The
evaluation of seismic safety of existing buildings is one of the matters
that are being investigated by the researchers especially in countries
of high seismic risk. In recent years, efforts have begun to establish
methods to evaluate the seismic safety of buildings to determine risks
and to suggest strengthening of existing buildings.
The
observations made after the recent earthquakes demonstrated that, the
buildings become less vulnerable to earthquakes with the developments in
the earthquake engineering, the changes in design methods, the
availability of new materials and the developments in the construction
technologies. Damage statistics from recent earthquakes indicated that
only a fraction of the existing buildings suffered severe earthquake
damage while the remaining larger fraction did not create any
life-safety hazard. Therefore, in the seismic vulnerability assessment,
the main thrust should be directed towards the identification of the
buildings, which create life-safety threats. Rather simple procedures
are desirable to screen-out the majority of safe buildings. In cases
where some deficiencies were detected, more detailed and sophisticated
methods may be utilized.
Serious and systematical
research in the area of seismic vulnerability assessment of buildings
has been realized only in the last two decades. The methodologies found
in the literature are not applicable world wide due to the differences
in the quality of the materials of construction, in the local
construction practices, in the locally common architectural patterns
etc. Therefore, rapid and yet reliable rehabilitation methodologies for
Turkey must be developed.
A reliable seismic
evaluation method, which reflects the actual performance of the
structure consist of three phases. These are;
(a) a rapid screening based on simple
tools,
(b) a more refined evaluation
process and
(c) the final evaluation stage.
The first
screening is an essential part of the study. It is in this level where
the gigantic size of the existing building stock is handled and those
found inadequate are identified as life-safety hazard. This step
requires identification of structural attributes that can be deemed as
hazardous from the point of view of seismic safety. The cities affected
by the 17 August 1999 Marmara earthquake and 12 November 1999 Düzce
Earthquake provide an open laboratory for this purpose. In this study,
the plan is to include basic building data (damage level, number of
stories, framing type, footprint, critical member sizes, location
coordinates) for as many building as possible. The correlation between
the damage distribution and the site conditions will also be studied.
Availability of these data, focused on specific locations of heavy,
medium and/or light damage, will provide a rich and useful database to
test and develop methods for assessment of earthquake vulnerability in
Turkey. Once the database is constructed, a rapid first-level screening
index will be established to screen-out the safe buildings. This index
will preferably be based on strength considerations and the expected
earthquake intensity at the site.
Later
somewhat more refined and yet simple indexes will be developed to
perform second and third level screening. While doing this, critical use
of the established database will be made in conjunction with the current
codes, i.e. the Turkish code of reinforced concrete practice
(TS500-2000) and Turkish seismic
code.
