Page 18: of Maritime Reporter Magazine (March 2016)

EYE ON DESIGN

Structural Stress Analysis

Tested vs. Predicted

FRITZ WALDORF se of strain gauges provides correlation for numerical

Finite Element Analysis,

Uand helps to identify real world stresses not always predicted with ideal analysis models. The fol- lowing case study documents the work performed on the foundation for an A-

Frame structure on the aft end of a sup- ply vessel.

The connection of the support arm of the A-Frame structure to the hinge structure at the base of the Frame had experienced a number of weld cracks over a relatively short operational life- time. A Finite Element Analysis (FEA) was commissioned to evaluate the structure, and determine if the design was adequate for the intended opera- tional service. The results of the initial

FEA indicated relatively low levels of stress in the connection of the support arms to the hinge structure, and were not indicative of the types of cracks that had been observed in the structure.

To provide further insight into the stresses in the A-Frame, a series of strain gauges were installed on the up- per and lower ? anges of the support arms. On each arm, strain gauges were located along the inboard and outboard edges of each ? ange to capture potential bending effects in both directions. The strain measurements were recorded as the A-Frame swung through a 90 degree 18 Maritime Reporter & Engineering News • MARCH 2016

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