COLUMN EFFECTIVE LENGTH
COLUMN EFFECTIVE LENGTH
(OP)
I have a column with a distributed uniform axial load
for the full length.
The column is pinned at both ends.
My question is how would one calculate the effective length
using the total axial load.
Or using the actual length, what would be an equivalent
axial load to use when designing the column.
Tanks for your help
for the full length.
The column is pinned at both ends.
My question is how would one calculate the effective length
using the total axial load.
Or using the actual length, what would be an equivalent
axial load to use when designing the column.
Tanks for your help






RE: COLUMN EFFECTIVE LENGTH
Effective length is equal to actual length for a pin-pin ended column.
RE: COLUMN EFFECTIVE LENGTH
The column is already designed.
Designing the col. for the full total axial load as if
it were applied at the top and using the full length as
the effective length would seem to me overly conservative.
Suppose the total axial load was applied at mid-height of
the column, what effective length to use?
Thanks again
RE: COLUMN EFFECTIVE LENGTH
RE: COLUMN EFFECTIVE LENGTH
The answer that I got from those wiser than me was that it was best to treat it as though the full length was the length for buckling under the full axial load.
But as others have said, it would be useful to know the situation.
RE: COLUMN EFFECTIVE LENGTH
RE: COLUMN EFFECTIVE LENGTH
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Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: COLUMN EFFECTIVE LENGTH
Intuitively, without checking any backup theory I would
tend to use the following:
For a concentrated load at mid-height of column,I would
assume an effective length of approx. 0.75xTotal length.
For a uniformly distributed axial load, I would assume
an effective length of approx. 0.6xTotal length.
I will check the references suggested, and do appreciate
them.
RE: COLUMN EFFECTIVE LENGTH
RE: COLUMN EFFECTIVE LENGTH
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: COLUMN EFFECTIVE LENGTH
BA
RE: COLUMN EFFECTIVE LENGTH
L(e) = pi/2*(EI/F)^.5
The critical length of a column under self weight, of total weight W, is given by Timoshenko's equation as:
L(d) = 3B/2(EI/W)^.5
where B is the first zero of the Bessel function of the first kind of order -1/3, which is equal to 1.86635085876156
http://en.wikipedia.org/wiki/Buckling
The effective length factor for the column under self weight (or uniformly distributed load) is therefore:
L(e)/L(d) = pi / (3B) = 0.561
This assumes that the applied load is equivalent to self weight, i.e. it moves with the column and does not provide any restraint.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: COLUMN EFFECTIVE LENGTH