secant formula 1

[WardHollowayPE]

When using the secant formula for eccentrically loaded colums, do I need to worry about end conditions? The book I have is not clear on the subject.

Ward Holloway, Jr, PE

 

[GregLocock]

In my opinion L is still the effective length you would use in the buckling calculation, since the secant (stress) formula is derived directly from the assumed buckled shape.

BUT you will probably need a definitive answer, the boys in the structural forum should be able to provide that. In my field buckled=broken, except for occasional special cases.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[JStephen]

I would say it depends on what you're doing.

The formula I'm looking at is for pinned end conditions, and would presumably be somewhat different for fixed ends. In terms of finding stress, it would probably be conservative to use the pinned end assumption.

The end conditions need to be such that the eccentricity used in the equation reflects the actual offset between load point and column centerline.

If it's a structural type application, refer to the structural codes for combined axial and bending loads.

 

[rb1957]

the secant formula allows for an offset load on a pinned column, so the deformed shape of the column is like a typical pinned column. if the ends of the column are fixed, don't you have a beam-column ?

 

[WardHollowayPE]

The column is fixed-free, a free standing structure. It seems logical to treat it as a beam with a moment at the end. If anyone sees any error in this logic let me know.

Thanks for the help.

Ward Holloway, Jr, PE

 

[rb1957]

if there's a compressive endload, then i think you need to consider it as a beam-column ...

 

[JStephen]

If the deflection and/or weight is substantial, do a P-delta analysis for it. IE, the deflection due to load should be included in the design moment calculation.