring safe and
satisfactory performance of these types of ancillary highway structures. The primary reason for compiling this guidance is increasing problems with wind induced vibration,
fatigue, and even structural collapse of these support systems, as seen in Figure 1. Documented problems with these structures include questionable design and details, poor
fabrication practices, and poor installation techniques.
16.3.3.2 Cracks
Weld crack problems with steel structures are easier to repair than aluminum. The repair may
be made ‘in-situ’ or that portion of the structure can be removed from service and repaired.
Corrections to weld problems may include hammer peening, hole drilling to arrest the crack,
vee-and-welding, or detail modification.
Hammer peening provides a compressive stress to the weld surface that helps to reduce the
tendency to crack and to keep any crack from propagating. It has been useful for fatigue
cracks up to 3 mm (1/8 inch) deep. Hammer peening followed by surface grinding can increase
the strength of the connection by one fatigue strength category. Ultrasonic Impact Treatment
(UIT), sometimes called ultrasonic peening, is a recently developed technique used to treat fillet
welds to increase their fatigue strength. This has been used in Texas to treat welds in ancillary
structures and is a patented process developed by Applied Ultrasonics.
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This page last revised: 04/24/2008