Economic assessment of the seismic retrofitting of low-cost apartment buildings

When structural retrofitting of buildings is required due to seismic safety considerations, building owners or government officials are faced with a crucial decision whether to demolish and rebuild their buildings, or retrofit them. Simple decisions based on fixed proportions, such as demolish and rebuild if retrofit costs exceed 40% of the replacement cost, may be misleading. A financial analysis should be carried out considering all the revenues and costs of the building during its life time. A low-cost residential apartment building that has a construction cost of $140/m(2) is selected in this study to represent the vulnerable buildings in developing countries under seismic risk. Life-cycle cost analysis approach is employed to value the rebuild or retrofit alternatives to compare economically. Economic assessment has been carried out for various parameters. It has been found that the age of the building and the retrofit ratio are dominant parameters among the others. The critical retrofit ratio (percent of retrofit cost to initial construction cost) varied from 25% for 40 year old buildings to 67% for 10 year old buildings. It is suggested that economical decisons should not be made simply by comparing the retrofit costs to initial construction costs.