Unipole billboard superstructure requires regular painting and maintenance, the design life of the upper structure should meet the requirements of the ad approval documents, the superstructure is a steel structure, its structural design life should not be too long, generally not more than 15 years. Superstructure design quality problem is mainly reflected in the following aspects: 1) the part of the structural members welded firmly, local members from falling; 2) painting and maintenance quality, but off, leading to serious corrosion, ugly color; 3) the structure of the sign face unreasonable or not firmly welded to the sign face distorted; 4) sign face, and the column is not firmly connected, leading to the sign face off.