Modelling of post-tensioned timber-framed buildings with seismic rocking mechanism at the column-foundation connections

The need to mitigate damage of buildings even after strong earthquakes has led to the development of high-performance seismic resisting systems. Extensive studies have been made in the last decade on the development and use of jointed ductile connections and on the effects of rocking vibration systems in reducing seismic damage of buildings. A recently developed technology for construction of multi-storey timber buildings called Pres-Lam system uses long lengths of prefabricated laminated timber and binds them together using pre-stressing steel tendons. When appropriately combining unbounded post-tensioned tendons, or rocking columns with additional sources of energy dissipation devices, a hybrid system is obtained, with self-centering and dissipative properties, leading to a characteristic flag-shape hysteresis behaviour. A three-dimensional, three-storey, two-third scaled, post-tensioned timber frame model was tested at the structural laboratory of the University of Basilicata. During shaking table tests, two different configurations of the test model have been studied considering column-table connections with and without the activation of dissipative steel angles. This paper focuses on different numerical modelling of the rocking mechanisms at the column-foundation connections. Two different modelling have been considered for two different test configurations by means of a pinned base or an appropriate combination of nonlinear rotational springs, for free rocking and a suitable combination of gap elements and linear springs or rotational springs, for dissipative rocking. The numerical outcomes of nonlinear dynamic analysis are compared with experimental test results providing an adequate representation of the seismic response.