Probabilistic Model Of Non-stationary Ground Motion And Seismic Dynamic Analysis Of The Gravity Dam

Seismic problems of high dam have been paid much attention as a research hotspot in recent years. In seismic research of high dam, seismic input model, structuralseismic response and seismic reliability analysis are indispensable and correlativeaspects for seismic analysis of dam structure. Because of ground motion has obviousrandom and non-stationary of strength and frequency, nonlinear dynamic responseanalysis of dam structure is influenced significantly. Thus, this paper establishes theprobability model of non-stationary ground motion based on specifications for seismicdesign of hydraulic structures, and uses probability density evolution method toanalyze random seismic response and calculate seismic reliability for Jinanqiao dam.The main contents of this paper are as follows:(1) A new kind spectral representation-random function method of fullynon-stationary ground motion is suggested. Firstly, two spectral representationmethods simulated by non-stationary random process are exported based on Priestleyevolution spectrum theory, namely, the first kind spectral representation is expressedby linear combinations of2N standard orthogonal random variables, the secondspectral representation is expressed by superposing cosine series of N Independentrandom phase angles. Secondly, comparing the advantages and disadvantagesbetween the two spectral representation methods, the first spectral representation isselected as simulating method for non-stationary ground motion. At the same time,spectral representation-random function method simulating fully non-stationaryground motion is established. In the spectral representation-random function method,the purpose that using one to two basic random variables expresses the originalrandom process on the second-order statistics achieves. Finally, spectralrepresentation-random function method is explained physically.(2) Generalized evolutionary spectrum model of fully non-stationary groundmotion is developed. Based on power spectrum density function, a kind of generalizedevolutionary spectrum model of time domain and frequency domain fullynon-stationary ground motion is developed. Generalized evolutionary spectrum modelcan reflect the time domain characteristics and frequency domain characteristicscomprehensively, such as non-stationary characteristic, duration, peak groundacceleration of strength and non-stationary characteristic, site characteristic, responsespectrum of frequency.(3) Ground motion probability model based on specifications for seismic design of hydraulic structures is established. On the basis of spectral representation-randomfunction method and fully evolutionary spectrum model above, non-stationary groundmotion probability model is established, one advantage of it is that generalizedevolutionary spectrum produces representative sample sets of specified probabilitydirectly by using discrete representative point sets of basic random variables, thusground motion can be studied at the level of representative sample sets. Combiningwith the current "specifications for seismic design of hydraulic structures"(DL5073-2000) of our country, representative history time sets of ground motion used byseismic design of hydraulic structures are established on the condition of4sites. Atthe same time, comparing the difference between second-order statistics and targetvalues of representative history time, and the fitting deviation between averageresponse spectrum and specification response spectrum of representative history time,the probability model above with the advantage of high efficiency and high accuracyhas been verified.(4) Nonlinear random seismic response of concrete gravity dam and probabilitydensity evolutionary analysis are conducted. The combination of non-stationaryground motion and probability density evolution theory of probability model cananalyze the random seismic response and seismic reliability of complicate engineeringstructures. For this reason, with the example of seismic analysis of Jinanqiao concretedam in our country, Nonlinear random seismic response analysis and seismicreliability calculation of Jinanqiao dam are conducted, and the probability model ofnon-stationary ground motion above has been verified further in the engineeringapplication of effectiveness.Finally, the content of this paper is summarized, the problems requiring furtherstudies are prospected.