The seismic risk index is a number lower or higher than one which defines the level of the risk of a construction under a definite earthquake. It is obtained by the ratio between the structural capacity and the seismic demand, generally expressed in terms of PGA (peak ground acceleration) or displacement or return period of the earthquake.
Published in Chapter:
On the Assessment of the Seismic Vulnerability of Ancient Churches: The Case of “San Francesco ad Alto” in Ancona (Italy)
Pardo Antonio Mezzapelle (Polytechnic University of Marche, Italy) and Stefano Lenci (Polytechnic University of Marche, Italy)
Copyright: © 2015
|Pages: 37
DOI: 10.4018/978-1-4666-8286-3.ch027
Abstract
The chapter deals with the assessment of the seismic vulnerability of the “San Francesco ad Alto” historical masonry building, a former church located in Ancona (Italy), which is currently used as a Regional Headquarter of the Marche Region by the Italian Army. The interest toward this building comes from a double motivation. From the one side, it underwent a series of structural changes, including the addition of a new floor splitting in two levels the original nave, which makes the structure very peculiar and closer to a classical building than to a church. From the other side, it is no longer used as a church, a fact that changes the hazard aspects. The construction schematically consists of two masonry boxes overlapping, the lower being wider than the upper. It has various characteristic structural elements, such as some semicircular arches, segmental arches, timber floors, a barrel vault, some wooden trusses on the roof and steel ties in retention of the facade and of the external walls. The equivalent frame method is used, and several pushover analyses are performed. The seismic action has been defined considering the building both with strategic (current situation) and with ordinary (possible future situation) importance during earthquakes. The role of the masonry spandrels on the response of the structure has been investigated in depth and the main effects highlighted. The result of the pushover analyses is a seismic risk index (IR), that defines the safety level of the construction with respect to one ultimate limit state (SLU), in particular the so-called limit state of “saving life” (SLV).