Experimental behaviour of wood columns under cyclic buckling: choice of damage parameters

During earthquakes, structural elements like columns can fail by loss of strength but also by geometric instability such as buckling. The aim of this work is to analyse the experimental carrying capacity of such elements. Buckling experiments on solid wood, laminated veneer lumber and glulam specimens are carried on. Monotonous buckling tests are first carried out, in order to determine loads and displacements at instability point. They are followed by cyclic tests in the post-buckling domain (after peak). The cyclic protocol is precisely defined from displacement values obtained in monotonous tests. A damage parameter is determined based on the evolution of the extreme compression or tension apparent stresses but also on the analysis of stiffness degradation and of variation of dissipated energy during cyclic tests.