ASCE7-05 6.5.12.2.1 gives huge pressures to design for, is this correct? 2

[ProLuke]

Hello,
I am designing a 5 story wood framed hotel building approx 53' x 180' footprint. I am ending up with large pressures to design my plywood shearwalls for, and no difference in pressure between interior and corner zones. Is this correct?

Here are some details about the project:
I am using ASCE7-05, category II building, Exposure C, 130 mph, h = 65 feet

So because this building is over 60 feet tall, I am using the general MWFRS equation in ACCE7-05 6.5.12.2.1
I am ending up with 63 psf acting at the top of the building down to 55 psf acting at the bottom of the building.

I am used to using the lambda value and Figure 6-2 that has much lower interior zone pressure values.
From figure 6-2 for a low-rise 60 foot tall building, the pressure would be 60 psf at the corner zones and 40 psf at the interior zones.

Is it correct that there is no reduced pressure at interior zones on non-lowrise buildings?

Thank you for your time!

--Luke

 

[ProLuke]

I figured out what I was doing wrong to get such large pressure values using ASCE7-05 equation (6-17).
Hopefully this can save someone the weekend stuck in the office I have had
You are supposed to use + or - 0.18 for your internal pressure coefficient to determine the windward and leeward pressures. I was independently finding the worst case of both the windward and leeward separately, then combining those two values to get the total force on the building at each level. What I learned is that you should have two cases, one for + 0.18 and one for -0.18 internal pressures, and find the windward and leeward for each case. This give me a max pressure at the top of the building of 46 psf instead of the 63 psf I had before.

This is what helped me figure it out - they have nice wind design table layouts that I used for my calculations:

http://www.woodworks.org/wp-content/uploads/5-over-1-Design-Example.pdf

--Luke

 

[DaveAtkins]

In general (there are exceptions), I do not include the internal pressure in the MWFRS loads, because internal pressures do not result in a net lateral pressure.

DaveAtkins

 

[JAE]

...unless the building has an expansion joint, then the internal pressures may be relevant but the windward and leeward may not combine in the same structure.


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