As a transportation hub, the girder bridge is often an important target for both sides in combat, and it is very important for wartime decision-making and subsequent fire planning to carry out assessment on the effect of the damage to the bridge after the fight. The use of images for target damage assessment is more secure and efficient compared with the traditional method of manual inspection. However, the current image-based damage assessment of girder bridges has the problems of neglecting the damage to bridge piers and the poor stability of the damage features. To address these issues, this paper proposes a functional damage assessment method for beam bridges after being hit by ammunition based on visible light images. This method decomposes the girder bridge into two main sub-targets (the abutment and deck), analyzes its functional characteristics, designs the residual bearing capacity of the bridge and the number of passable lanes in the damage features, proposes an algorithm for conversion from image features to damage features and a fusion algorithm for the damage features, and establishes the rules for the evaluation of the damage level accordingly. The MATLAB experiment verifies that the method is able to extract the residual bearing capacity and the number of passable lanes from the image of the post-fighting girder bridge and to obtain the damage assessment results, which provides a new method for the assessment of the effect of damage to girder bridges.
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