Approach On Beam Bridge Damage Identification Under Ambient Excitation

Structural damage identification is one of the premises to understand the structural health conditions and to choice the maintenance management strategy. Since the middle of the last century, the development of science and technology pushed the development of the bridge engineering. With the increasing bridge span and construction cost, the large-span bridge is becoming more and more important in the economy and social life. The people to the large-span bridge's security, the durability and the normal use function pay attention day after day. The bridge,as a key point of roads, if interrupted by inspecting work, will cause huge economic losses. The detection of a method without interrupting its operation and also identify their damage status is the key of this paper.Structural damage identification includes two steps: the first step is to identify the structural modal parameters. Stochastic subspace identification is an effective structural modal identification method developed at the end of the last century. During the identification process, artificial excitation is not needed;the structural modal parameters can be identified from the output signals without interrupting the operation of structure. The second step is structural damage identification. The curvature model has an advantage of reflecting the structural local damage, can be gain through the change of the modal shape. Because curvature mode is more sensitive than the modal shape, the curvature has the good application prospect in structural monitoring and damage identification. On the other hand, curvature mode has some disadvantages, for example, not sensitive to the small damage, the paper presents a combination index method to identify the damage location.In the paper, two numerical examples and two test examples are used to contrast analysis. The result show: the improvement method not only can identify the damage location and relative severity of damage, but also can identify the multiple damage locations.The method presented herein can sample and analyse the signals gained on the site without interrupting the operation of bridge. The improved method can be used in the health monitoring of bridge and structural condition assessment.