BEHAVIOUR AND STRENGTH OF PLATE TRUNNIONS SUBJECTED TO SHEAR LOADING

Abstract

The current design specifications and recommended practice for fabricated plate trunnions provide generic recommendations on the geometric dimensions only. The detailed designs for trunnions to transfer the sling loads to the structure are dependent on the ingenuity of experienced engineers using empirical equations for design checks. Current design specifications for fabricated plate trunnion recommend that the total sling load be transferred directly by the shear plate alone to the main plate. The trunnion pipe is regarded as a bent circumference for the sling or grommet to transfer load. However, the contribution of the trunnion pipe to the overall strength of the plate trunnion may be significant for certain geometric ranges. The detailed understanding of this strength combination will lead to a more rational and thus cost effective design.

The results of a series of nine plate trunnion specimens are presented. A fabricated plate trunnion generally consists of a shear plate and two stiffened side braces (pipes) attached to either side of the main body, in this case a plate. Each of the side braces provides an appropriate curved surface for the sling to transfer the shear load via sling tension to the trunnion brace. The research programme studies the effect of shear loading on 3 different types of plate trunnion specimens, namely pipe, shear plate and combined shear plate/pipe trunnions.

The plate trunnion specimens are modeled using the I/FEM software and the non­ linear analyses are run using the ABAQUS software. The finite element model is based on the mid-plane geometry of the specimen dimensions and only quarter models were analysed by considering appropriate symmetry conditions. Each of the specimens was modeled accordingly and the load-displacement plots of the trunnion brace results were compared with the results obtained in the experiments. The results showed that the finite element models were able to predict the elastic and inelastic behaviour of the trunnion brace. A shear strength design equation was proposed based on the numerical and experimental results obtained.