odd structure wind loading help needed

[jgeng]

I have a two story timber pile supported structure over water the first floor is enclosed only by screening but the second story is fully enclosed. I am trying to develop wind loads for a mwfrs analysis. Does any one have advice on how to treat this structure per asce 7? How will the wind see the underside of the first floor and or second floor behind the screening? Thanks

 

[ishvaaag]

I can't say by ASCE that I (not living in the US) don't practice, but this sounds as a situation where the wind will be able to produce, depending on the setup, both suction and inwards pressure (particularly if some side keeps being solid).

For practical purposes, on the suction case, quite likely a conservative assumption is to take suction as if it was a roof at the top of the first floor, and -for the suction- as if the screening was solid. For loads directly applied to the screening (overall) you may take the reduced pressures that account for permeability of the screen if there is such, and in any case you need to account for the localized effects as well.

Qualitatively maybe some CFD program may also help with the pressures whilst accounting with permeability of the screens if any, but after looking at it I would stick to more conventional and normative models.

 

[ron9876]

If you are in a high wind area the screen will likely blow out. I would probably look at freestanding wall loads for the piles. Again if you are in a high wind area wave forces on the piles will likely govern.

 

[Ron]

Agree with Ron9876...screen will blow away, leaving an open structure below. Consider wind on the underside of the exposed floor. Check wave action on piles.

If the screen is designed to withstand wind loads, then figure the open area and see if it meets the wall criteria. If so, design as partially enclosed.

 

[jgeng]

I think that you cannot disregard the screening since code requires it to be design for full wind loads. In addition someone else once commented to my…”what if a sign blew up against the screen?”…

Can you elaborate on how you would incorporate wind through the screen. All the walls are screened full height, if I remember correctly partially enclosed category is pretty limited requiring a large disproportionate opening on walls and otherwise the structure is considered enclosed? How will internal pressures and pressures on the underside of the 2nd floor work out?

The water body is relatively small so I was not planning to consider wave loading. Does anyone have a rule of thumb for small fetch distances where wave loading can be considered negligible?

Thanks again

 

[JAE]

I agree that the screen usually should be treated like a solid surface as debris/plastic/signs can and do blow up to cover the porosity of the screen. And, at a later date the owner could cover with windows, etc.

At the very most, you could eliminate the internal pressure portion of the wind load. This might not change the main wind force resisting system but would help with the component designs of walls/screens/columns/etc.

 

[MiketheEngineer]

On occasion - for very temporary structures I have used say 60% or 70% of the wind on screens depending on grid size openings. But as mentioned - they do clog and/or blow out. Sometimes - blowing out is a big help!!