ASCE 7-16 wind questions

[JStephen]

In ASCE 7-16, Table 26.13-1 categorizes buildings as enclosed, partially enclosed, or open based on area of openings Ao.
Ao is defined as "total area of openings", etc.
For openings that are screened, is that the gross screen area, or the net area through the screen openings?
For example, on a 12"x24" opening screened with a screen with 50% open area, is Ao going to be 1 square foot or 2 square feet?
(If you wonder, this is looking at circulation vents on a tank, so those screens are permanent and the "what if somebody opens the window" doesn't really enter in.)

Second question, Ao is further defined as the open area "in a wall that receives positive external pressure" and the area of that wall is Ag.
Figure 30.12-1 shows the distribution of pressure around a cylinder, described by Eq. 30.12-3 and 30.12-4. In both the figure and equations, pressure is positive for some fraction of the perimeter, negative elsewhere. Is it reasonable to take Ag as that portion of the cylindrical shell where pressure is positive?

Third question, Section 29.4.2 limits consideration of circular bins, silos, and tanks to h<120', D<120', and 0.25<H/D<4. What about the tanks that fall outside those ranges?

(For reference, we normally use AWWA D100 or API-650, but neither aligns with ASCE 7, and per 29.8, "No consensus standards...are referenced in this chapter.")

 

[HTURKAK]

Mr JStephen (Mechanical),

Pls find my responds to your questions,

- The net screen area is used for tank circulation calculations. However, ASCE 7-16, Table 26.13-1 could be used for non-standard silos etc . Say a silo at a swine farm. It is a mandatory requirement to follow API 650 rules if you are in a position to get API tank.

- The lateral wind load is calculated using the wind pressure on shell multiplying with vertical projection area (D*H)

- Section 29.4.2 could be applicable non-standard circular bins, silos, and tanks to h<120', D<120', and 0.25<H/D<4. You are expected to look specific standard ( API,AWWA, ASME, ) for PV and storage tanks ,

P.S.= API 650 uses only ASCE 7 only to get the design wind speed (V , the 3-sec gust design wind speed ) and since ASCE 7-16 wind velocities have LRFD load factors and importance factors built in, whereas API 650 uses the working stress and the 0.78 factor applied to the ASCE 7-16 wind speed provides a conversion to working stress levels.

My understanding only...



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