Isolated Substructural Damage Identification Using Flexibility Perturbation

With the rapid development of science and technology,civil engineering structure tends to be larger and more complicated.The design life of civil structures is usually over several decades,even more than hundred years.However,under the structure's own defects and external loads,some structures often fail before its design service life.Therefore,it is necessary to identify the damage of the structure during the using period,and to discover the disease and prevent the weight.A great safety accident.The object of the traditional damage identification method is the whole structure.It is necessary to install a large number of sensing devices to obtain the static and dynamic response of the structure,so as to realize the damage identification of the whole structure,which not only reduces the recognition efficiency,but also has a poor economy,and does not use the promotion and application of damage identification.However,for most large structures,early damage often occurs in key parts or components,such as damage identification for these key parts or components,which can greatly reduce the cost of damage identification.Therefore,by introducing the constraint substructure based on local mode and the theory of damage identification of flexibility perturbation method,a method of damage identification for constrained substructure based on flexibility perturbation method is proposed,and the applicability of the method is verified by a simple beam,a steel truss numerical model and an experimental frame structure.The research contents and results of this paper are as follows:(1)A virtual constraint support is added to the junction of the substructure and the whole structure,and the local modal information of the structure is obtained by a sensor set at the confining support and in the substructure,thus the flexibility matrix of the substructure is extracted based on the mechanics principle,and the boundary is self dependent by the boundary of the constraint substructure,even at the boundary freedom.The displacement is 0,and the separation between the substructure and the whole structure is realized.(2)The eigenvalues of the substructure flexibility are decomposed,and the eigenvalues after decomposition are taken as the characteristic indexes of damage identification.A method of flexibility disturbance damage identification is proposed.The numerical example shows that the proposed method can accurately locate the damage position under the three damage conditions,and the identification error of the damage degree is not more than 5%,and has high damage location ability and recognition accuracy.Without iterative computation,it has high convergence efficiency and good practicability.(3)The three layer and two span steel frame structure was built in the laboratory.The single and third layers of the frame structure were selected as substructures respectively,and the damage was simulated by cutting rod.The calculation results of the substructure damage identification method show that when single rod is used as a substructure,the recognition error of three different damage degrees is less than 6%.When a layer is used as a substructure,the identification error of three different damage degrees is less than 10%.This indicates that this method can meet the actual engineering needs,and provides a theoretical reference for future popularization and application.