STRUCTURAL ANALYSIS OF EARTHQUAKE-RESISTANT HISTORICAL DETAILS OF L'AQUILA (CENTRAL ITALY) BUILDINGS

The 2009 L'Aquila earthquake has induced very large damages in historical constructions. Surveys performed in the months after the main shock have brought to light construction details, meant to improve seismic performance, typical of the area. Most of them make use of timber elements, probably because the material was widely and inexpensively available. Timber wall anchors are used to tie horizontal timber floor/roof beams to the vertical masonry panels. Timber is used as well as part of ties that lie within the wall section and which are connected to facades through horizontal iron strips and vertical iron wall anchors. These connections are modelled as carpentry joints or within an up-to-date Johansen framework. Once the ultimate load causing the connection failure is established, out-of-plane verification of masonry facades is performed. Residential dwellings of both L'Aquila urban area (within an historical aggregate in the centre of Paganica) and L'Aquila province (in the municipality of Lucoli) are considered. The numerical analyses show that fully-timbered tied beams can prove very effective in preventing out-of-plane collapses, if the connection (which lies outside the masonry) is adequately maintained throughout the whole building's life. More controversial is the use of composite timber-andiron ties, because the timber within the masonry volume can easily decay, is complicated to maintain, and make the wall itself vulnerable because of the large size of timber elements.