Industrial shed design

[hamy08]

I am designing an industrial shed. Please see the attached picture. Can I enclose the shed all from the four sides up to the lowest purlin. I have analyzed this shed on staad.pro and its OK as per ASD design methodology under wind loads.
I have heard that it is important to give gap in corrugated sheets for free movement of wind.

 

[txeng91]

Usually you will have an eave strut at the roof/wall joint and a base angle at the wall/foundation joint. The sheeting is lapped at joints. Also your model shows wall girts with strong axis vertical, typically the strong axis is horizontal to resist wind loads.

Look through these details

http://www.nucorbuildingsystems.com/nbsproductandengineeringmanual/

 

[txeng91]

One other note, you should consider adding ports frames in one bay on each side for wind loading parallel to the ridge. For these type of buildings they usually do something like this:

http://www.robertsonbuildings.com/wp-content/uploads/2014/09/Portal-Brace.png

 

[Agent666]

What is the lateral structural system perpendicular to the portals?? The only way it would remotely work is if the base was fixed, not really an ideal system cantilevering about the minor axis of your columns?

 

[hamy08]

Dear txeng91:

My question is regarding wind movement through sheets. Can i fully closed the shed from all sides with corrugated sheets upto the lowest girt or i should keep gap for wind movement.
In full closed condition my shed is passing in analysis. Still do i have to keep gaps for the wind movement like the shed shown below.

 

[Harste]

Yes, you can enclose all four sides of the shed - you just need to make sure that you're designing for the correct wind loading. Internal pressure coefficients would change significantly.

I also agree with Agent666 - it doesn't seem like your system can resist end wall wind racking. Fixed base connections are required, otherwise you'll need to incorporate roof/wall cross bracing to give you a bit more lateral stability.

You should also check the closest corner column in your model - it seems as though the section shape rotates 90 degrees about half-way up the column??

 

[hamy08]

without opening enclosure with staad analysis is shown in attachment. The design is okay as per ASD.

 

[Agent666]

Its up to you whether there are gaps, but your wind loading needs to take account of the gaps as they will likely alter the wind pressure coefficients (internal and external).

There are also a lot of redundant members in your truss that are not required (they carry zero axial load). No point having them unless they are there for a specific purpose and you can deal with the chords spanning a little further?

I also suggest you have the design philosophy reviewed by someone else in your office as there seems to be a few fundamental things with the model that could be easily addressed by someone senior casting their eye over it.

 

[hamy08]

@agent666

Can you please highlight the redundant members in truss?

 

[Agent666]

The vertical members at that intersect with the two diagonals at top and bottom chord (EDIT - except for the middle one)

 

[hamy08]

@harste :

Columns are fixed at the base plate to the foundation. For column rotation, i agree its just a 3d mistake. However i have corrected it in analysis.

Can you provide any related reference regarding fully enclosure of shed like this. I am just worried about the uplift of roof sheets, if the force is exerted by small wind cyclones that enter in the shed through lower exposed half. Thanks for your response.

 

[hamy08]

@agent666 :

For wind analysis i have considered the gaps in shed as shown in picture. The gap is the lower half of the shed which is also used for the movement of pedestrian and other components.

 

[Ron247]

I am lost on the question about "gaps for wind movement". You can design this shed however you need it to be sheeted. There is no requirement I know of that you leave any gaps unless you want them there. The way you are posing your questions is also confusing me. "Wind movement through the sheets" sound like wind is actually penetrating the sheets. Do you mean wind moving over/under the sheets or do you mean "wind running parallel to two sheets walls like a tunnel"?

 

[hamy08]

Ron :

Wind moving under the sheets. In desert area where small cyclones are frequent. In that case wind could probably uplift the roof sheets if air doesn't find gap for moving out of the sheet interior.
I hope you understand it now. If not i can elaborate you further.

 

[Ron247]

I understand now. I would sheet the building however I wanted it sheeted. ASCE has a method of calculating how "open or enclosed" you structure is and then determining your coefficients based on that. Does the code you are using have a similar calculation?

 

[hamy08]

I am also using ASCE-7 (2010) in Staad.pro for partially closed buildings. Staad.pro than do the calculations and the results are with in allowable limits of ASD under ASCE wind loads.

 

[Ron247]

I am not familiar with Staad anymore. Have not used it in 20 years. The open and closed calculations should reflect your concerns. The calculation determines both how easily wind gets into your structure and how easily it gets out at the same time.