Fatigue Strength and Evaluation of Sign Structures. Volume 2: Sign Structure Inspection Manual

This report is a two-volume final report presenting the findings of the research work that was undertaken to evaluate the fatigue behavior of sign structures and, based on that evaluation, to recommend an inspection plan that can be effectively used to detect and minimize possible deterioration due to wind induced loadings of sign structures. The study included a number of signs that are commonly used in Indiana: single-mastarm and double-mastarm cantilever sign structures, box-truss sign structures, tri-chord sign structures, and monotube sign structures. Sign structures with typical dimensions and details were selected as prototypes for each of the various types of sign structures in the study and were subjected to various wind loading environments. The predicted fatigue behavior of the sign structures was used to identify the types of signs and the structural details that were most susceptible to fatigue damage. This information was used to develop an inspection guideline that provides information on where to look during an inspection for fatigue damage. An inspection plan was formulated by using a crack propagation analysis to evaluate crack growth under the most critical wind loading environment. Based on these analyses, an inspection period of four years was recommended for single and double mastarm cantilever sign structures (Class A) and an eight year inspection cycle was recommended for box-truss, tri-chord, and monotube sign structures.