Research On Damage Detection Method Of Simply-supported Beam Bridge Based On Statistical Property Of Dynamic Responses

The existing damage detection method is based on the difference between the response before and after the structural damage to construct the damage index to complete the damage detection of the structure,which requires the response information of damaged and undamaged structure.In this paper,in order to get rid of the dependency of information of intact structure,lifting wavelet transform signal processing technology and statistical theory are applied to damage detection of simply-supported beam bridge.The work is as follows:(1)A damage detection method under curvature index of strain statistical moment is proposed.Lifting wavelet decomposition is conducted to decompose the strain response of the simply supported beam,and then curvature index of the fourth strain statistical moment is calculated by using the reconstructed low frequency signal.Compared with the index calculated directly by the strain response,we can effectively locate the damage location using curvature index of the fourth statistical moment without the strain response of intact structure.The noise robustness of the index is analyzed.And the results show that the proposed method is robust against noise.(2)This paper defines a novel damage index-correlation coefficient curvature based on structure displacement response.We can effectively locate the damage location using this index without the displacement response of intact structure.However,this index is easily affected by vehicle speed.In order to reduce impact of vehicle speed,the correlation coefficient curvature index calculated with the displacement response transformed by lifting wavelet is applied to the damage detection,then the damage detection results is less effected by vehicle speed.However,there is no particularly prominent peak appears in the correlation coefficient curvature plot at the damaged location.Finally,applying the gapped-smoothing method,the correlation coefficient curvature of intact structure can be obtained from the damaged one.And the damage location can be identificated with the difference of correlation coefficient curvature between the damaged and undamaged structure.(3)Damage index(DI)and modified damage index(MDI)based on structural displacement response and structural curvature response are constructed respectively.The impact of the measurement noise and density of measurement points to the damage detection result are studied by finite element numerical simulation.Finally,the validity of the damage detection index is verified by experiments of the simply supported beam bridge model.