Elevated Building - Wind Load Underneath

[vmirat]

I have a 24'Wx72'Lx12'H building that is supported on columns elevated 16' above grade, so a building on stilts. The floor of the building will be conform deck with concrete supported by OWSJ's. The bottom of the OWSJ's will have a metal soffit panel to enclose the building, similar to a gas station canopy. My question is, what wind loading condition is on the soffit panels? My initial guess is that the air will flow under the building similar to how it will flow over the roof, so I was going to use C&C wind loads like a roof, but inverted, so the pressure would be away from the soffit panels towards the ground. Does this make sense?

 

[rowingengineer]

my code AS/NZS1170.2, givens cp,e vales of 0.8,-0.6, this of course is a completely different from your code, but if you were to compare it to roof loads this would be -0.9 and 0.2, so not exactly the same but kinda close.

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[ARS97]

I recently had to design a large elevated & enclosed gallery truss that housed a walkway and a conveyor. The cross section looked like a simple gable roof building, however, due to the elevated nature of the truss, I didn't think that using the wind pressures prescribed for buildings would apply. I used ASCE 7-10 Figure 29.5-1, which gives a more simplified (and conservative) procedure for a general cross sectional shape.

 

[Ron]

vmirat...considering the size of your building, your approach is appropriate.

 

[SAIL3]

There may be a venturi affect in the space beneath the bldg and as a result I would tend to go conservative on the loads for the soffit panels and their connections....so I would probably use -2.0 on zones around the edge of the bldg and -1.3 on the interior....what andysines suggested should be fine for the stucture as a whole......the codes can not address evry situation nor do we want them to...they are becoming hopelessly complicated and cumbersome as it is now....somewhere along the line the engineer has to use his own best judgement....

 

[paddingtongreen]

The Venturi effect should be less than for the same building on the ground. The air can only pass over the roof and around the sides of a building on the ground, it has an addition route to pass under an elevated building, the kinetic energy is not increased as much for the elevated structure.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

 

[SAIL3]

One other item I forgot to mention was the possibilty of blockage underneath the bldg.....the open space may not remain open in the future and depending on the type, location and extent of the blockage it may cause positive pressure on the bottom of the bldg which would add to any uplift on the roof and contribute to the overall uplift/overturning of the bldg as a whole....again, this would be an engineering judgement call....