Damage Diagnosis Of A Prestressed Concrete Beam Using Dynamic Test Data

With the development of economy, more and more large-span, tall and complicated structures are built. And the damage of such structures could lead to economic loss. So, it is necessary to build a good system of surveying and maintaining to detect the degree and position of damage. The importance and necessarity of doing the reliability detection is realized by more and more people. Based on the background, the main research work is as follows:This paper focus on the research of dynamic damage diagnosis of three prestressed concrete beams and a reinforced concrete beam. Static load, which was loaded and unloaded step by step, was put on the beam through two symmetric points crossing the beam. In the course of testing, some static data, such as deflection, strain and cracks of every load step are recorded. And these different data also made up of different damage patterns used in the dynamic testing. Dynamic tests are applied to the beams, and during the course of the dynamic testing, mode parameters were obtained under the initial state, prestressed state and different damage degrees of the beams. Dynamic damage diagnosis data is obtained from modal test at every condition. Acceleration sensor is used to test modal displacement, and strain sensors are used to test modal strain. Additionally, modal parameters are tested under different prestressed forces and during the course of the lose of prestressed forces. Finally, different vibration conditions, such as different rigidity of the hammer and different forces, are also studied.Based on the analysis of the damage pattern under static loads and the vibration test data, model-based damage diagnosis methods are studied and discussed, which include how to estimate the damage occurring in the structure and how to evaluate the damage position and degree, that is to say, through detecting structure, one can make sure if the damage exists and can tell the degree and position of the damage. Based on structural dynamics, different damage diagnosis index, such as modal frequency variety, modal assurance criterion, co-ordinate modal assurance criterion, modal strain energy, remains force vector, modal strain, rigidity change, flexibility matrix, modal curvature and so on, are studied in this thesis.I turns out to be that the position and degree of damage can not be well detected only by eigenfrequency, while only can detect if the damage has appeared. However, severe damage can be diagnosed if the modal shape and natural period are used...