Research On Damage Identification Method Of Transverse Connection Of Multi Beam Bridge

Due to the lack of consideration of structural structure in the design of small and medium-sized bridges and the frequent occurrence of vehicle overload,various kinds of diseases of different forms and degrees appear in small and medium-sized span multi beam bridges,among which the most typical disease is the damage of transverse connection,which will lead to the sharp decline of the lateral stress performance of the bridge,and the situation of"single beam stress"may appear in the most serious cases In addition,timely detection and accurate identification of lateral contact damage are important problems to be solved.Based on the problem of transverse connection damage of multi beam bridges,this paper summarizes the relevant dynamic parameters used in recent years,summarizes the characteristics and application scope of each dynamic parameter,and finally selects the parameter of vibration mode change and applies it to the damage identification method of transverse connection of multi beam bridges,aiming to accurately and comprehensively identify the damage of transverse connection.According to the characteristics of the mode surface function of the multi beam bridge structure,the vibration problem of the multi beam bridge is transformed into the consideration of orthotropic plate.Combining with the definition of curvature in the beam bending theory,the expressions of the transverse and longitudinal curvature of the multi beam structure are derived,and the relationship between the structural stiffness and curvature is obtained.The deficiency of using the change rate of the mode difference of the single curvature is analyzed,and the multi-order superimposed curvature is introduced The concept of the change rate of modal difference and the identification of the corresponding damage condition are given.The example shows that the new index can accurately identify the damage location of the lateral connection,and the identification effect is good.In order to solve the problem of large numerical fluctuation in undamaged area when using curvature mode difference for damage identification,the variation index of curvature mode difference is proposed,Based on the theory of orthotropic plate vibration,the relationship between the index and the structural stiffness coefficientηis deduced as(1-η)/η.The ratio is only related to the damage location,and the variation value of curvature mode difference can well offset the multiple damage locations The interaction of.The change value of curvature mode difference at different damage positions is used as the sample set to train RBF neural network algorithm,and the damage degree identification of corresponding working conditions is carried out.The result of damage identification is more accurate,and the identification error is within5%.Considering that the modal parameters will be interfered by the environmental noise in the actual measurement process,the anti noise ability of the damage identification method of the transverse connection of the multi beam bridge proposed in this paper is studied.The results show that when the noise level is 2%before the improvement of the data processing method,the ability to identify the damage location will be lost.By analyzing the randomness of the environmental noise interference and the characteristics of the damage identification index This paper presents a two-step data processing method of replacing the original curvature with straight-line fitting curvature and finding the average value of multiple groups of data.By using this processing method,the anti noise ability of the damage identification method is greatly improved.When the noise level is 5%,the damage of the transverse connection of the multi beam bridge can still be effectively located.