Overturning Moment & Stabilizing Moment

Structural Layout Vignette and Multiple Choice

Overturning Moment & Stabilizing Moment

Postby lilly9 » Sat Oct 03, 2015 8:11 pm

Can someone walk me through the steps of figuring out question #28 in the NCARB Exam Guide: http://www.ncarb.org/ARE/~/media/Files/ ... _Guide.pdf (see link for diagram)

What is the factor of safety against overturning for the concrete shear wall shown if resisted only by gravity forces? Assume the weight of concrete equals 150 lb/ft3, and the dead load equals 240 kips. Ignore the weight of the soil over the footing.
Answer: 4.2

Thank you!
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Re: Overturning Moment & Stabilizing Moment

Postby mono » Sun Oct 04, 2015 12:37 pm

Have you tried looking at Mikes notes for the NCARB exam guide?
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Re: Overturning Moment & Stabilizing Moment

Postby lilly9 » Sun Oct 04, 2015 1:01 pm

Thanks for the help -- I get it now!
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Re: Overturning Moment & Stabilizing Moment

Postby ballet3gal » Wed Jun 07, 2017 1:53 pm

I have this same question. How do you do it? Or where are Mike's notes as referenced above?
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Re: Overturning Moment & Stabilizing Moment

Postby Coach » Fri Jun 23, 2017 3:06 pm

ballet3gal wrote:I have this same question. How do you do it? Or where are Mike's notes as referenced above?


viewtopic.php?f=8&t=1171
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Re: Overturning Moment & Stabilizing Moment

Postby Coach » Fri Jun 23, 2017 3:26 pm

ballet3gal wrote:I have this same question. How do you do it? Or where are Mike's notes as referenced above?


Find total dead load moment about the lower right corner. Find the overturning moment. Divide DL moment by overturning moment.

[((((16*40*1.5)+(20*6*2))*150)/1000)+240]*10 = 4200'k
24*42 = 1008'k
4200/1008 = 4.17
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Re: Overturning Moment & Stabilizing Moment

Postby Femmemirage » Fri Jan 12, 2018 2:38 pm

How do you find the #10 in this equation?

[((((16*40*1.5)+(20*6*2))*150)/1000)+240]*10 = 4200'k
24*42 = 1008'k
4200/1008 = 4.17

Thanks!
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Re: Overturning Moment & Stabilizing Moment

Postby Coach » Fri Jan 12, 2018 2:54 pm

Femmemirage wrote:How do you find the #10 in this equation?

[((((16*40*1.5)+(20*6*2))*150)/1000)+240]*10 = 4200'k
24*42 = 1008'k
4200/1008 = 4.17

Thanks!

It's the moment arm for the dead load.
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