Stresses from Locally Applied External Loads
Most vessels are also subject to loadings at the supports, nozzles, and attachments. These loadings produce deflections, edge rotations, shears, bending moments, and membrane forces. The effect rapidly decreases with the distance from the point of application, where the maximum stress occurs. In practical applications, the number of variables is considerable, and some judgement must be exercised to choose the important ones and eliminate those of minor importance.
The procedure for determining local stresses is based on the concepts in Welding Research Council Bulletin No. 107. Calculation sheets are provided for local stresses at nozzles and attachments, which must be added to all the other calculated stresses.
If the maximum stress at the attachment is too great, the shell must be reinforced by a pad, or by increasing the thickness of the reinforcing pad required for internal pressure. To avoid stress concentrations at the corners of square or rectangular pads or structural clips, provide a radius of five to ten times the pad thickness, general Company practice.
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