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Applying Earthquake Risk Analysis Methods to a Town in Hungary
L'application des méthodes d'analyse du risque sismique dans le cas d'une ville de Hongrie
Kegyes-Brassai O., Ray R.P.
Széchenyi István University, Gy
ő
r, Hungary
ABSTRACT: Determining the earthquake risk of buildings in a town or settlement has lately become a more prominent issue. The
process can provide important data for governments, authorities, disaster management and insurance companies to better understand
risks to many buildings and engineering systems rather than a single building. This paper addresses the rapid evaluation of a large
number of similar buildings in one area using a forecasting approach. Back-casting mainly considers the effect of previous
earthquakes by listing and categorizing the damaged buildings and casualties. Forecasting offers a method to evaluate the possible
damages in advance, however many uncertainties need to be taken into consideration. A fast and simple method should be developed
to avoid the time and expertise required from research-based approaches. The steps involve determination of the hazard, assessing
building stock, and computing vulnerability. The method for determination of vulnerability functions is a non-linear static analysis
using a bilinear approximation of the capacity curve, assuming first mode force distribution and mode shape thus linear strength
distribution. From the curve of the seismic demand and the shear capacity of the building, the vulnerability function of the building
can be obtained. These vulnerability functions should be derived for typical layouts; offering a family of curves allowing the experts
to decide the vulnerability category of a specific building on-site based on visual screening. With the given value of possible PGA
(peak ground acceleration), expected damages can then be estimated.
RÉSUMÉ : La détermination du risque sismique des zones et des villes en considérant leur parcs immobiliers existants est devenu
récemment un problème saillant. Ce processus peut fournir des données importantes pour les gouvernements, les autorités, la gestion
des catastrophes et les compagnies d’assurance afin de mieux comprendre les risques liées á un ensemble d’édifices plutôt qu’ á un
bâtiment unique. Ce document porte sur l’évaluation rapide d’un grand nombre de bâtiments similaires situés dans le même terrain en
utilisant une approche de prévision.
L’approche rétrospective évalue les effets des tremblements de terre antérieurs par l’énumération
et la catégorisation des bâtiments endommagés et celles des blessés. La prévision offre une méthode par laquelle les dommages
possibles sont évalués á l’avance bien que nombreuses incertitudes doivent être prises en considération.
Une méthode rapide et simple
devrait être élaborée au lieu des app
roches basées sur la recherche qui exigent beaucoup de temps et de l’expertise. Les étapes de ce
processus impliquent la détermination du risque sismique, l’évaluation du parc immobilier et un calcul de vulnérabilité. Les fonctions
de vulnérabilité sont dé
terminées á l’aide d'une méthode d’analyse statique
non linéaire
qui utilise l’approximation bilinéaire de la
courbe de capacité en supposant la distribution des forces selon le premier mode, ainsi la distribution uniforme de tensions. La
fonction de vulnérabilité peut être obtenu á partir de la courbe de la demande sismique et de la capacité de cisaillement du bâtiment.
Dans le cas des plans de bâtiment typiques, la détermination des fonctions de vulnérabilité nous offre de courbes et l’expert ne pourra
dé
cider que sur place á la base d’une inspection visuelle. Avec la valeur donnée de l’accélération maximale du sol possible, les
dommages attendus peuvent être estimés.
KEYWORDS: earthquake risk analysis, seismic vulnerability assessment
1 INTRODUCTION
Recent earthquakes with high number of casualties and
enormous devastation proved that the hazard of natural disasters
should not be neglected (even in 2012 there were major events
around the world). Preventive approaches have received greater
attention recently. Research in earthquake hazard mitigation has
focused on evaluating possible damage scenarios for different
magnitude events.
Two widely different approaches exist; one considers the
effect of previous earthquakes; listing the damaged buildings
and casualties. The other offers a method to evaluate possible
damage prior to an event. The latter method facilitates
prevention by gathering information about the state of the
building stock and the expected damages, so the authorities can
strengthen the most vulnerable buildings in order to mitigate
risk. The challenge with this method is that many uncertainties
must be taken into consideration.
In order to determine earthquake risk within towns, a fast
and simple method should be developed. Otherwise, it would be
very time-consuming and it would require too much expert
participation.
This concept should be considered also in Hungary. Here,
there are about 100-120 smaller earthquakes per year, which are
below the perceptible level, and 4-5 perceptible earthquakes per
year (Földrengés Információs Rendszer / Earthquake
Information System /
).
Earthquakes with a greater effect, causing structural
damages, can be expected every 15-20 years, and in 40-50 years
major earthquakes with high economic and social effects. With
this earthquake hazard level, Hungary ranks with the medium-
hazardous countries.
In Hungary, the goal should be the reduction of the expected
damage during an earthquake. This provides an economic
motivation for funding and executing seismic engineering
research.
