huangyhg

calculate load from deflection.
i have a column made from w150 x 30 (w6 x 20) which is 3650mm (12 feet) tall. it is deflecting 102mm (4 inches) at the top. my calculations for the moment force (torque) at the base come to approximately 107 knm (78920 ft-lbs).
can anyone confirm my calculations.
we need more information. what is the elastic modulus you used? how is the load applied? is there any axial load? why don't you post your calculations for us to look at?
do you know if the base has rotated at all? this would have a large effect on the moment at the base.
is it strong axis or weak axis bending?
we actually need a little more information. the stiffness of the column will depend on the load type and location, whether thats a point load at the top of the column, a uniformly distributed load, or some other load type. because the stiffness varies with load type and position, the back-calculated load can also be different for a given deflection and hence the base moments would also be different.
jeesh ucfse - there we go again!

the column is ell shaped with a w6 x 20 base and is loaded by cantliver arms spaced evenly along one side with the top arm at 100" above the base. the 4" deflection was measured at 144" above the base. it is an assumption that the deflection measurement is accurate.
the arms and base are 48" long.
from the base up to the top the udl's are 6,000 lbs (on w6 x 20 base), 1,000 lbs, 1,000 lbs, 2,500 lbs, 2,000 lbs, 2,000 lbs, 2,000 lbs & 1,500 lbs.
if i can find a web link to a suitable picture i will add it to the thread.
ucfse,
what do you mean when you say the column stiffness varies with load type and location?
i just want to point out that your column is deflecting at a ratio of 1 : 36. is this of any concern to you?
dinosaur, the deflection is a concern but the column is not at my location so i can not confirm the deflection.
i have very little faith in the ability of people to measure this kind of thing unless they are required to sign off on a legal document regarding the accuracy of the measurement.
it is my opinion that the measurement was taken by an individual standing on the floor and guessing the measurement based on the spacing between the wall and the column.
i have personally stood beside people while they did the same type of measurement in similar situations. none of the people i have been with took into consideration the slope on the floor which can be a source of considerable lean.
my estimate for the true deflection for this column would be between 0.5" and 1". i have not calculated this kind of deflection for more than a year and a half. i do not trust that i am doing it 100% correctly, that is why i have opened it up in this forum.
bpeirson,
yes, definitely post a picture. you didn't provide the height of each arm and exactly where the loads are located on the arms.

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