Artificial Wave Fitting For Multi-damping Floor Spectrum Of Nuclear Power Plant

At present,as an efficient and clean energy,nuclear power is accepted and adopted by more and more countries.Having gone through the process of import,digestion,absorption and re-innovation.the nuclear power technology of China is gradually realizing self-development and localization after decades of accumulation and practice.With the implementation of the co-building of the Belt and Road Initiative,the selfdeveloped HPR1000(Hua-long Pressurized Reactor)is going out of the country and going to the world.Under this background,the analysis methods,means and software in the field of nuclear power are becoming more and more autonomous.According to the new requirements of anti-seismic analysis,full-time domain analysis of nuclear power structures is gradually being widely used instead of frequency domain analysis.Among them,seismic load is an important basis for anti-seismic analysis of nuclear power plants.Nuclear power equipment is mostly metal composite structure,consisting of pumps,valves,pipes and joints.And the damping ratio is related to structural form and material,as a result,the damping ratios of nuclear power equipment are numerous and complex.Belonging to the field of civil engineering disaster prevention and mitigation,the study of artificial wave fitting of multi-damping floor response spectrum is an important technical research topics of earthquake input in nuclear power plant and the basis of all dynamic analysis,which plays a decisive role in the safety analysis of the whole structure.In order to reduce the amount of calculation,the input ground motion in the analysis and design should be compatible with the damping of the structure.Therefore,it is suggested to adopt input conditions with multiple damping ratios.The fitting accuracy of floor spectra in nuclear power field is very high.At present,there is no recognized,effective and accurate method in the field of multi-damping artificial wave fitting.In order to solve the above problem,this paper mainly carries out the following work:(1)Firstly,this paper briefly introduces the background of artificial wave fitting for multidamped floor spectra of nuclear power plants,further describes the development status of artificial wave fitting for multi-damped floor spectra,analyzes the importance of multi-damped artificial wave matching,introduces the development history and current situation of artificial wave fitting technology for floor spectra at home and abroad.What’s more,the main methods and current status of artificial wave fitting for multi-damped floor spectra are described mainly.(2)Based on the nonstationary analysis of real seismic waves,through case study,this paper draws strength envelope model into time domain analysis of real seismic waves,which provides a convenient way and means for the modelling of time-domain non-stationarity of ground motion and the subsequent research process of artificial seismic wave fitting.During the study of frequency non-stationarity,this paper presents and describes the frequency distribution of real seismic wave and artificial seismic wave at different energy points with time through short-time Fourier transform innovatively.(3)While introducing and analyzing the principle and process of multi-damping ratio artificial wave fitting method based on time domain superimposed narrow-band time history method,this paper also introduces some shortcomings of this method,such as Gibbs phenomenon,the calculation of Fourier forward and inverse transformation is complex in iteration process,repeated construction of narrow-band time history leads to slow computation speed,etc.(4)This paper proposed a holistic method of multi-damping floor response spectrum artificial wave fitting based on variation amplitude harmonic time-domain adjustment.First,this method introduces a new wavelet function,which can change the frequency domain characteristics of artificial seismic waves at specific frequencies,and have a small impact on the time domain characteristics of artificial seismic waves.According to the features that the nuclear power floor response spectrums of different damping ratios are obtained independently and the correlation among them is wake,this paper proposed a new iterative fitting method.The holistic method of multi-damping floor response spectrum artificial wave fitting based on variation amplitude harmonic time-domain adjustment can generate a response spectrum artificial seismic wave,which satisfies the fitting accuracy requirements of multiple damping ratio target spectrums simultaneously.