Research On Damage Identification Method Of Simply Supported Beam Based On Displacement Influence Line

At present,the regular safety inspection of Bridges mostly adopts the form of manual visual scoring evaluation,whose effectiveness largely depends on the professional quality of maintenance and maintenance workers.In order to find a more efficient,objective and quantitative artificial safety inspection alternative than manual regular inspection,to intelligently perceive the safety state of Bridges and prevent disasters and accidents,Based on the National Natural Science Foundation project undertaken by my tutor,"Bridge Safety State Monitoring Method and Early warning Theory Research based on Deck morphology Change(51708068)",combined with finite element analysis and laboratory model bridge test,this paper proposes to conduct damage identification research on the structure by using the envelope of displacement influence line difference.The specific research contents are as follows:(1)According to the theory of displacement influence line,based on the simply supported beam,the formula for calculating the difference of displacement influence line in the middle span of elastic structure is given and verified by a numerical simulation.Considering the difference of displacement influence line in midspan,it is difficult to identify multiple damage positions near the end,combining with the concept of envelope,the concept of envelope of displacement influence line difference is put forward(2)Combined with displacement influence line difference,the concept of envelope is presented based on the displacement influence line deviation of the envelope and a method to identify the damage,the second derivative,and is verified by means of numerical simulation,the results showed that the displacement influence line difference of envelope structure of the single injury identification effect is better,more than for injury of high sensitivity is not enough;The first derivative of the envelope can only be used to determine the damage location of the structure.The damaged part of the structure can be identified by the second derivative of the envelope.(3)The verification experiment of the damage identification method based on the difference envelopment of displacement influence line is carried out.Damage conditions of different positions and degrees are set for a simply supported beam model in the laboratory.The measured displacement influence line envelopment dataare calculated and analyzed.The damage identification of simply supported beam structure is carried out by using the aforesaid displacement influence line difference envelopment method.