COMPONENTS AND CLADDING
COMPONENTS AND CLADDING
(OP)
In reference to wind loads on parts of buildings, what exactly is considered a "component and cladding". Specifically, would you consider a non-loadbearing masonry exterior wall (or a precast concrete panel) a "component and cladding"? By strict definition, it would be yes, but in the spirit of the design approach, I would hesitate to classify it in the same category as a metal stud wall. Any thoughts would be appreciated.






RE: COMPONENTS AND CLADDING
RE: COMPONENTS AND CLADDING
When wind is directed upon a building structure, there are vast amounts of chaos and randomness in the intensity of the pressure. At any one spot on the building exterior, the wind pressure could vary from negative 40 psf to 1 psf to positive 40 psf (or more). These variations occur over small areas across the building.
Therefore, at any one small piece of area, the potential,....or statistical probability, that the pressure will reach a certain high level is higher than if you look at a large area where the variations across the surface "average out" to a lesser magnitude.
So the codes are written to take this into account. A single steel stud in a wall supports a small area. There is a high chance that, due to the wide variations in wind pressure, the stud would receive a very high stress.
However, if you look at a horizontal wall girt that supports a full 30 ft + bay, the tributary area is much larger and the "chance" that the wind pressure would AVERAGE a high value just isn't there.
For a main wind force resisting system, the tributary area is huge...therefore the wind pressures are less than components.
ASCE 7-95 actually has a footnote in Table 6-1 that states "Major structural components supporting tributary areas greater than 700 sf shall be permitted to be designed using the provisions for main wind-force resisting systems".
So the definition sort of turns on the trib. area.
RE: COMPONENTS AND CLADDING
RE: COMPONENTS AND CLADDING
RE: COMPONENTS AND CLADDING
As JAE noted, the loading and interaction are essentially undefined except on an average basis, which is where the codes address them. To do otherwise would be a practicable impossibility, as conditions vary with locale, constituents, construction, materials, geometry, orientation, and a host of other variables.
I read IBC 2000 the same as JAE.
RE: COMPONENTS AND CLADDING
Sometimes, the girts, wall panels and fasteners of the roof or of the sidewalls are designed to be a diaphragm to resist lateral wind loads, for those cases, the forces in those elements would be calculted using the coefficients in ASCE 7 for main wind force resisting system.
But you need to recognize that for one load condition, those elements may be a MWFRS, for another, they may be classed as components and cladding. All possible load cases must be accounted for.
Masonry walls, whether or not they have grouted cells, are similar to those sidewall panels. For one load case they are main structural bracing, and thus MWFRS, and for another they are components and cladding.