The Research On Truss Structure Damage Indentification

Civil engineering structures inevitably arise injury in the long-run process, In order to ensure the structural safety and durability, Judgment of the state have become the focus of the research in the academic and engineering world at home and abroad through certain means and methods of detection of structural damage.The dynamic characteristics of structures are in closed relationship with the structural parameters, and structural damage will cause the dynamic characteristics shifts correspondently. Based on the vibration damage identification method is based on the structural dynamic test, Through the dynamic test measured data analysis, the emergence of injury, location and extent can be judged.In this paper, with the specific object of research (truss structure),the damage sensitive dynamic parameters of the structural diagnosis have been studied detailedly. The main contents include:Describing the status of research at home and abroad, this paper discusses and studies the diagnosis of structural damage theories and methods based on modal parameters.APDL programming of ANSYS development language is designed, the modal automatic solution process of structure in the different injury conditions have been realized, and define multi-dimensional array parameters of APDL, complete calculated modal parameters storage in the different injury conditions, ultimately extract the modal information into the data file of the result.Concretely discuss the technology of damage identification based on the frequency, vibration mode, stiffness, flexibility. using the example of the practical truss model, this paper compares damage identification results of the normalized rate of frequenc, modal curvature, flexibility curvature.According to the strain characteristics of pole element of the truss structure, this paper propose the injury indicator that is ration of the changes of strain modal and validate that the ration of the changes of strain modal of the only first mode can accurately identifiy the structural damage through the numetical simulation; further analyze the influence of different degree damage to the ration of the changes of strain modal and compare with sensitivity of ration of the changes of strain modal of the different pole to damage.Further this paper proposes the ration of the change of modal strain energy as a factor of structural damage based on the strain modal, using the model of space gridstructure to test it, and get the better identifiable results than the ration of the changes of strain modal.and use the parameter as the input feature parameter of BP artificial neural network to identify the structural damage, and obtain the ideal results.Making the actual steel truss model, the dynamic signal gathering analyzer is used to the dynamic performance determination of the model. The model structure is carried on the sweep frequency shock excitation by the simulation experiment, the structural strain model is obtained by sympathetic vibration, The validity and feasibility of this damage index which is the ration of the changes of strain modal has been confirmed.From the above analysis, we educe that the rate of change of strain modal and modal strain energe can preferably assess the state of the structural damage. It shows that the parameters is effective and practical, so have some realistic significance and value.