Field investigation and structural analysis of wind-induced collapse of outdoor single-post billboards

Abstract

Outdoor single-post billboards, which consist of a supporting steel column and two or three billboard panels, are widely used in public places. However, wind-induced collapse of these billboards has been frequently witnessed, which indicates that improvement to the current design would be worthwhile. To study the wind-induced collapse mechanism of single-post billboards, a field investigation and a dynamic simulation of billboards destroyed by the super-typhoon Mujigae were carried out. The results indicate that the current Chinese design standard might heavily underestimate the actual wind loads and dynamic responses. Moreover, two collapse modes were identified: an abrupt mode caused by fracture of the anchor bolts and a gradual mode caused by severe local buckling of the steel column. A further push-over analysis found that different design combinations of the steel column and the anchor bolts can lead to different collapse modes. Three types of design combinations were defined: elastic, acceptable and unacceptable designs. To avoid the abrupt collapse mode, either elastic or acceptable designs should be adopted in engineering practice. For the gradual collapse mode, local buckling resistance of billboards were evaluated based on the European Standard EN1993-1-6, which proved to be applicable for billboards through this evaluation. Moreover, some instructive suggestions were proposed for the design of single-post billboards.