Gilberto Bruno Ellwanger

Renewable energy sources have become an increasingly attractive alternative to fossil fuels thanks to technological advances and environmental care. The Brazilian Northeast Region has experienced significant development of wind farms, with notable rates of growth and energy generation. The positive results of these parks demonstrate the enormous po...

The tensile armors of flexible pipes are typically terminated in two configurations, i.e., hook and pigtail, essential to guarantee the tensile armors’ anchorage in the pipe’s end-fitting. However, despite its importance for the secure operation of flexible pipes, few works have dealt with the mechanical analysis of these terminations. Hence, this...

The assembly process makes flexible pipes susceptible to fatigue within the end fitting (EF). Notably, the tensile armors are folded and unfolded during this procedure to install the pipe’s inner sealing ring. This process induces a high level of plasticization at the tensile armors, which impacts their fatigue performance. Hence, initially, this w...

The assembly process makes flexible pipes susceptible to fatigue within the end fitting (EF). Notably, the tensile armors are folded and unfolded during this procedure to install the pipe's inner sealing ring. This process induces a high level of plasticization at the tensile armors, which impacts their fatigue performance. Hence, initially, this w...

The most common fixed offshore wind turbine (OWT) types are steel monopiles, jackets, tripods, and gravity-based structures (GBS). The fatigue analysis is a governing limit for these structures due to their dynamic behavior when subjected to wind and wave loads. In this article, the conceptual design, geotechnical capacity verification, and hydrody...

In this work, the wellhead axial movement of a subsea well was predicted with a previously presented multi-string model modified to account for a possible buckling of the well’s surface casing. This model represented the structural casing with a nonlinear spring that considers the casing-soil interaction using t-z curves with hysteretic behavior. I...

This work aims to study a steel jacket supporting a 10 MW offshore wind turbine (OWT) in a 40 m water depth on the Northeastern Brazilian Coast. In order to do so, various structural analyses were carried out. First, the system's natural frequencies were evaluated, and stresses caused by local environmental loads of wind, waves, and currents were a...

This article presents a numerical-based study on the vertical holding capacity of a typical finless torpedo anchor embedded in a pure cohesive isotropic sol considering setup effects. A strategy based on two axisymmetric nonlinear finite elements (FE) models is proposed. In these models, the soil is represented with continuous solid elements with b...

Fatigue is a governing limit state for the design of an offshore wind turbine (OWT). The fatigue loads are not only strongly dependent on the action of waves and wind but also on the site-specific soil properties. The present article is aimed at investigating the effects of cohesive and non-cohesive soils on the fatigue damage of a monopile foundat...

In this work, a gravity base foundation (GBF) was designed to support the DTU's 10 MW wind turbine. Recently, the industry is considering GBFs as a potential solution to the difficulties of driving monopile foundations in certain types of soil. Also, checking their feasibility in greater water depths is a pivotal question since these concrete struc...

In the past few years, gravity-based foundations (GBF) proved to be an advantageous solution for supporting offshore wind turbines (OWT) when soil conditions represent a hindrance to deep foundations as monopiles. In this type of support structure, soil-structure interaction (SSI) interferes directly in system stiffness. The available standard form...

The most common types of fixed offshore wind turbines (OWT) are steel monopiles, jackets, tripods, and gravity-based structures (GBS). For these structures, the fatigue analysis is a governing limit state due to its dynamic behavior when subjected to wind and wave loads. In this article, the effect of different hydrodynamic load models on the damag...

During the end fitting (EF) assembly, the tensile armors of flexible pipes are folded and then unfolded to allow the assessment to the inner sheath and the activation of the inner sealing system. This procedure leaves residual stresses and plastic deformations on these armors, which affect their fatigue resistance and, consequently, the overall per...

In subsea wells, the surface casing string should be fully cemented but, eventually, this is not possible due to the long length of the string and/or the soil characteristics. As the surface and the structural casings are the foundations of any subsea well, a partially cemented surface casing may allow significant wellhead movements, which affect t...

Due to technological advances, Offshore Wind Turbines (OWT) have proven to be a viable investment alternative in Brazil. However, unlike offshore structures originally developed for the oil and gas industry, OWT support structures are subject to large bending moments due to the wind and wave loads on the structure. One of the critical regions of an...

This work follows a worldwide trend of developing new wind farm projects on sea. Standard models used by the academy of 5 and 10 MW wind turbines are introduced to the Brazilian environment being supported by fixed foundations of the monopile type. The aim is to develop a sensitivity analysis of the fatigue damage in a critical point of the foundat...

The assessment of the pipe-soil interaction is an area of continuous research, either by the application of small- and full-scale tests in the attempt to reproduce accurately the interaction of the pipelines and the soil, or by the development of sophisticated numerical simulation models accounting for different sources of nonlinearities. Motivated...

In this work, a solid three-dimensional finite element (FE) approach is proposed to investigate the stress distribution along the tensile armors of flexible pipes inside their end fittings (EFs). This approach employs two different models. The first model consists of a single tensile armor, which is meshed with solid FEs, and a rigid surface that r...

The oil and gas industry is headed toward deep water in recent years. Oil companies are seeking new technologies to meet the challenges of deep-water oil exploration and in the near future, this will bring new discoveries. The most difficulty of exploring oil in this region is the depth where the equipment is installed and the production lines...

In the assessment of marine structures in shallow waters domain it is important to take into account the nonlinear (or non-Gaussian) nature of the irregular waves when predicting short and long-term responses of such structures. Other sources of nonlinearities in the response are also present due to some nonlinear effects such as: wet-dry surface e...

During the end fitting (EF) mounting process, the tensile armor wires of flexible pipes are folded and then unfolded. This process usually leaves plastic deformations and generates sharp curvatures on these wires just at the EF entrance. Dissections performed in several flexible risers, which were in operation or subjected to qualification tests, r...

A torpedo base is a type of conductor casing that embeds into the seabed mainly by free fall using its own weight as driving energy. One of the advantages of this concept is to install the conductor casing before the dynamic positioned (DP) drillship arrival at the location. This reduces the time of the well drilling leading to significant cost sav...

Curvas S-N e estimativas de dano são largamente utilizadas em projeto de estruturas offshore. Para tais estruturas, ocorrem carregamentos cíclicos oriundos de ações ambientais. Assim, a falha por fratura ou colapso plástico pode ser assistida em dois períodos distintos: um período de nucleação da trinca e um outro período de propagação estável. Ent...

A novel approach for modelling axial pipe–soil interaction, consisting of bespoke finite elements, is proposed. The purpose is to have a model that represents a two-dimensional slice of soil perpendicular to the pipe which is computationally cheap enough to be incorporated in global analysis of subsea pipelines, whilst capable of capturing detailed...

Thermal expansion of seabed pipelines may generate excess pore pressure in the surrounding soil. This paper discusses aspects of the excess pore pressure redistribution process and their effects on the effective stresses at pipe-soil interface, and the resulting soil resistance to pipeline axial movement. The discussion is supported by results of f...

As oil exploration moves into fields located in deep water, the need for developing new concepts of riser systems aiming at reducing the influence of environmental loads consequently increases. Therefore, a new riser configuration called RSAA (riser suspended and moored by chains - in Portuguese) is proposed. This structure consists on a rigid vert...

This work investigates numerically two different methods of moments applied to Hermite derived probability distribution model and variations of Weibull distribution fitted to the short-term time series peaks sample of stochastic response parameters of a simplified jack-up platform model which represents a source of high non-Gaussian responses. The...

This article studies the structural response of a 6.0” flexible pipe under pure tension considering intact and damaged conditions. In the damaged condition, several wires of the tensile armor layers are assumed to be broken. A three-dimensional nonlinear finite element (FE) model devoted to analyze the local mechanical response of flexible pipes is...

The behavior of a subsea pipeline when submitted to external loads is governed by the well predictable physical properties of the pipe and the not-so-well predictable pipe-soil interaction behavior. Understanding of the pipe-soil interaction behavior has advanced over the last years, however, the level of uncertainty in the available models is stil...

Torpedo anchors have been used in various offshore applications especially due to its low cost installation and the ability to withstand high inclined loads. This anchor consists of a shaft in which flukes are welded in order to increase the soil-anchor contact region and, consequently, its holding capacity. Since this anchor presents a singular ge...

As exploitation activities moves into fields located in deep water, the industry has been addressing studies aiming at concepts of platforms that reduce the influence of environmental loads on risers. The deep draft semi-submersible platform is one of these concepts [1]. The semi-submersible deep draft platform is described in a simplified way as a...

In this work, a bidimensional finite element (FE) approach is proposed to estimate the stresses induced in the tensile armor wires inside end fittings (EF) of flexible pipes. This approach accounts for the residual stresses caused by the mounting procedure and the deformed configuration of the wire. The resin and its interaction with the wires are...

This work investigates numerically two different methods of moments applied to Hermite derived probability distribution model and variations of Weibull distribution fitted to the short-term time series peaks sample of stochastic response parameters of a simplified jack-up platform model which represents a source of high non-Gaussian responses. The...

This work investigates numerically the Hermite polynomial model for the estimation of extreme values of short-term stochastic response parameters of jack-up platforms using time-domain simulations. In addition to this model, other variations of the Weibull probability distribution model fitted to the short-term time series peaks are also investigat...

The design of mooring systems for floating production units usually considers extreme environmental conditions as a primary design parameter. However, in the case of FPSO (Floating, Production, Storage and Offloading) units, the worst response for the mooring system may be associated with other sea state conditions due to the fact that its extreme...

Recently, in order to minimize the influence of the vertical motions in the risers and consequently allow the utilization of FPSOs in deep waters, a new riser configuration called RSAA (riser suspended and moored by chains - in Portuguese), composed of a rigid vertical riser, flexible structures and mooring line segments (top and bottom) was propos...

Torpedo anchors have proven to be one of the most important alternatives for mooring systems, especially in Brazilian offshore fields. Their installation involves many hydrodynamic and soil-structure interaction aspects and, therefore, their vertical stability cannot be always assured. This often results, after their installation, in an inclination...

This paper presents a numerical based study on the undrained load capacity of a typical torpedo anchor embedded in a purely cohesive isotropic soil using a three-dimensional nonlinear finite element model. In this model, the soil is simulated with solid elements capable of representing its nonlinear physical behavior and the large deformations invo...

Resumo – Risers Flexíveis são estruturas largamente empregadas na indústria do petróleo, nos últimos 30 anos. Diante das sucessivas marcas alcançadas, nos últimos anos, das profundidades de exploração de petróleo em alto mar, torna-se necessário um maior conhecimento do comportamento estrutural destas linhas flexíveis. Este comportamento estrutural...

This work investigates numerically the Hermite polynomial model for the estimation of extreme values of short-term stochastic response parameters of a jack-up. In addition to this model, other variations of the Weibull distribution model fitted to the short-term time series peaks are also investigated. A simplified linear jack-up structural model i...

This work investigates the Hermite polynomial model applied in the estimation of extreme values of short-term stochastic response parameters of a jack-up. In addition to this model, other variations of the Weibull distribution model fitted to the short-term time series peaks are also investigated. Before considering a jack-up model, other simple li...

Even though hydraulic collars are largely used to install flexible risers, neither the loads imposed by this equipment nor the response of the risers to these loads have been previously studied. Hence, this paper presents a three-dimensional nonlinear finite element (FE) model to predict the response of flexible risers to loads imposed by hydraulic...

The large Vortex Induced Motion (VIM) due to current acting on a circular-shaped monocolumn platform induces low-frequency stress variations on the SCRs (Steel Catenary Risers) connected to it. These stresses together with stress variations associated to wave effects must be accounted for in the fatigue analysis of these risers. Normally, the joint...

This paper focus on the structural analysis of a 2.5″ flexible pipe with one up to five broken wires in its outer tensile armor. The pipe is supposed to be under pure tension and the effect of the number of ruptured wires on its response is discussed. A three-dimensional nonlinear finite element model devoted to analyze the local mechanical respons...

This paper presents a numerical based study on the undrained load capacity of a typical torpedo anchor embedded in a purely cohesive isotropic soil using a three-dimensional nonlinear finite element (FE) model. In this model, the soil is simulated with solid elements capable of representing its nonlinear physical behavior as well as the large defor...

In the Campos Basin, offshore Brazil, catenary flexible risers are extensively used in marine production systems. One of the most important design phases of these systems is the riser extreme top load analysis, which provides results for riser and accessory designs as well as input for structural analysis of platform supports. In addition to the ri...

The offshore oil exploration in Brazil has been, traditionally, made by semi-submersible and moored ship-based units. The need for more restricted wave-induced motions has demanded new conceptions of floating structures, in which the mono-column concept distinguishes itself. Due to its cylindrical shape hull, this floating unit could present a sign...

Fatigue due to vortex-induced vibrations (VIV) is one of the major uncertainties today in the design of slender offshore structures, such as risers, pipelines, umbilicals, tendons and mooring lines, required for oil and gas production in deep waters. The absence of reliable tools for quantitative analyses of this phenomenon is a technological barri...

A fadiga provocada por vibrações induzidas por desprendimento de vórtices (VIV) é hoje uma das principais incertezas no projeto de estruturas esbeltas offshore, tais como risers, dutos submarinos, umbilicais, tendões e linhas de ancoragem, necessárias para a produção de óleo e gás em águas profundas. A inexistência de uma ferramenta confiável para...

When the oil exploration and exploitation moved away from the shore to deeper ocean, the riser interference became an important issue to be addressed during platform design. It became so important, particularly, when a great numbers of rigid risers are installed on the platform. Those kinds of risers are particularly used at Spar buoy and TLP platf...

The characteristic environmental load effect for the design of mooring systems of floating units can be defined by means of three procedures: (a) the one associated to an extreme sea state with a given return period, (b) the worst one from a set of sea states on a contour line associated to a return period or (c) the extreme one based on response s...

This paper presents an illustrative example of the reliability assessment of suction piles foundation in clayey soils for deepwater applications. The results of two reliability approaches, using suction piles as the foundation system for tension leg platforms (TLPs) under deep waters environmental conditions in the Campeche Bay (Mexico), are compar...

Fatigue verification is an important issue in steel risers design, demanding a good representation of the loading conditions that will occur during the riser entire lifetime. PETROBRAS has carried out a series of measurement and acquisition programs over the past decade, including the Campos Basin simultaneous acquisition of waves, current and wind...

Flexible pipes are composite structures made up of several steel and plastic structural layers which. working together, give strength and leakproofness, maintaining the necessary flexibility to conduct several fluids of the oil industry, mainly in the oil production offshore. In this work, a three-dimensional finite element model to predict the loc...

The steel catenary riser was adopted by Petrobras as a cost-effective alternative for oil and gas export and for water injection lines on deepwater fields, where large diameter flexible risers present technical and economic limitations. The installation of the P-18 SCR was a pioneer project of a free-hanging steel catenary riser linked to a semi-su...

This paper presents an application of the fuzzy logic theory for the prediction of the soil strength depth variation due to aging effects. The results of experimental tests with reconstituted clayey soils of the Bay of Campeche in Mexico were used for the fuzzy rule-based system training. The Evolutionary Strategy (ES) was employed as an optimizati...

This paper presents an insight into some different methods for prediction of extreme response values of slender structures belonging to moored floating units. The methods investigated are: Weibull-tail fitting, SRSS, SRSS modified, LS and LS modified (API). All these methods are based on a single time series sample of the response parameter. The st...

Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

Flexible risers are composite structures, made up of several steel and plastic layers, which has been largely used by the offshore oil industry. In this work, a three-dimensional finite element model to predict the local mechanical behaviour of these structures is proposed in order to overcome the lack of information about their compression respons...

This paper presents a time domain coupled numerical model, integrating the buoy and the slender structures, for the dynamic analysis of catenary anchor leg mooring (CALM) systems under random environmental loading. The model is based on the finite element discretization of the slender structures and the buoy hydrodynamics can be represented by two...

This paper presents a theoretical model to predict the dynamic response of steel cables subjected to harmonic loads. Not only the coupling between the extensional and torsional behaviour of the steel cable, but also the effects of interwire friction are taken into account by this theoretical model. Modal and dynamic analyses were carried out and th...

This paper presents a non-linear spring element in which the extensional and torsional bebaviour is coupled. The spring element development relies on a reported local analytical model that predicts the relationship between axial translation and rotation in wire ropes. This model also takes into account the effects of interwire friction by consideri...

The focus of this paper is on the development of a high effective practical approach to assess the short-term extreme response statistics of flexible risers excited by the first-order heave motion of a floating unit. The extreme response statistics is obtained by fitting a probability distribution directly to a sample of extreme response values. Ea...

A methodology is proposed to evaluate the wellhead loads due to the dtflling and completion phases for a subsea well. The loads transmitted by the drilling riser to the BOP stack at the flexjoint are determined using a static approach without the need of performing a detailed riser analysis. The flexjoint angle, as provided by the riser angle indic...

This work investigates numerically the Hermite polynomial model for the estimation of extreme values of short-term stochastic response parameters of a jack-up. In addition to this model, other variations of the Weibull distribution model fitted to the short-term time series peaks are also investigated. Before considering a jack-up model, other simp...

This paper presents a comparative reliability analyses between two design options for the number of tendons in a TLP under the environmental conditions of Campos Basin. In this paper only the tendons limit-states due to extreme environmental condition were taken into account for the reliability analyses. For the risk analysis, mainly the relative i...

Some aspects of a TLP basic behaviour analysis for offshore Brazil, carried out by PETROBRAS and COPPE/UFRJ, are presented. Particular emphasis is given to the non-linear time domain simulation using a modified Morison equation. The wave diffraction effects are considered by means of approximate methods. (A)