ASCE 7-05 Open Building Gable Wind Loading
ASCE 7-05 Open Building Gable Wind Loading
(OP)
Hello everyone,
I am working on a gabled portico which is going to be open on three sides and the fourth side is going to be against an existing building. The ridge runs perpedicular to the existing building which is attached at the rear of the portico.
To figure the lateral wind load normal to the ridge I took the horizontal component of the roof pressures as dictated by Figs 6-18A through 6-18D and equation 6-25.
I'm a little stumped as to the correct equation to use for calculating the wind pressure on the gable. As I mentioned before the front endwall is open except for the gable where the profile of the wood truss will be sheeted. The ASCE charts for an open structure and wind parallel to the ridge only gives values for pressure and suction on the roof. Should I just use the wall pressure for an enclosed structure and apply that to the area of the truss? Maybe treating it as a parapet or solid freestanding wall would be more accurate?
Thanks in advance for your thoughts!
~waytsh
I am working on a gabled portico which is going to be open on three sides and the fourth side is going to be against an existing building. The ridge runs perpedicular to the existing building which is attached at the rear of the portico.
To figure the lateral wind load normal to the ridge I took the horizontal component of the roof pressures as dictated by Figs 6-18A through 6-18D and equation 6-25.
I'm a little stumped as to the correct equation to use for calculating the wind pressure on the gable. As I mentioned before the front endwall is open except for the gable where the profile of the wood truss will be sheeted. The ASCE charts for an open structure and wind parallel to the ridge only gives values for pressure and suction on the roof. Should I just use the wall pressure for an enclosed structure and apply that to the area of the truss? Maybe treating it as a parapet or solid freestanding wall would be more accurate?
Thanks in advance for your thoughts!
~waytsh






RE: ASCE 7-05 Open Building Gable Wind Loading
Not knowing if 7-05 has something more specific now, I would have thought to use the partially enclosed structure provisions.
RE: ASCE 7-05 Open Building Gable Wind Loading
I suppose that is yet one more possibility. I had not really considered it because the bottom of the trusses are going to be sheeted over with soffit.
RE: ASCE 7-05 Open Building Gable Wind Loading
It doesn't address the gable end specifically, but there is an example where there's a porch open on two sides that connect to the main structure that has a roof overhead. Fairly similar to your description. The 'gable' for the porch is relatively small and the example doesn't include any load on that surface (doesn't include or not include, just kinds of omits that surface).
But, going along with that, the porch in the above example is attached to an enclosed structure, and the porch was designed using the enclosed structure equations, albeit modified due to it's open nature (no internal pressure, etc).
You don't say much about the existing building (enclosure, relative size, etc.). But that might be the way to approach it (design as enclosed or partially enclosed...no internal pressure, etc.).
RE: ASCE 7-05 Open Building Gable Wind Loading
The exsiting building is enclosed and is much wider and higher. In fact the rear portion of this porticoo is going to be supported off of that structure.
Thanks so much for your help!
RE: ASCE 7-05 Open Building Gable Wind Loading
That reference has been very helpful for me. I haven't heard of any updates for it to the updated asce 7.
Good luck.
RE: ASCE 7-05 Open Building Gable Wind Loading
But the one thing that seems counterintuitive is that I seem to recall getting lower uplift on the roof than if I had assumed it was partially enclosed with internal pressure.
DaveAtkins
RE: ASCE 7-05 Open Building Gable Wind Loading
Try to think of a few different realistic cases that your condition could meet, then use those to find a range of pressures you could use. Engineering judgment should take over from there. Note that you do have the option of referring to another code, such as the British code, if the ASCE 7 does not contain what you need. Also note the addition of components and cladding pressures for open structures in the ASCE 7-05 code.
RE: ASCE 7-05 Open Building Gable Wind Loading
If anyone has any further thoughts on the issue I would still be interested to hear them.
Thanks,
~waytsh