圆钢管平面K型间隙节点极限承载力及疲劳分析

发布时间：2018-02-25 10:16

  本文关键词： 圆钢管平面K型间隙节点 极限承载力 有限元 应力强度因子 疲劳寿命　出处：《长沙理工大学》2014年硕士论文　论文类型：学位论文

【摘要】：随着钢管结构在土木工程中的广泛应用,圆钢管K型节点也大量的出现在桁架、网架等结构中。尽管,目前有关K型节点受力性能方面的研究已取得了大量的研究成果,但仍有许多问题并没有得到完美的解决,仍需进一步关注。近年来,对K型节点受力性能的研究主要围绕节点极限承载力的问题而展开的,而对节点疲劳寿命方面的研究相对而言较少。此外,在国家钢结构规范中有关计算节点极限承载力的公式也并未考虑边界条件的影响,整体上偏于保守。因此,本文将以圆钢管平面K型间隙节点为研究对象,主要对节点的极限承载力、破坏模式以及疲劳寿命方面的问题进行了相关研究。首先,利用有限元方法对圆钢管平面K型间隙节点的极限承载力与破坏模式进行了探讨,并应用规范公式对部分圆钢管平面K型间隙节点的承载力进行了计算。分析时主要考虑了支、主管轴线间角度θ,支、主管直径比β(d/D),主管径厚比γ(D/T)以及四种不同边界条件与加载方式对节点极限承载力与破坏模式的影响。然后,将规范公式计算结果与有限元分析结果进行了对比,并分析了产生计算偏差的原因。研究表明节点的几何影响参数θ、β、γ对节点的极限承载力与破坏模式有不同程度的影响,并且γ是影响节点破坏模式的主要参数；当β、γ较小时,边界条件对节点极限承载力的影响基本可以忽略,当β、y较大时,边界条件对节点极限承载力的影响逐渐体现出来。其次,分析了圆钢管平面K型间隙节点的疲劳寿命问题,利用了Paris公式定量反推了节点疲劳扩展阶段的剩余寿命。分析中,一方面采用有限元软件建立了含二维表面穿透裂纹标准三点弯曲试样的有限元模型,并计算了试样的应力强度因子,另一方面应用理论公式法对试样应力强度因子进行了计算。然后将有限元分析结果与理论公式计算结果进行对比,验证了建立含裂纹体模型思路及方法的合理性。最后,将借鉴上述思路与方法建立含初始表面半椭圆裂纹圆钢管平面K型间隙节点有限元模型,并将节点应力强度因子有限元分析结果通过公式换算成有效应力强度因子代入Paris公式中计算节点的疲劳寿命。分析节点的疲劳寿命时,主要考虑了支、主管直径比β,主管径厚比γ以及裂纹深度与主管壁厚比a/T对节点疲劳寿命的影响。研究表明节点的疲劳寿命随γ、a/T值的增大而减小,随β值的增大而增大；对于主管较薄或支管直径较小的节点,β、γ的影响更加明显；对于主管较薄或初始裂纹a较大的节点,a增大,节点的疲劳寿命将急剧减小。
[Abstract]:With the wide application of steel pipe structure in civil engineering, K-joints of circular steel tube are also widely used in truss, grid structure and so on. However, there are still many problems that have not been solved perfectly and need further attention. In recent years, the research on the mechanical behavior of K-type joints is mainly focused on the ultimate bearing capacity of the joints. In addition, the formulas for calculating the ultimate bearing capacity of joints in the national code for steel structures do not take into account the influence of boundary conditions and are generally conservative. In this paper, the ultimate bearing capacity, failure mode and fatigue life of the joints with plane K clearance of circular steel pipe are studied. In this paper, the ultimate bearing capacity and failure mode of plane K type gap joints of circular steel pipe are discussed by using finite element method, and the bearing capacity of K type gap joints in plane plane of circular steel pipe is calculated by using the standard formula. The influence of angle 胃, branch, diameter ratio 尾 d / D, diameter ratio 纬 D / T) and four different boundary conditions and loading modes on ultimate bearing capacity and failure mode of joints. The calculation results of the specification formula are compared with the results of the finite element analysis, and the causes of the calculation deviation are analyzed. The results show that the geometric influence parameters 胃, 尾, 纬 of the joints have different effects on the ultimate bearing capacity and failure mode of the joints. When 尾, 纬 is small, the effect of boundary conditions on ultimate bearing capacity of joints can be neglected, and when 尾 = y is larger, the effect of boundary conditions on ultimate bearing capacity of joints is gradually reflected. Secondly, when 尾 and 纬 are small, the effect of boundary conditions on ultimate bearing capacity of joints can be neglected. In this paper, the fatigue life of plane K clearance joints of circular steel tubes is analyzed. The residual life of joints in fatigue growth stage is quantitatively deduced by using Paris formula. On the one hand, the finite element model of the standard three-point bending specimen with two-dimensional surface penetrating crack is established by using the finite element software, and the stress intensity factor of the specimen is calculated. On the other hand, the stress intensity factor of the specimen is calculated by the method of theoretical formula, and the result of finite element analysis is compared with the result of theoretical formula, which verifies the rationality of the idea and method of establishing the model of cracked body. The finite element model of plane K-type gap joints with initial surface semi-elliptic cracks of circular steel pipe is established by using the above ideas and methods. The results of finite element analysis of the joint stress intensity factor are converted into the effective stress intensity factor into the Paris formula to calculate the fatigue life of the node. In the analysis of the fatigue life of the node, the support is mainly considered. The effects of diameter ratio 尾, diameter thickness ratio 纬, crack depth to wall thickness ratio a / T on the fatigue life of joints are studied. The results show that the fatigue life of joints decreases with the increase of 纬 -a / T ratio, and increases with the increase of 尾 value. The effect of 尾, 纬 on the joints with thinner supervisor or smaller branch diameter is more obvious, and the fatigue life of the joints with thin supervisor or larger initial crack a increases sharply.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU392.3
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本文编号：1534014