Research On Truss Defects Identification Used Vibration Testing Data

Because of natural, man-made causes, engineering structures will occur cracks, loose and fall off damage. When it developed to a certain extent without being detected or treated, there may lead to catastrophic accidents, serious threat to lives and property of people. In order to timely detect the location of injury and extent, the domestic scholars have done a lot research for this, obtained a series of damage identification results, in which the most study is on the use of changing the modal parameters to diagnose structural damages.This article discusses the various damage identification methods based on the theory of modal analysis and their scope of use, advantages and disadvantages of features. Studied in detail the principle of damage identification base on the modal frequency method, mode shapes method, curvature mode method, strain mode method, flexibility and flexibility curvature difference method, modal strain energy principle.By the principles of compliance method, there are detailed analysis of the damage identification of a Structure in space. Because the spatial structure degree of freedom are many and more complicated modes, the space is transformed into a number of plane problems for sake of simplify the analysis and solve the flexibility slope, flexibility curvature by difference method. That finite element dynamic analysis get the structure the modal frequencies and mode shapes of the front steps. This calculated the structure of the flexibility by modal parameters and studied the structural damage cause the sensitivity of flexibility in all different directions; This has analyzed the mode regarding the flexibility influence.Flexibility and structure of natural frequency is inversely proportional.Thus the lower modes have the greatest impact on the flexibility. Flexibility can be a good estimate the damage useing the structure of the first modal, when using the structure of high model flexibility often can not be calculated accurately the location of structural damage; Also analyse structural damage to the flexibility curvature affect.The same frame structure made test analysis based on the finite element analysis. Using CRAS system measured modal parameters, then the measurement mode for the quality of normalization.Using flexibility curvature by the measured data calculateing analyse a single damage of element situations. This is not too sensitive in the small damage, for large damage can accurately determine the damage location. Another focuses on damage indentification methods based on the frequency change, finite element method calculated the frequency change by each element of the structure in different degree of injury. According to the calculated results established database, different frequency bands by the measured change in comparative data in the database to identify the damage location and relative degree of damage.There is still insufficient that predicted the extent of structural damage by compliance method, frequency method, and fail to determine the extent of structural life, therefore the actual application needs to do a lot of research.