1170.2 Internal Pressure

[m_struct]

Looking for clarification on using Table 5.1(A) and 5.1(B) for the internal pressure coefficient.

For table 5.1(A), it states "walls without openings greater than 0.5% of the wall area and impermeable roof".
- Does this mean a single opening or sum of the openings?
- Does wall area equal that face of the building or faces (sides)?

For Table 5.1(B), columns one states "ratio of area of openings on one surface to the sum the total open area (including permeability) of other wall and roof surfaces".
- Does this mean Σ(all openings on one surface)/ Σ(all openings on all other walls and roof)
- How is permeability included in there? Open area from permeable = % permeable * area?

 

[rather_be_riding]

My understanding is as follows:

- It is referring to the sum of the openings (refer note 1 below the table)
- That face of the building
- Correct
- Correct

Hope that helps

 

[m_struct]

Thank you for the response.

For the Σ of the openings < 0.5% of face, it seems that a building has to have essentially no openings to meet this requirement. If the walls have 0.1-0.3% permeability, it does not leave much left for openings. It would then kick down to Table 5.1(B) and likely be be the first row ratio < 0.5. When I think of Table 5.1(B), should I be thinking industrial buildings with large doors or do commercial buildings also fit in here?

Do most commercial office buildings and accommodation buildings fit under Table 5.1(B) row 1 rather than Table 5.1(A)? It is noted that the values of internal pressure coefficients are the same (0, -0.3) for both.

 

[rather_be_riding]

m_struct,

That is correct; there's not much opening area available if you have a degree of permeability. Of course, it's entirely possible you do not. Impermeably sheeted industrial wall fitted only with a couple of vents is a scenario that comes to mind. Both tables are applicable to all structures (unless you have a specific case defined by loading from another code of course). I could easily imagine a commercial building with lots of non-opening windows falling under table 5.1(A) in scenarios where the glass is assumed to be intact. I really think this is a case by case kind of deal and you shouldn't make too many assumptions about what will necessarily fit where without reviewing it first.