Global Seismic Damage Model of RC Structures Based on Structural Modal Properties

A macroscopic global seismic damage model is proposed for reinforced concrete structures by considering the dynamic modal contributions. Modal damage is defined using the concepts of dynamic modal stiffness and modal mass. Based on the kinetic energy inequality for damaged systems, a normalization method is chosen for the proposed modal mass contribution factor, which reflects the fluctuation of modal damage caused by a change in modal shape. Assuming an in-series independence between the modal damages, a customized combination rule is suggested. Global damage curves generated from the proposed model (PM) tend to have a segmented evolution, composed of a zero-damage segment, an acceleration segment, a constant velocity segment, a deceleration segment, and a converged segment, following the general damage evolution rule. The results from a case study indicate that the PM can explain the dynamic transition in the modal damage and exhibits a distinct convergence with the increasing peak ground acceleration level and number of modes included. The proposed damage model is proven to have a good correlation with the results from the incremental dynamic analysis at the collapse-critical point, indicating a potential application as a promising collapse criterion. The results have also confirmed the effectiveness of the five-segment damage evolution curve proposed previously.