Damage identification of a reinforced concrete frame at increasing damage levels by sensitivity-based finite element model updating

Abstract

This paper presents the damage identification results of an experimentally tested half-scale reinforced concrete portal frame using the sensitivity-based finite element model updating method. Progressively increasing story drifts are imposed on the frame by a displacement- controlled hydraulic actuator using single-cycle quasi-static lateral loading along the frame’s in-plane direction. System identification is performed using an output-only system identification method at different damage levels. Dynamic tests used for system identification are conducted using an electro-dynamic shaker. The objective function used for damage identification is constructed by the difference between the experimentally identified and numerically predicted modal parameters. Damage identification is performed in two steps: (1) The initial numerical model is updated to obtain a reference model using the modal parameters corresponding to the undamaged frame and (2) the reference model is updated for increasing damage levels using the modal parameters corresponding to these levels to identify existence of damage, its location and extent. The condition of the optimization problem is improved by reducing the number of design parameters. Damage identification results are presented in terms of stiffness reduction factors assigned to the column(s) bottom and beam ends and they correlate very well with the visual damage inspections done during the quasi-static tests.