Novel Design Approach to Create Deep Water Metallic Buoyancy Modules

Buoyancy modules are widely used ancillary equipment aiming to shape riser systems to resist harsh offshore environments. Due to their thermoset polymeric nature, they are sensitive to the manufacturing parameters as well as subject to water absorption along their service life. To overcome the challenges of polymer-based buoyancy module, this paper explores the design of metallic buoyancy modules that can be 3-D metal printed. An initial material selection is performed to identify suitable material candidates for the optimization algorithm. Steel and aluminum materials are considered and evaluated on a representative case combining density, mechanical stress and buckling criterion. Then a topology optimization algorithm called ‘Adaptative Bone Mineralization’ is applied on the best candidate material, adapting their modulus of elasticity at each iteration according to the current stress distribution, load case definition and boundary conditions. The optimized design incorporates additional requirements related to additive manufacturing processes. Results of the optimization algorithm are presented in a progressive order of complexity starting from the optimization of an angular section of 11.25 degrees opening with symmetrical boundary conditions up to a quarter of half-shell buoyancy module fully optimized in 3D. The optimization process log, capturing the volume fraction and the maximum stress at each iteration, is presented and compared with the selected set of criteria. Impact of the manual reconstruction process of the buoyancy module is assessed and the buckling stability is evaluated as a post-treatment. Two-dimensional and three-dimensional topologically optimized buoyancy modules are presented and comply with the strict mass requirement, stress criterion and buckling stability achieving deep water depth. This novel design approach to create deep water metallic buoyancy modules achieves the tailoring of the buoyancy module's internal structure to maximize the buoyancy performance while ensuring its structural integrity.

Buckling Stability Analysis for Piles in the Slope Foundation Based on Cusp Catastrophe Theory

The aim of this paper is to analyze the buckling stability problem for piles in the slope foundation based on cusp catastrophe theory. Formulation of critical buckling load of piles in the slope foundation is obtained. The influential factors of slope angle, distribution of landslide thrust behind the pile, pile-embedded ratio, pile constraints, pile-side friction, pile-side soil resistance, and pile socketed ratio upon buckling stability characteristic for piles in the slope foundation are examined. The results reveal that when pile diameter remains unchanged, critical buckling load increases with the increase of pile length when pile-embedded ratio reaches 60%. When pile length remains unchanged, critical buckling load increases with the increase of pile diameter. Critical buckling load with the assumption of nonlinear horizontal elastic resistance of pile-side soil in the paper is more close to the value based on horizontal elastic resistance of pile-side soil suggested in the code. When slope angle increases, decreased extent of buckling critical load for piles 30–60 m in length is more obvious than the piles which are 10–30 m in length. Strengthening of pile constraints and increase of pile-embedded ratio and socketed ratio are helpful to pile critical buckling load increase. The influential factors of pile-side friction and landslide thrust behind the pile upon pile critical buckling load are tiny and can be neglected.

Finite element analysis and neural network investigation of box columns under climate change

The behavior of box-shaped columns under heating is investigated. For this purpose, the various sections of thin-wall box-shaped columns were modeled and verified in different temperature ranges by ABAQUS software. The results of this research showed that increasing the thickness leads to increase the buckling stability of column under temperature change. Since the behavior of column will be better than thinner columns under climate change because of the increase in the modulus of elasticity. The solid columns have better buckling stability than hollow columns in normal conditions.

Experimental research on effect of opening configuration and reinforcement method on buckling and strength analyses of spar web made of composite material

This study experimentally investigates the effect of the opening configuration on the buckling stability and bearing performance of a structural beam web used in a commercial aircraft made of composite materials. The buckling and strength analyses on three opening configurations (circular, oblong, and rhombic) were carried out using test samples with identical web surface size. It is found that the rhombic opening has the minimum effect on the buckling stability and strength of the structure. To compensate for the effect of the opening, two reinforcement methods, using reinforcement rib and thickening the sample, were also investigated in this study. It is concluded that thickening the sample can more effectively improve the buckling stability and strength performance of beam web structure and hence has relatively higher structural reinforcement efficiency.