Wind Design for Flat Roof Carpark

[eerrbb]

Good day everyone!
I am a newly grad.. Can you help me on the Wind Design Calculation of flat roof carpark?
I will design a carpark with flat roof and no enclosing walls.. supported by circular hollow steel section columns.

 

[MotorCity]

Take a look at ASCE 7 for guidance on wind load calculations and then come back with specific questions

 

[TehMightyEngineer]

Assuming you're in the US; start in ASCE 7 (either 2005 or 2010 depending on your jurisdiction) and look at wind loads on open structures. Might want to find an example or two for open structures to follow along with. You also have a cantilevered column system so you actually might get seismic controlling even in a low-seismic area; but thankfully your mass is low so it should be fine. Anchoring design to the footing and footing overturning is going to be your biggest headache. Thankfully your steel design should be quite easy; looks like you're doing it in STAAD. Make sure you have your unbraced lengths setup properly.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

http://www.americanconcrete.com

 

[FishTheStructure]

I'm interested in the responses you get to this question.

In Canada, our codes and design guides don't specifically cover wind loading on this type of structure. I analyzed a similar structure recently but struggled in determining an accurate wind loading value and what should be considered for partial wind loading.

1. To determine roof uplift, I used the typical roof suction combined with the internal pressure for Category 3 (buildings with large openings through which gusts are transmitted to the interior). Does anyone have a comment on if this is an acceptable application of Category 3 internal pressure?
2. In calculating overturning moment, I considered partial wind loading comprised of 100% of the uplift on half of the roof and 50% of the uplift on the opposite half of the roof. This case was not explicitly covered by the code but I felt it was a rationale approach. Does anyone have a comment on partial wind loading on this type of open structure?


Great spirits have always encountered violent opposition from mediocre minds - Albert Einstein

 

[thaidavid40]

In most of the US, the design of a lightly-framed and loaded structure like this will usually be governed by the wind loads. For moment resistance, you would expect either drilled pier foundations, or spread footings, extended in the cross direction to take the wind moments. The diagonal braces will simply create a place for birds to sit and poop. Most people simply frame the roof beams directly to the column with a moment connection and 86 the braces. If you are given the leeway, anticipate roof-mounted PV panel loads in the future - that is happening a lot in these parts nowadays.
Good luck,
Dave

Thaidavid

 

[Ron]

Assume since the OP refers to this as a "carpark" he/she is not in the US; however, I agree that ASCE 7 is a good reference for such.

Check your reference codes for the actual requirements. I've designed hundreds of similar canopies in the US and other areas. They are "monoslope roofs over an open structure" for general characterization of where you might start. Wind loads will have to be checked in multiple directions to determine the worst condition.

 

[Retrograde]

The Australian Wind Code AS1170.2 covers this situation in Appendix D.

 

[SAIL3]

engineering judgement will certainly be involved and the Cp values from the Australian code will help...
I would try and get an upper-bound solution to this problem..
Main members and fdns
a)for wind perpendicular to the long direction, I would assume a deflection/rotation of the roof
of say a value of alpha between 20 and 30 degrees and blocked underneath. Check the theoretical
deflection/rotation using those values. May back off on the values of alpha if the theoretical
value of deflction/rotation is much much less than the assumed values. But also realizing that
the deflection/rotation of the fdn is an inexact science depending on type of fdn used.

b)for wind parallel to long direction...probably no significant rotation of roof except, perhaps,
for the leading edge.....

c)check wind for from multiple directions

Cladding
use values in applicable codes in combination with the above assumptions...

 

[SAIL3]

another case I might check is for pure uplift....say, use a total Cp of -2.0(vertical) on entire roof to account for the affects of blockage underneath...at the end of the day, the OP should use engineering judgement to arrive at a sound solution...the above assumptions were based on the roof being initally flat horizontally(alpha=0)....