Determination of Yield Point and Ductility of Timber Assemblies: in Search for a Harmonised Approach

Knowledge of the yield point and ductility of a structure is important in seismic design. The yield point of an assembly is defined as a point where it begins to plastically deform, while ductility describes its ability to yield without substantial reduction in strength. These parameters can be determined from the analysis of the load-deformation curves resulting from destructive tests. To date, several methods have been adopted around the world to quantify these properties for timber structures, however, there is no standardised approach. There is a need for a uniform approach to the yield point and ductility calculations because of the growing interest in harmonisation of standard testing and analysis procedures and the increased attention to seismic design of timber construction systems. This study is focused on comparing six analysis methods commonly used in the determination of yield load and deformation and examines the applicability of these methods to various types of assemblies in an attempt to identify the most universal approach to estimating ductility and overstrength-related force modification factors used in seismic design of timber structures. Results are discussed and recommendations are provided.