Subspace based identification of structural parameters of the base isolation level

One of the common methods in controlling the seismic response of structures is the use of seismic isolators. Isolators reduce the base shear as well as the relative displacement of the floors by increasing the period of the structure. Typically, extreme deformation of the isolator level occurs due to severe environmental factors, which can lead to damage to the isolators; As a result, there is a possibility of permanent deformation in the isolator and also the collision of the structure with adjacent buildings. Therefore, to prevent damage to buildings equipped with base isolations due to severe ground motions, it is important to identify damage at the isolators. In this study, assuming the linear behavior of the main structure, a proposed subspace-based method for identifying the stiffness of the base isolation with a limited number of sensors is presented. For this purpose, using the compression technique, the structure equipped with a separator with a large number of degree of freedom (DOF) is transformed into a two DOF structure; So that the stiffness associated with the first DOF in the reduced system corresponds to the stiffness of the Isolator level in the original structure. Then, using the identified Markov parameters of the system, the reduced structural stiffness is identified. Numerical examples are used to evaluate and compare the performance of the proposed method. The results show that even in the presence of noises in the measured responses, the proposed method detects the amount of damage at the isolator level with acceptable accuracy.