All signs requiring structural engineers drawings shall be constructed to the standards contained in the Municipal Code of the City of Chicago, except that for compressive stresses for columns and other compression members of structural grade steel, the ratio of l/r shall not exceed 120. Main structural members shall not be less than 5/16 inch (8 mm) thick and secondary members and bracing shall not be less than 1/4 inch (6.4 mm) thick. Signs erected entirely above a roof shall have the calculated center of the wind pressure not higher above the roof than 75 percent of the vertical distance between the roof and the top of the display.
(Added Coun. J. 11-3-99, p. 13842, § 3)