Multi Storey Car Park and Rain Blown In
Multi Storey Car Park and Rain Blown In
(OP)
Hello,
I am looking at carrying out the draiange design for a multi storey car park. Does anybody know a good method to estimate the rain that might be blown onto the surface of the car park through the sides. Obviously the middle floors in the car park have a roof but the sides are exposed to the elements.
BS EN 12056-3 2000 suggests wind driven rain 26 degree to the vertical can be calculated as follows:
A = length of roof x (width of roof + (length of gap/2) )
The height of each story is 1.8m so for a 10 x 10 m roof:
A= 10 x (10 + (1.8/2) ) = 109m^2
Clearly this is to much because it's bigger than the plan area of the car park itself.
Any suggestions would be greatly appreciated.
I am looking at carrying out the draiange design for a multi storey car park. Does anybody know a good method to estimate the rain that might be blown onto the surface of the car park through the sides. Obviously the middle floors in the car park have a roof but the sides are exposed to the elements.
BS EN 12056-3 2000 suggests wind driven rain 26 degree to the vertical can be calculated as follows:
A = length of roof x (width of roof + (length of gap/2) )
The height of each story is 1.8m so for a 10 x 10 m roof:
A= 10 x (10 + (1.8/2) ) = 109m^2
Clearly this is to much because it's bigger than the plan area of the car park itself.
Any suggestions would be greatly appreciated.





RE: Multi Storey Car Park and Rain Blown In
I believe the exposure to rain though the gap on one side will be 10 * 1.8 * sin(26) = 7.89 m^2
Note that if the angle were 30 degrees sin(30)=1/2 which is presumably the final term in your equation.
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Multi Storey Car Park and Rain Blown In
RE: Multi Storey Car Park and Rain Blown In
RE: Multi Storey Car Park and Rain Blown In
But I believe the rain will be falling at a fairly constant (26 degree) angle, so the the top of the triangle should be sloped at 26 degrees, making it perpendicular to the rainfall. In this scenario the correct solution would be the sine.
Of course, the difference is pretty small in this case (about 10%), and the exact behavior will depend on whether the wind velocity through the open side of the car park is higher or lower than the prevailing wind above.
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Multi Storey Car Park and Rain Blown In
Another way to look at it: You're calculating the width of a hypothetical roof overhang that would completely shelter the floor from rain at the specified angle.
Peter Smart
HydroCAD Software
www.hydrocad.net