Stiffness of dowel-type timber connections and its influence on structures Finite element analysis of high performance timber connections and their impact in a case study

Examensarbete för masterexamen
Master's Thesis
Structural engineering and building technology (MPSEB), MSc
Timber is one of the oldest construction materials and are used for many purposes in the field. Although, timber has not been prioritized as a structural material for multi-storey buildings, today’s new technologies which generate engineering wood products, allow to build in larger scale than ever before. Connections between timber members in structural systems are critical details, but detailed design standards and guidelines for large-scale timber connections are still lacking. The stiffness and ductility of timber connections are important parameters for the response of a structural system. However the methods for evaluating stiffness in standards such as Eurocode 5 are limited. For this reason, detailed information on stiffness and ductility of connections might be neglected in design process. This might results in inefficient material utilisation and unknown effects. Therefor, the aim of this thesis is to analyze the stiffness of timber connections, and the impact the stiffness can have on a structural system. The research is accomplished by identifying and using appropriate modeling methods for dowel-type timber connections, and then investigating the design of a 5-storey building with timber beam-column structural system. Firstly, the rotational stiffness of the most used connection in the case study was calculated by finite element analysis in Abaqus. Then, modified variations of the chosen connection were analysed to study the influence of different design choices on the rotational stiffness. Lastly, the calculated stiffness is inserted to the joints of the model of the reference building in RFEM software to study the contribution of connection’s stiffness to internal forces and global deformations. The findings of this thesis can be summed up to that other than those provided by the standards, there are applicable methods that provide more sophisticated load- deformation relations and estimate stiffness for dowel-type timber connections. For the studied case, the stiffness of the beam-to-column connections had limited impact on the global deformations and some impact on internal forces in the structural system. In addition, accounting for stiffness in the joints of a timber beam reduces the span moment and might allow for reduced design cross-sectional area. However, some more aspects and parameters than the treated ones in this thesis should be taken into account when rising the stiffness and ductility of a connection.
Rotational stiffness, ductility, glulam, dowel-type connection, structural system, shear plane, FEM, Eurocode.
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