huangyhg

p-delta effect for steel structure
what percentage the p-delta contribute to stress ratio
for column of steel structure you found?
i got 1% for braced frame and 5% for moment resistent frame.
a good estimate would be the b1-b2 multipliers in aisc. there is not a set percentage. if there were, it would be put in the code and we could avoid the detailed analysis.
to enginering，
i see.
just want to know a common situation. for example, one would like to control kl/r around 90-150 for column.
p-delta effect was some thing we can control by change the
rigidity of structure, as i understand. similar as kl/r, i think it may have a allowance value.
i usually look more to the total deflection (or drift) than to the amount of the p-delta increase in moment. i have done water towers where the p-delta effect with seismic has added over 50% to the design moment.
i don't know off-hand what it would usually be for buildings. i don't really consider them without p-delta to know the difference. it would be proportional to the gravity load and the drift - both of which can vary from job to job.
i have had around the 40% mark before under normal live and wind loads.
it really depends on how slender the structure is.
i expect that your code would give you a maximum allowable before you have to do an advanced analysis.
i'd estimate that a total amplification of about 5 to 10% is common for building type structures. but, that is just a ball park number for those of us in seismic country.
this can increase if there are very few moment frames with a lot of "leaning" columns that don't participate in resisting the lateral forces.... more common for structures where the lateral design is entirely controlled by wind.

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