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Engineering challenge:

Steel hollow sections are commonly used as supporting structures in onshore and offshore engineering. In these structures, the members are jointed together by welding the profiled ends of the brace into the circumference of the chord. The connections between the brace and the chord are defined as structural joints. According to different sectional shapes, the types of structural joints can be classified either as circular or rectangular joints. Circular hollow sections (CHS) are more widely adopted in practice due to their excellent structural and mechanical properties such as having high strength and low weight ratio. The continuous smooth curved surfaces also decrease the frictional forces caused by wind/wave, and thus increase the capacity of resistance against the environmental loads. 

In these welded tubular joints, the stiffness around the intersection is not uniform. This will result in a non-uniform geometrical stress distribution.  This non-uniform stress is usually caused by curvature discontinuity at the intersecting curve, which will then cause stress concentration at this region. The peak stress around the intersection is known as the hot spot stress (HSS) which is an important parameter used in design and analysis. The HSS is normally dependent on the geometry of the joints as well as on the external loadings. 

The objective is to  study the Stress Concentration Factor (SCF) and Hot Spot Stress (HSS) of different CHS joint namely 40 degree K-joint, 60 degree K-joint and N-joint. For the analysis, first different joints are modeled and meshed (Pre-Processing). The mesh file is then imported to a solver and different material property required for solving has to be specified. The necessary boundary conditions should also be given. The solving is then carried out and various results are then viewed in a Post-Processor.

Result:


Von-mises Stress for 45° K-Joint


Von-mises Stress for 60o K-Joint


Von-mises Stress for N-Joint
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