Research On The Dynamic Characteristics Of Beam Structure And Its Application

Engineering structure in the design period,not only to consider the structure strength,stiffness and stability,also need to square up the structure dynamic response.The structural dynamics involves three aspects: structural response analysis,structural parameter identification and structural load identification.In particular,the structural parameters identification and structural technical status assessment are more and more widely used in engineering.It mainly includes structural dynamic design optimization,structural finite element model updating and structural damage identification.To design a structure with excellent dynamic characteristics for ensuring its safety,reliability and durability,and extending the operational lifecycle of the structure,it is great theoretical value and social significant.In this paper,the dynamic characteristics of beam structure and its engineering application are studied.The main research contents are as follows:Firstly,the paper focuses on the hot issues of structural engineering,such as structural experiment modal analysis,structural finite element model updating,structural damage identification and structural dynamic characteristics modification,which summarizes the research status and the prospect of structural dynamic characteristics and engineering application.Secondly,from the energy point of view,the change of the dynamic characteristics of the structure caused by the local stiffness change and the local mass change are studied.And the relationship between the modal damping energy dissipation and the displacement slope modeshape is established.Three conclusions as follows:(1)The relative change of the natural frequency of the beam structure caused by the local stiffness change is proportional to the square of the curvature modal value of the beam at the stiffness change;(2)The relative change of the natural frequency of the beam structure caused by the local mass change is proportional to the square of the displacement modal value of the structural at the mass change;(3)The modal damping energy dissipation of the structure is proportional to the square of the displacement slope modal value of the structural.It provides important theory for structural dynamic characteristics modification,structural finite element model updating,structural damage identification and so on.Thirdly,the existing structural damping identification methods such as logarithmic attenuation method,step response method,dynamic coefficient method,amplification factor method and half power bandwidth method are introduced.Then,a time domain method of structural modal damping ratio identification is put forward,which have clear physical concept,efficient and easy to implement.At the same time,it is especially pointed out that the structural damping ratio identification by the structural dynamic exprement is the modal damping ratio of the structure.Combining the time domain method of structural modal damping ratio,a method of identifying the proportional coefficient in the Rayleigh proportional damping model is proposed.Finally,using the relationship between the relative change of the natural frequency caused by the change of the stiffness of the beam structure and the curvature mode,the damage position of the beam structure is successfully identified by extracting the eigenvectors reflecting the change of the stiffness of the beam structure.At the same time,under the condition of natural frequency constraint of beam structure,structural stiffness modification is carried out by using structural curvature mode,and structural displacement mode is used to modify the structure mass,which made the dynamic characteristics of the structure can be changed according to the intended target.It is combined with the structural finite element method to further improve and is expected to be applied to the engineering structure.