Research On Damage Identification Method Of Beam Structure Influencing Line Curvature Difference And Fractal Dimension

Due to the long-term natural environment and loading,structural damage inevitably occurs on bridges in service,and timely identification of structural damage can effectively ensure the health status and safety of bridges.The structural damage identification method is one of the core technologies of bridge structural health monitoring system,which has been studied by many scholars.In this paper,we study the structural damage identification method based on the influence lines of static parameters.The curvature difference and fractal dimension of the influence line of each static parameter are processed,structural damage identification can be achieved according to its change rule.The specific research contents are as follows.1.In order to achieve damage identification of equal-section beam structures using only damage state information,a damage identification method for beam structures based on the differential curvature of the influence line of static parameters is proposed.The static parameters are specifically deflection,angle and support reaction force:(1)The damage identification method of beam structure based on the curvature difference of the deflection influence line takes the simply supported beam as the research object,and after doing curvature difference processing on the points of the deflection influence line,it is found that the curvature difference curve of the deflection influence line changes abruptly at the damage location,and the damage location is determined according to this feature,and the numerical law of the curvature difference of the deflection influence line is determined according to the damage location,and the calculation method of the damage degree is established.(2)The damage identification method of beam structure based on the curvature difference of angle influence line,such as a simple-supported beam and a two-span continuous beam as the research object,the curvature difference of the corner influence line at the beam measurement point is processed,it has a sudden change in the fraction of the curvature difference of the influence line at the corner of the beam structure at the damage location,so the curvature difference of the influence line at the corner is used as an indicator of the damage location,and the calculation method of the damage degree is further deduced.(3)The damage identification method of continuous beam based on the curvature difference of the support reaction force influence line,taking the two-span unequal-span continuous beam as the research object,the curvature difference of the middle support reaction force influence line is processed,and it is found that there is a sudden change in the curvature difference curve of the support reaction force influence line at the damage of the continuous beam,based on this phenomenon,a damage localization method is proposed,and the damage degree calculation method is further established.The applicability of damage localization and corresponding damage degree quantification methods for deflection,turning angle,and support reaction force influencing line curvature differential index damage were verified by damage simulation analysis of equal-section simply supported and continuous beams.2.Improving on the basis of Katz fractal dimension,a damage identification method for beam structures based on the static parameter influence line Katz1 fractal dimension is proposed.(1)The beam structural damage identification technique uses the fractal dimension of the deflection influence line Katz1 as the study object,and calculates the Fractal dimension of Katz1 after subtracting the deflection influence line of the same measurement point before and after the beam damage.The Katz1 fractal dimension of the deflection influence line difference at the damage is not zero,according to the results.As a result,the Katz1 fractal dimension of the difference in deflection influence lines may be employed as a damage location index.In addition,the method for calculating damage degree is based on the variation rule of fractal dimension Katz1 of the deflection influence line before and after damage.(2)The fractal dimension of the Angle influence line Katz1 is used to identify damage in beam structures.The fractal dimension of Katz1 is determined using the difference of the Angle influence line at the beam support before and after the damage.Similar to the deflection,using the simply supported beam as the study object.Katz1’s fractal dimension of the Angle influence line difference at the damage is not zero,but it is zero in other places.As a result,the damage location index is the Katz1 fractal dimension of the line difference caused by the Angle.The variation rule of Katz1 fractal dimension of influence line of rotation Angle before and after damage was analyzed,and the calculation method of damage degree was further established.(3)The fractal dimension of the influence line Katz1 of the support reaction force is used to identify damage in a continuous beam.The difference of fractal dimension of influence line Katz1 of middle support reaction force before and after beam damage is calculated using a two-span continuous beam as the research object,and it is discovered that there is mutation in the difference curve of fractal dimension of influence line Katz1 of support reaction force at the damage location.A method for determining the location of damage is presented based on the features.Furthermore,the variation rule of Katz1 fractal dimension of support reaction influence line before and after the damage was used to build a technique for calculating the degree of damage.Finite element models such as simply-supported beams and continuous beams are established,and different damage conditions were set to verify the damage identification effect of the above static parameter influence line Katz1 fractal dimension,showing that the method can achieve accurate localization and quantification of beam structure damage.A four-span continuous beam engineering model is used to validate the damage identification methods based on the curvature difference of the static parameter influence line and the damage identification methods based on the Katz1 fractal dimension of the static parameter influence line.Through the noise simulation analysis,it is discovered that the deflection,angle,and support reaction force three parameters of the influence line of curvature difference and Katz1 fractal dimension damage identification method have certain noise resistance,where the deflection and angle noise resistance performance is better.Katz1 fractal dimension has stronger noise immunity compared to curvature differencing.