Wind Load on Roof Wall

[WiSEiwish]

Hello,

I have a building in which there are rooftop structures that are enclosed by a 14ft high wall on all four sides. The wall is going to be supported off of vertical members with kicker braces going back to points on the roof. The mean roof elevation is around 22ft. In reading ASCE 7-05 it seems like the appropriate method for analysis is to consider it a solid freestanding wall and set h = the height of the top of the wall and to consider the ground surface as actually the roof elevation as there is no wind passing below the wall. However, it is on a roof, so I'm unsure as to whether or not this would be considered a rooftop structure. I would think "rooftop structure" mostly refers to penthouses, or other equipment in which there are typically four walls and a roof.

Any thoughts from the community?

Thank you.

 

[SAIL3]

The increase in wind load on roof stuctures is to account for wind turbulance, possibility of velocity increase over the roof of a structure, etc. Even though, for some unusal reason, there is no wind load on the structure below, these walls may still experience the wind affects noted above due to the overall configuration of the structure as awhole. Supplying more complete info on the entire structure would help in getting more accurate feedback.

 

[WiSEiwish]

The building is 22ft high and a simple rectangle. The screen wall is 14ft high and has the same length as the building but it is set in from each edge in the other direction between 10 and 12 ft. Approximate wall dimensions are 100x43ft and approximate building dimensions are 100x68ft. The wall is centered on the building.

There is nothing exciting about either wind or seismic. It is SDC A and 90mph wind exposure B. Lateral support for building is masonry shear walls and gravity support is steel columns.

 

[structSU10]

well ASCE 7-05 6.5.15.1 would seem to apply, where you can reduce the increased wind pressure coefficient for rooftop structures based on its relationship to the size of the building. If the wall you are talking about is just on one side, however, I may be inclined to treat it like a parapet.

 

[charliealphabravo]

The mean height of the sign 'h' for wind calculations will be the building height plus half the height of the sign so 29'. I don't know of anything in ASCE7 that would allow you to set the ground level at the roof surface. This may not make much difference tho since many of the tables and formulas round up to h=30ft anyway.