Study On Structural Modeling And Damage Identification Methods Of Cracked Beam

Local damages that are potentially dangerous to the whole structure will occur as a result of kinds of exterior loadings and other paroxysmal factors when the structures are under complicated working circumstances.Further more,the damages will gradually increase due to the stress concentration,the fatigue and so on,and finally result in the decrease of the load-bearing ability,even the collapse of the whole structure.The earlier the local damages are located,the earlier the whole structure can be restored.It is so important to locate the cracks and evaluate their degrees in a structure for the restoration of structure and the safeguard of people's lives and properties.The work analyses current methods and problems of structural modeling with damages in depth,and put over a new structural modeling method of cracked beam under static loads, then the closed form solution of the deflection is obtained.Firstly,in the framework of the consistent beam theory,the Diracδfunction was adopted to simulate the local flexibility caused by the crack.The differential governing equation of the cracked Timoshenko beam was built by using of the generalized functions,and then the deflection was deduced in a closed form.Secondly,according to the linearly elastic fracture mechanics,the model parameters of the cracked Timoshenko beam were derived from the relationship between the crack depth and the sudden changes in the deflection and slope.Finally,the effects of crack depth on the deflection,slop and curvature were analyzed,and the damage sensitivity of the structural responses was studied.Meanwhile,the numerical simulation was carried out by introducing the singular crack element into the FEM analysis.The numerical simulations were compared with the analysis solution to validate the proposed approach for cracked Timoshenko beam.The results demonstrate that the proposed model and solutions are accurate and efficient.Though structural static test needs higher test conditions in damage identification,static test datas have higher accuracy and stability.Besides,the deflection can reflect changes in flexibility,it is a great totalistic eigenvalue.So the result of structural damage identification based on static test is precise.The work trys to seek an intelligentized method for model urdating.Differential evolution algorithm is used to identify damage Location and damage depth of cracked beam in the meanwhile.Firstly,the work introduces the basic principle of differential evolution algorithm and its application in damage identification.Secondly,the work codes the program of differential evolution algorithm applying to damage identification of cracked beam.As an example of a simply supported beam,the program can identify cracked location and cracked depth under different conditions in the meanwhile.The results show that the analytical model of cracked beam and the damage identification method have good stability and robustness.