enclosed structure - wind load basic question 2

[delagina]

do you consider sidewall pressure for MWFRS (global design)?

 

[a2mfk]

Great point and example JAE. This is probably on the checklist for PEMBs, which is a popular building type for the example you described. And their calcs often look like what Toad was talking about, I can barely ever understand them for doing foundation design. It can take an hour to find the stinkin' worse case, which for base plate bolt design on a PEMB may be one of these cases we may not normally check, as JAE explained.

I think we are all thinking for your average box-like structure, low rise, with tilt or CMU walls, the side wall pressures usually do not come into play...

 

[JAE]

delagina,

The whole discussion above is based on the Figure 6-6 that shows sidewall pressure. Your question: "what does ASCE fig 6-6 mean?" is too general. Please be more specific.

Thanks.

 

[delagina]

jae,

fig 6-6 shows direction of wind in horizontal but it shows there are sidewall pressure. so i am confuse why i shouldnt add sidewall pressure.

others say it will cancel out but i dont agree if you have isolated footings. isolated footings will have bi-axial moment due to sidewall pressure.

i do see in wind load guide by mehta examples that sidewall is not considered for mwfrs.

 

[firai]

Sidewall pressures are in the code, and we know from large quantities of test data that it certainly exists, so there shouldn't be any reason not to consider it in some way. Now when I say consider it, it doesn't mean that you have you have necessarily add another several load cases and a dozen more load combos. I usually take the strategy of doing some back of the envelope calculations to evaluate if it might be critical locally so that I can design accordingly. Usually the buildings we design have the facade anchored directly to rigid diaphragms, so I wouldn't worry about it for the primary members of the MWFRS unless it happens to combine with the local effects.

Structural Design Engineer
New York, NY

 

[a2mfk]

delagina- quite simply, there are as many building types and structures as architects' and engineers' imaginations can dream up...

So if sidewall pressures will affect your structure, consider it in design. For your average box-like structure with shear walls, it will not control.