Robustness of large-span timber roof structures — Structural aspects

Design rules for robustness require insensitivity to local failure and the prevention of progressive collapse. This is often verified by applying the load case “removal of a limited part of the structure”. This paper will evaluate typical structural systems for large-span timber roof structures against these requirements, comparing the results against typical reasons for damages and failures. Applying the finding that most failures of timber structures are not caused by random occurrences or local defects, but by global (repetitive) defects (e.g. from systematic mistakes), it is shown that the objective of load transfer–often mentioned as preferable–should be critically analysed for such structures. Based on these findings, proposals for structural systems and details towards a robust design of large-span timber roof structures are given.