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Snow drift for adjacent building (complex situation!) 3

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SleeplessEngineer

Structural
Jul 12, 2020
46
We are adding a building to the rear of existing row house. The elevation is shown here.
Screenshot_2020-12-12_155437_msvxxa.png



Unfortunately, the adjacent property is owned by another structural engineering firm and seems to caused lot of problem to the client already.
The proposed addition is 2 story higher than existing structure and then its set out 13'from existing structure to go 2 more stories higher. We can check the client's existing property for snow drift and reframe if required.

But the problem, I am not sure how to check adjacent property. It is located "diagonal" to the proposed addition( it only shares a corner to the proposed addition). I do understand corner portion might have some additional load due to drifting. We tried discussing with them saying it would be insignificant. But they want to submit a report with assessment.
Screenshot_2020-12-12_154540_bjn8p8.png


ASCE only gives scenarios when the building right next it. I am not sure how to determine the drift width and height. Do I take the diagonal length for length of lower and higher roof? That feels too much since the clearance from high roof will go more and more as you go from corner?? Do I need to something to determine more realistic loading?

Can someone please help me understand/ solve this puzzle? Thanks.
 
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Roof heights?

image_phjc4a.png


Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik
 
The code has provisions for a gap between buildings. Other than right at the corner, you have a gap. I think you could calculate this for several points on the diagonal along the roof (each will have a different fetch and a different gap) and then connect the dots. I think the drift will decease very quickly away from the corners where the two buildings touch.



 
I'd suggest that you first imagine that the adjacent building goes all the way back to the property line with the same roof elevation. Then, determine the drift loads in two directions (plan west and plan south of the vertical addition). The effect on the adjacent building would be the intersection of the two drifts.

Then you can talk to the neighbors about how to reinforce their building for this additional load.
 
You pretent the existing building comes up to the new construction, and neglect the snow accumulation for the part of the building that's not there.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik
 
Thank you JLNJ, kipfoot and dik for your repsonse. Appreciate it very much!!
We inspected and found that their roof framing is luckily very good (2x10 drop beam spanning 19' across brick wall @ 12"). So we just conservatively applied the drift load as if we are adding adjacent to their property and still passed!
 
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