Controlled loop substructure identification for shear structures

In this paper, a substructure identification method is proposed to estimate the parameters of any story in a shear structure by using only limited floor accelerations. A two-story standard substructure is used to divide a shear structure into substructures; two identification problems are derived for the standard substructure, each of which identifies the parameters of one story given that the parameters of the other are known. By connecting these two identification problems in a loop manner, the loop substructure identification (LSI) method formulates a sequence of estimation problems to directly identify both story parameters of the standard substructure. If the structural masses are unknown, this loop identification method can still be applied to estimate mass-normalized structural parameters as well as the relative mass distribution of the structure. An error analysis is carried out for the two identification problems, the results of which are used to derive the condition for convergence of the LSI. The result shows that the loop identification sequence is conditionally converged and some structural responses play a vital role in determining the convergence. To ensure the convergence and the subsequent accurate estimates, the controlled LSI method is proposed, which utilizes specially designed structural control systems to temporarily change the structural dynamic closed-loop responses and achieve converged accurate identification results. A five-story shear building is used to verify the convergence condition and to demonstrate that the specially designed control systems can provide the converged estimation results.