Quality assurance of timber structures
Creators: name: Franke, Bettina
name: Franke, Steffen
name: Schiere, Marcus Jacob
name: Müller, Andreas
Publisher: name: Bern University of Applied Sciences
Year: 2019
Subjects: Moisture content
building environments
moisture content simulation
moisture gradient
moisture induced stresses
monitoring campaigns
quality assurance

description: The combination of modern architecture with the renewable raw material wood leads to impressive and demanding timber structures with high requirements for planning, production, logistics, commissioning and use. The demands placed on modern wooden structures are constantly increasing in terms of design, appearance, slender cross sections and large spans. Meanwhile, quality assurance during the construction and operational phase is crucial. The realistic estimation of the risks for the timber structure during the construction and operation phase as well as the distribution of wood moisture content in the timber load bearing elements, the risk of cracking and the shape stability of the cross sections are important. The research project focuses on impacts of the local climate, the resulting wood moisture distribution, dimensional stability, moisture induced stresses and possible cracks in the cross-sections. The aim is to provide recommendations for the erection of wooden structures with new research results. The focus lies on the transfer of results from the developed numerical models and methods to secure recommendations for design and planning in practice.
description: The used and developed basics of the project are the climate data of Switzerland, measurements of climate and moisture content in load bearing cross-sections obtained from long-term monitoring campaigns, and the developed numerical model to calculate the moisture diffusion, the dimensional change and the resulting moisture induced stresses. In addition, required material parameters were determined in small laboratory series that improve and support measurements made during the monitoring campaigns. The climatic data and wood moisture content values obtained within the long-term measurement were classified according to the building type and visualized accordingly for the practicing engineers. Published data from other research institutes were also included into the analyses where possible. In addition to the general information on moisture content as listed in the SIA 265:2012, useable climate profiles are now available for a variety of building types and for bridges, too. Specific questions concerning bridges that still led to discussion and unanswered questions were considered and evaluated. The application of a quality assurance monitoring method and system is described. The created numerical model was validated and used in parameter studies to assess the effects of cross-section size or the impact of the construction period. realistic climate profiles found in ice rinks, riding halls and bridges were used to calculate dimensional changes and moisture induced stresses.
description: Recommendations are given on the seasonal fluctuations of humidity and its effects on the timber structures. This could support engineers during the planning and building phase. In addition to the expected fluctuations listed in the SIA 265:2012, obtained results give the planning engineer and authorities new benchmarks for the estimation of the expected wood moisture content within a supporting structure. Of interest could be the distribution across the section width during erection and operation.