Beams, Plate, Grid Structure Damage Diagnosis

In the most general terms, structural damage can be defined as changes introduced into a system that adversely affects its current or future performance. Structural damage detection is to detect, locate, and assess its severity. According to the detection result, the structure reliability and the damage trend are evaluated.Traditional structure reliability is ensured by design. But structural design can not guarantee reliability in it's life period, as a number of structures are deficient owing to many factors such as they might be inadequately or constructed and are unable to meet current standard, or they are aging and deteriorating due to environmental hazards such as wind, earthquakes, and higher service loads so many years of use. This damage could imperil the structure safety. How to detect availability and reliability the damage exist, distribute and the degree is a object that many civil engineer pay more passion to research.Previous structural damage detecting method in civil engineering are reviewed. The theory and experimentation of damage detection by mode factors for beam, plate and spatial truss are studied.First:The relationship of curvature mode and displacement mode is discussed. The sensitivity of curvature mode for structure damage is revealed; Second:The two stage method for structure damage detection is established. first stage is using curvature mode index(CMI) to locate damage, as curvature mode has high relating to geometrical coordinate but not sensitive to the damage degree. Second stage, basing the location of the damage, the value difference of the element mode strain energy (mode moment index MMI) before and after damage is used to evaluate the damage degree. The CMI and MMI are calculated by a program of MATALAB. Numerical results for beam and plate demonstrate the ability of this method by Finite Element Method simulating. The factors that affect the damage detection by this method are discussed.The test results demonstrate the availability of CMI and MMI for 5 steel beams mode that they have different damage location and degree. The two stage method could detect the damage location exactly and evaluate damage degree.