An Italian historic timber framed wall: damage progression through DIC analysis

A key factor to define the vulnerability of a building under seismic actions is represented by the knowledge of the damage severity in relation to the earthquake excitation intensity and its evolution, in correspondence to increasing displacements. Timber structures, thanks to their intrinsic flexibility, do not show evident strength degradation under moderate displacement during reversed cyclic loads. However, high lateral loading values entail, in general, the characteristic elasto-fragile rupture modality, with a collapse in linear field and consequent low values of dissipated energy. Such a theoretical model is brought into question if the analysis is conducted on a compound structure, for instance constituted by timber and masonry, in which the latter undergoes bed-joint cracks and plastic deformations. The so-called "casa baraccata", developed in South Italy at the end of the 18th century, as an implementation of the first European anti-seismic code, consists of masonry braced with timber frames. In September 2013, a full-scale replica of this type of wall has been tested under quasi-static cyclic loads at CNR-IVALSA as a result of a joint research with University of Calabria. The time-resolved sequence of images of the wall under examination was acquired during the test with a camera. Digital image correlation was applied to map the deformation of the wall components. Image analyses provide valuable indicators of the damage evolution and assist interpretation of the effect of construction design on the failure process.