Damage Detection of RC Bridge Piers under Ambient Vibration Using Optimization Method

The vibrations applied to bridges during their normal operation conditions can be defined as ambient vibrations. These vibrations include the effects of traffic, wind and other low excitations imposed to the structure. Detection and evaluation of the location and dimensions of the damages are accounted as one of the most important stages for structural maintenance. These damages may often occur due to ignorance of standard clauses during structural design, neglecting proper construction regulations, high age of the structure and improper structural maintenance. Using a simple and classic method for damage detection in bridge piers can be significantly efficient. Nowadays, metaheuristic algorithms are widely used in structures. Although in this study, it is aimed to use only mathematical and classic methods of optimization, which imply better physical understanding, however in this paper, a new method based on inverse problem, is proposed to detect ambient damages in bridge piers. In this proposed method, firstly the damage percentage and its location are assumed based on a typical damage scenario. Then, assuming lack of sufficient vibration data, the variable (stiffness degradation percentage) is defined using optimization method and introducing objective function for axial flexural member of the bridge pier. Assuming linear damage up to spalling of the concrete, the errors at three modes using linear optimization simplex method are revealed 0.7, 0.1 and 1.45 percent (mostly three equations). The obtained results showed good agreement with the initial values. Also, results of an experiment are used to validate the models. Evaluation of the experimental and analytical results showed that the proposed method for damage detection of RC bridge piers can be precisely applied