Hydrostatic Loading Research Articles

Large-scale experiments on tsunami inundation and overtopping forces at vertical sea walls

Tsunami are very long gravity waves that may cause significant damage to coastal sea walls. The majority of relevant design codes and research papers that describe methods for predicting tsunami loads on coastal walls consider the scenario of transitory force from a bore-led wave. This does not relate to tsunami that do not form bore waves. Bore fronts generally cause short term spikes in force, which may have little effect on the vulnerability of massive structures. Post disaster accounts suggest that most coastal walls show damage that implies failure modes that occur over moderate to long durations. Therefore it is likely that the bore front assumption gives an overly conservative prediction of maximum force, and may not capture the full timescale of tsunami loading. This paper uses a pneumatic tsunami generation facility to determine the force loading on two vertical coastal sea walls during tsunami inundation. Two sea-wall models, 0.15 and 0.25 m high, with crown widths of 0.1 m (7.5 and 12.5 m at a nominal prototype scale of 1:50) are tested. It is shown that bore fronts only occur for short period waves over the bathymetry tested. Bore fronts cause a very short period spike in force, which is followed by a transitory force approximated by the hydrostatic pressure equation. The loading of tsunami length waves of periods ≥ 40 s (280 s prototype at 1:50 scale), which do not break is not greater than 1.2 times the hydrostatic force. Overtopping volume is positively correlated to the time duration of positive upstream head over the crest, rather than its maximum value. Overtopping causes a small increase in the horizontal load due to the addition of a drag and momentum load. The magnitude and time of these effects are small and short-lived in comparison to the hydrostatic load. The results compare well with available equations based on hydrostatic force and the engineer may apply a desired multiplying coefficient of a factor of at least 1.2 to account for any added pressure and momentum, and the factor of safety intended. • Tsunami loads on vertical walls are no greater than 1.2 times the theoretical hydrostatic load. • Only shorter wave periods break and form bores; longer tsunami-length waves do not break. • Tsunami overtopping volume is related to the duration of positive head over the crest. • Tsunami overtopping applies a relatively small (against the hydrostatic load) additional horizontal force.

Study on the Sealing Performance of O-ring under High-Pressure Environment

The sealing properties of the O-ring of the hydraulic cylinder plunger rod under a high-pressure environment are related to a variety of factors. In this paper, we first establish a simulation model based on an O-ring reciprocating shaft seal under a high pressure-environment through finite element software and study the influence of the compression rate, static pressure, and reciprocating speed of the plunger rod on the sealing performance of O-ring through the simulation model, and then analyze the maximum stress of O-ring during installation, hydrostatic loading and reciprocating motion with the variation of structural parameters. The results indicate that the compression rate of the installation process has a significant effect on the sealing performance of the enhanced O-ring. In the hydrostatic loading process, the equivalent stress of the O-ring is increased with the increase of the compression rate, when the static pressure is low and decreases, and when the static pressure is high, and the equivalent stress shows an increasing trend and the same increase; in the reciprocating motion process, when the static pressure is low, the equivalent stress and contact stress of the O-ring does not change significantly with the compression rate, and when the static pressure is high, there is an obvious phenomenon of abrupt change. The frictional stress of the reciprocating motion is increasing, then decreases, and then increases with the change in static pressure.

Finite Element Implementation of the Exponential Drucker–Prager Plasticity Model for Adhesive Joints

This paper deals with the numerical implementation of the exponential Drucker-Parger plasticity model in the commercial finite element software, ABAQUS, via user subroutine UMAT for adhesive joint simulations. The influence of hydrostatic pressure on adhesive strength was investigated by a modified Arcan fixture designed particularly to induce a different state of hydrostatic pressure within an adhesive layer. The developed user subroutine UMAT, which utilizes an associated plastic flow during a plastic deformation, can provide a good agreement between the simulations and the experimental data. Better numerical stability at highly positive hydrostatic pressure loads for a very high order of exponential function can also be achieved compared to when a non-associated flow is used.

Natural vibrations of composite cylindrical shells partially filled with fluid

The article presents the results of studies of natural vibrations of circular vertical multilayer cylindrical shells completely or partially filled with a stationary compressible fluid and subjected to hydrostatic load. The behavior of the elastic structure and the fluid medium is described using the classical shell theory and the Euler equations. The effects of sloshing on the free surface of the fluid are not considered. The linearized equations of motion for shells together with the corresponding geometric and physical relations are reduced to a system of ordinary differential equations with respect to new unknowns. The acoustic wave equation is transformed to a system of differential equations using the generalized differential quadrature method. The formulated boundary value problem is solved by Godunov’s method of orthogonal sweep. The natural frequencies of vibrations are calculated based on the combination of a stepwise procedure and subsequent refinement by the method of dividing in half. The reliability of the obtained results is verified by comparison with the known numerical solutions. The dependence of low vibration frequencies on the reinforcing angle and the level of the structure filling with a fluid for simply supported rigidly clamped and cantilevered two-layer and three-layer cylindrical shells with a fluid are analyzed in detail. It is demonstrated that the possibility of changing the frequencies and vibration modes through a suitable choice of the layer arrangement scheme and the reinforcing angle of the composite material is notably determined by a prescribed combination of boundary conditions for an elastic body.

Active responses of nanoparticle-polymer interface/interphase via the interfacial interaction redistribution

Physical responses of nanoparticle (NP)-polymer interphase/interface to external stimulus are a topic of great interest in nanocomposites. Previously, the interphase was tacitly assumed to have passive responses with constant material properties during deformation while the interface was mainly studied under hydrostatic loadings. To explore the unique features of the interphase we used a full-atom molecular dynamics simulation to monitor the evolution of its mass density and atomic stress profiles during deformation. A cohesive zone model was then used to define the key parameters for the NP-polymer interaction, which enable one to study the responses of the interface without spherical symmetry and understand the unique behavior of the stretched interphase/interface. The conceptual change has been achieved showing that an external strain can redistribute the NP-polymer interaction to affect the high compression in the interphase, the physical origin of the interface confinement effect in the nanocomposite. This eventually triggers the active responses of the interphase leading to the apparent strain-dependence of the mass density and some other properties. The redistribution of the interfacial interaction also brings about the stable, metastable and unstable status of the stretched interface characterized by the strain-dependent modulus and interface debonding.

Stress sensitivity of multiscale elastic properties under hydrostatic loading conditions of organic shales at different thermal maturity stages

Shales serve essential functions as seals for conventional hydrocarbon reservoirs, waste storage repositories and unconventional plays. Exploration and evaluation of shales rely on the characterization of their multiscale elastic properties. However, there are limited studies on the geologic controls of elastic stress sensitivity in organic shales. This study investigated dry Lokpanta, Bakken, and Niobrara shales of different thermal maturity stages. First, we used a pulse-transmission ultrasonic setup to conduct multidirectional (0o, 45o and 90o) hydrostatic-stress sensitivity (0–27.58 MPa) tests to measure elastic waves and derive other elastic properties. Furthermore, we inverted microscopic parameters from the elastic measurements based on effective medium theories such as damage parameters (αij and βijkl), crack density (ρ), normal to tangential microcrack compliance (B), specific tangential crack compliance (snBT) and microcracks orientation anisotropy (η). Finally, we studied the effects of organic matter maturity and clay diagenesis on the multi-scaled elastic stress sensitivity. Under applied hydrostatic stress, the non-linear elastic response in the shales is consistent with the closure of aligned microcracks. Microcrack closure decreased the elastic anisotropy at lower stress (<10 MPa), while aligned clays and organic matter control the stress-insensitive anisotropy at higher stress. As organic matter matures and smectite transforms to illite, orthogonal velocity stress sensitivity increases and extrinsic contribution to elastic anisotropy increases. There is also a corresponding increase in orthogonal damage second-rank tensor (α33) and a decrease in orthogonal damage fourth-rank tensor (β3333) with organic matter-clay thermal maturity. These relationships are due to the thermally-induced development of new and/or extensional roughly-textured microcracks parallel to the laminated microfabric, which is of higher compliance in the shear than compression. Microcrack closure also decreases ρ under applied pressure. Most of the samples had B < 0.5, suggesting the presence of non-idealized roughly textured microcracks. Generally, snBT broadly decreases and η increases with clay diagenesis and organic matter maturity also because of the generation and/or enhancement of aligned microcracks resulting in higher tangential stiffness.

Coupled rigid-flexible dynamics modeling and validations of floating offshore wind turbine

Floating offshore wind turbine (FOWT) is a complex dynamical system, and reasonable dynamic model is significant to the structural response analysis and reliability evaluation of FOWTs. In this paper, a coupled rigid-flexible modeling method is proposed to predict the dynamic response of spar-type FOWTs and validated by experimental results. The dynamic modeling framework of the method is firstly presented, including the multi-rigid-body (MRB) module and the flexible tower module. The integrated kinematics formulation of MRB module considering the servo control mechanism is derived based on the quasi-coordinates Lagrange's equation. The equation of motion of the flexible tower is established by synthesizing the finite element method (FEM) and Kane's approach. Next, the external loads modules including gravity effects, hydrostatic and hydrodynamic loads, aerodynamic and mooring loads are addressed and incorporated into the equations of motion of the system. The proposed method is then validated against a scaled experiment and full-scale numerical results of FAST, and the aerodynamic performance, the hydrodynamic performance, the MRB module, the flexible analysis module, the mooring system and the servo control mechanism are systematically valuated. The results indicate that the proposed method has a satisfactory ability to predict the dynamic responses of FOWTs under different conditions.

An elasticity solution of laminated cylindrical panel

In this paper, an exact elasticity solution of cylindrical panel under cylindrical bending is presented. The formulation is based on the displacement approach in which 3D elasticity equations are reduced to 2-D equations using plane-strain conditions. In the present formulation, an exact elasticity solution is feasible due to the consideration of simply supported boundary conditions with applied loads expressed in harmonic forms. Single layered and multi-layered orthotropic composite panels subjected to realistic transverse normal loads are analysed. Solutions have been presented for uni-directional, bi-directional, and symmetric three-layered cross-ply laminated composite cylindrical panels. Variation of displacements and stresses through the thickness has been investigated for the panel subjected to single sinusoidal load, uniformly distributed load, hydrostatic load, and strip load. Validation of results is presented using reference results in the literature. The extensive results presented in this paper can be served as benchmark solutions for the assessment of improved panel theories.

Mean-field descriptions for the viscoelastic response of thermorheologically complex reinforced solids

Mean-field descriptions for the thermo-viscoelastic response of reinforced solids undergoing small deformations but large temperature changes are presented. The descriptions follow from an approximate homogenization scheme that identifies macroscopic internal variables with low-order statistics of the microscopic internal variable fields as a result of a variational model reduction. Unlike descriptions based on the correspondence principle, these descriptions can account for thermorheologically complex constitutive laws with multiple internal times and/or temperature-dependent stiffnesses, and can provide information not only on the macroscopic response but also on the statistics of the microscopic mechanical fields; it is further demonstrated that the descriptions can even accommodate a special class of hereditary laws often employed for polymeric materials. Simple expressions for material systems with elastically rigid but thermally dilatant reinforcements are provided. By way of example, reduced descriptions are presented for a special class of material systems for which the thermomechanical response can be computed exactly by means of the correspondence principle. In the case of isotropic particle-reinforced solids under hydrostatic loadings, the reduced descriptions can reproduce the exact response identically; in the case of transversely isotropic fiber-reinforced solids subject to monotonic coolings, the reduced and exact descriptions provide indistinguishable macroscopic strains and stresses for the entire range of temperature drops and cooling rates considered.

Studies on glass/epoxy and basalt/epoxy thin-walled pressure vessels subjected to internal pressure using ultrasonic ‘C’ scan technique

Fiber reinforced nanocomposite tubes are playing a vital role in the transportation of fluids in petrochemical industries, where these composite tubes store fluid under pressure. Therefore, it is important to estimate the amount of pressure that can be handled by the tubes and investigate the damage mechanisms of composite tubes using non-destructive testing techniques. In this work, mechanical properties and the pressure withstanding capability of different weight percentages (0, 0.5, 1 and 1.5 wt%) of silica nanoparticles added in glass/epoxy and basalt/epoxy composite tubes are investigated. Before performing these tests, the transmission electron microscopy (TEM) analysis was performed to ensure the uniform distribution of silica nanoparticles in the epoxy. Further, mechanical tests were carried out. The fractured surface of composites was analyzed using scanning electron microscopy (SEM). The Weibull modeling was used to predict the theoretical tensile, flexural and impact strength values. Further, hydrostatic pressure tests were performed, and then full-field damage assessments were performed using the ultrasonic ‘C’ scan. It was found that basalt/epoxy/silica nanocomposite tubes exhibited better mechanical and pressure withstanding capability, owing to the presence of higher amounts of iron and aluminum oxides, than their counterparts of glass/epoxy/silica nanocomposite tubes. Numerical analysis was also performed to confirm the allowable pressure limits of the composites under hydrostatic load. The failure of tubes has not occurred below allowable pressure values, which indicate good correlations with experimental results. The results of the study will help to design and manufacture composite tubes with better pressure withstanding capability at a reasonable cost.

Evaluating the impact of intermediate and deep sound speed uncertainty in the Irminger Sea on acoustic situational awareness

High-resolution observations from moorings and transect data can provide new insights into ocean structures, their variability, and the downstream effects on acoustic operations. Previously, we established a framework to maintain optimal communication and navigation for small-scale, under-ice operations that focused on spatio-temporal variability in the upper water column and around an autonomous underwater vehicle. However, mid- and deep-water sound speed fidelity are crucial for larger operations that exploit convergence zone ranging. The Irminger Sea is a useful case study for understanding how sound speed uncertainty, whether from partial data or models, obscures the informational content from acoustics. Generally, the density gradient dominates the sound speed at depth. In the Irminger Sea, hydrographic variability comes from the advection of different water masses through the region at all depths and also from water mass modification by local air-sea interaction. Instead of a uniform gradient as a result of hydrostatic loading, a shifted gradient in the mid-water column and a negative gradient near the bottom are often observed in mooring and transect data. This talk presents initial results for understanding the impacts of the environment through the lens of impact on acoustic propagation. [Work supported by the Office of Naval Research]

Hydrostatic high strain rate loading response of closed-cell polymeric foams as a function of mass density

Closed cell polymeric foams are widely used in naval structures as sandwich core material owing to their lightweight and high energy absorption capabilities. There has been a great push towards understanding their material response under multiple loading scenarios, however, the loading scenarios have been limited to uniaxial or multiaxial in air loadings at different strain rates. Here, the hydrostatic elastic response and yield behavior of PVC foams with varying mass densities under a high strain rate hydrostatic loading state have been investigated. A novel underwater high strain rate loading facility is utilized to subject these foams to near blast strain rate hydrostatic loading. Using the 3-D Digital Image Correlation (DIC) technique in conjunction with ultra-high-speed photography, full-field volumetric deformation data is obtained. The dynamic loading data is obtained using a piezoelectric pressure sensor. This enables the measurement of material yield strength and bulk modulus for these materials under high strain rate hydrostatic loading conditions. The foams demonstrate increment in bulk modulus and yield strength under high strain rate loading. Further, the increment observed is highly sensitive to the material bulk mass density.

Method and a Device for Testing the Friction Force in Precision Pairs of Injection Apparatus of the Self-Ignition Engines

This article reviews the state of the knowledge and technology in the field of friction-loss measurements in internal combustion piston engines. The dependencies that describe the loss of energy in combustion engines and injection apparatus are presented. Currently, very little can be found in the literature on the study of frictional forces in injection apparatus, but mainly in the piston–cylinder group, so this work significantly fills that gap. The aim of this article is to construct a device and to develop a method for assessing the technical state of injector nozzles to minimize friction losses in internal combustion engines at the stages of evaluation, design, production and operation. This article presents a stand for determining the maximum friction forces due to gravity loading by water-jet control. This article also presents test results on the maximum friction force between a needle and a body of injector nozzles in piston combustion engines on a designed and purpose-built stand outside of the combustion engine. Various designs and injector nozzles are made from various types of alloy steel for marine and automotive piston internal combustion engines fueled with distillation or residual fuels, and are tested. The research concerned conventional elements for the injection apparatus as well as electronically controlled subsystems. Precision pairs of injection equipment are selected for the tests: new ones are employed after the storage period and operated in natural conditions. The elements dismantled from the internal combustion engines are tested in the presence of fuel or calibration oil of similar properties. The maximum static frictional forces under the hydrostatic loading are measured, alongside the parameters for the dynamic movement of the nozzle needles from bodies of the injector nozzle as time, speed, acceleration and dynamic force. The influence of the angular position of the needle in relation to the bodies of the precision pairs conventional internal combustion engines, the diametral clearance between the nozzle body and needle, and the surface conditions on the values of the maximum friction force are also presented. Errors in shape and position result in the uniqueness of the friction force at the mutual angular position of the needle in relation to the nozzle body, and the decrease in diametral clearance and deterioration of the surface state increase the friction losses. A model was elaborated of the influence of various factors on the value of the maximum friction force.

Transition from equatorial to whole-shell buckling in embedded spherical shells under axisymmetric far-field loading

Motivated by the need to understand the compression of syntactic foam composites, we solve the canonical problem of buckling of a thin spherical shell embedded in a medium that is much softer than the shell. Syntactic foams comprise shells that usually have diameters in the micron range and are distributed inside a matrix medium that is typically polymeric. Such foams are commonly employed in a range of applications where high stiffness to density ratios are of interest. This can be tailored via choice of shell thickness and type, and filler volume fraction.Embedded glass microspheres fracture under sufficiently high loading, leading to a permanent softening of the syntactic foam. Embedded polymeric Expancel microspheres however are thought to buckle because the associated softening of the foam is recoverable. We determine critical buckling pressures in the practical scenarios of hydrostatic and uniaxial compressive loading states by solving a more general uniaxial loading problem. Critically, we investigate the thin-stiff shell limit, which yields very different results from a standard thin-shell limit under the assumption that the shell and matrix have stiffnesses of the same order. We employ nonlinear shell theory, linear stability analysis and rigorous asymptotics. We present numerical results for the critical buckling pressure over a wide range of shell thickness and contrasts in shell/matrix stiffnesses. Results for hydrostatic loading are compared against existing analytical and semi-analytical models for embedded shells. Under uniaxial loading we note that there are two distinct regions of parameter space, corresponding to equatorial and non-equatorial buckling regimes. The two non-dimensional parameters of critical importance are the shell thickness to radius ratio h/R and the shell to matrix shear modulus ratio μm/μs. By fixing one whilst varying the other we observe and describe the transition between these two regimes.

Triaxial behavior of a stabilized and a highly porous oil well cement paste at different saturation and drainage conditions

Well cement is the most common barrier material in wells for geothermal and hydrocarbon production. As cements are exposed to hydrostatic loads and periods of deviatoric loading in wellbore environments, it is important to understand the mechanical behavior of cement under relevant conditions. We study effects of porosity, saturation, confining pressure and drainage conditions on the mechanical behavior of class G well cement using two basic formulations, one which produces a highly porous cement paste. The high-porosity cement exhibited lower strength and reduced elastic moduli compared to the stabilized formulation. The elastic moduli for both formulations were reduced with increasing confining pressure, and the most pronounced effect of confinement was increased ductility and pronounced strain hardening behavior of the two cements, likely due to compaction. Under saturated and undrained conditions, the stabilized cement exhibited an increase in stiffness and essentially brittle failure even at 20 MPa confining pressure. The porous cement showed less sensitivity to drainage conditions. We attribute this observation to possible generation of internal micro-cracks and dislocations instead of a macroscopic failure plane. The results contribute to increased understanding of the mechanical response of conventional and porous cements under relevant confining pressures and different saturation and drainage conditions.

Next Generation Cartilage Repair and the Pre-arthroplasty Patient

The NeoCart® implant (Histogenics Corporation, Waltham, MA) is a cell-based therapeutic for the restoration of articular cartilage defects. The implant is composed of a type I collagen scaffold, inoculated with expanded autologous chondrocytes, and preconditioned under hydrostatic loading and low oxygen tension. The process was designed to create an autogenous chondrogenic construct for application during a surgical biologic reconstruction procedure for patients with symptomatic cartilage disease. Favorable pre-clinical basic science and animal studies characterizing the regenerative potential of NeoCart led to application for United States Food and Drug Administration (FDA) approval as the first autologous tissue therapeutic for articular cartilage restoration, beginning with a Phase I safety trial in 2003. Deemed safe in Phase I and efficacious in Phase II relative to “standard of care” microfracture, a Phase III randomized controlled superiority trial versus microfracture was authorized by FDA in 2010. The primary outcome measure of a statistically significant difference in the number of responders to treatment versus control cohorts based on meeting a dual-criteria threshold of >20-point and >12-point improvement in International Knee Documentation Committee (IKDC) and Knee Injury and Osteoarthritis Outcome Score (KOOS) pain domain scores, respectively, was established. The 1-year protocol assessment metric for superiority was narrowly missed, which led to termination of the trial in 2019. Ultimately, the therapy was not approved for use by the FDA. The history of this case example: quelching a biologically safe and effective therapeutic, highlights hurdles in the complex process of bringing scientifically sound products to patients through regulatory processes in the United States.

Optimization of Composite Cylindrical Shell Structures for Hydrostatic Pressure Loading

Abstract Deep-sea structures will collapse/implode under hydrostatic pressure when the structure dives below an instability threshold, leading to catastrophic failure. To better understand how the layup angle of composite cylindrical shells influences this instability threshold, this work explores how composite cylinders can achieve the highest (optimum) critical collapse pressure under hydrostatic loading conditions. To perform this analysis, a closed-form analytical cylinder buckling solution developed by previous work is used in conjunction with different cylindrical geometrical configurations and composite properties for glass, carbon, and intraply hybrid composite properties for woven and unidirectional structures. The results show that a composite structure's optimum layup configuration is unique to the structure's geometry and material system. However, general trends are observed for these different systems, such as how symmetric and asymmetric constructions place the axial-resistant layers near the neutral plane of the composite system. In addition, both constructions need an increase in shear-resistance layers as the L/D ratio decreases regardless of the material system. Lastly, the analytical approach presented in this work can be used to accurately determine the optimum layup angle for thin composite cylindrical structures that are subjected to external hydrostatic pressure.

Thermomechanical processing of Type-4 composite cylinders under static load

Type-4 composite cylinders have recently gained recognition in global markets for storage of compressed gas as an alternative to the existing metallic cylinders. The developed cylinders are certified before commercial deployments, based on the safety requirements of the available standards for onboard compressed gas storage. However, various accidents relating to the sudden burst of these cylinders have been reported previously. The failure depends on a variety of reasons; failure due to thermal degradation has been addressed in this study. Finite element analysis is used to predict the ultimate hoop stress of composite rings; the model is experimentally validated using the NOL ring test as per the ASTM standards. An FEA model to virtually test the cylinder for hydrostatic pressure burst test, high temperature creep test and accelerated stress rupture test is also developed and experimentally validated. The composite cylinders are tested as per the testing criteria mentioned in ISO 11439 which is the safety standard for onboard compressed natural gas storage. The validated FEA models can be used to analyze the thermomechanical response of composite cylinders when subjected to a hydrostatic load under temporary thermal conditions or when operated at temperatures higher than the service temperature mentioned in the ISO standard.

Vertical velocity at hydrostatic and anisotropic stresses

Sonic and dipole wireline tools measure Vp and Vs along the vertical direction. The state of stress in the subsurface is predominantly anisotropic, while most laboratory experiments measuring the dynamic elastic properties are conducted under hydrostatic stress. The question we ask is whether such laboratory experiments provide the velocities that are close to those measured in the vertical wellbore where the stresses are anisotropic. To address this question, we conducted ultrasonic pulse transmission experiments on several room-dry rock samples. The comparison was made between the P- and S-wave velocities obtained at pure hydrostatic loading conditions and those at a smaller hydrostatic stress with added axial stress, so that the total stress along the axis of a cylindrical plug was the same as under pure hydrostatic loading. These differences were significant in the extreme case of only 1 MPa hydrostatic confining stress with the axial stress increasing up to 40 MPa. However, as the hydrostatic (confining) stress increased, the differences between the velocities along the axis of the sample became smaller and smaller. For example, at 1 MPa confining and 30 MPa axial stress, the relative difference in Vp was about 10%, while that in Vs was about 20%. However, at 10 MPa confining stress, these differences became about 3% and 6%, respectively, and further decreased as the confining stress increased. This means that even at strong in-situ contrasts between the vertical and horizontal stresses, the results of laboratory hydrostatic experiments can be used for in-situ velocity estimates. These results also appear to be consistent with a theoretical model that predicts the directional velocities at any triaxial stress conditions from those measured versus hydrostatic stress.

Improving extreme response prediction of a subsea shuttle tanker hovering in ocean current using an alternative highly correlated response signal

A subsea shuttle tanker (SST) is a pioneering underwater submarine specifically designed to economically transport CO2 to smaller hydrocarbon fields. During loading and unloading of the CO2, the SST hovers over the well and experiences extreme heave motions resulting in extreme hydrostatic loading. Sustaining the hydrostatic loading is indispensable as it forms the dominating load and is a driving factor determining the SST hull's collapse design. Furthermore, the SST's extreme surge motion regulates the length of the flowline to evade snap loads. This paper focuses on the problem of determining these extreme positional responses at one location when the aft thruster fails during offloading using data with a shorter time record from another location at the SST. This scenario could be of practical engineering importance when either one of the sensors is malfunctioning or another similar vessel is being designed for the same environmental condition. A 2D planar Simulink model is used to generate the empirical data required for the study.