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Re: EQ resistant Design

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Dear Christopher

You are right that we assume 100% seismic load in one direction only as this
is permitted by our code (Probably because the code being pretty old the
normal method of analysis was plane frame analysis and not the 3-D which is
quite easy now). To find out the force in the columns when the EQ is in
direction 45 deg to the axis we would simply find the resolved components of
the moments and shears in the columns and would design for the worst case.

However the new draft code for earthquake (in my country) has come and is yet
to be finalized and adopted by the authorities. This code does give the 100%
+ 30% rule i.e. assume 100% of seismic force in one direction and 30% in the
second and assume they act simultaneously. There are other methods also which
I will write after I go thro the draft code in detail.

Vijay Patil



Christopher Wright wrote:

> >This would mean that you
> >would analyze the brace frame system for 100% of the seismic load (since
> >it is taking ALL of the seismic load in one direction) and likewise you
> >would analyze the moment frame for 100% of the seismic load.
> Doesn't this imply that the structure was resisting a total seismic load
> of 1.414 times the design seismic loading at an orientation of 45 deg? If
> you meant that the seismic loading is to be applied separately in each of
> the two directions, is it also implied that seismic loading is to be
> applied in the 'worst' direction which might not in either the 'braced
> frame' or 'moment frame' direction, but at an angle to both.
>
> Christopher Wright P.E.    |"They couldn't hit an elephant from
> chrisw(--nospam--at)skypoint.com        | this distance"   (last words of Gen.
> ___________________________| John Sedgwick, Spotsylvania 1864)
> http://www.skypoint.com/~chrisw
>
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