Research On Interface Damage Detection Of Steel Plate-Concrete Composite Slabs Based On Lamb Waves

Steel plate-concrete composite slabs are currently being widely used in a variety of building structures and large bridge structures.Due to various reasons,the interface between the steel plate and concrete slab is often prone to cracks,voids and emptiness,which affect the bond strength of the interface,so as to weaken the composite effect between the steel plate and the concrete slab.In severe cases,it will cause large strips of steel and concrete slabs,losing composite effects,and destructing composite structures,seriously affecting people's lives and property safety.Therefore,the internal interface damage assessment of the steel-concrete composite slabs structure during service can be found early and grasp the early damage state of the structure,so that timely maintenance and reinforcement measures can be taken to ensure that the structure operates safely and reliably under low maintenance costs.Therefore,the non-destructive testing(NDT)of steel-concrete composite slabs has important practical significance.However,the traditional NDT methods(radiation detection method,magnetic particle detection method,etc.)are expensive,low in sensitivity,and require high requirements on the structure to be tested,etc.Active detection technology based on piezoceramic ultrasonic guided wave(UGW)has become a new tool for NDT of large-scale structures such as steel-concrete composite bridge decks due to its advantages of active sensing,low cost,fast response,and simple implementation.In this paper,the interface destructive damage in the steel-concrete composite slabs was studied by using the theoretical derivation and experimental verification.This paper aims to proposing an interface damage recognition algorithm for steel plate-concrete composite slabs based on piezoceramic(Lead Zirconite Titannite,PZT)UGWS.Firstly,the propagation mechanism of Lamb waves in medium is briefly introduced.The frequency dispersion equations of Lamb wave in double-layer and single-layer plates are given based on the comprehensive matrix method.The Matlab software is used to numerically solve the frequency dispersion equations of Lamb wave in the plate,and the group velocity and phase velocity dispersion curve of Lamb wave in steel plate and concrete slab are obtained.Secondly,the initial interface damage of the steel plate-concrete composite slabs is experimentally studied based on Lamb waves.A damage identification system is established by using a PZT transducer array.A set of experiments in healthy state detection unit at different center frequencies and a set of experiments in different state detection units at the same center frequency are performed,respectively.A method for identifying the interface damage of steel plate-concrete composite slabs based on signal energy value is proposed.Then,the failure process of the steel-concrete composite slabs specimen under monotonic loading is experimentally studied.Since the health state can be used as a prototype for comparison with the damage states,a damage index is defined by the sensing signal energy attenuation comparison between the healthy state and damaged one for the steel plate-concrete composite slabs under different loading levels,and the feasibility of the interface damage identification method in the steel plate-concrete composite slabs based on Lamb waves is verified.Finally,the main conclusions are summarized,and some futture challenge issues needed further researched are proposed.