基于能量的随机有限断层法研究

发布时间：2018-03-25 10:06

本文选题：随机有限断层法　切入点：地震动　出处：《南昌航空大学》2015年硕士论文

【摘要】：工程中常用时程分析法研究结构在地震作用下的反应。人工合成的加速度时程在结构振动分析中不可或缺。随机有限断层法因在模拟高频地震动方面有着独到的优势,常应用于实际工程中。在加速度时程模拟过程中,随机有限断层法采用的震源参数对模拟结果有很大的影响,往往因为不同研究者所关注的角度不同,所采用的震源参数也会有所不同,从而得到不同的结果。比如应力降的取值将影响地震动的幅值,kappa因子对高频地震动会有影响,断层的走向、倾角、场址类别以及场址的位置等都会影响所合成的地震动。此外,随机有限断层法在模拟近场基岩地震动时,在某些频段存在能量偏低的现象。本文采用随机有限断层法模拟近场基岩地震动,计算模拟加速度时程的能量在各个频段分布,通过对模拟时程与实际地震近场基岩记录的能量在频域的分布情况的对比分析,找出两者间的差异;采取调整某些频段的能量分布的方法,以实现调整后的模拟近场基岩地震动与实际记录时程相符或更为接近的目的。主要的研究内容如下:1)以美国工程强震中心数据库中的近场基岩场地的加速度记录为数据基础,运用傅氏变换得到记录的能量分布曲线,分析能量在频域的分布特征以及能量与震级和震源距的关系,揭示了水平向和竖向地震动时程的能量分布规律。2)利用基于随机有限断层法的EXSIM模拟程序,探讨了震源参数—kappa因子、应力降、方位角和断层倾角等对模拟加速度时程的幅值、反应谱和能量分布曲线的影响规律。3)提出了一种基于能量的改进随机有限断层法。该法通过调整能量在频域的分布比例,得到与实际地震记录更为逼近的模拟地震动时程。分别以具有丰富近场基岩地震记录资料的美国北岭地震及汶川地震为例,选取合理的震源模型和震源参数,模拟得到了近场基岩地震动时程。通过对比分析模拟地震动与实际记录在能量分布、加速度峰值和反应谱等方面的差异,以验证改进方法的合理性和可行性。
[Abstract]:Time history analysis is commonly used in engineering to study the response of structures to earthquake. Synthetic acceleration time history is indispensable in structural vibration analysis. Stochastic finite fault method has unique advantages in simulating high frequency ground motion. In the process of acceleration time history simulation, the focal parameters used by stochastic finite fault method have great influence on the simulation results, often because different researchers pay attention to different angles. For example, the magnitude of the stress drop will affect the amplitude of the ground motion and the kappa factor will have an effect on the high frequency ground motion, the strike of the fault, the angle of inclination, The type of site and the location of the site will affect the synthetic ground motion. In addition, the stochastic finite fault method is used to simulate the near-field ground motion of bedrock. There is a phenomenon of low energy in some frequency bands. In this paper, stochastic finite fault method is used to simulate near-field bedrock ground motion, and the energy distribution of simulated acceleration time history is calculated in each frequency band. By comparing and analyzing the distribution of energy in the frequency domain between the simulated time history and the actual seismic near field bedrock record, the difference between them is found out, and the method of adjusting the energy distribution in some frequency bands is adopted. In order to achieve the objective that the adjusted simulation of near-field bedrock ground motion is consistent with or closer to the actual recorded time history, the main research contents are as follows: 1) based on the acceleration records of the near-field bedrock site in the American Engineering strong earthquake Center Database, The energy distribution curve recorded by Fourier transform is used to analyze the distribution characteristics of energy in frequency domain and the relationship between energy and magnitude and focal distance. The energy distribution of horizontal and vertical ground motion is revealed. 2) using the EXSIM simulation program based on stochastic finite fault method, the amplitude of focal parameter -kappa factor, stress drop, azimuth angle and fault dip angle on the simulated acceleration time history is discussed. This paper presents an improved stochastic finite fault method based on energy, which adjusts the distribution of energy in frequency domain by adjusting the distribution ratio of energy in frequency domain. The time history of simulated ground motion, which is more approximate to the actual seismic record, is obtained. Taking the North Ridge earthquake and Wenchuan earthquake with abundant near-field bedrock seismic records as examples, a reasonable focal model and source parameters are selected. In order to verify the rationality and feasibility of the improved method, the difference of energy distribution, acceleration peak value and response spectrum between the simulated ground motion and the actual record is analyzed by comparing the time history of near-field bedrock ground motion.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P315.9

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