Numerical Investigation Of Detecting Interfacial Debonding In FRP Strengthened Steel Beams Using Rayleigh Wave

With the rapid development of large-span steel structure in recent years, thenumber of the large-span steel structure strengthened with FRP increases because ofinsufficient bearing capacity of the original structure, detecting the interfacialdebonding damage between FRP and steel structure for the maintenance of steelstructures strengthened with FRP is of great significance to ensure the safety andreliability of large steel structures. This paper studies how to use the the variation of thedispersion curves of Rayleigh wave group velocity to identify interfacial debondingdamage between FRP and steel structure.Rayleigh wave dispersion curves of velocity reflects the dispersion characteristicsof Rayleigh waves which will change when Rayleigh waves traveling in the surfacelayer of steel beams reinforced with FRP. In order to study how to use the dispersioncharacteristics of Rayleigh wave to identify damage, the paper established a finiteelement model of FRP and steel, studied the generation and propagation of the Rayleighwaves at the surface of FRP reinforced beams, identified Rayleigh waves from the wavefield, determined the various influencing parameters for the numerical simulation of theRayleigh wave field, simulated the interfacial debonding damage of the FRP reinforcedsteel beams, introduced the cross-correlation analysis method to solve the Rayleighwave group velocity dispersion curves Through the contrast the value of Rayleigh wavevelocity from simulation of finite element method with theoretical Rayleigh wavevelocity, the accuracy of the simulation is verified.The two-dimensional finite element model of steel beams reinforced with FRPcross the whole span is established, the effect of interfacial debonding damage andcrack in the beams to the propagation of Rayleigh waves is analyzed, the Rayleigh wavegroup velocity dispersion curves is solved, the relationship between the interfacialdebonding damage and the variation of Rayleigh wave velocity dispersion curves isfound. The amplitude of Rayleigh wave group velocity between the same detectionpoints in the frequency band reduced When interfacial debonding damage occurs, that isthe Rayleigh wave group velocity dispersion curves move downward in this band, andthe larger the length of interfacial debonding damage,the greater the amount of offset ofthe curves; the difference of the dispersion curves of Rayleigh wave group velocity ofthe same structure between the different detection points has a relationship with theinterfacial debonding damage. The Euclidean distance and the angular differencedistance is used to measure the difference between the dispersion curves, and when theangular difference distance of of the two curves is greater than0.9, the data is effectiveand the corresponding Euclidean distance can be used as indicators of damage detectionof interfacial debonding damage. Accordingly, this paper proposes detection method of interfacial debonding damage based on Rayleigh wave velocity dispersion curves.This paper establishs the normalized average Euclidean distance as the detectionindex of the interfacial debonding. A three-dimensional finite element model is createdto accomplish the simulation of damage detection based numerical model. The threefactors of the minimum detectable size are analyzed, and the same to comparativeadvantages of the detection methods.