steel tube brace buckling
steel tube brace buckling
(OP)
I am developing options for strengthening a steel tube brace that cannot be upsized due to architectural constraints. One option I have considered in order to increase the buckling strength is filling the tube with concrete. Does anyone know of a good reference (preferably based on U.S. codes) for calculating the buckling strenth of a concrete-filled tube? This will not be a composite member, the concrete would be for stability only (i.e. increasing the radius of gyration).






RE: steel tube brace buckling
By filling the tube, you will essentially create a composite action whether you utilize it or not.
RE: steel tube brace buckling
RE: steel tube brace buckling
H.D. Wright, Local Stability of Filled and Encased Steel Sections, J.of Struct.Eng., Oct., 1995.
RE: steel tube brace buckling
RE: steel tube brace buckling
RE: steel tube brace buckling
Don't know of any direct publications that deal with this other than what you might find through AISC.
One thing to note, though. If you're trying to add to your radius of gyration by adding concrete, you need to remember that the r is based on the square root of I / A. To increase r, you need to add to I in a way that I increase faster than A. To add to I, you can go non-composite with the concrete, but it would only amount to the transformed concrete by itself, not using the total shape of the steel and concrete.
So the new I would be Is plus Ic.
In addition, the Ic by itself may not do you a whole lot of good as a singular piece of concrete within the tube as it will likely crack at a very low flexural stress. Thus, composite action is really required to be effective in adding to your "r".
I didn't notice the I2.4 section...thanks for pointing that out. Is there a way you can use a cap plate (per chandr) to create a bearing reaction at each end?
RE: steel tube brace buckling
Another possible solution would be to put a cruciform piece of steel down the centre of the tube. Then cut holes in the tube at intervals so you can weld the tube to the internal cruciform. A bit messy perhaps but if it was the only solution it might work.
Carl Bauer
www.bauerconsultbotswana.com
RE: steel tube brace buckling
Frank Hartzell
Jacobs Engineering
Conshohocken, PA
frank.hartzell@jacobs.com