Study On Damage Identification Of Grid Structures Based On The Dynamic Test

Grid structure is widely used in industrial and civil construction because of its structural and architectural advantages. There are many questions to be studied and solved in the damage identification because the most grid structures are relatively large and grids are more. Combined with the task writing the quality measure code of space grid structure, the dynamic test of the full-scale grid structure is carried out, the major research results include:1. Based on the difference of strain variation rate, the grid structure damage identification method is proposed. The damage identification formula of the three-dimensional grid structure is derived.2. Combining dynamic testing, the modal analysis program of the grid structure is developed by means of APDL programming languages and ANSYS from the finite element command. Parametric modeling of the grid structure, the load parameters and its solving, as well as parametric post-processing results can be displayed. In the grid model, the numerical simulation process of parametric analysis, repeated analysis of different parameters to achieve damage variety can simply modified by this program. Meanwhile, the damage of measured grid under various conditions can be simulated. The damage identification method of grid structure is applied to the experimental grid structure, and is compared with the test results. Both results show good agreement.3. A full-scale grid of 12x9x1.4m is designed and tested in the structure laboratory. The tests of 20 different damage conditions are carried out by means of hammer encourage single-input and single-out. Some problems relating to the dynamic test method, incentive method, optimizing layout of sensors and frequency respondence evaluation of grid structure are studied.4. The grid structure damage identification methods based on the dynamic test are studied, and the feasibility of damage identification for the grid structure is subsequently verified using the frequency, COMAC indicators, strain, and other dynamic parameters. Additionally, identification process based on variation rate of axial strain for grid structure is also given. The feasibility of damage identification in the three-dimensional grid structure using above method is demonstrated. Meanwhile the difference of variation rate of axial strain before and after grid element damage is obtained under the action of outer encourage force, by which the damage location and element damage degree can be well reflected. 5. Grid structure damage identification method based on variation rate of axial strain is established. Then three stage method of damage identification for grid structures is proposed, and the "damage factor" of grid structure is determined. Through the comparison of the calculation results with the engineering examples it is shown that the damage location is good agreement and that this method is reliable, therefore, it is valuable in theories and the applications for the damage identification of the practice engineering.