SEISMIC VULNERABILITY ASSESSMENT OF SUBSTANDARD REINFORCED CONCRETE BUILDINGS. CASE STUDY: MARMARA REGION

Rapid urbanisation and population growth in developing countries have increased seismic risk regardless of the advances in our knowledge on the seismic behaviour of structures. The need to cover the demand for a low-cost building stock has led a large proportion of residential buildings to be constructed with substandard materials, insufficient designs and poor construction practices. These are the reasons that developing countries have exhibited considerably higher death rates compared to the developed world. Extensive losses and mortality rates observed during recent major earthquakes in developing countries highlight the high seismic vulnerability of existing substandard RC buildings.
This research aims to develop a vulnerability framework (for substandard RC buildings) which can produce advanced adaptive vulnerability curves. For this, an analytical modelling procedure was proposed and validated against field and large-scale tests data.
OpenSees is employed for modelling full-scale substandard RC columns and shake-table RC frames and the analytical model is verified against the experimental results, at both local and global level. An advanced probabilistic seismic vulnerability framework is developed using Matlab code linked with OpenSees.
General vulnerability curves are derived (using an improved CSM) for substandard RC columns as well as an existing 4-storey substandard RC building (case study for Marmara region). The general fragility curves are then disaggregated to derive adaptive fragility curves based on various considered parameters e.g. steel grade, concrete strength, transverse rebar spacing, axial load level. Upgraded fragility curves are obtained by considering external retrofitting with FRP sheets on the case study building. Finally, vulnerability curves are derived for the RC columns and the case study building, using an existing conversion matrix for the case study region.
The developed framework showed that the use of advanced adaptive vulnerability curves can improve the accuracy by up to 20% compared to general vulnerability curves. The study on the upgraded vulnerability analysis using 3 layers of CFRP (for the case study building), revealed that seismic vulnerability can be reduced up to 85% and 45% for slight and collapse damage limit states, respectively.