“Advanced models for seismic analyses of timber buildings.”

The paper discusses the seismic analysis of multi-storey buildings made from cross-laminated timber panels ('crosslam'). The different analysis procedures allowed by the Eurocode 8 for seismic design, namely: (i) linear static ('lateral force'); (ii) linear dynamic ('modal response spectrum'); (iii) non-linear static ('push-over'); and (iv) non-linear ('time-history') analyses, are introduced. Some recommendations are given for an effective modelling of the building. Cross-laminated panels are schematized with two-dimensional Finite Elements with linear-elastic behaviour. Connections are modelled using linear elastic, non-linear elastic, and hysteretic springs for (i) and (ii), (iii), and (iv) analysis methods, respectively. Some suggestions on how to model non-symmetric connections such as hold-downs and angle brackets loaded in tension/compression using an elastic spring are given, as well as on how to approximate the actual non-linear behaviour with a linear elastic or an elasto-plastic equivalent behaviour. Information on push-over analyses and the N2 method for the seismic design of timber buildings is also provided. An advanced numerical model to describe accurately the features of the connection cyclic behaviour, namely: pinching effects, strength and stiffness degradation, and softening after the attainment of the peak strength is also introduced. This model allows the user to correctly characterize the non-linear behaviour of the connections, and to calculate the dissipated energy for single fasteners and also for more complex structures. A case study cross-lam multi-storey building analysed using the linear-dynamic and the non-linear static is also presented, together with the non-linear analysis of a wall panel subjected to cyclic tests, demonstrating the excellent approximation achievable using the proposed advanced model.