Exploration On Damage Identification Method Of Simply Supported Beam Model Bridge Based On Video Data

The safety inspection of bridges currently mainly relies on manual inspections,and the lack of quantitative scientific basis is its obvious deficiency.In order to explore a more convenient,holographic,credible,efficient,and economical bridge state detection and evaluation method,this article relies on the National Natural Science Foundation of China project "based on image contour overlap analysis to obtain bridge holographic deformation and structural state deduction method exploration(51778094)”,carried out the research on the acquisition method of the full-field displacement time history signal of the bridge structure based on video data,and explored the method of bridge damage identification.The main contents of this paper are as follows:According to the basic formulas and principles of structural dynamics,a structural damage identification index that can effectively take advantage of the holographic advantages of video data is proposed,that is,the damage index DI1 based on the difference of the full-field displacement time history signal.Aiming at the limitations of the original indicators,some improvements and attempts were made to the original damage indicators according to the relevant mechanical knowledge and mathematical methods combined with the proportional finite element model,and finally the damage identification indicator DI3,which has a better effect on identifying the damage location,was obtained.Based on the basic theoretical formulas related to structural dynamics and material mechanics,as well as the changes in structural flexural stiffness caused by structural damage and changes in structural parameters,this paper proposes a damage identification index based on the full-field displacement time history signal,and according to the relevant mechanics Knowledge and mathematics methods and combined with equal-scale finite element model tests are carried out to improve and try to some extent,and finally get the damage identification index DI3 which has a better effect on the damage location identification.Aiming at the finite element model,using the method of controlled variables,the influence factors of the damage identification index are parametrically analyzed,combined with mathematical statistics and mechanics-related theories to study the regularity between the influence factors and the damage index,and finally the finite element Estimation function relation of damage degree under the model.Verification by the experimental data of the finite element model shows that it is feasible to use the damage estimation formula to accurately determine the damage.For a single-box five-chamber simply supported beam bridge in the structure laboratory,a dial indicator,an LVDT displacement meter and a camera are used to simultaneously collect the displacement information of the bridge under the load,which verifies the accuracy and reliability of the displacement obtained by the video data.The damage test is conducted on the model bridge,and the results show that the damage identification index proposed in this paper is effective in judging the damage location and the quantification of the damage degree through the damage index is feasible through multiple sets of load conditions and damage conditions.