Modal Identification And Damage Diagnosis Method For Hydraulic Concrete Structures Under Environmental Excitation

Hydraulic concrete structures include concrete dams,ship locks,spillways and diversion towers.Once damaged,these structures may bring great hidden dangers to people's lives and property safety downstream.Therefore,the safety monitoring of the hydraulic concrete structure is very important.Traditional manual monitoring is time-consuming and laborious,and it is difficult to make timely and effective judgments on the real-time state inside the structure.For the monitoring of static stress,displacement,water level and other static elements of the reservoir dam,the statistical model can be used to make a certain degree of operation state of the structure.Dynamics monitoring can monitor the structure of the division and the whole in real time by means of the role of environmental incentives such as earthquakes,flow discharge and human activities,and has outstanding advantages in terms of timeliness and economy.In this paper,the modal identification and damage diagnosis of hydraulic concrete structures under environmental excitation are studied on the basis of seismic response and numerical simulation of measured structures.The main research contents and results are as follows:The modal identification method is mainly divided into time domain,frequency domain and time-frequency domain according to the identification domain.In the structural modal identification,even if the structure does not change,the recognition results of each structure often have some randomness due to different excitation sources and noise,especially in the case of more data,the extraction structure There are certain difficulties in the stable mode.In this paper,the dynamic clustering extraction method based on modal identification for stable modal dynamics is studied.The practical engineering examples of a gravity dam are used to verify the applicability and operability of the stable modal dynamic clustering method.Aiming at the problem of the influence of environmental quantity on structural mode,combined with structural dynamics theory,finite element method and modal identification technology.The additional mass method is used to simulate the effect of reservoir dynamic water on the upstream of the dam.By means of finite element numerical calculation and modal identification technology,the influence of water level on the modal of hydraulic concrete gravity dam is analyzed,and the characteristic frequency of the gravity dam is increased with the decrease of water level.According to the research results of relevant scholars,that is,the change of structural mode caused by temperature change is mainly due to the change of elastic modulus.By means of finite element numerical calculation and modal identification technology,the influence of temperature on the modal of hydraulic concrete gravity dam is analyzed..The results show that the characteristic frequency of gravity dam decreases with the increase of ambient temperature at different water levels.This paper summarizes the structural modal damage diagnostic indicators proposed by some scholars,and points out the advantages and disadvantages and applicability of each index.The mechanism of the change of the frequency index of structural damage diagnosis under structural damage is analyzed.Aiming at the problem that the structural modal change amplitude may be difficult to identify due to damage in actual engineering,the local outliers algorithm is introduced into the damage diagnosis of hydraulic concrete structures,and the LOF-based concrete dam damage diagnosis model is proposed.Good results have been achieved in numerical simulations and practical engineering studies.In this paper,the modal identification and damage diagnosis of hydraulic concrete structures are studied to some extent.The modal clustering method is pointed out.The influence of environmental quantity on the hydraulic concrete structure mode is analyzed.The damage diagnosis model of hydraulic concrete structure based on LOF provides a new idea for identifying the minor change of modal index caused by damage,and provides a basis for further research in the future.