Load-bearing capacity of imperfection-sensitive timber members under combined bending and compression

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This thesis discusses the load-bearing behaviour of imperfection-sensitive timber
members under combined bending and axial compression. As there is a fl uent transition
between the stability phenomena of fl exural buckling and lateral torsional
buckling, the stability phenomena were studied holistically.

Imperfection measurements in 23 timber buildings, fl exural buckling tests on beech
LVL columns, and lateral torsional buckling tests on glulam beams were conducted.
Through analytical investigations, the knowledge of the theoretical background
of the stability behaviour was broadened. For the detailed study of the infl uence
of structural and geometrical imperfections and combined bending and axial compression,
numerical models were developed and employed in extensive parameter
studies and Monte Carlo simulations.

Thereby, the nonlinear Nx,c-My,1-interaction of the kc-km-method was validated, and
consistent equivalent imperfections for design were derived. Additionally, it was
demonstrated that the shear and compressive plasticising and the cross-sectional
warping due to shear can have a signifi cant infl uence on the load-bearing capacity.
Design proposals were developed that modify and extend the design rules in EN
1995-1-1, in favour of a more reliable, consistent, and economical design.

For the fi rst time, by means of comprehensive experimental, analytical, and numerical
investigations, fl exural buckling and lateral torsional buckling of timber members
were combined in consistent analysis and design models. This provides a sound
foundation on which subsequent research can build and expand.