Damage Identification Of Space Truss Structures Based On Measurement Data Of Static Displacement And Strain

The space truss structure has been widely used in large span structure because of its variety of species.The space truss structures are subjected to load,environmental corrosion or natural disasters and other effects in the long-term operation process,and will inevitably be degeneration and damage,if not found and repaired in time,may lead to local damage or even the overall structure of the collapse,which poses a great threat to the safety of life and property.Therefore,it is of great engineering application value to identify damage of large space truss structure.Based on static measurement data,this paper presents a new method of damage identification of truss structure.The contents of this paper are summarized as follows:(1)This paper describes the method of spatial truss damage identification based on static displacement data.Based on the finite element method and probability theory,the stochastic structural modeling considering the initial model error and the measurement error is studied.Based on this,the stochastic damage control equation of the structure is established by using the initial model data and the damage data.The perturbation method is used to push the deterministic solution process of the damage control equation,and the series expression and statistical characteristics of the damage indexes are obtained.An improved measure based on statistical probability is proposed to improve the recognition accuracy and stability of the method.Due to the technical and conditional constraints in the actual measurement,the measured data will be incomplete,which makes the method appear non-unique solution in the process of solving.In order to solve this problem,the degree of freedom of the structure is decomposed,and the unmeasured part of the damage structure is expressed as a function of the measured data and the initial stiffness of the structure.Several sets of experimental examples show that this method has some applicability when some nodes are known.(2)According to the characteristics and composition of the space truss structure,the method of space truss damage identification based on static strain is proposed.First,the stress of the truss model is simulated by ANSYS and MATLAB.Based onthis,The basic assumptions.On the basis of this,we establish the function relation of the strain before and after the damage and obtain the degree of deterministic damage of the rod element.Considering the uncertainty of the elastic modulus of the structural model and the influence of the measurement error,we introduce a random Variable,according to the principle of recursive stochastic finite element method to solve the stochastic control equation,and then obtain the probability distribution on the damage index.The validity of the method is verified by several numerical examples.(3)Due to the limitations of the measurement accuracy and conditions and the complexity of the space truss structure itself,the static displacement or static strain can not effectively identify the damage of the structure.In this paper,a new two-stage damage identification method is proposed.First,the range of damage search is reduced according to the partial static displacement measured by the test.Then,the static strain of the local bar is measured by secondary loading,and the strain of the truss structure is diagnosed by comparing the unit strain of initial model and damage model.