A2.2 Discussion

All the simplified methods show a rather wide scatter when compared to the general method.

This is inevitable; a method giving close agreement with the general method over a wide range of parameter values would no longer be simple.

An illustration is given in figure A2-1. The "curvature method" gives reasonable results for low to moderate slenderness, but becomes extremely conservative for high slenderness ratios.

This is because the factor Kr (K2 in ENV) gives no reduction of the curvature at all when n < 0,4, and for high A values n is practically always < 0,4. The same is true for the simplest version of the stiffness method (expr. 5.26). With correction of the stiffness for normal force and slenderness, expression (5.22) to (5.24), the result is much improved.

It is difficult to calibrate a simple method so that it accurately follows the general method, particularly for high slenderness ratios and small eccentricities. This is true for all methods, see the first and second rows of diagrams in table A2-1.


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