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Re: Dynamic base shears, is it considered?

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Abdi (A.S. Moghadam) wrote:
> Could you please help me with a couple points so I be able to apply
> this method to an example building (I want to do a comparison with
> pushover analysis). Which one of the following methods were applied
> those days:
> 1- Perform linear response spectrum analysis then trace the hinge
>    formation, modify the building model and again perform next
>    linear response spectrum analysis ... ...
>    My question: Was the 'same spectrum' used at all the stages? I mean
>                 every time that building model was changed, was each
>                 new damaged model of building subjected to the original
>                 response spectrum again and again?

I would do it this way, first perform linear response spectrum analysis
and trace the first hinge formation, let's say your spectrum's ZPA is
0.4g, by scaling the spectrum down to the stress level of first hinge
formation, say 0.2g, 0.3g etc. Then modify the computer model with the
appropriate first hinge(s) and reload the structure with the same UNIT
spectrum to find out where is the stress level for next hinge formation,
whether it's 0.35g, 0.36g whatever and keep on repeating the same
procedure until you find a collapse mechanism.

Good luck and please let me know how is that compared to push-over
analysis.  It should be interesting.

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Tom Chiu, SE
Thomas Engineering