N. GUCCI(1), G. MARIANI(2) and M. SASSU(2)
(1)Department of Civil Engineering – University of Pisa (Italy)
(2)Department of Structural Engineering – University of Pisa (Italy)

A case of the incipient collapse of a large masonry building caused by vibration is described. The building studied was part of economical housing erected in the Tuscan port city of Leghorn (Italy) in 1930, for the most part with poor materials. For over 50 years it had been subjected to high levels of stress from the heavy traffic to and from the nearby harbour. Recently, the action of a dry compactor used to pack the ground in a nearby storage depot exacerbated its already precarious state and caused microcracks in extensive portions of the masonry structure. A simple method of dynamic analysis is proposed to study the effects of “modal localisation” of axial strains due to growing areas of damage in masonry columns. Also evaluated is the effect of traffic random loading.