User talk:Ahnielsen

Buckling
In the article it is stated: "Examination of this formula [the Euler load] reveals the following interesting facts with regard to the load bearing ability of columns: that elasticity and not compressive strength of the materials of the column determines the critical load."

On this backgriound I am wondering why in Codes of Practice such as BS 5950 the load-carrying capacity of members in compression is dependent on material strength and not Young's modulus? The article does hint at a number of possible reasons ("a number of empirical column formulae have been developed to agree with test data" and "buckling will generally occur slightly before the theoretical buckling strength of a structure due to plasticity of the material"), but it would benefit the article to devote an entire section to this question. Does anyone know the answer? Is it already in the article? --Ahnielsen 21:11, 26 June 2006 (UTC)


 * In structural engineering, there are many different modes of failure. Failure in direct compression, occurs when the applied load exceeds the ultimate strength of the load bearing material.  As the name implies, the Euler buckling equation deals with a different failure mode, that of buckling.  In the case of buckling, any slight eccentricity of the load will cause a moment in the member and when the load (and corresponding moment) reach the critical load, the member will buckle.  The only thing resisting this type of failure is the restoring force resulting from the material stiffness (Young's modulus * moment of inertia in the axis of bending).  If the member buckles, it is implied that the critical load must have been less than the ultimate load, otherwise failure in direct compression would have already occurred.


 * I'm not familiar with British design standards, so I can't comment on BS 5950, but the Building Code of Canada requires that several different failure modes must be considered to determine the load capacity of any member (be it in tension or compression). The lowest failure load is taken to be the design load.


 * Some other articles that might be of interest on the subject might be: physical compression, limit state design, or compressive stress.


 * I hope that helps clear some things up. If you have any questions I'd be happy to try and answer them as best I can.  Alangstone 22:54, 26 June 2006 (UTC)