Design of safe timber structures - How can we learn from structural failures in concrete, steel and timber?

During recent years, several spectacular collapses happened in large timber structures and the question is what can be done to prevent future failures. The main hypothesis for this project has been that quality assurance, control systems and improved training may be necessary, since the unwanted events are primarily related to human errors. A survey of failures in 127 timber structures has been made and results with an analysis of the underlying causes and associated conclusions and
recommendations are presented. The most common failure causes are poor strength design (41%), poor principles during erection (14%), on-site alterations (13%) and poor design with respect to environmental actions (11%). Wood quality, production methods and production principles only
cause a small part (together about 11%) of the failures. The problem is therefore not the wood material, but designers and workers in the building process.