ABSTRACT
This paper describes a damage identification methodology based on a genetic algorithm and its application to the numerical model of a railway bridge. The identification method is based on an iterative process that in each iteration compares the values of the bridge’s dynamic responses for a test damage scenario with the response values for a reference damage scenario. The introduction of damage in the test numerical model is based on the modification of preselected numerical parameters values. The genetic algorithm allows the identification of damage by minimizing the residue of an objective function constructed from the responses of the test and reference model, and based on damage indicators (Fig. 1). Flowchart of the iterative methodology. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig133_1.tif"/>
In this study are defined and tested damage indicators based on the deck accelerations of the bridge under action of Alfa Pendular train defined as a set of moving loads. The proposed methodology for identifying damage was tested based on a two-dimensional numerical finite element model of a railway bridge including railway track. Two damage indicators (ID1 and ID2) based on basic signal statistics were defined. The first one, ID1, clusters the minimum peak amplitude, the maximum peak amplitude and the standard deviation. The second one, ID2, is based on the sum of the squared differences between the reference acceleration and the acceleration resulting from the numerical scenario. The tests performed involved multi-damage scenarios which differ in the number of parameters that reproduce the damage, equal to 6, 8 or 10, for scenarios C1, C2 and C3, respectively.
In Figure 2 the differences between the parameter values that reproduce the damage and the reference values, for different damage scenarios and considering the damage indicators ID1 and ID2, are illustrated. Differences between numerical parameters and reference values, depending on the damage scenario (C1, C2 and C3) and damage indicator (ID1 and ID2). https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig133_2.tif"/>
The performance assessment of damage indicators revealed the high efficiency of the indicators, especially the indicator ID1, in the detection, localization and quantification of the damages introduced into the numerical model of a railway bridge.
