NUTS + BOLTS When modifying existing sign structures, all proposed details must be evaluated and approved by professional engineers. structures including signage. Section 11 (Fatigue Design) of AASHTO's Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals incorporates comparisons of relative fatigue resistance among various, common types of structural connections (welded and non-welded). AASHTO ranks the durability of these structural connections according to stress categories that range in descending order from "A" to "E." Section 11 also incorporates drawings identifying the most common types of structural connections, thus enabling sign companies and their engineers to make informed choices when creating designs for outdoor structures. 34 SIGNS OF THE TIMES OCTOBER 2017 Familiarity with these guidelines is useful in every phase of outdoor sign projects, from manufacturing to installation and maintenance. Particularly when modifications are proposed for existing structures such as replacing old signs or installing additional signs, preliminary evaluations and approvals by professional engineers are essential. In these cases, the structures' original design specifications must be referenced by project engineers to determine the suitability of proposed modifications.http://www.asantesigngroup.com