Pounding Quesiton

Structural Layout Vignette and Multiple Choice

Pounding Quesiton

Postby k4dm0nky » Sat Sep 21, 2013 7:24 pm

So to avoid pounding you separate the buildings by the sum of the drift of the two buildings.

Now the million dollar question... is there a factor safety included in the sum of the drift of the two buildings? I've been seeing conflicting information in my study material and honestly wouldn't have a clue on how to answer this question on exam day?!!!
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Re: Pounding Quesiton

Postby Mike-SE » Sun Sep 22, 2013 8:17 am

No factor of safety. Factor of safety is used in stability and strength. (I want you to use the proper terms)
However, the design earthquake force uses the factor "R" to determine the force. R is always greater than 1.0. An R=1.0 translate to a design force equal to 100% of the estimate earthquake force. An R=3.0 translate into an earthquake force of 1/3 of the actual force.
When you check the drift of the building using the force that has been reduced your estimated drift is the drift caused by the reduced force not the actual earthquake.
So, we multiply the calculated drift by the R factor to determine the actual movement of the building.
On a ten story building with an R of 3 and a the calculated drift of 5" the actual drift for checking building separation would be 15" !!!!!! BUT THIS IS NOT A FACTOR OF SAFETY!!! It is reality.
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Re: Pounding Quesiton

Postby k4dm0nky » Sun Sep 22, 2013 11:17 am

Thanks Mike! Kaplan and Archiflash state there are factors of safety included in that sum. Ballast does not... I will take your word and run with it! Thank you!!!!
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