Public defence in civil engineering, Steven Collins, M.Sc.

Investigating the mechanical behavior of birch timber for structural applications

This thesis investigates the potential of using birch timber as a structural material. Investigations focus on the hardwood species, silver birch (Betula pendula Roth). Structural timber elements are cut out of logs of various qualities (obtained from southern Finland), and experimentally investigated. Non-destructive testing techniques are applied to measure the growth characteristics on the individual specimens, and the specimens are tested mechanically, under compression and tension loads. The purpose of the study is to describe the mechanical behavior of birch timber under these loads and develop prediction models for the strength and stiffness.

Results contribute knowledge on the deformation behavior and failure modes from mechanical testing, and the influence of growth characteristics on the mechanical properties are statistically described. The efficacy of non-destructive test methods is assessed for birch timber, including the use of a laser light scattering technique for the determination of wood fiber orientation. The developed prediction models suggest suitable methods for estimating the strength and stiffness of timber boards and the local variability within the timber boards. The models constitute a step towards the further development of material models and quality assessment techniques for birch timber.

The study is relevant for the timber construction industry and research fields related to hardwood strength grading and the development of hardwood engineered-timber-products. Through the continued develop of birch as a structural material, a wider diversity of tree species may become available for structural applications, the auspicious mechanical properties may be taken advantage of in value-added timber products, and the use of birch may be upcycled to longer life-cycle applications.

Opponent: Docent, PhD. Henrik Heräjärvi, Natural Resources Institute Finland

Custos: Assistant professor Gerhard Fink, Aalto University School of Engineering, Department of Civil Engineering

Contact information of the doctoral student: Steven Collins, [email protected], +358 (0)50 3242410.

The public defence will be organised on campus (auditorium M1, Otakaari 1).

The thesis is publicly displayed 10 days before the defence in the publication archive Aaltodoc of Aalto University.

Electronic thesis