Damage Identification Of Concrete Simply Supported Beam Bridge Based On Strain Response Reconstruction And Statistical Theory

Bridges play an important role in both railway transportation and road transportation.Due to aging of materials,increasing of vehicle loads,shortage of maintenance and repair of bridges,etc.,leads to the decline of bearing capacity and becomes a safety hazard.Therefore,it is necessary to explore an effective and fast and accurate method for identifying the damage of bridge structures.Most of the existing methods require the structural response,or the excitation input.However,this is difficult to achieve.In order to improve the applicability of damage identification method,this paper combines the statistical characteristics of strain response,response reconstruction and the model-updating method to identify the damage of beam bridge.The specific work is as follows:(1)In order to get rid of the dependency on the information before damage,a damage identification method based on strain index and D-S evidence theory is proposed.Based on the D-S evidence theory,two improved indexes are fused to locate the damage.It was found that SSD and APSED have strong robustness to noise,and has a high accuracy of damage identification.Finally,the effectiveness of the proposed method is verified by experimental investigation.(2)The strain response reconstruction equation of simply supported beam bridge under moving load is derived.The Tikhonov regularization method is used to solve the reconstructed strain response.Numerical examples show that the least squares method is heavy.The reconstructed response is unstable.Under the condition of adding noise,the Tikhonov regularization method can still control the relative error between the reconstructed response and the original response.(3)A two-step method based on strain response reconstruction and statistical theory is proposed for beam bridge local damage identification in this study.The damage can be identified without needing of dynamic response of undamaged structure.SSDs at damage state are used to locate roughly potential damage elements;The model updating method based on the least square algorithm is applied to quantify the damage extents of those identified elements.Numerical and experimental studies on a simply supported beam bridge show that the proposed method is effective to identify damage elements and to quantify the damage extents.