Wooden roof box structure for the anti-seismic strengthening of historic buildings

A wooden roof strengthening technique aimed at transforming the roof pitches into anti-seismic shear-resisting diaphragms is presented in this article. Shear diaphragms gather and transfer the seismic loads to the shear-resisting walls. Diaphragms are built on top of the existing structures without significantly modifying the roof overall layout. The proposed strengthening technique is mainly reversible, minimally impairing the building integrity, and can be easily applied for the construction of anti-seismic wooden roofs in new buildings. A simplified design approach is presented, which allows identification of the static role of each element. An analytical method for the estimate of the box structure displacements, as well as a short digression on the displacement control requirements is also illustrated. The diaphragm technique was recently applied for the anti-seismic retrofit of some monumental buildings in Italy. A few case studies, as well as the basic design criteria for applying this technique are presented in this article.