Assessment of Change in Vibration Responses for Reinforced Concrete Beams Strengthened with FRP Sheets Under Various Loadings

Structural health monitoring (SHM) is a crucial field in evaluating the health status of structures, especially for complex structures commonly used in modern construction. The durability of these structures is affected by several factors, such as material degradation, corrosion, and overloading, which result in damage over their lifetime. In this study, the changes in natural frequencies and mode shapes for reinforced concrete beams strengthened with Fiber Reinforced Polymer (FRP) sheets are assessed. First, a reinforced concrete beam strengthened with FRP sheets is simulated by the finite element method to analyze the beam’s behavior and get vibration responses. The reliability of the simulation is verified by comparing the load-displacement relationship between numerical and experimental results. Next, the frequency change-based damage detection method and the modal assurance criterion are employed to alarm the damages (cracking and debonding) in the beam. The damage’s occurrence in the beam is analyzed and assessed according to each load level corresponding to the actual working state of the target beam. The results show that the frequency change-based damage detection method and the modal assurance criterion have high accuracy in existing damages.