Investigation of Sign
Support Truss Structure
About the research
A sign support truss over eastbound I-80 about 2 miles west of the west
interchange near Des Moines, IA was removed in the spring of 2000. A
inspection of the truss found that one of the bottom chord members was
deteriorated. Corrosion of the bottom chord has caused significant
thickness loss of cross
section area of many members. This deterioration led to a concern about
adequacy of the truss.
The truss is a galvanized steel, four chord truss with a span of
approximately 60 ft and
carries a single 14 ft x 40 ft sign and associated lighting.
The Iowa DOT initiated this investigation to evaluate the structural
behavior of sign
support trusses that have structural deficiencies and to assess the
urgency to remove or
retrofit these trusses.
Objective: The primary objectives of this investigation are:
(1) Perform a load test of a damaged truss to assess the impact of the
on the overall performance of the truss.
(2) Compare the load test results with the results of structural analysis of
the truss with
the intent of assessing the accuracy of predicting the structural behavior
and undamaged sign support trusses.
(3) Provide recommendations for managing damaged trusses.