Long-term deformation behaviour of a Timber-Concrete Hybrid Structure A parametric and analytical study of vertical deformation behaviour and differences between timber and concrete

Abstract

The population of Sweden increases every year, requiring more housing and a further developed infrastructure, thus densifying the cities. One solution to increase the amount of housing while preserving green areas within the city is to build taller buildings. The interest of using timber in buildings has increased in recent years, mainly due to its environmental benefits. However, a pure timber high-rise building present limitations and challenges which introduces a solution combining different materials. A building with a mix of different materials is called a hybrid building. Timber-concrete hybrid structures present challenges. Aspects to consider are different material properties, construction processes, structural systems and their elements as well as joints between elements. The thesis work aimed to analyse vertical deformations in a tall hybrid building of mainly timber, with a concrete core. Deformation differences that arises when timber is connected to concrete have been investigated for time dependent loads and surrounding climate conditions. Possible solutions to minimize the differences have been suggested. The work of the thesis started with a literature study to acquire understanding of the topic and to establish a basis for the analysis of vertical deformations. Structural components were dimensioned and based on the literature study and material models were created in MATLAB. Lastly, a parametric as well as a general study were performed on a fictitious building. The parametric study consists of six different scenarios and the result is showed with a plot of deformation over time for a bottom column or wall element. The general analysis shows that differences of deformations between the timber and concrete components will occur along the height of the building. The total number of floors determines how large the differences will be and also where along the height the maximum difference will emerge. From the parametric study, the most efficient parameters to adjust to reduce the differences are the timber strength classes as well as the timber component dimensions.