MecaStack considers the stack as a series of beam elements. The loads are applied to each element, therefore it is most convenient to simulate the wind loads on the ladders and platforms by applying them as uniformly distributed wind loads. To do this we need to calculate the wind load per unit length of stack. So the Wind areas calculated have the units (Length^2 / Length) which effectively reduce to (Length). This can be physically interpreted as the wind area that exists in 1 linear foot of stack (Or meter). The following is the basis for the loads used within MecaStack:
Ladders:
Ladder Only: Area = 0.5 ft^2/ft [0.15 m^2/m] Wt = 15 lb/ft [22.3 Kg/m]
Caged Ladder Only: Area = 0.75 ft^2/ft [0.23 m^2/m] Wt = 23 lb/ft [34.2 Kg/m]
Caged ladder w/ Platform every 30 ft [9.1 m]: Area = 1.0 ft^2/ft [0.30 m^2/m] Wt = 35 lb/ft [52.1 Kg/m]
Cf = Shape Factor for L&P {Default 2.0}
Note this shape factor of 2.0 was based upon the publication "Wind Loads for Petrochemical and Other Industrial Facilities" by Task Committee on Wind-Induced Forces ASCE.
Wind_Area = Area * Cf {ft or m}
Total_Wind_Area = Wind_Area * (Length of Ladder)
Platforms:
If the Platform is 90 degrees or less, then the following is the wind area:
W = Platform Width
if the Platform is > 90 degress then
W = Platform Width * 2 {Since platform exists on both sides of stack}
H = Platform Height (3 ft [0.9144 m])
Cf = Shape Factor for L&P's (2.0 by default)
Fac = Solidity Ratio (0.5), since wind hits front side and then back side of platform.
Wind_Area = (W + Stack_OD) * Fac * Cf {Length^2 / Length}
Total_Wind_Area = Wind_Area * H
Weight of Platform Calcualted using this formula: (Uses a curve fit from some old company standards)
Platform Weight = (165 * Stack_OD + 1150) * (Plat_Ang / 360) * (Plat_Width / 3.5)^2
note: Stack_OD and Plat_Width are in feet. 3.5 is assumed height of platform handrail in feet.