Finite element analysis of an old building façade and reinforcement

Abstract

The Podestà Palace, a historical masonry construction, is dated from the XII century and is situated in Foligno, central Italy. This building has a high heritage and artistic value associated to it, mainly due to existing paintings in both the internal and external parts of the façade. Its current deteriorated state, coupled with the high seismic hazard of the region, stresses the pronounced seismic risk associated to this building. However, possible conservation and strengthening measures to be potentially applied should not affect the architectural and historical value of the Palace, i.e. its authenticity. In order to assess the seismic vulnerability of the building, a numerical model was developed. The reduced global dimensions of the building made possible the development of a simple model comprising only the consideration of the façade. The boundary conditions, due to effects of the walls perpendicular to the façade, pavements and vaults as well as the effect of the neighbouring building and later additions were duly considered. A previous and detailed structural survey of the building, together with existing architectural drawings, made possible the development and construction of a finite element mesh of the Palace’s façade. The numerical model was subjected to the self-weight of the structure and to lateral loads that took into account earthquake loads according to the Italian code. The results demonstrate that during a standard earthquake, partial or total collapse of the building should be expected. The careful analysis of the critical areas that lead the structure to collapse made possible to determine an appropriate methodology for structural strengthening, having always in mind the minimum intervention - maximum efficiency approach. Through a careful analysis of the weakened areas that caused the building collapse, it became possible to determine the best methodology for the structural strengthening, being chosen the reinforcement with carbon fibers, that allowed a localized reinforcement. In the last part of the study, the model was updated with the inclusion of the FRP strengthening and subjected to the same loads applied on the second part of the study. The results show that, due to the use of FRP composites, the collapse was avoided through the reduction of the displacements normal to the façade surface. As a conclusion, the carbon fibres located in strategic areas, increased the building façade resistance by reducing the perpendicular displacements. The strategic location of the carbon fibre becomes imperceptible, and this way, less intrusive to the patrimonial value of the construction.