Theoretical And Experimental Study On The Damage Localization Of Beams Based On Natural Frequencies

The engineering structures have defects in them during the operation period because of all kinds of functions both from man and the nature. When these damages accumulate to some extent, the load bearing capability of the structures will decrease a lot, hence influencing the use of them, even leading to great accidents, causing great loss of money and human lives. Thus, the damage detection and localization of these structures are meaningful.The theory and the research situation of dynamic detection of engineering structures, the method of dynamic detection are presented in this passage in the first place. The feasibility and advantages of damage detection from the changes in natural frequencies are also expatiated through listing the advantages and disadvantages of these methods. After that, the characteristic of natural frequencies of beams in local vibration is studied, involving the influence of boundary condition. Then, through the analysis of natural frequencies of beams of three different boundary conditions before and after damage appears, based on the theory of damage detection and localization of beams, the universal bank of natural frequency indexes for damage location of beams is established. There are three boundary conditions in total: simple beam, beam with fixed ends and simple beam with rotational springs at its ends. The effectiveness and universality of the bank are confirmed by different numerical beam models. Finally, 4 beam models are made to confirm the theory and the method of this passage. In order to get the first 5 natural frequencies of the model beam before and after the damage is made, a dynamic modal test is conducted. With the test results of the natural frequencies and the universal bank of natural frequency indexes for damage location of beams presented in the passage, the location of the damage is correctly identified, confirming the validity and the practicability of the bank.