During operations on offshore platforms, lifting of objects (i.e. containers) brings with it dropped object risks. In the occurrence of a dropped object event, production is temporarily interrupted, resulting in unintended costs. Chicago Bridge & Iron Company (CB&I), a leading engineering company in the design of offshore topside structures, is continuously seeking for innovative solutions which minimize costs. To date, protection of vulnerable equipment against dropped objects is provided by conservative stiffened steel plates. An alternative in the form of Sandwich Plate System panels has been researched, as it could potentially reduce costs due to their high failure load to mass ratio.

Multiple design thicknesses for simply supported Sandwich Plate System (SPS) beam and plate structures have been considered analytically and numerically. Their masses and failure loads when subjected to quasi-static loads have been compared with a Stiffened Steel Plate (SSP) reference structure. ANSYS, a Finite Element Analysis software package has been used to analyse the force-deflection curves associated with each design and to compare the plots and results with the results obtained analytically.

Analytical calculations of the bending moment resistance have shown to be adequate for the beam models under strict assumptions only. For more comprehensive non linear analyses including circular impact loads, an analytical analysis is no longer readily accessible and a numerical analysis is required. While for stiffened steel structures subjected to a line load a ’beam to plate’ simplification assumption is justified, this is not the case for SPS due to its additional transverse stiffness. For beam structures subject to line or circular failure mechanisms, the SSP layout offers a greater yield resistance with respect to its mass than SPS. For plated structures subject to a circular failure mechanism the yield resistance increases more strongly for the SPS type, taking full potential of the increase in failure load through the additional transverse stiffness.

It can be concluded configurations of SPS with low face plate to core thickness ratios come closest to providing similar yield resistances as SSP, while maintaining a low mass. For the configurations investigated, SPS 5-45-5 seems to provide a best fit as a replacement for SSP-600, since the weight is lowest with respect to the minimum required yield resistance. No configurations for SPS are found to be better than SSP-600 when the models are considered 2D. For 3D models the additional stiffness in transverse direction significantly increases the
maximum failure load of SPS. However, for the considered cases in this report no beneficial SPS configurations regarding yield failure were found.