Wind Load - Internal Pressure Applicable
Wind Load - Internal Pressure Applicable
(OP)
I'm performing a design check on temporary staging used to repair concrete on an existing structure. The staging consists of a 8' wide floor and a 16' high outside wall and encircles the existing 150' diameter structure. The staging is not covered (i.e. no roof). The floor and the wall are completely cladded with no openings. The top of the staging is in line with the roof of the existing structure and is approximately 130' above grade.
Should internal wind pressures be considered to act on the staging surfaces with this configuration?
Should internal wind pressures be considered to act on the staging surfaces with this configuration?






RE: Wind Load - Internal Pressure Applicable
RE: Wind Load - Internal Pressure Applicable
HTH,
Andrew Kester, PE
RE: Wind Load - Internal Pressure Applicable
RE: Wind Load - Internal Pressure Applicable
If I understand this correctly, I can see that the loads that are seen by your structure will HEAVILY depend on the shape (slope) of the existing concrete structure roof.
Sketch would be good... Real good.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Wind Load - Internal Pressure Applicable
BA
RE: Wind Load - Internal Pressure Applicable
RE: Wind Load - Internal Pressure Applicable
Since the structure is round I thought that external pressures for stacks, chimneys and tanks may apply.
RE: Wind Load - Internal Pressure Applicable
I agree with the tank scenario for the wind application, just verify the slope of the roof and use the worst case.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Wind Load - Internal Pressure Applicable
RE: Wind Load - Internal Pressure Applicable
My reference is the NBCC (National Buiding Code of Canada) and it doesn't discuss parapets directly. What pressure coefficients (+) and (-) typically act on a parapet?
RE: Wind Load - Internal Pressure Applicable
Figure I-1 is a Flow Chart for calculating wind load and effects on buildings. Proceeding down the left hand side,you have Velocity Pressure q50 for your area.
Structural components and cladding...yes
Static Procedure...yes
Ce (exposure factor)...open terrain?
H < 20m? No...Cg = 2.5
Cp = +1.0 to -1.7 (Fig. I-24)
Cgi = 2.0, Cpi = +/-0.7
It is not very precise, but it's the best you can do.
BA
RE: Wind Load - Internal Pressure Applicable
RE: Wind Load - Internal Pressure Applicable
-treat the floor like a roof overhang
-wall as the worse case of a parapet or wall cladding
A few extra PSF to be safe is worth it, I cannot see how your structural design will have a large effect on the cost of this entire operation and the temporary structure. A little bit more framing and bolting to make sure this temporary structure at a NUKE plant stays in place and is safe is worth it.
RE: Wind Load - Internal Pressure Applicable
There will also be additional uplift on the underside of the structure as it the wind that hits the front wall will then deflect in all directions.
In this situation I would apply the following factors:
For the front wall I would apply the positive external front face pressure plus an internal pressure equal to the external pressure in the middle of the roof (as it is averaged around the circumference).
For the floor I would apply the same uplift pressure plus a force on the underside same as that for an elevated structure.