Abstract:
[n recent past, severe earthquakes have caused substantial physical losses and
casualties in this sub-continent. Parts of Bangladesh are in high risk of facing
devastating earthquakes. Since a majority of the population is living in earthquakeprone
areas, it is probable that such terrible events may take place again in the near
future. Moreover, it is not easy to cope with the substantial direct and indirect
economical losses after each devastating earthquake for a developing country like
Bangladesh. Because in this country many reinforced concrete buildings are not
designed according to the current building code, seismic behavior is not taken into
consideration during selection of the structural system and in most cases supervision
in the construction phase is not adequate which in turn induces deficiencies like poor
concrete quality, inadequate detailing of reinforcement etc. It is, therefore, vital to
quantifY the earthquake risk and to develop strategies for disaster mitigation. In order
to achieve this goal, an extensive and inter-disciplinary study is required.
This study describes the methods by which it is possible to determine the vulnerability
of existing engineering structures and building stock. The tool thai is employed to
assess the seismic performance of reinforced concrete frame structures is the fragility
curve. By definition, fragility curves provide estimates for the probabilities of
reaching or exceeding various limit states at given levels of ground shaking intensity
for an individual structure or population of structures. A limit state, which is in the
same terms as the response, usually represents a damage condition or a limitation of
usage. The primary focus of this research is to present a proper methodology that can
be followed to construct fragility curves for RCC frame structures in Bangladesh and
to generate fragility curves for common type of RCC frame structures using this
methodology. The findings of the study i.e. the suggested guideline can be used to
develop fragility curves for any structures in Bangladesh analytically. Following these
guidelines fragility curves are constructed for three story and six story frame
structures of Dhaka city which can be used to assess the seismic vulnerability of these
types of RCC structures in Dhaka. From the fragility curves of 3-story RCC structures
it is found that if an earthquake of DAD g occurs then 90% of this type of structures
V[
would suffer light damages. In case of 6-story RCC building the probability of
exceedance of severe damage is 100% for the same magnitude of earthquake.
Similarly the seismic vulnerability of these structures for different earthquake can be
interpreted from the developed fragility curves. A rough estimation of damages in
terms of cost is also calculated from the fragility curves for these structures for
different earthquakes. Utilizing the suggested guidelines fragility curves for any RCC
frame structures in any region of Bangladesh can be constructed and corresponding
regional loss estimation studies in different earthquake prone zones of Bangladesh can
be conducted.
