Fatigue analysis is one of the most important case studies in marine structures design in which stress concentration factor is used as a parameter including the structural specifications. Codes and standards present different formula for determination of stress concentration factors at offshore structures joints that their accuracies and validations are not clear. This study is an attempt to create a 3-dimensional model, using finite element method and employ appropriate elements, as to discuss stress concentration factors. At current research, the finite element model of unplanned and multiplanar K joints, including the weld, was produced using ANSYS-5.4 general-purpose Finite element software and related stress concentration factors were compared. A simple and relatively accurate method is used to simulate the weld. It was shown that the common methods for determination of stress concentration factors of multiplanar joints, in which an equivalent planar approach is employed, are not economical. Comparing the results of numerical method and those of parametric equations, some suitable equations were derived and their validation range was discussed. With respect to parametric studies of K & KK joints, optimum geometrical dimensions for an economical design were determined. At the end, two equations for determination of stress concentration factors of K & KK joints were presented as research result.

Background: The diameter of the appendix is a key parameter in diagnosing appendicitis. The diagnostic threshold for this parameter is 6 mm, originally established through graded compression sonography of the right lower quadrant (RLQ) of the abdomen. However, without corroborative findings from computed tomography (CT), this threshold may not be a reliable indicator of appendicitis. To ensure accurate diagnosis, clinicians should perform a comprehensive, multiparameter imaging assessment of the appendix, rather than relying solely on appendix diameter. Objectives: This study aimed to identify key factors for predicting appendicitis using contrast-enhanced coronal and sagittal CT images obtained through multiplanar reconstruction. Patients and Methods: This single-center, retrospective, cross-sectional study included patients who presented to our emergency department (ED) with RLQ abdominal pain and subsequently underwent contrast-enhanced CT between July 2019 and September 2020. The primary study outcome was pathologically confirmed appendicitis. Two experienced radiologists assessed parameters such as appendix diameter, wall thickness, abnormal appendix enhancement, abnormal appendix content, appendix erection, and periappendiceal fat stranding. Multivariate logistic regression was performed to identify significant predictive factors for appendicitis. Results: The study included 173 patients (median age: 37 years; women: 86). They were divided into appendicitis (n = 102) and alternative diagnosis (n = 71) groups. Significant differences were observed between the groups in terms of appendix diameter, wall thickness, wall enhancement, luminal content, appendix erection, and periappendiceal fat stranding (P < 0.001). The diagnostic sensitivity and specificity values for an appendix diameter threshold of 7.7 mm were 91% and 82%, respectively. An appendix diameter of > 7.7 mm (OR: 15.3; P < 0.001), abnormal appendix enhancement (OR: 12.5; P < 0.001), and appendix erection (OR: 6.1; P = 0.004) emerged as significant independent predictors of appendicitis. Conclusion: An appendix diameter of 7.7 mm appears to be the optimal threshold for diagnosing appendicitis. Additionally, the detection of abnormal appendix enhancement and appendix erection on contrast-enhanced CT images holds considerable diagnostic value.