sessione 2.3 - Ogs

GNGTS 2009 SESSIONE 2.3
SEISMIC SITE EFFECTS FOR A PRELIMINARY EVALUATION
OF SEISMIC RISK OF SCHOOL BUILDINGS: A FIRST APPLICATION
ON GEMONA DEL FRIULI AND TARCENTO CASE STUDIES
P. Malisan, S. Grimaz, F. Barazza
Dipartimento Georisorse e Territorio, Università degli Studi di Udine
In Friuli Venezia Giulia (North-Eastern Italy) the ASSESS project (financed by the Regional
Civil Protection and developed by the Istituto Nazionale di Oceanografia e Geofisica Sperimentale,
the University of Trieste and the University of Udine) studies the seismic scenarios of strategically
school buildings. Due to the large amount of buildings that should be investigated (1022) the work
develops in several steps with different widening.
The purpose of the first step is to set a ranking among all the buildings (prioritization), in order
to define the subsequent ranking analyses. The ranking is based on values of risk evaluated simply
by computing the potential damage of a building, and sorting the results first in descending order of
potential damage, and secondly by considering the number of students presents in each building.
The data used are obtained from the “Anagrafe degli edifici scolastici” database (from now on,
called “Anagrafe” database, i.e. a register of school buildings), available for almost all the school
buildings of the Region. In this paper the authors present the results on potential damage obtained
using the macroseismic method proposed by Lagomarsino and Giovinazzi (2006). This method has
been adapted to the available data (i.e. the ones of the “Anagrafe” database). Shortly, the Lagormarsino
and Giovinazzi method consists in assigning to each building a vulnerability base score
depending from its typology; afterwards some modifiers are computed by looking at all the features
(available into the database) able to affect the seismic behavior. The method and the ranges derive
from the EMS-98 macroseismic scale (Grünthal, 1998), and are defined starting from statistical
considerations. For further information on the application and the results of the method, see Malisan
et al. (2009).
In this work the authors will highlight the importance of the evaluation of the action (seismic
input) in the final definition of the potential damage. The function that defines the potential damage
is defined in Lagomarsino and Giovinazzi (2006) article, and characterizes the potential
(expected) damage through the EMS-98 damage grades.
First of all, the vulnerability index for each school building has been computed, as described
above. The evaluation of the potential damage has been done by using the values of peak ground
acceleration both starting from the values of the seismic zones both from the “punctual” values of
PGA defined by Gruppo di Lavoro (2004) for the
whole Nation.
In the Friuli Venezia Giulia Region exists also a
map of the NEHRP zones (ASSESS, 2009). The data
of this map have been used to improve the evaluation
of the potential damage in the first level of the project.
The results are plot in Fig. 1, where in most of the
cases the value of potential damage calculated from the
value of PGA of the zone is higher than the one calculated
with the punctual PGA, but there are some cases
particularly significant in which the value of a g punctual
is higher than the other (i.e. the ones in zone 4 and
some buildings in the 3 rd zone). In the figure, the dots
Fig. 1 – Comparison among potential damage calculated from
the value of PGA of the zone and the one calculated with the
punctual PGA.
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