Research On Structure Damage Identification Based On Modal Parameters

Beam and plate is a kind of common engineering structure in housing building, bridges and other structures. When these buildings suffer from earthquake, fire and fatigue load, they will produce damage and if the damage reach to a certain extent, it will affect the safety of the structure, causing catastrophic accident and bringing a great economic loss to the society. So, to identify the damage of beam and plate structure has become an important issue.If the structure has damage, it will cause the change of physical parameters such as stiffness, mass and damping, because the structure modal parameters (frequency, vibration mode) is a function of the physical parameters, so the damage can also cause the change of modal parameters. The problem of damage identification which using the change of structural modal parameters base on modal parameters of the restructuring. This article is based on the relationship of the modal parameters and damage identification. This article uses a mathematical expression by the modal parameters before and after damage, thus making the damage labeled amount and making research to the beam and plate.Using the beam as the research object and using flexibility matrix of beam before and after the structural damage, this paper constructed a amount of damage marked based on the rate of change of flexibility matrix part of diagonal elements before and after the damage. With the help of finite element software, this paper established the model of the continuous beam with injury and the structure stiffness matrix can be got. Then with the tools of programming, this paper can draw the indicating quantity figure of beam under different working condition of damage, thus the damage location of beam can be pointed out.Using the plate as the research object and based on the characteristics of vibration mode and frequency change before and after structural damage, this paper constructed a amount of damage marked based on the combination of vibration mode and frequency. With the help of finite element software, the model of the simply supported plate with injury was established. The paper used the finite element software structure to get the structure stiffness matrix and frequency. Then with the tools of programming, this paper can draw the indicating quantity figure of plate under different working condition of damage, thus damage location of plate can be pointed out.Research results show that the method of beam damage identification no matter for a single damage, several damage or the same location of different damage degree can all identify the damage location accurately; the three types of damage model of the plate in the numerical example results also show that no matter for a single damage or several damage, the method can all identify the damage location accurately. So, the method proposed in this paper has an important guiding significance to the damage identification of beam and plate structure.