Research On Damage Identification Of Beam Structure Based On Dynamic Analysis

With the rapid development of infrastructure at home and abroad,construction engineering structure in service has been inevitably experiencing potential safety problems like aging and damage.Thus,the study on structural health monitoring is of great significance to ensure the safety and reliability of structure in its service,in which the structural damage identification is an important part.In this paper,effects of stiffness and mass variation on dynamic behavior of beam structure were investigated through theoretical analysis.Meanwhile,combined with numerical simulation and test,the structural damage pattern identification technology was deeply studied to rapidly and accurately identify structural damage,and the main research contents are as follows:Firstly,the influences of stiffness and mass variation on dynamic behavior of beam structure were discussed theoretically.The relative variation of natural frequency induced by structural stiffness damage is proportional to squared curvature modal value at the stiffness damage.Similarly,the relative variation of natural frequency induced by structural mass damage is proportional to squared displacement modal value at the mass damage.Secondly,according to the relation between relative variation of natural frequency and structural stiffness damage,the stiffness damage identification was established using damage identification technology.A single stiffness damage pattern vector was constructed by numerical calculation,and then the similarity between actual damage eigenvector and model vector was classified by the aid of a distance classifier,which obtained the pattern vector with the highest similarity to actual damage vectors.Additionally,the damage location and degree of structural stiffness were determined through numerical calculation of cantilever beam pattern identification,and the reliability of structural stiffness damage pattern identification was verified by carrying out damage tests on simple supported beams.Then the mass damage identification was also established according to the relation between relative variation of natural frequency and structural mass damage.A single mass damage pattern vector was constructed by numerical calculation,and then the pattern vector with the highest similarity to actual damage vectors was identified utilizing the distance classifier.Moreover,to simplify the pattern classification,a stepby-step damage pattern identification method(i.e.,identifying damage degree after determining the damage location)was adopted in this paper,which was verified effective by the numerical simulation and experiments on cantilever beams.Finally,two symmetrical damage locations of the symmetrical structures were identified by employing additional mass method.Since damage at any symmetrical position of a symmetrical structure would result in the variation in natural frequency,an additional mass was attached to one side of the symmetrical structure to break its symmetry,thus the unique identification of damage location could be achieved.At the end of this paper,the additional mass method was verified feasible by the numerical simulation and damage tests on simple supported beams.