Model tests of a stiffness-similar jack-up, Part 1: Model design, fabrication and structural pre-tests

Abstract

This paper forms Part 1 of a paper series on jack-up model tests describing model design, fabrication and an extensive set of structural pre-tests. The model tests were aimed to provide high quality data-sets for the development of structural digital twin, therefore realistic and representative model of a jack-up platform at model-scale would be essential. In this regard, a generic jack-up model at 1:30 scale was designed such that the dynamic behaviour at full-scale was representative of actual jack-ups as reported in the literature. The main novelty was the use of Polycarbonate (PC) material to construct the leg structure, such that stiffness-similarity at model-scale could be achieved, both in terms of bending and axial rigidity. The benefits are two-fold. First, this allows direct strain/stress measurements along the legs to obtain axial member forces. Second, foundation fixity and leg-to-hull fixity at model-scale can also be representatively modelled such that the measured boundary forces were meaningful. The design and structural pre-tests of the key components of the jack-up model, which included the legs, spudcan, leg-to-hull connection, hull and cantilever, are thoroughly described in this paper. In general, good linear behaviours were observed, although small non-linear behaviour was noted for the spudcan module at lower loading amplitude. Additional pre-tests of the assembled jack-up model were also conducted prior to the start of model tests, and similar observations were drawn. A numerical Finite Element model of the jack-up was set up using ABAQUS, and in general, good agreement was achieved between measurements and numerical simulations for the boundary forces, moments and strains, as well as the overall dynamic characteristics. The numerical model could form the basis for development of structural digital twin tapping on the model test results for validation and proof-of-concept.