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Extremely low cycle fatigue assessment method for structural steel members

钢结构构件极低周疲劳评估方法

基本信息

批准号：
18360217
负责人：
TATEISHI Kazuo
金额：
$ 5.89万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18360217/
关键词：
Extremely low cycle fatigue Low cycle fatigue assessment method Structural steel members Welded joints Local strain Crack initiation life 低サイクル疲労溶接形状耐震設計ひずみ地震応答解析

项目摘要

In order to assess the extremely low cycle fatigue strength of welded joints, the strain at weld toe where cracks usually initiates (local strain), should be estimated. For obtaining the local strain by FEA, the use of very fine elements is inevitable to simulate the accurate weld toe shape. It is not practical, however, to use fine mesh in engineering practice. Therefore in this study, the correlation between the load strain at the weld toe and the nominal strain of the member, which can be obtained by beam model conventionally used in design phase, was established. Namely, the strain ranges computed with fine mesh model taking into account the weld toe profile were correlated to the strains obtained with the 1mm mesh size model, which does not model the weld toe profile. The strain by three-dimensional FE analysis with 1mm mesh size model was correlated with the strain by beam element model. Based on these results, the relationship between the kcal strain range and the nominal strain range was established. Finally, the extremely low cycle fatigue assessment method based on the nominal strain was proposed. In the method, the nominal strain obtained by beam analysis can be converted to the local stain with the established correlation. Then, the extremely low cycle fatigue life can be evaluated by using the proposed fatigue strength curves and Miner's linear cumulative damage rule. In order to vat the proposed assessment method, steel pier specimens were fabricated and subjected to large cyclic deformations. After the test, it was indicated that correlation between the test results and the lives estimated by proposed approach was good enough, and the proposed assessment method can be used to predict the fatigue life of the pier

为了评估焊接接头的极低周疲劳强度，应估计裂纹通常开始的焊趾处的应变（局部应变）。为了通过有限元分析获得局部应变，不可避免地要使用非常精细的单元来模拟精确的焊趾形状。然而，在工程实践中使用细网格是不切实际的。因此，在这项研究中，焊趾处的载荷应变和构件的名义应变之间的相关性，这可以通过梁模型在设计阶段通常使用，建立。也就是说，考虑焊趾轮廓的细网格模型计算的应变范围与1mm网格尺寸模型获得的应变相关，该模型不模拟焊趾轮廓。采用1mm网格模型进行三维有限元分析得到的应变与梁单元模型得到的应变进行了相关性分析。基于这些结果，建立了kcal应变范围和标称应变范围之间的关系。最后提出了基于名义应变的极低周疲劳评定方法。该方法利用梁的名义应变与局部应变之间的关系，将梁的名义应变转换为局部应变。然后，极低周疲劳寿命可以评估由建议的疲劳强度曲线和Miner的线性累积损伤规则。为了验证所提出的评估方法，制作了钢桥墩试件，并进行了大循环变形试验。试验结果表明，该方法与试验结果具有较好的相关性，可用于桥墩的疲劳寿命预测