A Study Of Structural Damage Detection Based On Vibration Information Of Concrete Dam

Concrete dams are an indispensable part of water conservancy projects,and damage identification during their service is essential.Taking the disaster of the Koyna concrete gravity dam as an example,composite materials are used for seismic reinforcement of the weak parts of the dam,and corresponding damage indicators were proposed to evaluate the reinforcement method.A method for describing and identifying the structural damage was proposed based on the vibration data of the dam.The main research contents of this paper are as follows。(1)Once the concrete structure has cracks,it will have a serious impact on the normal use of the structure.Reinforcing measures on the structure can effectively suppress the generation of cracks.It was proposed to use steel fiber reinforced concrete to reinforce concrete gravity dams,and three reinforcement schemes were designed.A finite element model of Koyna concrete gravity dams with reinforcement measures was established,and its damage distribution under earthquake action was numerically analyzed.In order to analysis the reinforcement effect of each group of reinforcement schemes on the seismic performance of concrete gravity dams,the damage distribution maps of dams with three sets of reinforcement schemes and those without reinforcement were compared and analyzed.(2)In order to evaluate the seismic performance of concrete gravity dams,the damage index of concrete gravity dams based on Hilbert-Huang Transform(HHT)was proposed.The Hilbert transform was performed on the response signal of the dam under earthquake,and the Hilbert time-frequency curve was obtained.Comprehensive analysis of the influence of signal amplitude and frequency,the HHT-based structural displacement spectrum difference damage index recognition model was proposed.The damage area of the dam body under earthquake action obtained through finite element numerical simulation verifies that the damage index can accurately evaluate the seismic performance of the dam body.(3)The damage index based on HHT can only evaluate the damage degree of the structure.In order to obtain more comprehensive damage information of the dam structure under the action of earthquake,a frequency-weighted least squares method is proposed to identify the modal parameters of the structure,so as to describe the damage of the structure.The accuracy of structural modal parameter identification by frequency-weighted least squares method isverified by numerical examples.The results show that the method proposed in this paper can more accurately identify the modal parameters of the structure,and the least square method with ordinary Kriging interpolation as the weight value has the highest recognition accuracy.(4)The frequency division weighted least squares identification method was extended to a time-varying system.According to the identified natural frequency time course of the dam body,the development process of structural damage can be accurately described.The damage location of the structure can be determined by the change of the modal identification value of the dam body before and after damage.Finally,the seismic response of the Koyna concrete gravity dam was numerically simulated.The accuracy of the identification results was verified by the dam body damage evolution process.