Buckling vs. Flexural Bending

[Okiryu]

Hi, what is the difference between Buckling and Flexural Bending. I am trying to understand the failure mechanism of piles under liquefaction. When liquefaction occurs, there will be a decrease of lateral soil support and the pile may suffer buclinkg instability (if the pile is socketed into the bedrock). I read that if there is a non-liquefied layer above a liquefiable layer, the pile may fail by flexural bending rather than bucking. This is more critical where there is potential of lateral spreading, since the pile will be subjected to large passive lateral pressure by the non-liquefied layer.

Is there any important difference between those 2 terms? Are the boundary conditions involve in this?

 

[IDS]

In the context of vertical piles, pure buckling failure is failure due to an initial very small load eccentricity being magnified because the resisting moment generated by deflection is smaller than the additional moment due to that deflection.

Pure flexure failure is failure due to an externally applied moment or deflection exceeding the moment capacity of the section.

In any real situation failure will be due to a combination of the two, if the pile has a compressive axial load.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[Okiryu]

IDS, thanks for your comments. What I am understanding from your post, is that P-delta effect may cause buckling failure. And pure flexure failure is due mainly to lateral loading. Is that correct?