Numerical modelling strategies and design methods for timber structures

Over the last years timber constructions are gaining back a primary role in the building industry after decades in which they were almost abandoned in favor of concrete and steel structures. A sign of this change is the appearance in the last years in many Italian universities of courses dedicated to the design of timber structures. One of the main reasons behind this success must be sought in the development of new engineered timber materials, such as glued-laminated and cross-lam timber, that allowed to wooden structures to reach structural potentialities that until some decades ago were prerogative of concrete or steel building materials. Tests recently carried out on full-scale buildings have also proven the excellent capabilities of these new timber technologies in providing reliable and highly-performant multi-storey building able to withstand high seismic intensities. Since the employment of timber to build multi-storey buildings in seismic-prone areas is quite recent, many aspects relating the understanding of their structural behavior and their correct design are still to be sought, as demonstrated by the lack of provisions in current building codes and standards and the still ongoing great amount of research activity on seismic behavior of timber structures. Modern timber technologies also allow to cover very large spans with long glued-laminated timber beams, satisfying the need of large open spaces and architectural flexibility required by modern building design approaches. These bulky big-size elements anyway result quite expensive in production, transportation and installation phases undermining the economic competitiveness of timber structures. To cope with this problem, the prototype of an innovative timber-steel composite beam consisting of sub-elements assembled on-site to create longer members has been ideated at KTH Royal Institute of Technology of Stockholm in Sweden. One of the objectives of this thesis is therefore to provide an advance in the state of knowledge of timber building technology adopted for seismic-prone areas, focusing in particular on both numerical modelling strategies and design methods for cross-laminated timber buildings, illustrated respectively in the first and second part of the thesis. The other goal is the development of an analytical tool for the enhancement and the investigation of the structural performances of the innovative composite beam ideated at KTH Royal Institute of Technology, and it will be exposed in the third and last part of the thesis.