| In recent decades,China's infrastructure construction has been developing rapidly,and the technology of damming has become in the forefront of the world with numerous world-class dams built.Furthermore,China is the country with the largest number of concrete gravity dams around the world as well.These large-scale water conservancy projects often have long service time and poor operating conditions.As a result,cracks,fatigue damage,corrosion effects and other phenomena are prone to occur under complicated stress state.It is known that the aging and deterioration of dam materials have significant impact on the mechanical behavior of structures,and inevitably result in the accumulation of damage and the decline of stability.In this sense,the damage detection and health monitoring of structures or dams are of an extremely important significance.From another perspective,China is also one of the countries with the most serious earthquake disasters and the frequency of seismic activity is high,which means that once the concrete gravity dam fails under the action of earthquake,great damage and the loss of life and property would be caused.Therefore,it is of great significance to evaluate the earthquake performance of concrete gravity dam.The identification of modal parameters and damage evaluation of concrete gravity dams are common methods for understanding the overall properties of structures and dams.In this paper,the field dynamic test of one large-scale water conservancy project is carried out.The parameters inversion of concrete material of dam body are employed based on the dynamics test data,and the frequency characteristic library of the 4# dam section is established.In addition,the applicability of visco-elastic artificial boundary and the application of Finite Element Analysis(FEA)using a generic software is introduced and validated with the purpose of evaluating the earthquake performance of the dam.The main research contents and results are as follows.(1)The modal parameters of the dam were obtained through the field dynamic test.In order to comprehensively acquire the vibration characteristics of the structure,the test was divided into five parts,including the vibration characteristics of each dam section.And the modal parameters identification is analyzed using Stochastic Subspace Identification(SSI)method and Enhanced Frequency Domain Decomposition(EFFD)method for the two field dynamic test respectively.(2)The dynamic material parameters of the finite element model are modified with the inversion analysis,and the frequency characteristic library of the 4# dam section has been built.Firstly,the initial finite element model of the dam is established and the sensitivity analysis of the model material parameters is used to determine the inversion parameters.Then the parameter inversion is transformed into the solution of the optimal value.The rationality of the material dynamic parameters obtained by the inversion is verified.On this account,the frequency characteristic library of 4# dam section is then established.With comparions between the detection data and the frequency characteristic library,it is accessible to determine or evaluate the damage position of the dam.(3)The derivation process of visco-elastic artificial boundary is introduced,and the implementation of three dimensional visco-elastic artificial boundary program in a large generic finite element software is applied.Finally,the accuracy and validity of visco-elastic artificial boundary are computationally verified.(4)The three-dimensional finite element model of the dam is established,and the static or dynamic conditions under different characteristic levels are calculated.The response of the concrete gravity dam under earthquake action is then analyzed,and finally the seismic safety performance of the dam is evaluated. |
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