Structural Of Beam Damage Identification Research Based On Element Modal Strain Energy And Interval Estimation

Since the beginning of the new century,more and more people lost their life and the property because of the damage to the structure.Therefore it’s quite important to take some measures,such as the damage identification,the detection and the reinforcement of the structure.In order to reinforce the damage structure,it’s necessary to do a good job to detect the damage work first.This paper mainly studies the damage identification method of structures.So what is damage identification?Damage identification is mainly based on the dynamic parameters of the structures and also the related monitoring data,and then we have to judge whether the structural damage exist,where the location is and how mush is it.This paper begin with the background and the significance of damage identification,then make a summary on the research of structural damage identification.After that,the methods of structural damage identification are classified.And then a brief version of the literature review is also made which focus on modal strain energy and structural damage identification method of interval estimation.According to the basic idea of the finite element, this paper derives the basic theory of finite element beam and two Vera bar unit.Combined with the knowledge of the structure’s dynamic characteristics and the model strain energy in the material mechanics,this paper also derives the expression of the modal strain energy on the beam element and two dimensional bar element.On this foundation,by deriving the parametric unit modal strain,and introducing the structural rigidity damage index,the probability density function of the damage index of the structural stiffness is acquired.After that,this paper need to solve the the posterior probability density function of each element.And then maximum likelihood equation is set up by using the method of maximum likelihood estimation.At last,by optimizing the objective function, the stiffness damage index of each element can be acquired,which is the damage index of the structural damage identification method of interval estimation.Make further efforts,the paper integrates the stiffness damage index unit of the posterior probability density function so that the damage probability of each element can be acquired.And this damage probability can be used as the damage location index of the interval estimation method.In this paper, the above theory is applied to the damage identification of a simply supported beam and cantilever.On this condition which is low-end model of the structure(the structure of the five-order mode shapes) and low noise case(noise level of 0.05 or less), the results showed that the effect made by the interval estimation method to make sure the damage location and damage quantification is quite good.However, this method can not be used on the truss structure. From this perspective, the author attempts to transform the truss structure into a beam structure.But it’s a failure. Finally, the author try to equivalent the simply supported beam to simply supported equivalent,and the Element Modal Strain Energy Index is used to detect the damage of simply supported beam.In this method,a lot of Index are used,such as the unit modal strain energy rate index, unit modal strain energy dissipation rate index, unit modal strain energy targets and cell-based modal strain energy equivalent index.Simulation results show that it can give priority to the use of the equivalent element modal strain energy index to identify the damage of the simply supported equivalent.