Nonlinear Dynamic Response of a RC Frame for Different Structural Conditions Including the Effect of FE Model Updating

After destructive events such as earthquakes, attempts have generally been made to repair and strengthen structures using such methods as filling cracks by injection, wrapping structural elements with fiber-reinforced polymer (FRP). These applications can allow the recovery of lost structural performance. In this paper, the aim was to investigate the structural performance of an RC frame under different conditions-undamaged, damaged, repaired, and strengthened-by comparing results of nonlinear dynamic analyses. In addition, finite-element (FE) model updating effects were investigated in the case of the undamaged condition. To this end, an RC frame model was first constructed in the laboratory, and then, the model was damaged by lateral forces, repaired with epoxy injection, and lastly strengthened by wrapping with FRP. To obtain the dynamic characteristics of the RC frame under the different conditions, ambient vibration tests were performed for each condition. The FE model of the RC frame, obtained through global and local model updating using the ambient vibration test results, was modeled to achieve the nonlinear dynamic analyses. The results of the analyses were presented in the form of maximum displacements, principal stresses, and strains with contours diagrams. The maximum displacement increased significantly (133%) with the degree of damage, sharply decreased with the repaired (32%), and strengthened (36%) applications. The maximum and minimum principal stresses decreased by 24% and 35%, respectively, with the damaged condition. In addition, maximum differences between the undamaged and strengthened conditions were calculated as 17% for the maximum principal stress and 38% for the minimum principal stress. Findings indicated that the epoxy injection with FRP wrapping eliminates effect of the damage and recovers the model's performance to its initial state. In addition, it is demonstrated in this paper that the updating procedure considerably changes the dynamic analysis results.