Analysis of structural failures in timber structures: Typical causes for failure and failure modes

Collapses of timber structures are negative for the competitiveness of timber on the construction market. The question is what can be done to reduce the risk for failure in timber structures in the future. For this purpose a comprehensive survey and analysis of failures in 127 timber structures have been made. The present paper summarises the results from this survey with an analysis of the underlying causes and associated conclusions and recommendations. The most common cause of failure is related to weaknesses in or lack of strength design (41.5%), followed by poor principles during erection (14.1%), on-site alterations (12.5%) and insufficient or lack of design with respect to environmental actions (11.4%). In total, about half of the failures are caused by the designer and about one fourth of the failures are caused by the personnel working at the building site. Wood quality, production methods and production principles only cause a small part (together about 11%) of the failures.