Caratterizzazione del comportamento di giunti semirigidi per strutture lignee in zona sismica

The thesis investigates the seismic behaviour of moment resisting joint in timber structures. The problem is analyzed starting from the single connector to get the understanding of seismic response of a complete frame structure. The design of earthquake resistant timber structures requires a deep knowledge of the mechanical behaviour of the structure as a whole and of its single component elements, especially for what concerns ductility and energy dissipation capability. In many timber structures, the ability to absorb kinetic energy and to attenuate effects of large amplitude ground motions is strongly dependent on energy dissipation associated with plastic deformation of metal parts in mechanical connections. The first part of the thesis illustrates some recent researches on timber joints assembled with traditional and innovative dowel type connectors. Experimental results are presented in terms of force-displacement relationship for specimens tested under monotonic procedure, or in terms of hysteretic diagrams for specimens tested under cyclic procedure. The goal is to find out some quantitative values from the experimental data, in order to characterize the ductility and dissipation capability of timber joints, taking into account the definition proposed by Standards for the design of earthquake resistant structures. The last chapters of the thesis present an analytical - numerical - experimental study aimed at the characterization of beam – to – column moment resisting joint behaviour. Through theoretical analysis it is possible to define a model able to describe the mechanical behaviour of tested moment resisting joint in terms of moment – rotation curve. The primary experiments are static and cyclic deformation tests on large timber moment connections. According to the standards, and applying the analytical model it is possible to obtain a reliable prediction of the resistance mechanism of each tested joint, but also to correct values of initial stiffness, maximum slip capability, reduction of resistance under fully reversed loading cycles and energy dissipation capacity. The mechanical characterization of the joint enables the implementation of a finite element model, aimed at predicting the seismical behaviour of wood multi-storey frames. The pushover analysis, performed through the FEM model, enables to assess the behaviour factors for frames built using the different typology of joint studied within the thesis.