Earthquake vulnerability assessment of the buildings for densely distributed residential areas in Dhaka city

Abstract

Earthquake is one of the most extreme hazards that can neither be predicted nor be controlled out of all the natural hazard reported. It has a major ability to degrade an urban socio-economics structure with geological components. For this reason, the main objective of this thesis is to assess the seismic vulnerability including ground factors, building's physical conditions and socioeconomic aspects, so that earthquake-prone buildings can be identified in terms of minimal loss of life and damage. Most of the present earthquake-vulnerability evaluation processes focus on structural loss evaluation without focusing on socio-economic features. In this research, a combined strategy for vulnerability evaluation has been developed for earthquake-prone areas in Dhaka District of Bangladesh. In order to fulfil the objective, seismic vulnerability of Reinforced Cement Concrete (RCC) structures has been evaluated in the study area using the Turkish method as proposed by the Turkey government and Japan International Cooperation Agency (JICA). 240 different reinforced concrete residential buildings within three selected wards of Dhaka city were assessed using a developed checklist. The physical vulnerability was estimated by walk-down procedure (site visit) of Turkish method to calculate the E.R.S (Earthquake Risk Score) value of each building, while the economic and social components with various indicators were determined through statistical studies which is a simple coding system to collect the data provided in the questionnaires. After that, calculated the proportion of respondents answering for each category of each question by SPSS software. This scoring was then calculated using a simple additive weighting (SAW) method to determine the most fragile area within the selected territory based on the social and economic status. The results revealed that only 10 out of 240 structures were considered as high risk, whereas 84 structures were of moderate risk. So, more methodical evaluations were suggested for such structures before confirming the building have an earthquake risk. On the other hand, ward no. 51 was the most vulnerable area against earthquakes according to social vulnerability, whereas ward no. 46 was more susceptible to earthquake due to economic vulnerability. However, this research has only been conducted in three Dhaka city zones. Similar work can be carried out in other parts of the town that belongs to vulnerable areas of the earthquake. Also, the assessment result of vulnerability features to develop the vulnerability index would therefore provide an excellent basis for the theoretical research.