Friday, September 30, 2011

Re: Wind forces on the columns of open structure

I'd assume 2-d flow and calc the force per ft, on each column and for each direction as: = Cd x q x S,
Cd =1.2 for round column; = 2 for square column
q = dynamic pressure @ 110 mph
S = Frontal Area


--- On Fri, 9/30/11, nma <> wrote:

From: nma <>
Subject: Re: Wind forces on the columns of open structure
Date: Friday, September 30, 2011, 1:59 PM


How big are the columns?  I would load up all the columns and ignore any shielding effects.  One of the things I've seen in this kind of a structure is vibration - i.e. small shaking of the whole thing.  It may also makes a small difference in the shape of the columns - round or rectangular?  You didn't say what the wind speed or exposure factor is or where the structure is located - i.e. on a hill or in the middle of a city. 

For the flying bit - I've have been criticized for larger footings than the city inspector thinks the footings should be.  But I signed for the structure and not him.   I've also seen the result of a roof flying off its supports - had my back turned with it happened.


On 9/30/2011 10:47 AM, Joseph Grill wrote:

Thanks, I understand the flying bit.  But there is going to be a lateral wind load on the columns themselves. I am looking for the criteria to determine the horizontal load to the columns.

On Sep 30, 2011 1:38 PM, "nma" <> wrote:
> Joe:
> Just figure it is going to try to fly.
> Neil
> On 9/30/2011 10:16 AM, Joseph Grill wrote:
>> I tried to send a message yesterday on this subject. But with new
>> phones, new wireless providers, a move across country etc i'm not sure
>> it went through.
>> Anyway I am designing an outdoor picnic pavilion. The plan dimensions
>> are about 60' x 30'. It will have monoslope roof supported by 4 bays
>> of 3 columns. I have calculated the wind loads for the MWFRS at the
>> roof. I can't decide on what ASCE requirements/equations to use for
>> the MWFRS loads to the columns and if that load should be applied to
>> each column in each row parallel to the load direction. In another
>> words if there are 4 columns in line parallel to the wind load would
>> all 4 columns be loaded?
>> I have considered using loads calculated from section 6.5.15 "Design
>> Wind Loads on Other Structures". Am I wrong? If so can anyone suggest
>> what i should be doing?
>> Thanks,
>> Joseph R. Grill, PE
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