Billboard Wind-Load Example - Part B

The subject of this example is a 50’ wide by 20’ high interstate billboard sign located in rural Nebraska on a site characterized by flat and open grasslands. The billboard is mounted on two 16” diameter steel posts, with the top of the sign reaching 80 feet above ground level. Part A of the Example is Available Here: https://youtu.be/jCIGUeYygMo Part B of the billboard wind load example focuses on determining additional wind load parameters and force coefficients, and then calculating the actual wind forces for the structure using the ASCE 7-22 standard. Building upon the velocity pressure (qh=35.46psf) established in Part 1, Part B of the example evaluates three mandatory wind load cases to identify which one governs the structural design. These steps include: 0:00: Introduction 2:00: Directionality Factor (Kd): Per ASCE 7 Table 26.6-1, a factor of 0.85 is assigned for solid freestanding signs. 2:45: Gust Factor (G): While many structures use a standard 0.85, billboards are often flexible. 5:00: Force Coefficients (Cf): These are derived from ASCE 7 Figure 29.3-1 based on the sign's aspect ratio and clearance ratio. 5:52: Introduction of the wind cases for solid freestanding walls and solid freestanding signs. 8:34: Calculation of Wind Force due to Wind Case A - Direct and Uniform Wind: This case assumes a uniform pressure distribution perpendicular to the sign face. 12:15: Calculation of Wind Force due to Wind Case B - Eccentric Torsional Wind: This case accounts for horizontal shifts in pressure caused by oblique wind. 14:09: Calculation of Wind Force due to Wind Case C - Oblique Wind: Intended for signs where the width is more than twice the height, this case models intensified pressure at the leading (windward) edge. 17:29: Summary and Conclusions