Seismic fragility of buildings damaged by past earthquakes

Fragility analysis plays an important role in seismic risk assessment. Current fragility models of buildings are mostly focusing on the as-built condition of the structure while ignoring the possibility of having multiple earthquakes during the service life of the structure. However, considering the relatively high probability of multiple earthquakes (including main shock-aftershock sequence) and the reality that some buildings might not satisfy the previous seismic design requirement anymore, it is important to include the effect of past earthquakes in fragility estimation of buildings. In this research, the degradation of important pushover properties of structural columns is applied to represent the damage caused by a past earthquake and new deformation capacity will also be obtained using static pushover analysis. New fragility estimates are conducted to give the fragility of buildings already damaged by earthquakes. By using this mythology, the effect of past earthquakes are included and the new fragility curves can give a more accurate fragility estimate for low rise reinforced concrete building during its service life. This method can be helpful to the decision making process after earthquake hits