Wooden Roof Box Structure for the Anti-Seismic Strengthening of HistoricBuildings

A wooden roof strengthening technique aimed at transforming the roof pitches into anti-seismic shear resisting diaphragms is presented in this paper. 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 to identify 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 paper

Experiences from the Northern Italy 2004 earthquake: Vulnerability assessment and strengthening of historic churches

This work is about the lesson learnt from the analysis of the damages caused to some churches by the strong earthquake, which struck Northern Italy in the year 2004. Focus is paid to some mechanisms which are not well known in the literature: the excessive and differential rocking of neighbouring transverse arches, the differential deflection of single leaf vault rings, the tie over-tension induced by the transverse arch rocking. In the paper, the structural solutions appositely studied to repair and to reduce the structure seismic vulnerability of these buildings are presented. Among these solutions: internal perimeter ties, lightweight wooden roof box structure, lightweight spandrel ribs are illustrated

Extrados Strengthening of Single-Leaf Vaults Against Seismic Actions

Single-leaf vaults are acknowledged among the most vulnerable components of historical masonry constructions with respect to earthquake loads, particularly when featuring large span to thickness ratios, as in the case of single leaf covering the main nave of churches. These elements often require structural strengthening against seismic actions. In this paper, two different extradostechniques are tested: lightweight plywood restraining elements and FRP laminates embedded in a lime mortar layer. The techniques are tested on single leaf vaults having a very unfavorable span to thickness ratio. A previous study on less slender vaults, showed that lightweight plywood centerings, applying passive confinement to the vault extrados, inhibit the onset of the typical four-hinges failure mechanism. This lightweight, dry solution can be easily prefabricated, transferred and assembled at the construction site. The technique is reversible and fully compliant with the major preservation principles. FRP is also effective against the onset of the failure mechanism but entails larger deformations of the retrofitted vault, which may be detrimental in the case of possible decorations. The solution requires special man labor to ensure correct smoothening and cleaning of the vault extrados and to trigger effective bond between the mortar and the vault extrados. Both solutions are shown to enable small relative displacements of the vault springing, which may follow the deformation of possible internal ties. The effectiveness of these retrofit techniques was comparatively verified through experimental tests on single-leaf barrel vault stripes at 1:2 scale subjected to cyclic distributed unsymmetrical loads and through comparison with the seismic response of a reference unreinforced single-leaf vault

Il percorso delle indagini e degli studi per gli interventi sulla struttura del Palazzo della Loggia

Atti del Convegno di studi "Storia e problemi statici del palazzo della Loggia di Brescia" - Università degli Studi di Brescia - Facoltà di Ingengeria - ottobre 200

Coperture in legno antisismiche

TECHNICAL REPORT N.