Study On Damage Identification Of Engineering Structure Based On Modal Analysis

Modal parameters of the structure reflect the information of its quality, stiffness and damping. So we can get the state information of structures by monitoring its modal parameters. In this paper, the research is damage identification of engineering structure based on modal parameters.The main researches in this paper are as following:1. Analyzing the characters of damage identification of engineering structure based on flexibility difference. In a simple beam example, it calculates the stiffness decreased of the beam damaged in various degree and units by the decrease of unit's stiffness. It discerns the damage of the beam by the flexibility difference and tells the method's advantage comparing with the methods based on structure's natural frequency or the mode of vibration. But it also points out this method need the mode information before damaging, which is often difficult to acquire in actual engineering structure and it is generally used in monitoring of large-scale engineering structures.2. Analyzing the characters of damage identification of engineering structure based on structural curvature modal. The identification application of the simple beams based on structural curvature modal confirms that: When structure has damage, structural displacement's change is so small that we can't discern the damage by it. But structural curvature modal is sensitive to the damage, and we can use it to discern the damage. Though the curvature modal method need not rely on the structural parameters before damage, it only relies on the curvature's sudden change. The valuing of the curvature's sudden change is difficult and the method also has the problems of wrong location. To avoid it, we should apply multi-modal in factual application. So it has limitation in practice.3. In order to solve these problems, it sets forth the methods and principles of discerning engineering structures damage by the flexibility difference curvature. It use some examples to confirm that: Flexibility difference curvature can be the basis of judging the damage degree; Even if only 15% damage, the flexibility difference curvature cure change is also significant; Though the second unit which is near to bearing of beam has varying degrees of damage, the location of the damage can be acquire. So the method has notable advantages such as high sensitivity, strong reliability, visualization and simplicity in amount and graph analysis, unparalleled reliability and applicability, it could be apply in the factual project structures.