焊接圆钢管K型节点焊缝周围热点应力分布规律研究

【作者】 杜之富；

【导师】 邵永波；

【作者基本信息】 烟台大学 ， 结构工程， 2008， 硕士

【摘要】 圆截面管状节点作为一种支撑结构已被广泛应用于海洋平台、铁路、公路桥梁等结构工程。圆钢管K型节点是管状节点其中一种类型,被非常广泛应用于实际工程。在实际工程中,K型节点往往长期承受由风、海浪、冰和潮汐等引起的循环荷载作用。在这些循环荷载长期作用下,管节点焊缝处容易发生疲劳破坏。这就需要对管节点的疲劳性能进行研究以及对节点疲劳寿命进行预测。管节点的疲劳寿命可以用其所能承受的循环荷载的循环次数表示。本文采用了S—N曲线法来对K型节点疲劳性能进行研究。热点应力可以用一个参数应力集中系数来描述。本文应用有限元方法对K型节点焊缝周围的热点应力分布规律进行了分析。首先,采用有限元网格分区产生方法生成了K型节点的有限元模型,这种方法可以根据计算精度的需要把整个K型节点结构划分为几个不同的子区域,其中每个子区域可以由不同类型的单元和网格密度组成。然后,在提出有限元模型的基础上,应用有限元软件ABAQUS计算了一个在三种基本荷载作用下的K型节点有限元模型,并把计算结果与文献中的试验结果进行了对比,发现两种方法得到的结果吻合很好,从而证明了本文所建立的焊接圆钢管K型节点的有限元模型分析节点焊缝周围应力分布情况的可行性和准确性。应用试验验证后的有限元模型,产生1152个K型节点模型分析了几何参数α、β、γ、τ和θ对承受基本荷载的K型节点焊缝周围的热点应力分布规律影响。通过模型参数分析,发现在三种基本荷载作用下K型节点焊缝周围热点应力分布情况是受几何参数影响的。在几何参数不同的情况下,热点应力的位置将会在冠点和鞍点之间发生移动。在上述几何参数分析的基础上,分别提出了三种基本荷载作用下的K型节点沿焊缝的应力集中系数的参数公式,并进行了参数公式的误差分析,通过误差分析可知本文拟合出的K型节点焊缝周围应力集中系数分布的参数公式计算焊缝周围的应力集中系数是准确的、可行的。本文所提出的公式可以用于实际工程中的管节点设计和分析,而且也为我国钢结构规范在对管节点疲劳性能方面进行规定提供有力的依据。更多还原

【Abstract】 Circular hollow section joints, as supporting structure, have been widely used in offshore engineering, railway and highway bridge engineering. Circular tubular K-joints are one type of these joints, and have been adopted in practical structures. In practice, K-joints are frequently subjected to cyclic loads caused by wind, seawater wave, current, and so on. Under these cyclic loads, fatigue failure will easily occur at the weld toe of tubular joints. So fatigue behaviors of tubular joints should be studied. And the fatigue life of tubular joints should be predicted, which can be expressed using the number of cycles to failure. In this study, S-N curve method has been used to analyze the fatigue behavior of circular tubular K-joints. It is well known that hot spot stress can be expressed using a parameter named stress concentration factor (SCF).In this thesis, the finite element method has been adopted to analyze the distribution of hot spot stress along the weld of circular tubular K-joints. Firstly, sub-zone method for producing the finite element mesh has been used to produce the finite element models of tubular K-joints. According to the requirement of computation accuracy, the entire K-joint can be divided into several sub-zones using this method. In different zones, the element type and the mesh density can be different. Secondly, based on the produced finite element model, a K-joint model, which is subjected to three basic loads ( i.e. axial load, in-plane bending load and out-plane bending load ), has been calculated and analyzed respectively. And the numerical results have been compared with the experimental results from reference [23], it can be found that the results from the finite element model agree much better with the experimental results, and therefore it is proved that it is feasible and accurate to study the distribution of hot spot stress along the weld of tubular K-joint using the proposed finite element model of K-joints.Using the finite element models proved by experiment, 1152 models have been produced and used to analyze the effect of geometrical parametersα、β、γ、τandθon the distribution of hot spot stress along the weld of tubular K-joint which is subjected to three basic loads. Through the numerical analysis on these models, it is found that the hot spot stress distribution along the weld of tubular K-joints under three basic loads is determined by some geometrical parameters. When some geometrical parameters are different, the position of the hot spot stress shifts between the crown and the saddle.Based on the analysis of the effect of geometrical parameters, a set of parametric SCF equations for tubular K-joints subjected to three basic loads have been proposed respectively, and then error analysis has been done. From the error analysis, it can be found that parametric SCF equations for tubular K-joints is feasible, accurate and agree very well with most models. The SCF equations proposed in this thesis could be used to design and analyze the tubular joints in practical engineering, and could provide the effectively dependence for the regulations on the fatigue behaviors of tubular joints in China’s code for design of steel structure.更多还原