Research On Structure Damage Identification Based On Modal Parameters

Damage will cause the relevant characteristics of the structure such as stiffness and damping change,which can also cause the frequency of the structure,modes and other modal parameters change.In most cases,the modal flexibility is more sensitive to local damage than the natural frequency or mode shape,and it can be applied to determine the location of damage.On the basis of the modal flexibility to raise the relative change rate of flexibility curvature matrix method and the change rate of flexibility curvature method,two new damage identification index are obtained.The specific work is as follows:(1)Introduces the background and significance of selected topic,the research situation and research methods of damage identification are summarized.(2)The theory of modal analysis is introduced,several common damage identification methods are summarized(3)With the beam structure as the object,the model of single and multiple damage structures is studied.By using the new index?H? and ?N? to determine the damage position,while providing the recognition results of?AFCR? and ?MFCD?.The results show that: the damage location of structures can be effectively identified by ?H? and ?N? in one place or multiple places of damage cases,which is better than ?AFCR? and ?MFCD? indicators.(4)To further verify the damage identification effectiveness of the new indicators ?H? and ?N?.A clamped beam,a three span continuous beam,a cross layer framework and Frame structure with different elastic modulus model are simulated above structure of single and multiple damage.Still use ?H?,?N? to discriminate structural damage location,and compare with the recognition result of?AFCR?,?MFCD?.The analysis results show that the recognition effect of ?H?,?N? is still better than that of ?AFCR? and ?MFCD?,and has the advantages of small amount of calculation and easy to realize.(5)Flexibility quadratic extension of the concept is proposed in this paper.Combined with the flexibility quadratic extension of the concept.A simplysupported beam,a clamped beam,a three span continuous beam,a cross layer framework and a Frame structure with different elastic modulus as the research object,take only the first structure 1 modal parameters,and use ?H? and ?N? to determine the location of structural damage.Compared with the damage identification results that use the first 3 modal parameters,the extended recognition results can also achieve the desired effect,and greatly reduce the computational workload,and reduce the dependence on the higher order modes.(6)With the simply supported beam model as the object,combined with flexibility for the second time extended concept,10% and 15% of artificial noise is introduced.Use the new indicators?H? and ?N? to identify the single and multiple damage location.The results show that:after the introduction of 10% and 15% artificial noise,the new indicators ?H? and ?N? still better identify damage location.It show that after the flexibility in a second expansion,the new indicators ?H? and ?N? has a certain anti noise ability.(7)The new index ?N?compares to ?H?,the calculation amount is small and easy to calculate.This paper establishes a simple model of the elastic sheet.Combined with the concept of flexibility secondary expansion,use ?N? that a new index of smaller amount of calculation to identify edge plate structure of horn,central damage location.The identification results show that: the new index ?N? can better determine the edge angle,central plate structure damage position,and achieve the desired effect.