Column load - determine failure loads? 1

[IFRs]

The AISC and Aluminum Association have formulas to calculate the allowable load on a column. This is fine.

I assume that allowable loads have some factors of safety built in.

How would I predict the failure load on a concentrically loaded pipe column?

 

[plasgears]

Roark provides a range of column formulas for your choice. Choose a formula that will account for short columns and eccentricity. Study the effect of eccentricity to give insights into sensitivity to offset.

 

[dik]

Can you give an indication of the size? and the length? and the manner of loading it?

In addition to eccentricities, depending on the length, the internal stresses have a fair impact on overall strength

 

[haynewp]

Go to LRFD code column tables and find your pipe size, yield stress and effective length. Divide that number by 0.85. I think that would give you the failure load.

 

[amokhta]

If you have a short column and the load is applied exactly along its longitudinal axis, then the failure happens when yielding occurs. Therefore your failure load is P=A*Fy (area times yield strength).

However, a long and slender column under a concentric load will fail due to buckling before the applied load reaches the above value. This buckling load can be calculated using Euler's formula.

A word of caution: Eventhough the load may look exactly concentric to you, the columns are not manufactured perfectly straight, and there always exist residual stresses in the column due to manufacturing and fabrication. All these will result in bending stresses that can substantially reduce your final failure load. A perfectly straight conncentric loaded column is only theoretical and not attainable in practice.