A new stress-relieving device for superstructure expansion joints 1

Abstract

In the course of measuring strain in a passenger ship at sea it was noted that a stress concentration of 17 occurred at the root of the superstructure expansion joint [1]; very early cracking of the plating resulted. Exploratory tests were therefore made with a view to designing a device to reduce the stress concentration. Photoelasticity was used to study the effect on the stress concentration of variations in the proportions of anchorshaped cut-outs; based on these experiments, a new design (Figure 6) has been developed, and incorporated in a larger steel model which was subjected to a stress distribution representative of that occurring in a ship. The stress concentration at the root of the expansion joint is 1.4 and the maximum value, which occurs away from the root, is 3.0; it is probable that the latter value could be further reduced by modifying the shape of the cut. The new design requires a long, but only narrow cut, which could perhaps be filled with a flexible material.