Open issues on timber engineering: q-behaviour factor of Light Frame Timber buildings and vibration comfort assessment of timber joisted floors

The renewed focus on timber structures in recent decades has led to a rapid evolution of the research but, despite the significant progress, codes and regulations still require continuous updating, as many open issues remain to be studied. This dissertation, in fact, analyse two open topics. The first part of the thesis analyses the seismic behaviour of Light-Frame Timber LFT structures, to obtain a reliable range of the q-behaviour factor for the seismic design. Current codes, in fact, suggest values that are not consistent with the actual response of LFT walls. First, a literature review studied different structural typologies, focusing then on LFT structures and their hysteretic cyclic behaviour. Successively, a laboratory tested full-scale LFT wall was used to calibrate FEM models, and the sheathing-to-framing connection was parameterised, varying its ductility and the shear capacity, in order to define a set of LFT walls. These walls, in fact, were used to assemble six reference buildings, which were subjected to Incremental Dynamic Analysis. Twenty seismic events were considered, and each pair of accelerograms was applied simultaneously in both principal directions of the buildings. The over 7000 non-linear dynamic analysis were then used to calculate the q-behaviour factors. The second part of the dissertation considered the comfort vibration assessment for timber joisted floors. Since assessment methods are typically expensive and time consuming, this work proposes a valid alternative using smartphone devices. A preliminary review is reported, highlighting typical structural solutions for joisted timber floors, but also human-induced load models and key parameters to define comfort. Successively, a full-scale timber floor was built and tested. The specimen was equipped with force-balance accelerometers and smartphone. Corrective coefficient for the smartphone outcomes were extracted and a test protocol was proposed. Moreover, starting from a FEM model of the tested floor, a parametric analysis was developed. Varying a set of 12 parameters, 15,000 different floor configurations were obtained. Each configuration was then subjected to probabilistic walking loads, in order to provide useful information to improve the vibration check according to Eurocode. Finally, the smartphone-based assessment was successfully applied to three case studies in L’Aquila.

The renewed focus on timber structures in recent decades has led to a rapid evolution of the research but, despite the significant progress, codes and regulations still require continuous updating, as many open issues remain to be studied. This dissertation, in fact, analyse two open topics. The first part of the thesis analyses the seismic behaviour of Light-Frame Timber LFT structures, to obtain a reliable range of the q-behaviour factor for the seismic design. Current codes, in fact, suggest values that are not consistent with the actual response of LFT walls. First, a literature review studied different structural typologies, focusing then on LFT structures and their hysteretic cyclic behaviour. Successively, a laboratory tested full-scale LFT wall was used to calibrate FEM models, and the sheathing-to-framing connection was parameterised, varying its ductility and the shear capacity, in order to define a set of LFT walls. These walls, in fact, were used to assemble six reference buildings, which were subjected to Incremental Dynamic Analysis. Twenty seismic events were considered, and each pair of accelerograms was applied simultaneously in both principal directions of the buildings. The over 7000 non-linear dynamic analysis were then used to calculate the q-behaviour factors. The second part of the dissertation considered the comfort vibration assessment for timber joisted floors. Since assessment methods are typically expensive and time consuming, this work proposes a valid alternative using smartphone devices. A preliminary review is reported, highlighting typical structural solutions for joisted timber floors, but also human-induced load models and key parameters to define comfort. Successively, a full-scale timber floor was built and tested. The specimen was equipped with force-balance accelerometers and smartphone. Corrective coefficient for the smartphone outcomes were extracted and a test protocol was proposed. Moreover, starting from a FEM model of the tested floor, a parametric analysis was developed. Varying a set of 12 parameters, 15,000 different floor configurations were obtained. Each configuration was then subjected to probabilistic walking loads, in order to provide useful information to improve the vibration check according to Eurocode. Finally, the smartphone-based assessment was successfully applied to three case studies in L’Aquila.