The seismic behaviour of Cross-Laminated Timber buildings: Evaluation of the behaviour factor for the revision of the Eurocode 8

Over the last 15 years, the wood-based structural industry has achieved general growth around the world. This positive trend is due to many reasons: the awareness of the importance of sustainable development and the high structural performance of timber structures in seismic-prone areas. Several researches were conducted in these years, leading to a deeper knowledge of seismic timber design. In particular, the Cross-Laminated Timber (CLT) system was widely investigated, becoming a competitive choice in seismic areas compared to other structural materials. Starting from 2015, the revision process of the overall structural Eurocodes is leading to a significant change even in the section dedicated to timber buildings’ seismic behaviour. The aim of this thesis is to evaluate and to propose the behaviour factors of CLT structures designed with dissipative behaviours for the revision of EN 1998:2004 (Eurocode 8). The work combines the review process of Eurocode 8 and of EN 12512. The two norms are linked since Eurocode 8 defines the demand whereas the EN 12512 describes the metodology to estimate the capacity of dissipative joints. The results, which came from ongoing studies, have been obtained using the Eurocode 8 version-prEN1998-1-2:2020 (EC8 draft) dated 30/04/2020. The motivations of a new estimation of the q-factor for CLT buildings are highlighted within a critical review of the current Eurocode 8. In specific, the behaviour factor will be divided into three contributions due to the new material independent formulation, and new seismic design rules will be introduced in the EN 1998 for CLT buildings. The definition of the intrinsic q-factor component has been carried out via numerical investigations based on experimental results on traditional CLT connections analysed with the EN 12512 draft. A significant amount of analysis has been done to define the conservative values. At the beginning, static non-linear analyses have been performed on several 2D configurations, and subsequentially, dynamic non-linear analyses have been done on some of the previous configurations. The obtained outcomes propose conservative values of the q-factors for the moderate and high ductility classes. Moreover, a new finite element (FE) strategy has been developed, starting from a state-of-the-art for practice-oriented purpose. The FE model allows integrating into a linear-elastic model the non-linearities of the seismic behaviour of CLT buildings, often neglected.