Numerical study of the dynamic response of Inflatable Offshore Fender Barrier Structures using the Coupled Eulerian–Lagrangian discretization technique

Inflatable Offshore Fender Barrier Structures (IOFBS) are anti-terrorist security structures that function primarily to either stop terror bound vessels from reaching valuable offshore structures, incapacitate its crew or delay the vessel׳s progress until secondary security measures can be put in place. In this study, an advanced and efficient modelling method for impact simulation of the structure and similar multi-physics systems is presented. Numerical implementation of this modelling technique, using Abaqus finite element code is described and used in the impact simulation of the inflatable structure based on its current design as well as an alternative design of the structure. Results from the two designs provisions were compared and from these results, recommendation for improvement of the current design is also reported. This is desirable in ensuring high reliability in application of the structure in meeting its design objectives

Failure Modes and Bearing Capacity Estimation for Strip Foundations in C-ɸ Soils: A Numerical Study

In this study, typical c-ɸ soils subjected to loadings were assessed with a view to understand the general stress distribution and settlement behaviour of the soils under drained conditions. Numerical estimations of the non-dimensional bearing capacity factors, Nq and Nγ for varied angles of friction in the soil mass were obtained using PLAXIS. Ultimate bearing capacity values over a Ф range of 0-30 degrees were also computed and compared with analytical results obtained from the traditional simplified uncoupled approach of Terzaghi and Meyerhof. Results from the numerical study agree well with theoretical findings

A literature review on the technologies of bonded hoses for marine applications

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

Structural performance assessment of a woven-fabric reinforced composite as applied in construction of inflatable offshore fender barrier structures

This paper investigates the dynamic structural behavior of woven-fabric reinforced composites with high matrix–fabric volume fraction as applied in the construction of crash or security barriers typified by the Inflatable Offshore Fender Barrier Structure (IOFBS). Dynamic analysis of the IOFBS comprising of over 98% of the composite under impact loading was carried out using the finite element method employing the Coupled Eulerian–Lagrangian (CEL) formulation. The barriers were inflated to 6 kPa and 7 kPa initial pneumatic fluid pressures and subjected to crash loadings from a high velocity vessel. The enclosed fluid of the structure was modeled based on the Shomate equation and fluid behavior of water on which the structure floats was modeled using Us-Up Hugoniot equation of state. The barriers' membrane stresses distributions, deformations, internal fluid pressure surge and volume variations of the structures after impact as well as vessel's degree of instability and deceleration after impact for different initial inflation pressures were computed and studied. The developed models and numerical results obtained are useful in assessing the performance of the composite as used in the IOFBS and similar structures and in improving the design of the structure

Experimental investigation of the mechanical properties of neoprene coated nylon woven reinforced composites

In this study, the mechanical behaviour of neoprene coated nylon woven fabric composites was assessed using biaxial loading based on hydraulic bulge test method and uniaxial tensile method at varied environmental testing conditions. Results indicating failure modes, ultimate strengths and strains from the uniaxial testing of the composites were compared and recommendations for application of the composite material in structural design are reported. A through thickness approximate homogeneous modulus from the weft and warp uniaxial tests results of the membrane for a simple linear elastic anisotropic material model was used in ABAQUS finite element software to simulate the bulge test experiments. Results from the numerical analysis were found to replicate the bulge experiments to a first approximation. This approach offers useful application for the FE modelling and design of offshore inflatable structures made of coated woven fabrics which are typified by large size and complex geometries, as it reduces computational cost and potentially eliminates the need for a complex material description involving detailed theoretical derivations and advanced programming to implement

New constitutive model for anisotropic hyperelastic biased woven fibre reinforced composite

This paper presents an improved constitutive model having application in finite element analysis of composites made of hyperelastic matrix with biased woven fabric reinforcement and is based on a pragmatic approach and the continuum mechanics theory. A generalised strain energy function is developed via a series of uniaxial tests in fibre warp and weft directions and via shear tests of representative samples of composite fabric. The proposed material characterisation approach is demonstrated on composites made of neoprene rubber matrix with nylon biased woven reinforcements having volume fraction composition 0·74 vol.-% neoprene and 0·26 vol.-% nylon. The material parameters in the anisotropic hyperelastic model are obtained by minimisation of least square residuals of uniaxial and pure shear energy densities against the respective strain invariants. Numerical simulations of uniaxial and bulge tests of the composites using the material model presented in this paper are shown to correspond well with results obtained from laboratory experiment

Dynamic Response of Inflatable Offshore Fender Barrier Structures under Impact Loading

Inflatable offshore fender barrier structures are anti terrorist structures that function primarily to either stop an impacting vessel, incapacitate its crew or delay terror events. In a quest to ensure effective utilization of the compressed air in the barrier which functions to increase barrier stiffness, dissipate impact energy and potential for high vessel instability after impact; a new design of the structure is proposed in this paper. Its dynamic response under a vessel of 0.16MJ of kinetic energy impacting on the barrier was assessed using the finite element method. Fluid structure interaction of the structure was achieved using the Eulerian-Lagrangian formulation and the enclosed air in the barrier structure was modelled using the 'surface based cavities' capabilities in ABAQUS. The results indicate desirable response of the structure following impact by the vessel. This is important as low initial inflation could be utilised for the proposed design compared with the current design and the likelihood to delay terror events is maximized