Dynamic properties of cross-laminated timber and timber truss building systems

Abstract

Incorrect prediction of dynamic behaviour of tall buildings can lead to discomfort for humans. It is therefore important to understand the dynamic characteristics such as natural frequency, mode shape, damping and the influence they have on acceleration levels. The aim of this study is to compare two timber building types, cross laminated panels and post-and-beam with stabilising diagonals, through a parameter study applying modal analysis. Empirical formulae for predicting the natural frequency and mode shape are compared to measured and numerical results. Tall building assumptions such as ‘line-like’ behaviour and lumped mass at certain points were evaluated for both systems. The post-and-beam system showed a stiffer behaviour than the cross laminated system where more shear deformation occurred. Empirical formulae should be used with care until more data is collected. For the post-and-beam systems an assumption of linearity may be appropriate, but for cross laminated systems the approximation can give results on the unsafe side. Finally, the relationship between stiffness and mass for cross laminated timber systems and its effect on dynamic properties needs to be further investigated.