Prediction of Drag Force Coefficient for Single- Column-Supported Billboard Structures

A code-based approach can only be used to determine the wind loading on conventional single-plate billboards for normal wind direction. Based on the literature, no simplified method is available to estimate the drag force coefficient for single-plate and two-plate billboards for various aspects, clearance ratios, and wind angles. With the many experimental kinds of research done on single-plate billboards, a database was created for the drag force coefficient, for various aspects, clearance ratios, and wind angles. For the case of two-plate billboards, a very limited number of experimental results have been reported. In order to generate adequate data, CFD simulations were done. However, only limited publications are available regarding the selection of mesh size and the most suitable turbulence model. Based on the trial and error approach, a 2-equation k- ω SST model was selected and a mesh sensitivity analysis was done to identify the proper mesh size. Linear-Static analyses were carried out using the pressure values obtained from the CFD analysis to compute the drag force and the torsional moment about the base, which governs the structural design of billboards. With the results obtained, two separate equations were developed to predict the drag force coefficients for the required aspect, clearance ratios, and wind angle for single-plate and two-plate billboards. For both types of billboards, the critical range of wind angle was identified as -45° to +45°. The maximum torsion about the base can be estimated by multiplying the maximum drag force with 16% of the billboard width for single-plate billboards and 22% for two-plate billboards.