UBC 1997 earthquake vertical component

[drasticxxxx]

Hello

I have one question which is not clear to me,according to UBC ,and based on orthogonality requirement ,do we need to consider the earthquake component in z direction multiplexed by 1.3(30 percent orthogonality, or it just for x and y)

0.5CA*I*D OR 1.3*0.5*CA*I*D


Regards

 

[sponton]

Just for X and Y

 

[drasticxxxx]

Thanks

 

[drasticxxxx]

One more question in the same topic

when I made the combination for orthogonality


spec x+0.3 spec y only(I don't need to consider directions, since spectrum is both positive and negative)

so on this case does he consider 4 cases??
+-
++
-+
--

Thank you again

 

[sponton]

Yes, you would have to consider the main four cases and their counterparts like this


X + .3Y
X -.3Y
-X + .3Y
-X -.3Y

Y + .3X
Y -.3X
-Y + .3X
-Y -.3X

[and remember that within these cases you have cases with different eccentricities]

you get the drill

I'm not sure whether it is applicable under UBC, but it is permitted under ASCE-10 to only do a single orthogonal loading case if you're in a category A or B.

 

[drasticxxxx]

Sponton

This under static method ,but for spectrum I don't need to specify negative or positive ,only direction U1 or U2(and he will consider -,+ in Etabs)

I am right??

Thank you

 

[sponton]

I don't reaLLY use ETABS built-in seismic analysis because of the application of seismic provisions i'm not really acquainted with [I deselect the option], so i manually input the forces and their respective load combinations.

But using the response spectrum, you're supposed to do each case individually. Here's a youtube video

https://www.youtube.com/watch?v=vq_8B2-WRJI

 

[drasticxxxx]

Many thanks