Tubular offshore structures are commonly assembled using welded joints, creating areas of stress concentration and potential fatigue failure. This study focuses on tubular T, Y and K joints, a common offshore structural component. Finite element modeling is used to predict stress concentration factors (Kt) for various loading conditions on the T, Y and K joints. The goal is to calculate Kt values and compare them to existing theoretical solutions from literature. Additionally, the influence of different loading modes (tension, bending) on the Kt values is investigated. By using advanced modeling techniques, this work aims to provide new insight into the behavior of tubular T, Y and K joints connections under realistic offshore loading conditions. The results can help improve design standards and fatigue life predictions for these critical structural joints.

The number of types of wire welding that circulate on the market and the development of welding technology, especially related to current welding, create a lack of information related to the quality of welding results for several types of materials. This can cause the strength of the welding connection to not be maximized. Therefore, this study aims to optimize the use of three types of wire welding and three current welding on the strength of the welding connection in two types of material testing using the response surface methodology. Box-Behnken, coupled with the RSM and the desirability function, was used to optimize the strength of the welding connection of the wire types (RD-46, LB-52, and RB-26), and current welding (100, 130, and 160 A) against two types of material testing (IWF-150 and ASTM-A517-G70). The strength of the welding connection observed in response included the tensile strength, Charpy impact-absorbed energy, hardness values in the welding metal and the hardness values in the main metal. Optimization of the strength of the welding connection in this study recommends the application of wire types RB-26, current welding of 100 A, and ASTM-A517-G70 material testing with the highest desirability value of 71.6%. Optimization of tensile strength, Charpy impact-absorbed energy, hardness values in welding metal, and hardness values in main metal by applying this parameter are 575.64 MPa, 110.69 J, 216.75 (HV10) and 126.6 (HV10), respectively. The results proved that an appropriate welding connection strength could be achieved using wire welding types and current welding in material testing.

Every day in workplaces, continues events occur that cause death and injury. These accidents usually happen because of lack of exploring the potential hazards and lack of training of employees. Hence, with exploring and evaluating the hazards of workplace and utilizing the suitable procedures, it is possible to prevent from many of these hazardous incidents. Exploring, evaluating and controlling the potential hazards have been the initial stages of scientific safety assurance in every system. Preliminary hazard analyzing is the first effort in analyzing hazards. In this method, usual hazards in sighted job are explored, using the usual hazards table for developing the basis of PHA, the PHA checklist is prepared and at last the PHA table completed and the appropriate suggestions are given. In this paper, we present an implementation of PHA method in one of industries located in city of Tehran, Iran. The proposed study uses 15 explored hazards, where 2 are unacceptable, 9 are undesirable and 4 are acceptable with need of revisal. By eliminating and reducing each hazards risk, some controlling solutions are suggested. The most important of these solutions are utilizing and using the regulations of the welding with electrical archer.

Generation of residual stress and structure deformation are the most important problems in the process of structure welding. Residual stresses inside and around the welded joints are harmful for integrity and proper functioning of the welded part. Tensile residual stresses near the weld zone may cause in developing brittle fracture, reduction of fatigue life or crack propagation caused by corrosion stresses. Welding residual stresses may even reach the yield stress of the part and can affect the thermal or mechanical working properties of it. Different thermal and mechanical approaches have been developed in the past in order to reduce these residual effects. Thus, both radiative and convective heat transfer methods have important roles in distribution of residual stresses during the welding process. In this study, convection and radiation effects on distribution of residual stress inside a welded part have been investigated for three different cases. In the first case, convection heat transfer was ignored and only effect of radiation on residual stress distribution was considered. In the second case, just the convection heat transfer applied on the model during the welding process. In another case, effects of radiation and convection heat transfer methods were investigated, simultaneously. Results of the current study showed that both radiative and convective heat transfer mechanisms have a significant share on distribution of residual stresses inside the welded part. It was also shown that the share of convection is greater than that of radiation heat transfer method.