Connessioni legno-legno, legno-acciaio e legno-calcestruzzo: studio sperimentale, modellazione analitica e agli elementi finiti

Connections can be used to join all kinds of wood products between them or with steel or concrete member to realize composite elements or to join structural elements of a building having different functions. The screws, thanks to their dual resisting mechanism, namely axial and transversal, allow for the realization of high performance shear, bending moment and axial force resisting connections. In determining the most relevant mechanical parameters for connection design, namely slip modulus and failure load, several parameters may have an influence both at the component level and at interaction between components level. Withdrawal, embedment and yielding strengths are currently regarded as influencing parameters. Depending on the angle between connection slip direction and the screw axis, axial, transversal or a combination of axial and transversal screw capacity can be exploited. Slip modulus and strength are found to considerably increase for increasing screw inclination. Interlayers having poor mechanical properties compared to connected members are often used in connections to ensure human comfort in the buildings or because it is required by the structural system. Interlayers were often considered as secondary components, while recent studies testified their influence on the connection mechanical behavior. In this thesis the influence of soundproofing and OSB interlayer in connections with screws perpendicular or inclined with respect to the sliding plane is experimentally assessed. Analytical models for stiffness prediction are developed, validated and used to derive elementary formulas suitable for design purposes. A novel one-dimensional finite element model is proposed to study the full load-displacement connection behavior, including non-linear effects. Three dimensional models are used to assess interlayer mechanical properties influence, interlayer connection, setup influence and friction contribution on connection strength and stiffness. Empirical models are used to reproduce the constitutive law of a timber-to-steel connection.