Experimental evaluation of the elastic buckling and compressive capacity of laced columns

• The Southwell plot technique was modified to account for shear effects.
• Engesser's formula predicts the elastic critical load of laced columns precisely.
• The ultimate capacity curves method gives a good prediction of column's capacity.

To investigate the static behavior of laced columns, 18 tests were conducted on sample columns constructed from pairs of u-section profiles with various lengths and various distances between the main chords, all with an initial imperfection. To study the behavior of built-up columns in the plane parallel to the lacing planes, the test set-up was arranged in such a way that buckling occurred in this plane. There was generally good agreement between the test results and the theoretical results for the elastic critical loads. The SSRC method overestimated the results with a high error, whereas Engesser's method was more conservative, with a minor error. Bleich's method and Paul's method both led to results with moderate error. The compressive capacity of the sample columns, obtained by the tests, were compared to those obtained by the Ayrton–Perry and capacity curves methods, of which the first gave conservative results and the second led to the results being slightly overestimated. The experimental results showed that the amount of initial imperfection has a significant effect on reducing the compressive capacity of the samples.