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Tubular pipe structures have been used in various applications—domestic, aviation, marine, manufacturing and material testing. The applications of tubular pipes have been considered greatly in the installation of tubular pipes, marine risers and pipe bending. For the investigation of plastic strains and the mechanical behaviour of a tube under bending, considerations were made utilising an exponent model with assumptions on the plane strain. The bending moment, wall thickness effect, cross-sectional distribution, stresses during bending and neutral layer boundaries were all presented as necessary theoretical formulations on the physics of tubular pipe bending. This model was based on the analytical and numerical investigation. In principle, the application can be observed as the spooling of pipes, bending of pipes and reeling. Comparisons were made on two models developed on the finite element analysis in Simscale OpenFEA, namely the linear-elastic and the elasto-plastic models. This study presents visualization profiles using plastic strain to assess its effect on the tubular pipes. This can increase due to the limitation of plastic deformation on the composite materials selected.

The advances observed in the offshore-renewable industry include the recent development of a deep draft paired column semisubmersible platform developed for application on dry trees in Gulf of Mexico (GoM). These developments led to the recent innovation of the Paired Colum Semisubmersible by Jun Zou of Houston Offshore Engineering. This paper presents a detailed investigation on the mooring line analysis for two different configurations on the hull of a Paired Column Semisubmersible (PCSemi). The numerical research of the PCSemi platform coupled with mooring lines was conducted, and the model was validated. Two different mooring configurations were investigated: Chain-Polyester-Chain (CPC) and Polyester-Polyester (PP) configurations, with dynamic coupling in frequency domain (FD) and time domain (TD) using ANSYS AQWA and Orcaflex. A comparative study of the mooring lines is also investigated in 2,438m water depth at GoM, using 16 mooring lines with catenary mooring design. Results of this study gives the natural period of floating PCSemi’s heave motion ranged from 21s to 22s. Also, the effect of a damaged mooring line increased the tension in other mooring lines. Lastly, the CPC configuration has a smaller amplitude for wave-frequency platform motions compared to the PP mooring configuration from the depicted PCSemi global performance.

The application of marine bonded hoses has increased in recent times, due to the need for more flexible conduits and flexible applications in the offshore industry. These marine structures include Catenary Anchor Leg Moorings (CALM) buoys and ocean monitoring buoys. Their attachments include floating hoses, submarine hoses and submarine cables. However, the structural performance challenges of a CALM buoy system from its hydrodynamics-water waves and other global loadings, have led to the need for this investigation. In this study, a detailed presentation on the motion characterization of CALM buoy hose system is presented. The CALM buoy is a structure with six degrees of freedom (6DoF). A well detailed experimental presentation on the CALM buoy hose model conducted in Lancaster University Wave Tank is presented using three novel techniques, which are: a digital image capturing using Imetrum systems, using Akaso 4K underwater camera, using wave gauges arranged in a unique pattern and using underwater Bluetooth sensors. The buoy model was also found to respond uniquely for each motion investigated under water waves. The results showed the higher the profile, the higher the response of the buoy. Thus, this study confirms the existence of flow patterns on the CALM buoy while floating on the water body.

This research fills the gap in understanding fluid–structure interaction (FSI) from wave diffraction forces on CALM buoys and cylindrical structures, based on the hydrodynamics with connections. Recently, there is an increased application of (un)loading marine hoses for Catenary Anchor Leg Moorings (CALM) buoy systems in the offshore industry due to the need for more flexible marine structures that are cost-saving, easier to install, and service. However, different operational issues challenge these hoses, like during hose disconnection. Also, the fluid behaviour was investigated based on the analytical and numerical models. The numerical modelling involves the boundary element method (BEM) and Orcaflex line theory. Hydrodynamic analysis is conducted on the disconnection-induced load response of marine bonded hoses during normal operation and accidental operation under irregular waves. A comparative study on hose performance during normal operation and accidental operation is also presented. Results of statistical analysis on CALM buoy system shows good motion characteristics.

Marine bonded hoses are conduit-tubular structures used for loading, discharging, transferring and transporting fluid products like oil, gas, and water. These marine conduits are applied in the offshore industry by utilising novel marine materials and sustainable technologies. Based on sustainability, there are advances made as solutions for challenging environments. These challenges include scouring gases, deep water regions, changing sea water temperatures, platform loads and vessel motions. These environments also require sustainable materials like marine composites. This paper reviews historical timeline and patent development of hoses in the marine environment. It highlights key developments on marine hoses and their configurations. These configurations include FPSO-FSO with hose attachments in catenary configurations and CALM buoy-PLEM in Lazy-S configurations. The review also discusses the evolutions in the hose designs, potentials of the hoses, and recent state-of-the-art developments in the industry. Comprehensive discussions with necessary recommendations are made for fluid applications in the offshore industry.

Currently, the properties of composites have been harnessed on pipelines in the marine offshore industry. In this study, Marine Bonded Composite Hose (MBCH) has been presented. It is aimed at understanding the stress/strain distribution on marine bonded hoses using local design pressure under burst and collapse cases. This study also investigates on composite material modelling, hose modelling, liner wrinkling, helical spring deformation and two MBCH models- with and without ovalisation. The ovalized model is considered the simplified model in this research. Mesh study was carried out on meshing the hose layers. In this study, local design pressure was considered and not operational pressure. This finite element model was adopted to predict the deformation and mechanical response behaviour of MBCH. From this study, composites could be considered to improve conventional marine hoses. The study findings include identification of buckled sections on the hose, and stressed zones on the helix reinforcement. Highly reinforced hose ends are recommended in ends of the MBCH as they had maximum stress and strain values.

There is an increase in the utilisation of the floating offshore structure (FOS) called Catenary Anchor Leg Mooring (CALM) buoys and the attached marine hoses due to the increasing demand for oil and gas products. These hoses are flexible and easier to use but have a short service life of about 25 years. They are adaptable in ocean locations of shallow, intermediate, and deep waters. In this research, the numerical model was developed using a coupling method modelled by utilising ANSYS AQWA and Orcaflex dynamic models of the CALM buoy hoses. Two cases were compar-atively studied: Lazy-S and Chinese-lantern configurations, under ocean waves and current. Comparisons were also made between coupled and uncoupled models. This research presents the hydrodynamic characteristics with sensitivity analysis on the influence of waves, current attack angle, soil gradient, soil stiffness, and environmental conditions that influence the performance of marine hoses. The study comparatively looked at the configurations from dynamic amplification factors (DAF) on marine hoses. The results show that marine hoses can be configured easily to suit the designer’s need, seabed soil type, seabed topography, and the profiles are useful for manu-facturers. The sensitivity analysis also shows the effect of hose parameters on its hydrodynamic behaviour from wave-current interaction (WCI).

An essential aspect of Catenary Anchor Leg Moorings (CALM) buoy structures are the components of hydrodynamics like waves, underwater current, and wind. In this study, numerical investigations on CALM buoy were carried out. Firstly, motion study of free-floating CALM buoy was conducted in ANSYS AQWA. Then an Orcaflex-coupled model of the CALM buoy system with submarine hoses in Lazy-S configuration, was presented. It was attached to six mooring lines under 100 m water depth. Two types of buoy geometries have been investigated: Square Buoy (SB) and the Cylindrical Buoy (CB). Different cases with the same buoy widths were considered using three buoy skirts at 13.90m, 12.90m, and 11.90m. Diffraction analysis was used to obtain the motion behaviour. Results on the CALM buoy motion responses in six degrees of freedom (6DoF) like surge and heave motions, response amplitude operators (RAOs), radiation damping, and added mass, were also presented. The buoy geometry and skirt both influence its hydrodynamics. The study successfully achieved good reports on motion characteristics and wave-current interaction (WCI) for CALM buoys.

This research fills the gap in understanding fluid–structure interaction (FSI) from wave diffraction forces on CALM buoys and cylindrical structures, based on the hydrodynamics with connections. Recently, there is an increased application of (un)loading marine hoses for Catenary Anchor Leg Moorings (CALM) buoy systems in the offshore industry due to the need for more flexible marine structures that are cost-saving, easier to install, and service. However, different operational issues challenge these hoses, like during hose disconnection. Also, the fluid behaviour was investigated based on the analytical and numerical models. The numerical modelling involves the boundary element method (BEM) and Orcaflex line theory. Hydrodynamic analysis is conducted on the disconnection-induced load response of marine bonded hoses during normal operation and accidental operation under irregular waves. A comparative study on hose performance during normal operation and accidental operation is also presented. Results of statistical analysis on CALM buoy system shows good motion characteristics.