A study of the behaviour of typical connections in a multi-storey modular CLT building using Irish-grown timber

Due to the increasing focus on sustainable construction methods in recent years, cross-laminated timber (CLT) has emerged as an excellent construction material in terms of structural properties as well as environmental impact. CLT is widely used for medium- to high-rise timber structures because of its lightweight and high strength-to-weight ratio and can rival traditional building materials like concrete and steel. Across Europe, CLT is primarily manufactured using C24 strength class timber or a combination of C24 with small proportions of lower grades, like C16, in the interior layers. As such, most of the literature available is typically concerned with C24 timber, and very limited studies have been conducted for lower-grade timber. Ireland has an increasing supply of Irish Sitka spruce, which is primarily graded as C16, and studies have shown that Irish timber is suitable for use in CLT. This research studies a seven-storey modular building constructed with cross-laminated timber manufactured using only C16 Irish timber. A modular building that consists of stackable and scalable prefabricated modular units, which are manufactured off-site and transported and assembled on-site. Connections are the most important part of a mass timber building, and they are designed to resist gravity loads and lateral loads. The elastic and ductile behaviour of the connections in the proposed modular building is investigated and studied thoroughly in this research. Small-scale tests on wall-to-floor connections are performed under compression and shear loads. Subsequently, racking tests are performed on full-scale C16 CLT wall systems. The results from the experimental analysis are compared with the analytical models. Finite element models or numerical models are also created, which are validated using experimental results. The results from the small-scale tests demonstrated that the edge distance on the loaded end may need to be increased from the edge distance prescribed in the standards to prevent the failure of timber when using high-grade steel connectors with lower-grade timber. The racking test results demonstrated that the racking stiffness of a CLT panel is significantly influenced by the connectors utilised to fix the CLT panel. The detailed numerical models captured the global behaviour of the connections; however, timber failure was not fully represented due to the use of elastic timber properties, and further refinement of the model is required. The simplified numerical models also exhibited the global deformation of the experimental racking tests; however, the models can be refined by using experimentally deduced stiffness values for the connector elements. Therefore, the numerical models provide a reliable framework for modelling and analysing the behaviour of C16 CLT connections while also offering deeper insights into the responses observed in the experimental tests. The research presented in this thesis addresses the gap in knowledge regarding the behaviour of C16 CLT connections, thereby facilitating the design and detailing of a modular mass timber building using C16 Irish CLT. These findings will provide engineering practitioners with confidence in CLT and encourage the production of CLT using C16 Irish timber.

Funder

Department of Agriculture, Food and the Marine, Ireland

Publisher

University of Galway

Rights

CC BY-NC-ND

cbn

Collections

University of Galway Theses (PhD Theses)