發(fā)布時間：2018-06-25 03:23

  本文選題：導管架海洋平臺 + 節(jié)點局部柔度��； 參考：《煙臺大學》2017年碩士論文

【摘要】：空心圓鋼管結(jié)構(gòu)由于其受力性能的優(yōu)越性、施工的簡單快捷性以及外觀的美觀性被廣泛的應用在日常的大型空間鋼結(jié)構(gòu)建筑以及導管架海洋平臺結(jié)構(gòu)中。鋼管結(jié)構(gòu)的管件之間一般使用焊接連接進而形成相貫節(jié)點,由于節(jié)點處弦管的徑向剛度遠小于支管的軸向剛度,因此當荷載由支管傳遞到主管時,節(jié)點相貫線處的主管壁會發(fā)生局部變形,節(jié)點出現(xiàn)半剛性的特性,而在實際工程中,鋼管桁架結(jié)構(gòu)常被簡化為普通梁單元模型,這種方法建模簡單,分析速度快,但忽略了節(jié)點柔度的影響,因此不能確保分析結(jié)果的準確性,對結(jié)構(gòu)的安全設計造成影響。在計算中如果想準確的模擬節(jié)點的局部柔度就需要使用實體單元或殼單元建立整個結(jié)構(gòu)的有限元模型,而這種方法對于大型的管桁架結(jié)構(gòu)來說建模過程極為復雜,占用大量電腦內(nèi)存,且分析效率低。為了解決這個問題,本文提出了在普通梁單元模型中引入虛擬梁單元(FBE,Fictitious Beam Element)的方法,在結(jié)構(gòu)的彈性變形階段,通過定義虛擬梁單元的軸向剛度和抗彎剛度來實現(xiàn)節(jié)點處的局部軸向變形和彎曲變形,虛擬梁單元的軸向剛度和抗彎剛度可使用相關(guān)文獻給出的節(jié)點局部柔度計算公式進行等效。共設計12組不同幾何參數(shù)的T/Y型節(jié)點管桁架模型,并用ABAQUS軟件構(gòu)建各組模型的殼單元模型,同時用Fortran編寫剛架程序構(gòu)建剛架模型和簡化模型。通過對比三種不同建模方法的計算結(jié)果,驗證了簡化模型在管桁架結(jié)構(gòu)彈性變形階段的精確性,并直觀地反映了節(jié)點局部柔度在鋼管結(jié)構(gòu)靜力分析中的顯著影響。在結(jié)構(gòu)的彈塑性變形階段,對虛擬梁單元的材料屬性進行了等效定義,其方法為:首先用有限元軟件對管節(jié)點單獨建模并計算其荷載-位移曲線,然后將求出的曲線通過公式轉(zhuǎn)換為虛擬梁單元的應力-應變曲線。建立簡化模型時,將這種等效的本構(gòu)關(guān)系應用到虛擬梁單元的彈塑性材料屬性中,以虛擬梁單元模擬管節(jié)點進入塑性階段后的局部變形。對設計的12組T/Y型節(jié)點管桁架進行彈塑性分析,通過對比殼單元模型、簡化模型和剛架模型計算出的荷載-位移曲線,驗證了簡化模型在結(jié)構(gòu)的彈塑性變形階段受力分析中的精確性。為了研究節(jié)點柔度對導管架海洋平臺Pushover分析的影響,本文取一導管架海洋平臺結(jié)構(gòu)實例進行靜力彈塑性分析,借助SAP2000結(jié)構(gòu)設計軟件用能力譜的方法求解出結(jié)構(gòu)在8度罕遇地震作用下的目標位移,然后用ABAQUS有限元分析軟件對結(jié)構(gòu)分別建立殼單元模型、簡化模型和剛架模型,并進行推覆分析得出Pushover曲線,發(fā)現(xiàn)剛架模型會過高估計結(jié)構(gòu)的側(cè)向剛度,造成Pushover分析結(jié)果有很大偏差,不利于結(jié)構(gòu)的安全抗震評估,而簡化模型計算出的Pushover曲線與殼單元模型計算出的曲線有很高的吻合度,可以在實際工程的靜力彈塑性分析中推廣采用。
[Abstract]:The hollow circular steel pipe structure is widely used in large space steel structure and jacket offshore platform structure because of its superiority of mechanical performance, simplicity of construction and beauty of appearance. Welded joints are usually used to form intersecting joints between pipe fittings of steel pipe. Because the radial stiffness of chord at the joint is much smaller than the axial stiffness of the branch pipe, when the load is transferred from the branch tube to the supervisor, The superstructure of the joint intersecting line will be partially deformed and the joint will be semi-rigid. However, in practical engineering, the steel tube truss structure is often simplified as a common beam element model. This method is simple in modeling and fast in analysis. However, the influence of node flexibility is ignored, so the accuracy of the analysis results can not be ensured, which will affect the safety design of the structure. In order to simulate the local flexibility of nodes accurately, the finite element model of the whole structure needs to be established by using solid element or shell element, and this method is very complicated for large tubular truss structures. Takes up a lot of computer memory, and the analysis efficiency is low. In order to solve this problem, a method of introducing FBE-Based beam element into the ordinary beam element model is proposed in this paper, which is used in the elastic deformation stage of the structure. By defining the axial stiffness and bending stiffness of the virtual beam element, the local axial deformation and bending deformation are realized. The axial stiffness and flexural stiffness of the virtual beam element can be equivalent by using the local flexibility formula given in the relevant literature. Twelve groups of T / Y node tube truss models with different geometric parameters are designed. The shell element models of each model are constructed by Abaqus software. Fortran is used to program the rigid frame model and simplify the model. By comparing the results of three different modeling methods, the accuracy of the simplified model in the elastic deformation stage of the tubular truss structure is verified, and the obvious influence of the local flexibility of the joints on the static analysis of the steel tube structure is reflected intuitively. In the elastic-plastic deformation stage of the structure, the material properties of the virtual beam element are defined equivalent. The method is as follows: firstly, the pipe joints are modeled separately by finite element software and the load-displacement curves are calculated. Then the obtained curve is converted into the stress-strain curve of the virtual beam element through the formula. When the simplified model is established, the equivalent constitutive relation is applied to the elastic-plastic material properties of the virtual beam element, and the virtual beam element is used to simulate the local deformation of the pipe joint after it enters the plastic stage. The elastoplastic analysis of 12 groups of T / Y type tubular truss is carried out. The load-displacement curves calculated by comparing the shell element model with the rigid frame model are simplified. The accuracy of the simplified model in the stress analysis of the elastoplastic deformation stage of the structure is verified. In order to study the effect of node flexibility on pushover analysis of jacket offshore platform, the static elastic-plastic analysis of a jacket offshore platform is carried out in this paper. With the help of SAP2000 structural design software, the target displacement of the structure under the action of 8 degrees rare earthquake is calculated by the method of capability spectrum, and then the shell element model, simplified model and rigid frame model of the structure are established by Abaqus finite element analysis software. The pushover curve is obtained by push-over analysis. It is found that the rigid frame model can overestimate the lateral stiffness of the structure, which results in a great deviation of the pushover analysis results, which is not conducive to the seismic assessment of the safety of the structure. The pushover curve calculated by the simplified model has a high coincidence with the curve calculated by the shell element model, which can be widely used in the static elastoplastic analysis of practical engineering.
【學位授予單位】：煙臺大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P75

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