Research On Damage Identification Of Concrete Structures Based On Sldv Vibration Measurement

During the service of concrete structures,with the extension of service life and the influence of external environmental factors,the structures will be damaged to some extent,such as concrete cracking.If damage status of the structures is not timely detected and damage is allowed to develop,it will pose a certain threat to people's life and property safety.In order to ensure the safe use of structures,it is necessary to find an accurate damage identification method to determine damage status(e.g.,damage location and damage degree)of structures.Based on damage detection of concrete beams and slabs in service and using the theory of modal analysis,this thesis investigates damage location of concrete slabs and damage degree of concrete beams by combining numerical finite element simulation with experimental testing.The main research contents are as follows.(1)The development status of damage identification methods for concrete structures is introduced,and the advantages and disadvantages of various damage identification methods are discussed.The dynamic characteristics of a four-sided fixed plate and a cantilever beam are described.The basic principles of curvature transform,curvature difference and wavelet transform for structural damage identification are also expounded.(2)The finite element simulation by software ABAQUS is used to establish the finite element model of the concrete slab under different damage conditions,and the corresponding first several modal parameters are obtained.The damage of the structure is identified from four aspects,i.e.,displacement mode,curvature mode,curvature mode difference,and wavelet transform.The results show that among the four data analysis methods,the curvature mode difference performs the best in damage identification,followed by the wavelet transform and then the curvature mode.Damage can be hardly identified by the displacement mode.(3)The finite element simulation by software ABAQUS is also used to establish the finite element model of cantilever concrete beams with fixed support at one end with different damage degrees,and the corresponding first several modal parameters are obtained.From smooth gapping,curvature change,wavelet transform,the three different kinds of structural damage degrees are analyzed,and the results show that three methods of data analysis can effectively and quantitatively analyze the damage degree of concrete cantilever beams.The three considered analysis methods,with correspondence to the damage degree of fitting formula are capable of detecting early damage of the beam.(4)The Scanning Laser Doppler Vibrometer(SLDV)—shaker modal test system is used to conduct modal test on the healthy and two different damage degrees of concrete cantilever beams,and the corresponding modal parameters of the first several orders are measured.The damage degree is calculated by using the damage degree fitting formula of smooth gappingand curvature variation,and the specific size of the damage degree is obtained.