The present work illustrates some early considerations on the effects of the 6 April 2009 earthquake and of the following seismic sequence in some towns in the neighbourhood of L’Aquila, in central Italy. Such considerations were recorded, during technical surveys to assess the structural usability of buildings using the first-level AeDES form, by technicians of the Ground, Seismic and Geological Survey Group of Emilia-Romagna Region with the volunteer assistance of experts from Universities of Bologna, Ferrara and Parma. In the paper the attention is focused on masonry buildings since they experienced, particularly the older ones, the major damage. The seismic behaviour and the most frequent damages of recurrent typologies of masonry structures in the inspected area are described. Most of buildings are characterized by masonry structures with raw stones and sub-horizontal disposition, or by concrete bricks and large mortar joints with concrete-brick floors and roofs. Inspections in masonry structures allowed the detection of four frequent failure modes: partial decohesion of masonry walls, overall out-of-plane rotation of walls, out-of-plane flexure, in-plane flexure and shear. Moreover the behaviour of buildings strengthened with different techniques, including reinforced plaster or steel ties, is examined. Finally some considerations are made on the failure of churches.
For this paper is available an extended abstract after the text in Italian