A two-step method for beam bridge damage identification based on strain response reconstruction and statistical theory

In this work, a two-step damage identification method has been proposed for simply supported beam bridge local damage identification based on strain response reconstruction and statistical theory under moving loads. Damage could be identified without the response of healthy structure. Strain reconstruction equation was derived based on state space model. Strain responses were divided into two groups and corresponding reconstructed strain response of each group was obtained. Strain standard deviation (SSD) index was proposed based on the theory of static. The developed two-step method could be summarized as the following: first, SSD curves at damage state were employed to locate damage elements. Then, least square-based model updating method was applied to evaluate damage severity in the identified damage elements. Numerical evaluations on simply supported beams showed that the proposed method effectively identified damage elements and revealed damage severity even at noise intensities of up to 15%. In addition, it was found that SSD index was more robust to noise than strain response. Decreasing measurement noise and increasing the sampling frequency decreased the relative error of reconstructed SSD index. Finally, experimental investigation on a simple supported beam bridge model under moving vehicle condition showed that the obtained results were in accordance with pre-set damage scenarios, which proved the effectiveness of the proposed method.