Vertical irregularity is one of the major causes of the failure of the structure. Buildings with vertical irregularities are widespread and unavoidable during rapid urbanization in almost all countries. The safety of such buildings is most important against vulnerability in an earthquake. The vulnerability of structures is assessed using the damage indices of fragility curves. These fragility curves were developed using the HAZUS method, which is used to find the probability of structural damage due to various seismic excitations. This fragility curve determines the probability of none, slight, moderate, extensive, and complete damage to the structures. These fragility curves help to identify the vulnerability percentage of vertical irregularities compared to the regular building. Research also reveals that the vulnerability of the irregular building is similar to the vulnerability identified in terms of roof displacement, base shear, and drift ratio using the THA method. This research also helps to determine the possibility of damage being observed for the structures carrying stiffness and mass irregularities. It is found that stiffness irregularity is more vulnerable than mass irregularity. An increment in collapse probability is observed in stiffness and mass irregularity on the ground floor. Considerable slight to moderate damage possibility is observed in mass irregularity models, and collapse possibility is observed high in stiffness irregularity models. Also, it is observed that the SSI affects adversely on the structures.
