Stochastic Modeling Of Near-fault Pulse-like Ground Motion And Seismic Reliability Of Frame Structure

Ground motion disaster is one of the most destructive natural disasters because of its randomness and non-stationarity.The near-fault pulse ground motion has significant low-frequency velocity pulse component and will cause severe damage to the structure.Therefore,it has gradually become a research hotspot in academia in recent years.However,at present,the common simulation methods of near-fault ground motion are mainly limited to deterministic simulation,and the simulation results of deterministic method are not capable of reliability evaluation.Therefore,in this paper,the forward directivity effect,slip effect and vertical component velocity pulse characteristics are considered respectively.Based on the traditional spectral representation method and the stochastic function constraint form,the dimensionality reduction simulation models of three types of pulse ground motion are established.Finally,two types of horizontal ground motions simulated by the proposed method were applied to a four-story frame-shear wall structure.Combined with the probability density evolution theory,the seismic response analysis and reliability evaluation were carried out.The main contents of this paper are as follows:(1)In this paper,50 groups of 100 velocity pulse records generated by forward effect were selected from the NGA-West2 strong earthquake database of the Pacific Earthquake Engineering Research Center(PEER).The strongest velocity pulse component was extracted by continuous wavelet transform,and the statistical model of the peak time of the strongest velocity pulse was established.At the same time,the evolution power spectrum model parameters of the high frequency component of the near-fault ground motion acceleration are identified,and the dimensionality reduction simulation is implemented using the spectral representation-random function method,and then the high frequency component of the velocity is integrated.Secondly,the pulse parameters are randomized,and the improved Gabor wavelet model is used to simulate the velocity and low frequency components randomly.Finally,the response spectrum and amplitude spectrum recorded by simulated values and measured values are compared to verify the correctness of the proposed method.(2)A new method to extract one-way velocity pulses based on biorthogonal wavelet basis function and a random half-wave model to simulate one-direction half-periodic velocity pulses are proposed in this paper.The probability distribution of model parameters is studied by combining 40 slip-impact ground motion records.Secondly,the power spectrum parameters of the evolution of the high-frequency components of acceleration are identified,and the dimensionality reduction is simulated by using the spectral representation-random function method,and then the high-frequency components of acceleration are integrated.At the same time,the random half wave model is used to simulate the low frequency component of velocity.Finally,the time history of the sliding impact ground motion is obtained by directly stacking the two.Finally,the correctness of the proposed method is verified by the comparison of response spectrum and amplitude spectrum recorded by actual measurement.(3)In this paper,34 near-fault ground motion records with vertical pulse type characteristics(peak velocity greater than 25cm/s,pulse index greater than 0.85)are selected,and the proposed values of high-frequency evolution power spectrum model parameters and the probability distribution of low-frequency velocity pulse model parameters are given to simulate vertical pulse type ground motion.Combined with 22 groups of measured data with horizontal and vertical pulse characteristics,Copula theory was used to systematically study the correlation of horizontal and vertical pulse parameters,and the prediction model of vertical pulse parameters under the condition of horizontal pulse parameters was established.Secondly,the correlation of peak acceleration of horizontal and vertical components was analyzed by Copula function.Furthermore,the relationship between acceleration response spectrum ratio of pulse type ground motion and period,magnitude and fault distance is studied,and a four-stage model of response spectrum of pulse type ground motion design near fault is proposed based on the current seismic code.Finally,the vertical pulse ground motion samples are generated by the method of dimension reduction simulation.(4)The finite element model of the frame-shear wall structure was established using Etabs finite element software.Two types of horizontal pulse ground motion time history samples were applied to the finite element model to calculate the structural dynamic response.The dynamic response of the frame-shear wall structure under earthquake is analyzed,and the probability density evolution theory is used to analyze and evaluate the structural dynamic reliability of the structure under random ground motion at the probability level,which verifies the effectiveness and superiority of the proposed method.