Research On Damage Identification Method Of Steel Structures Using Hybrid Method

Structural damage identification is the core part of structural health monitoring,which is of great significance to the state assessment and maintenance of civil engineering structures.In traditional damage location methods,averaging is used to deal with multilevel damage indicators.Although it helps reduce errors,it also weakens the difference between different modes.Based on the element relative modal strain energy method,this paper tries to take different modes for damage location of different elements,and combines the sensor placement method and model updating method to propose a method for steel structure damage identification based on the hybrid method.The main contents and results are listed as follows:（1）Based on the energy coefficient-effective independence method,an improved effective independence method based on relative modal strain energy is proposed.The relative modal strain energy is used to replace the modal strain energy to modify the effective independent vector,which can reduce the interference of the difference in modal strain energy of different modes.The results of numerical examples show that the improved method can obtain a more reasonable sensor placement plan than the energy coefficient-effective independent method.（2）Aiming at the “nodal effect” problem that the damage index of the element with small modal strain energy is not prominent when the element relative modal strain energy is applied,the element relative modal strain energy method considering the nodal effect is proposed.Elements with different proportions of modal strain energy adopt different modes,and a verification link is introduced to reduce contingency.The numerical results show that the proposed method can reduce the "nodal effect" and has better locating ability than the traditional element relative modal strain energy method.（3）The model updating method based on sensitivity analysis is used for the quantitative analysis of damage degree,and considering that only a few elements or substructures are damaged when the actual structure is damaged,a sparsity constraint is introduced in the sensitivity analysis to optimize the structure of the solution.Aiming at the difficulty of inversion caused by too many updating parameters during sensitivity analysis,the element sensitivity analysis is used to improve it to reduce the number of updating parameters.Numerical example results show that the sparsity constraint and the element sensitivity analysis can improve the accuracy of damage identification.（4）Combining the locating ability of the relative modal strain energy method considering the nodal effect and the quantitative analysis ability of the sensitivity analysis method considering the sparsity constraint,a steel structure damage identification process based on the hybrid method is proposed.First,the sensor placement is determined by the improved effective independence method.After obtaining the modal parameters of the undamaged structures and damaged structures,the set of suspected damage elements are determined by the relative modal strain energy method considering the nodal effect.Finally,the set is substituted into the sensitivity analysis method considering the sparsity constraint to iteratively solve the damage coefficients.Numerical simulations are carried out on the ASCE Benchmark model to verify the effectiveness of the hybrid method in this paper.