API 650 11th Edition Wind Load Shape Factor

[TankTheFrank]

In the definition for "Wind" (Section 5.2.1.j), is the shape factor already included in the pressure? For a cylindrical shell, it is typically 0.67.

Also, where does the 18lbf/ft^2 come from... because when I check ASCE 7, I can't find that number anywhere.

 

[JoeTank]

API-650 shape factor for cylinder = 0.6. For cones and spheres = 0.5. 18 psf = 30 psf Flat surface at 120 mph) x 0.6 (shape factor.

Joe Tank

 

[JStephen]

The 30 psf/ 18 psf/ 15 psf have been in use for many years in tank standards. Generally, ASCE 7 will give pressures in that range, but they were not derived from ASCE 7.