Curvature Mode Technique Of Damage Identification For Beam Bridge Structures

Since the 50s of this century, people have realized the importance of health monitoring for bridges. Many bridges have been installed with monitoring system presently. A primary objective of long-span bridge health monitoring is to obtain the information on bridge condition through online monitoring of the structural performance. In this paper, after a brief overview of the development of bridge health monitoring, the connotation of bridge health monitoring is pointed out in an extended sense. The present bridge health monitoring systems have not the capacity to detect the damage in bridges. Further study is needed as to how to design an effective automatic damage detection systems for structural damage identification.Automatic damage detection becomes a core technique of bridge health monitoring systems, which attracts the attention of many researchers. Actuality of damage identification for structures is expatiated and comments are made on the methods of them. These methods include natural frequency, strain modal shape, COM AC, flexibility matrix, wavelet analysis, genetic algorithms etc.Considering that Curvature Mode can identificate the damage of structures and can show the change of local state of bridges, and it can be used to inspect the location and degree of damage. The theoretical basis was developed emphatically for the curvature modal analysis and the curvature mode properties in the paper. The relation between the curvature mode and the strain mode for structures such as bridges subjected to bending and vibration was discussed. The curvature mode is rather sensitive to the local change of structures. And the results show that the curvature mode will be more conveniently used than the strain mode.In this paper(Chapter 4), curvature mode method is adopted to the calculation of damage imitation to one prestressed concrete continuous beam bridge. Three conditions is divided to carry out analysis and study and compare the diagnose ability about the displacement mode and curvature mode method to the different conditions of single damage location and a couples of ones, and theeffect of different damage degree to damage identification for structures.In Chapter 5, a experiment about a slotted steel cantilever beam is given to inspect further the effect of curvature mode method to both location and degree of damage. The effect of different depth crackle to curvature mode was stood out as an emphasis. The conclusion is given as follows:1. The curvature mode is rather sensitive to the damage of structure. It is more sensitive than frequency and displacement mode and can be used to locate the damage of structures like a beam, and it is also sensitive to several damage. Interact is not happened between damage positions. So it meets the need of actual detection.2. Curvature mode can be used to carry out qualitative analysis to damage degree of structure. Experiment shows that curvature mode value will increase with the increase of the crack depth. It is conform completely with the theory.3. Under the prerequisite of guaranteeing the measurement precision, the method can be used to the actual application on the project.