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  本文選題：自升式平臺　切入點：管節(jié)點　出處：《江蘇科技大學》2015年碩士論文　論文類型：學位論文

【摘要】：自升式海洋平臺其所處的工作環(huán)境極其惡劣,一旦出現(xiàn)安全性問題,往往造成巨大經(jīng)濟的損失,所以很有必要對平臺進行疲勞壽命分析。本文以Super M2自升式平臺為研究對象,結合波浪理論及相關環(huán)境載荷公式對其進行靜力強度分析;然后,針對平臺樁腿薄弱處即管節(jié)點位置,分析了該管節(jié)點在軸力作用下的沿焊縫周圍的應力分布規(guī)律及其各幾何參數(shù)對應力的敏感性;最后,基于兩種疲勞理論對平臺樁腿關鍵點進行平臺的疲勞壽命分析并對其結果進行對比討論。其具體的研究內(nèi)容如下:(1)本文以Super M2自升式平臺為研究對象,探討了相關疲勞理論及環(huán)境載荷理論。通過合理的簡化建立了平臺的有限元模型,其中采用彈簧單元模擬平臺與樁腿之間的連接關系,通過在定義的質(zhì)量點上施加重力場的方式來模擬平臺重物的分布。另外,考慮到樁靴與土壤連接的復雜性,采用Abaqus中有的線彈性模型進行處理,從而提高了自升式平臺模擬分析的準確度。(2)設置合理的環(huán)境變量,采用斯托克斯5階波波浪理論及Morision公式,并且考慮了波浪的動壓力與靜水壓力所造成的浮力效應,分析計算了自升式平臺在預壓和風暴自存工況下的應力分布情況。并依據(jù)CCS規(guī)范進行強度校核,結果滿足強度要求。(3)針對平臺樁腿薄弱處即管節(jié)點位置,分析了該處在軸力作用下的沿焊縫周圍的應力分布規(guī)律。然后結合正交試驗理論,分析了管節(jié)點各幾何參數(shù)對其應力影響的敏感性。(4)采用譜分析法對平臺關鍵節(jié)點剩余壽命進行疲勞壽命分析,首先利用stokes fifth-order波浪理論來分析計算了不同浪向角及波浪頻率下典型節(jié)點的熱點應力傳遞函數(shù),再結合中國南海波浪散布圖以及疲勞理論,完成對樁腿各典型節(jié)點的疲勞強度評估。得出樁腿疲勞壽命為41.3年,其位于水面附近即為樁腿的飛濺區(qū)。(5)對裂紋尖端進行數(shù)值模擬分析,得出了其附近的應力場和位移場的分布情況。依據(jù)ABS設計規(guī)范,基于斷裂力學對海洋平臺樁腿危險點進行疲勞壽命計算,最終獲得樁腿的使用壽命為33.2年,滿足平臺服役年限的要求。相比S-N曲線的疲勞設計的計算方法,裂紋擴展的計算方法考慮了結構件本身存在的焊接缺陷,因而使得其計算的疲勞壽命要短,更為保守。
[Abstract]:The working environment of jack-up offshore platform is extremely bad, once safety problems appear, it often causes huge economic losses, so it is necessary to analyze the fatigue life of the platform. This paper takes Super M2 jack-up platform as the research object. Combined with wave theory and related environmental load formula, the static strength analysis is carried out, and then, aiming at the weak position of the platform pile leg, that is, the position of the pipe joint, The stress distribution law and the sensitivity of the geometric parameters to the stress of the pipe joints around the weld under axial force are analyzed. Based on two kinds of fatigue theory, the fatigue life of platform is analyzed and the results are compared and discussed. The concrete research contents are as follows: 1) this paper takes Super M2 bootstrap platform as the research object. The related fatigue theory and environmental load theory are discussed. The finite element model of the platform is established by reasonable simplification, in which spring element is used to simulate the connection between the platform and the pile leg. The distribution of platform weight is simulated by applying gravity field to the defined mass point. Considering the complexity of the connection between the pile boots and the soil, the linear elastic model in Abaqus is used to deal with the problem. Therefore, the accuracy of simulation and analysis of the jack-up platform is improved. The reasonable environmental variable is set up. The Stokes' fifth order wave theory and Morision formula are adopted, and the buoyancy effect caused by the dynamic pressure and hydrostatic pressure of the wave is considered. The stress distribution of the jack-up platform under preloading and storm self-storage is analyzed and calculated. According to the CCS code, the strength of the platform is checked, and the results meet the strength requirements. 3) aiming at the position of the pipe joint where the pile leg is weak, the stress distribution of the platform is calculated under the condition of pre-loading and storm self-storage. The stress distribution around the weld under axial force is analyzed, and then the orthogonal test theory is used to analyze the stress distribution around the weld. The sensitivity of the geometric parameters of pipe joints to the stress is analyzed. (4) the residual life of the key joints of the platform is analyzed by spectrum analysis method, and the fatigue life of the key joints of the platform is analyzed by the method of spectrum analysis. In this paper, stokes fifth-order wave theory is used to analyze and calculate the stress transfer function of typical nodes at different wave angles and wave frequencies, and then combined with wave dispersion diagram and fatigue theory in the South China Sea. The fatigue strength of the typical joints of the pile leg is evaluated. The fatigue life of the pile leg is 41.3 years, which is located near the water surface as the spatter zone of the pile leg. (5) the crack tip is numerically simulated and analyzed. The distribution of stress field and displacement field in the vicinity is obtained. According to ABS design code, the fatigue life of pile leg is calculated based on fracture mechanics, and the service life of pile leg is 33.2 years. Compared with the fatigue design method of S-N curve, the calculation method of crack propagation takes into account the welding defects in the structure itself, which makes the fatigue life of the platform shorter and more conservative.
【學位授予單位】：江蘇科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P75

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本文編號：1636878