José Renato Mendes de Sousa

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José Renato verified their affiliation via an institutional email.

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• DSc
• Professor at Federal University of Rio de Janeiro

The design of monopile foundations for offshore wind turbines (OWTs) is usually performed using simplified (1D) models based on the p-y method. When deriving p-y curves, the main issues arise from the soil reaction profiles (p), commonly obtained by double differentiating the bending moment profiles. Several authors have proposed modified p-y curve...

The migration of acid gases through the pressure sheath of flexible pipes may induce a corrosive environment that can lead to steel armors’ failure by SCC (stress corrosion cracking). This permeation process depends on temperature, partial pressures, materials, and the pipe’s geometry. However, there are few works related to permeation modeling in...

The notch effect of semicrystalline PVDF was investigated using U- and V-notch geometries with different depths, and tensile tests were performed at 23 °C using the DIC technique and FEA. Both unnotched and notched dumbbell-shaped specimens were subjected to tensile loading with the DIC technique to obtain mechanical curves and strain maps. The exp...

Rising demand for thermoplastic composite pipes (TCPs) in the oil and gas industry is due to their lightweight, strength, and resistance to stress corrosion cracking (SCC). TCPs are utilized in hybrid flexible pipes, replacing steel armors, particularly in the central core, to withstand pressure in deepwater operations. In this context, this study...

Flexible pipes are fundamental in various offshore oil and gas exploration applications, such as production, gas injection, gas lift, or water injection lines. However, such structures can be damaged infield, reducing their structural capacity and leading to costs associated with replacements, production loss, or oil leakage. Among the various fail...

The Floating Production Storage and Offload system (FPSO) is widely used in offshore oil and gas exploitation. Traditional FPSO hull structures are typically constructed employing stiffened steel panels consisting of steel plates and closely spaced stiffeners. Classification societies require periodic full inspections of the cargo tanks. Neverthele...

In Brazilian offshore fields, torpedo anchors are extensively used in deep-water mooring systems. These anchors are known to be cost-effective and capable of withstanding high vertical loads. Despite their successful usage in the offshore industry, the increasing loads imposed by the mooring systems in ultra-deepwater applications demand higher anc...

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...

This study introduces a Finite Element (FE) hybrid methodology for analyzing deepwater offshore oil and gas floating production systems. In these systems, flexible risers convey the production and are connected to a balcony on one side of the platform. The proposed methodology couples, in a cost-effective manner, the hydrodynamic model of the platf...

The design of monopile foundations for offshore wind turbines (OWTs) is usually performed using simplified (1D) models based on the p-y method. When deriving p-y curves, the main issues arise from the soil reaction profiles (p), commonly obtained by double differentiating the bending moment profiles. Several authors have proposed modified p-y curve...

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...

Hybrid flexible pipes, consisting of typical flexible pipes with composite layers replacing steel armors, are an alternative to traditional flexible pipes because they are lighter and insensitive to Stress Corrosion Cracking (SCC). Hence, the present work proposes analytical and finite element (FE) models for analyzing the behavior of offshore hybr...

Most of the routine work concerning the design of laterally loaded monopile foundations is conducted using simplified one-dimensional (1D) models based on p-y curves. However, many of these curves have been derived from slender piles typically used in the oil and gas industry, which behave differently than rigid monopiles used as offshore wind t...

Considering the importance of studying fatigue failure in offshore structures, the stress concentration factor (SCF) is one of the most relevant parameters for its evaluation, obtained through equations that vary according to the geometry of the tubular joint; the type of joint in question; and the load to which it is subjected. Even though numeric...

Oil & Gas companies have been looking for new hydrocarbon deposits in deep and ultradeep waters. However, this scenario has shown numerous challenges related to exploiting these natural resources, forcing the offshore industry to invest in new technologies to resist extreme environmental conditions and increase operational safety. Therefore, unders...

An essential aspect of hydrocarbon exploitation in offshore fields is ensuring the integrity of the employed flexible pipes. In deep and ultradeep waters, new materials, structural configurations, and numerical and experimental methodologies are required to obtain viable solutions depending on the operational and environmental conditions. For insta...

The aim of this study is evaluating the mechanical behavior using shape U notch into two grades of Polyvinylidene fluoride (PVDF) applied as pressure sheath in flexible line. Firstly, tensile tests using Digital Image Correlate (DIC) were performed in specimens with and without notch to get assessed to notch effect in the PVDF(s). Finally, a num...

The Brazilian offshore oil and gas industry uses flexible pipes to transport water, oil, and/or gas. Currently, the high concentration of acid gases, such as carbon dioxide (CO2) and hydrogen sulfide (H2S), in Brazilian pre-salt wells has been introducing new challenges to these pipes. The acid gases may migrate from the bore to the annulus of thes...

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 proposes closed-form equations to calculate the bisymmetric dry and wet hydrostatic collapse strengths of flexible pipes with imperfections. Initially, the bisymmetric hydrostatic collapse is discussed, relying on the classic Timoshenko's equation. Then, the main parameters involved in the collapse mechanism are indicated. Particularly, a...

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...

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...

During drilling operations, the wellhead system and top hole casings shall be designed to support dynamic loads from the connected riser through the BOP stack/LMRP. As dynamic motions are associated to stress variations, fatigue becomes a major concern for designers. The accumulation of damage at the wellhead and close regions is dependent on sever...

Periodic shutdowns, which decompress service pressure down to atmospheric pressure, are common in offshore flexible pipe systems. In high pressure and high temperature operations, the use of multi-layer barrier flexible pipes is also common. A multi-layer barrier usually combines inner sacrificial and pressure sheaths and, under certain circumstanc...

Polyvinylidene fluoride (PVDF) is an engineering thermoplastic having a high degree of sensibility to crack, which affects long-term mechanical behavior. This study evaluates the crack-sensitive of PVDF for one commercial-grade through the development of a numerical model. Firstly, tensile tests using DIC were performed on both uncrack and pre-crac...

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...

The hydrostatic collapse strength of a flexible pipe is largely dependent on the ability of its carcass and/or pressure armor to resist radial loading and, therefore, its prediction involves an adequate modeling of these layers. Hence, initially, this work proposes a set of equations to estimate equivalent mechanical properties for these layers, wh...

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...

This paper proposes a finite element (FE) modal approach to determine the critical loads and buckling mode shapes associated with the lateral buckling of the tensile armors in flexible pipes. This approach is based on pre-curved and twisted beam finite elements that are restrained to slide on the surface of a torus. The influence of the pipe's bend...

In this work, a previously proposed finite element is applied in conjunction with a modal approach to predict the lateral buckling resistance of the tensile armors in flexible pipes. The finite element represents the mechanical behavior of tensile armors settled on elastic foundations, which model the frictional interaction between these armors and...

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...

Traditionally, fatigue life calculations are very expensive in terms of time and computer resources. They are usually performed during riser design phases, when several lines with similar characteristics need to be analyzed. While operating, when problems are detected, fatigue analyses are also necessary to help to decide if any action is needed. I...

Due to compressive loads, offshore flexible pipes may exhibit global and local instabilities and as a consequence structural failures. This work presents an experimental investigation concerning the local structural behavior of a real 2.5-inch flexible pipe under compressive load. Three instabilities events were observed in the experimental test: e...

This work investigates the extensional-torsional response of a flexible pipe with one up to ten wires broken in its outer tensile armor. Experimental tests were conducted, and the results obtained are compared to those from a finite element (FE) and a simplified analytical model. In these tests, the pipe was firstly subjected to pure tension and, t...

The hydrostatic collapse strength of a flexible pipe is largely dependent on the ability of its carcass and pressure armor to resist radial loading and, therefore, its prediction involves an adequate modeling of these layers. Hence, initially, this work proposes a set of equations to estimate equivalent thicknesses and physical properties for these...

In some mechanical models, the tensile armors of bent flexible pipes are treated as geodesics on a torus and, based on this hypothesis, the curvatures of these curves are calculated to obtain the acting stresses. However, a closed-form solution of the geodesic differential equations is not possible, which imposes difficulties on determining these c...

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...

Bonded flexible marine hoses are frequently used in offshore offloading operations. The proper performance of these hoses throughout the service life is important. Many studies have been developed considering the global dynamic behavior of such hoses; however, only a few considered its local structural behavior. The present work aims to better unde...

The offshore operational experience has shown that the flexible pipe end fitting (EF) may be the weakest point in terms of fatigue resistance of the tensile armor layers. The findings observed in dissections from risers which were in operation or subjected to qualification tests reveal that there is a key point with respect to fatigue inside the en...

In this paper, the coupled extensional-torsional behavior of a 4 in. flexible pipe is studied. The pipe is subjected to pure tension and two different boundary conditions are considered: ends free and prevented from axially rotating. The response of the pipe is predicted with a three-dimensional nonlinear finite element (FE) model. Some aspects of...

Unbonded flexible pipes are multi-layered structures with their typical cross-section composed by a combination of steel armoring layers (inner carcass, tensile and pressure armors) and polymeric conduits and tapes. This paper presents a finite element model, entirely developed in ABAQUS® environment, fully capable of calculating stresses and strai...

During installation, the tensioners of the pipe laying support vessels may impose asymmetric stress states on the inner carcass and the pressure armor of flexible pipes. Moreover, the possibility of admitting residual deformations in the cross section of flexible pipes after their installation is fundamental to allow the use of these structures in...

In this work, the mechanical response of a damaged 2.5″ flexible pipe under combined tensile and bending loads is studied. A set of experimental tests was carried out either considering the pipe intact or with one up to four broken wires in its outer tensile armor. In these tests, the deflections along the pipe as well as the strains in its outer t...

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...

Currently, it is common the use of marine hoses on the realization of unloading operations (offloading) of oil in offshore areas. Due to the obvious damage to the environment that a fault (leak) in these hoses may cause, a need of understanding and of analyzing more accurately the behavior of these pipelines emerges. The marine hoses may be regarde...

Due to its compound cross-section, the prediction of the structural response of flexible pipes to loads such as their self-weight, internal and external pressure, movements imposed by the floating system and environmental loads such as currents, waves and wind is quite complex. All these loads generate stresses and strains in the cross section of t...

This work focuses on the structural analysis of a damaged 9.13″ flexible pipe to pure and combined axisymmetric loads. A set of experimental tests was carried out considering one up to ten broken wires in the outer tensile armor of the pipe and the results obtained are compared to those provided by a previously presented finite element (FE) model a...

In this work, an approach to predict the remaining fatigue life of flexible pipes with damages in their tensile armor wires is proposed. This approach relies on a previous proposed approach to calculate the fatigue life of intact flexible pipes. By relying on results from theoretical and experimental investigations, the previous proposed expression...

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...

In this work, the response of a 2.5″ flexible pipe to combined and pure axisymmetric loads is studied. A set of experimental tests was carried out and the results obtained are compared to those provided by a previously presented finite element model. The pipe was firstly subjected to pure tension. After that, the response to torsion superimposed wi...

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...

Inspections in flexible risers have detected a considerable number of damages in their top section caused by the installation process or generated during their operation, due to the contact with another riser or components of the floating facility. Among the most common damages detected, the rupture of the tensile armor wires is critical to the str...

The structural behavior of the flexible pipe tensile armors inside the end fitting (EF) is different from the one observed in the pipe body. The actual design methodology shows that the end fitting of the riser top section (at the interface with the floating unit) is critical with respect to fatigue, as stress concentration that occurs in this regi...

This work focuses on a methodology to predict the fatigue life of flexible pipes with wires broken in their tensile armors. Initially, the mechanical behavior of these pipes is discussed. Relying on this discussion, a simple set of equations is proposed in order to calculate the stresses in the armors of these pipes. These equations employ pre-esti...

The use of powerful numerical tools based on the finite-element method has been improving the prediction of the holding capacity of fixed anchors employed by the offshore oil industry. One of the main achievements of these tools is the reduction of the uncertainty related to the holding capacity calculation of these anchors. Therefore, it is also p...

This paper focuses on a theoretical approach to access the fatigue life of flexible pipes. This methodology employs functions that convert forces and moments obtained in time-domain global analyses into stresses in their tensile armors. The stresses are then processed by well-known cycle counting methods, and S-N curves are used to evaluate the fat...

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...

The torsional behavior of a 4″ flexible pipe is here studied. The pipe was subjected to clockwise and anticlockwise torsion and also to torsion combined with tension. For pure torsion, two different boundary conditions were considered: ends free to elongate and prevented from elongating. When tensional and torsional loads are imposed to the pipe, o...

This paper deals with a nonlinear three-dimensional finite element (FE) model capable of predicting the mechanical response of flexible pipes subjected to axisymmetric loads focusing on their axial compression response. Moreover, in order to validate this model, experimental tests carried out at COPPE/UFRJ are also described. In these tests, a typi...

The use of powerful numerical tools based on the finite element method has been improving the prediction of the ultimate bearing capacity of fixed anchors applied in the offshore oil industry. One of the main achievements of these numerical tools is the reduction of the uncertainty related to the bearing capacity prediction of these anchors. Theref...

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...

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...

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 this paper, the coupled extensional-torsional behavior of a 4″ flexible pipe is studied. The pipe was subjected to pure tension and two different boundary conditions were considered: ends free and prevented from axially rotating. The response of the pipe is predicted with a three-dimensional nonlinear finite element (FE) model. Some aspects of t...

PETROBRAS has been developing several studies in order to verify the structural feasibility of SCRs connected to production units such as FPSOs, semi-submersible and monocolumn platforms. Due to the great stresses developed at the top region as a consequence of the platforms rotation movements, robust stress joints or flex joints are always require...

Some PETROBRAS fields are near mature now, around 15 years of production, and their production still important to the company portfolio, the possibility of extending the service life of these flexible risers becomes extremely attractive. This work addresses the re-evaluation of the fatigue life of old flexible risers aiming to extend their fatigue...

The experience in the Brazilian offshore production systems is to adopt the traditional riser solution composed of unbonded flexible pipes at a free-hanging catenary configuration. In deep waters, the tendency has been to use different pipe length sections (normally two), each of them designed to resist typical loadings. At the bottom, pipe structu...

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...

This paper proposes a three-dimensional beam element that can predict the dynamic response of flexible risers considering their bending hysteretic behaviour. The finite element implementation relies on a previously presented co-rotated beam finite element and an analytical formulation for determining the bending moment vs. curvature relationship fo...

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...

Offshore tests conducted with flexible risers have shown that axial compression is a critical issue to be considered in deep-water applications. The objective of the paper is to present a strategy for design verification of typical unbonded flexible risers devoted to check their capacity against axial compression failure modes. A free hanging caten...

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...