【摘要】：海洋平臺(tái)結(jié)構(gòu)龐大,受風(fēng)、浪、流和冰等環(huán)境因素長(zhǎng)期作用,同時(shí)還受到地震、臺(tái)風(fēng)、海嘯和船舶碰撞等意外作用的威脅。在載荷作用下,導(dǎo)管架海洋平臺(tái)會(huì)出現(xiàn)裂紋。由于平臺(tái)部分結(jié)構(gòu)位于海面以下,裂紋不易被發(fā)現(xiàn),難以直接進(jìn)行人工檢測(cè)。當(dāng)重要部件發(fā)生裂紋并在極端海況下產(chǎn)生擴(kuò)展時(shí),會(huì)導(dǎo)致整個(gè)結(jié)構(gòu)失效,危及工作人員的生命安全,產(chǎn)生重大的經(jīng)濟(jì)損失和海洋環(huán)境污染。所以,及時(shí)并盡早地發(fā)現(xiàn)結(jié)構(gòu)的裂紋具有重要意義。 本文以某一含四分之一跨處單裂紋的簡(jiǎn)支梁為例,計(jì)算了該梁的非貫穿單邊裂紋損傷側(cè)上、下表面、貫穿裂紋的上表面和內(nèi)部非貫穿裂紋表面裂紋和內(nèi)部裂紋等情況的不同損傷程度的位移模態(tài)和應(yīng)變模態(tài)。根據(jù)已有的基于應(yīng)變模態(tài)差分原理的損傷位置直接指標(biāo)法ISMSD,利用等間距差分格式計(jì)算該簡(jiǎn)支梁非貫穿單邊裂紋應(yīng)變模態(tài)差分曲線,經(jīng)Matlab編程計(jì)算將曲線進(jìn)行光滑,計(jì)算得到直接指標(biāo)值。由直接指標(biāo)值的最大值找到對(duì)應(yīng)的兩有效極值點(diǎn),這兩個(gè)有效極值點(diǎn)間即是損傷位置。實(shí)例計(jì)算簡(jiǎn)支梁非貫穿單邊裂紋損傷應(yīng)變模態(tài)差分曲線,這些應(yīng)變模態(tài)差分曲線在損傷處發(fā)生劇烈變化。差分曲線非峰值點(diǎn)損傷在損傷處不出現(xiàn)極值,因而損傷處的差分值不為零。損傷量不同,差分曲線損傷處突變程度略有不同,其規(guī)律相似。 運(yùn)用帶有Grubbs的支持向量機(jī)法和帶有Grubbs的BP神經(jīng)網(wǎng)絡(luò)法對(duì)該非貫穿裂紋簡(jiǎn)支梁進(jìn)行損傷程度智能識(shí)別,識(shí)別并評(píng)估了四分之一跨處單裂紋的損傷程度,并從性能及準(zhǔn)確度方面對(duì)兩種方法進(jìn)行了比較。若選取應(yīng)變模態(tài)差作為網(wǎng)絡(luò)輸入指標(biāo),本文采用的兩種方法都可以得到比較高的識(shí)別精度,而且有良好適應(yīng)性。支持向量機(jī)方法相對(duì)誤差更小。 采用有限元軟件ANSYS計(jì)算了某導(dǎo)管架海洋平臺(tái)模型的一水平管件在完整狀態(tài)、含單裂紋、含雙裂紋三種情形時(shí)不同位置和不同損傷程度的頻率和應(yīng)變模態(tài)。驗(yàn)證了損傷會(huì)引起結(jié)構(gòu)的頻率降低和應(yīng)變模態(tài)突變,頻率降低的幅度隨損傷程度的增加而增大。此外還發(fā)現(xiàn),微小裂紋損傷時(shí)引起的頻率變化很小：水平管端點(diǎn)損傷和中點(diǎn)損傷的頻率下降幅度基本一致；雙裂紋情形時(shí)的頻率下降幅度均高于單裂紋情形時(shí)；損傷處應(yīng)變模態(tài)曲線發(fā)生了顯著改變,隨損傷量的增加,應(yīng)變模態(tài)曲線突變?cè)龃蟆?采用SCE-UA算法和粗粒度并行遺傳算法對(duì)平臺(tái)模型的10處單裂紋進(jìn)行了損傷程度的逐一智能識(shí)別。將應(yīng)變模態(tài)差作為SCE-UA算法和遺傳算法的輸入數(shù)據(jù),這兩種方法均能取得較高的識(shí)別精度,具有良好的適應(yīng)性。其中SCE-UA算法損傷識(shí)別結(jié)果誤差更小,更精確。 振動(dòng)診斷中的應(yīng)變模態(tài)法具有相對(duì)簡(jiǎn)單,成本較低,具有實(shí)時(shí)性、在線性、提取信號(hào)方便性和遙測(cè)性、可控性等諸多優(yōu)點(diǎn)。本文的研究為工程實(shí)際應(yīng)用提供了一定的參考價(jià)值,在結(jié)構(gòu)損傷診斷識(shí)別中具有推廣價(jià)值。
[Abstract]:The offshore platform has a large structure and is subject to environmental factors such as wind, waves, currents and ice for a long time, and is also threatened by unexpected effects such as earthquakes, typhoons, tsunamis and ship collisions. Under the load, cracks will appear in the jacket offshore platform. Because part of the platform structure is located below the sea level, the cracks are not easy to be found, so it is difficult to detect directly by hand. When an important component is cracked and propagated under extreme sea conditions, it will lead to the failure of the whole structure, endanger the life of the staff, and cause serious economic losses and marine environmental pollution. Therefore, it is of great significance to discover the cracks of the structure in time and as early as possible. In this paper, a simple supported beam with a single crack of 1/4 span is taken as an example to calculate the upper and lower surface of the non-penetrating unilateral crack damage side. The displacement modes and strain modes of different damage degree of the upper surface and inner non-penetrating crack surface crack and internal crack of penetrating crack. According to the existing damage location direct index method based on strain mode difference principle, ISMSD, calculates the strain mode difference curve of the simple supported beam by equal distance difference scheme. The curve is smoothed by Matlab programming. The direct index value is calculated. The corresponding two effective extremum points are found from the maximum value of the direct index value, and the damage position is between the two effective extremum points. An example is given to calculate the strain mode difference curves of non-perforating unilateral crack damage of simply supported beams, which change dramatically at the damage site. There is no extreme value at the damage point, so the difference value of the damage is not zero. The degree of mutation at the damage point of the difference curve is slightly different with different damage amount, and the law is similar. The support vector machine with Grubbs and the BP neural network with Grubbs are used to identify the damage degree of the non-penetrating crack beam, and the damage degree of 1/4 span single crack is identified and evaluated. The performance and accuracy of the two methods are compared. If the strain modal difference is selected as the input index of the network, the two methods used in this paper can obtain high recognition accuracy and good adaptability. The relative error of support vector machine is smaller. The finite element software ANSYS is used to calculate the frequencies and strain modes of a horizontal pipe fitting in a jacket offshore platform model under three conditions: complete state, single crack and double crack. It is proved that the damage can cause the frequency decrease and the strain mode mutation of the structure, and the amplitude of the frequency decrease increases with the increase of the damage degree. It is also found that the frequency variation caused by micro-crack damage is very small: the frequency decrease range of horizontal tube end damage and midpoint damage is basically the same, and the frequency decrease amplitude of double crack case is higher than that of single crack case. The strain mode curve of the damage site changed obviously, and the sudden change of the strain mode curve increased with the increase of the damage amount. SCE-UA algorithm and coarse-grained parallel genetic algorithm are used to identify the damage degree of 10 single cracks in the platform model one by one. The strain modal difference is used as the input data of SCE-UA algorithm and genetic algorithm. These two methods can achieve high recognition accuracy and have good adaptability. The result of SCE-UA damage detection is less and more accurate. The strain mode method in vibration diagnosis has many advantages, such as relatively simple, low cost, real-time, linear, easy to extract signal and telemetry, controllability and so on. The research in this paper provides a certain reference value for the practical application of engineering, and it is worth popularizing in the structural damage diagnosis and identification.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2013
【分類號(hào)】：TU317;P742

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 瞿偉廉,陳偉;多層及高層框架結(jié)構(gòu)地震損傷診斷的神經(jīng)網(wǎng)絡(luò)方法[J];地震工程與工程振動(dòng);2002年01期

2 瞿偉廉,黃東梅;高聳塔架結(jié)構(gòu)節(jié)點(diǎn)損傷基于神經(jīng)網(wǎng)絡(luò)的兩步診斷法[J];地震工程與工程振動(dòng);2003年02期

3 孫增壽,韓建剛,任偉新;基于小波分析的結(jié)構(gòu)損傷檢測(cè)研究進(jìn)展[J];地震工程與工程振動(dòng);2005年02期

4 孫增壽,韓建剛,任偉新;基于曲率模態(tài)和小波變換的結(jié)構(gòu)損傷位置識(shí)別[J];地震工程與工程振動(dòng);2005年04期

5 顧培英,陳厚群,李同春,鄧昌;用應(yīng)變模態(tài)技術(shù)診斷梁結(jié)構(gòu)的損傷[J];地震工程與工程振動(dòng);2005年04期

6 任權(quán) ,李洪升 ,郭杏林;基于應(yīng)變模態(tài)變化率的壓力管道無(wú)損檢測(cè)[J];大連理工大學(xué)學(xué)報(bào);2001年06期

7 張紅梅,李巖,裴強(qiáng);低溫下鋼結(jié)構(gòu)裂縫損傷識(shí)別方法(I)[J];低溫建筑技術(shù);2004年05期

8 涂志華，張忠，，趙立中，張培強(qiáng);鋁合金板低溫動(dòng)態(tài)特性及力學(xué)參數(shù)的實(shí)驗(yàn)研究[J];低溫工程;1995年02期

9 袁穎;林皋;柳春光;周愛紅;;遺傳算法在結(jié)構(gòu)損傷識(shí)別中的應(yīng)用研究[J];防災(zāi)減災(zāi)工程學(xué)報(bào);2005年04期

10 易偉建,劉霞;基于遺傳算法的結(jié)構(gòu)損傷診斷研究[J];工程力學(xué);2001年02期

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