【摘要】：核電工程中的防波堤主要為核電廠(chǎng)的廠(chǎng)區(qū)及循環(huán)冷卻水和核安全用水等的取排水設(shè)施提供保護(hù),使其免受波浪的襲擊,保護(hù)泵房取水不受波浪的影響。其地基通常是工程性質(zhì)差的海岸海床地基土,在地震等外界作用下,易造成地質(zhì)災(zāi)害,其穩(wěn)定性對(duì)廠(chǎng)區(qū)及取排水設(shè)施的正常運(yùn)行有很大影響。防波堤地基土以及筑堤材料強(qiáng)度變異性較大,僅僅用安全系數(shù)評(píng)價(jià)其穩(wěn)定性是不夠的,而目前對(duì)核電工程中防波堤的可靠度研究比較少。本文研究了一種新的樣本取樣方法,在傳統(tǒng)的響應(yīng)面法和改進(jìn)的Kriging模型基礎(chǔ)上構(gòu)造功能函數(shù),再利用Hasofer-Lind可靠度指標(biāo)計(jì)算方法進(jìn)行可靠度分析。 首先利用了傳統(tǒng)的二次多項(xiàng)式響應(yīng)面進(jìn)行了防波堤的可靠度研究。由于采用響應(yīng)面法計(jì)算結(jié)構(gòu)可靠性時(shí)都需要迭代,直至可靠度指標(biāo)收斂。迭代過(guò)程中每次都是在當(dāng)前驗(yàn)算點(diǎn)附近抽取新的樣本來(lái)構(gòu)造響應(yīng)面。對(duì)于復(fù)雜問(wèn)題,每次抽樣都需要大量的計(jì)算時(shí)間。本文提出了一個(gè)響應(yīng)面構(gòu)造的改進(jìn)方法——樣本累積法,即用新樣本和本次迭代以前所有的樣本一起來(lái)構(gòu)造響應(yīng)面,從而最大程度地利用已有樣本點(diǎn)的信息,避免了可靠度迭代陷入局部極值或往復(fù)震蕩難以收斂的問(wèn)題,提高了計(jì)算效率。如果僅選擇離極限狀態(tài)曲面很近的樣本點(diǎn)參與累積和響應(yīng)面的構(gòu)造,可以進(jìn)一步提高計(jì)算效率。通過(guò)兩個(gè)算例驗(yàn)證了樣本累積法的準(zhǔn)確性和計(jì)算效率。最后采用改進(jìn)方法分析了某核電工程防波堤的穩(wěn)定可靠性。 傳統(tǒng)的響應(yīng)面法常采用二次多項(xiàng)式構(gòu)造功能函數(shù),難以擬合非線(xiàn)性程度高的隱式的極限狀態(tài)曲面,且對(duì)抽樣中心的選擇以及抽樣方法敏感。本文利用粒子群算法的全局優(yōu)化能力改進(jìn)了Kriging模型,解決了相關(guān)參數(shù)的優(yōu)化求解問(wèn)題,能夠更好地模擬非線(xiàn)性程度高的隱式的極限狀態(tài)曲面。在樣本選取上仍采用了樣本累積的方法。算例表明基于樣本累積的改進(jìn)Kriging模型能夠很好地?cái)M合極限狀態(tài)曲面,效率和精度較傳統(tǒng)響應(yīng)面法有較大提高。進(jìn)一步研究發(fā)現(xiàn)選擇離極限狀態(tài)曲面近的樣本點(diǎn)進(jìn)行樣本累積和功能函數(shù)構(gòu)造能夠提高計(jì)算效率。根據(jù)邊坡穩(wěn)定可靠度分析的實(shí)例,發(fā)現(xiàn)選取安全系數(shù)在[0.9,1.1]范圍內(nèi)的樣本點(diǎn)進(jìn)行累積是合適的�；跇颖纠鄯e的改進(jìn)Kriging模型對(duì)抽樣中心和抽樣方法不敏感,具有更好的適應(yīng)性。最后分析了某核電工程防波堤穩(wěn)定的可靠性。
[Abstract]:The breakwater in the nuclear power project mainly provides protection for the plant area of the nuclear power plant and water collection and drainage facilities such as circulating cooling water and nuclear safety water to protect it from the wave attack and to protect the pumping station from the influence of the wave. The foundation is usually shoreline subsoil with poor engineering properties, which is easy to cause geological disasters under earthquake and other external effects, and its stability has a great influence on the normal operation of the plant area and drainage facilities. It is not enough to evaluate the stability of breakwater foundation soil and embankment material by safety factor, but the reliability of breakwater in nuclear power engineering is less studied at present. In this paper, a new sample sampling method is studied. On the basis of the traditional response surface method and the improved Kriging model, the function is constructed, and then the reliability analysis is carried out by using the Hasofer-Lind reliability index calculation method. Firstly, the reliability of breakwater is studied by using the traditional quadratic polynomial response surface. Since the response surface method is used to calculate the reliability of structures, it is necessary to iterate until the reliability index converges. In each iteration, new samples are taken near the current check point to construct the response surface. For complex problems, it takes a lot of calculation time for each sampling. In this paper, an improved method of response surface construction-sample accumulation method is proposed, that is, the new sample is used to construct the response surface together with all the samples prior to this iteration, so that the information of the existing sample points can be used to the maximum extent. The reliability iteration can avoid the problem that it is difficult to converge in local extremum or reciprocating oscillation, and the computational efficiency is improved. If only the sample points close to the limit state surface are selected to participate in the construction of cumulative and response surfaces, the computational efficiency can be further improved. Two examples are given to verify the accuracy and efficiency of the sample accumulation method. Finally, the stability and reliability of the breakwater of a nuclear power project are analyzed by the improved method. The traditional response surface method often uses quadratic polynomial to construct the function, which makes it difficult to fit the implicit limit state surface with high nonlinearity, and is sensitive to the selection of sampling center and sampling method. In this paper, the global optimization ability of particle swarm optimization (PSO) is used to improve the Kriging model, solve the optimization problem of related parameters, and can better simulate the implicit limit state surface with high nonlinearity. The method of sample accumulation is still used in the selection of samples. An example shows that the improved Kriging model based on sample accumulation can fit the limit state surface very well, and the efficiency and accuracy are greatly improved compared with the traditional response surface method. Furthermore, it is found that selecting the sample point close to the limit state surface to construct the sample accumulation and function can improve the computational efficiency. According to the example of slope stability reliability analysis, it is found that it is appropriate to select the sample point with safety factor in the range of [0.9, 1.1] to accumulate. The improved Kriging model based on sample accumulation is not sensitive to sampling center and sampling method, and has better adaptability. Finally, the reliability of breakwater stability in a nuclear power project is analyzed.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TM623;U656.2

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