Spyros A. Karamanos

University of Thessaly | UTH · Department of Mechanical Engineering

Among many factors affecting the collapse limit of pipelines, the line pipe fabrication process has the strongest impact. The present study examines the collapse resistance of pipes fabricated by the High Frequency Welding (HFW) method and focuses on quantifying the effects of heat treatment with respect to the collapse limit of this class of cold...

The present study examines alternative design configurations on the main tubular welded connections of a prototype deep-water floating tension-leg platform suitable for hosting a wind turbine and three wave energy converters under extreme loading conditions. Several configurations of the brace-to-cylinder connection are examined numerically to impr...

The paper examines the collapse resistance of thick-walled steel pipes, candidates for deep offshore applications, fabricated with the JCO-E process. It describes primarily a combined experimental, numerical and analytical work on the collapse of two JCO-E pipes, a 30-inch-diameter X60 pipe and a 24-inch-diameter X65 pipe, both with D ∕t ratio appr...

A numerical method for the simulation of the JCO-E pipe fabrication process is presented. The deformation and stresses induced by the manufacturing process, namely the edge crimping, the JCO forming, the LSAW welding, and the expansion (E) operation are calculated utilizing finite element simulation tools. This paper continues a recent work of the...

The present paper offers an overview of the structural analysis and design of the prototype REFOS TLP platform, suitable for hosting offshore wind turbines and wave energy converters, under extreme environmental loading conditions. Detailed calculations are also performed, using appropriate sections of DNV-RP-C202 and API RP 2A-WSD design standards...

The research work includes monotonic and cyclic loading experiments on 1/6-scale stiffened steel joints representing the welded connection between the tubular braces and the vertical cylinders of offshore floating structures for wind-wave energy production. The ultimate strength and fatigue life of the welded joints is investigated. High-frequency...

The work reported in the present paper is part of a European research program aimed at developing a hybrid tension‐leg floating platform, suitable for combined offshore wind and wave energy exploitation. Eight (8) fatigue tests on welded tubular joint specimens are performed, which represent the full penetration brace‐to‐cylindrical column welded c...

The paper presents a combined experimental and numerical investigation of cyclic loading response of an internally pressurized 8-inch-diameter steel piping system. The piping system comprises three elbows and is subjected to quasi-static end-displacement excitation. Global deformation and local strain measurements are obtained, indicating significa...

The present paper continues the work reported in previous publications of the authors and presents the application of advanced finite element tools to predict the influence of cold-forming on material properties and collapse resistance of steel JCO-E pipes. Results are obtained for a thick-walled 30-inch diameter pipe, with diameter-to-thickness ra...

The present paper presents the application of advanced finite element tools to predict the influence of cold-forming on material properties and collapse resistance of steel JCO-E pipes. Results are obtained for a thick-walled 30-inch-diameter pipe, corresponding to diameter-to-thickness ratio value less than 20. The numerical simulations are suppor...

Pipe bends (elbows) are commonly used components in subsea piping systems. They are quite flexible compared to the corresponding straight pipes and are used to reduce the reaction forces and moments at the supports and the bending moments within the piping system, as well as to accommodate pipeline thermal expansion requirements. Because of their f...

During deep-water pipeline installation, the pipe is subjected to high external pressure, which may trigger structural instability is the form of collapse, with catastrophic effects. Pipe resistance of against this instability is a major issue for safeguarding offshore pipeline integrity. In the present paper, the collapse resistance of steel pipes...

Lap-welded steel joints are widely used in steel pipelines for water transmission, and their structural resistance is essential for safeguarding pipeline integrity and functionality after severe earthquakes or other geohazards. These pipelines are thin-walled with a diameter-to-thickness ratio ranging between 100 and 240 and are susceptible to buck...

In modelling the behavior of thick-walled metal shells under compressive loads, the use of J2 flow theory can lead to unrealistic buckling estimates, while alternative ‘corner’ models, despite offering good predictions, have not been widely adopted for structural computations due to their complexity. The present work develops a new and efficient pl...

A three-dimensional numerical model of a mechanically bonded lined pipe is developed, simulating its structural response during the reeling installation method. An installation/failure-repair scenario is considered with five winding-unwinding cycles, accounting for the straightening process. The cyclic deformation of a lined pipe is presented, moni...

Motivated by reeling installation of mechanically-lined offshore steel pipes, the present paper investigates the structural performance of a bi-material lined pipe under cyclic bending, using advanced finite element tools. A three-dimensional finite element model is developed, simulating the manufacturing process of the lined pipe in the first stag...

The paper describes the application of a novel and promising concept, aimed at absorbing ground-induced displacements due to soil subsidence in buried steel pipelines entering or exiting concrete or rigid structures. In particular, the use of a patent pending concept of small projections is proposed, appropriately located along the pipeline, at the...

This paper describes the structural design of a large-diameter buried steel pipeline crossing two areas of substantial soil settlement, which impose fault-type actions in the pipeline. Those ground-induced deformations are associated with the development of high levels of strain, well beyond the elastic limit of the pipe material. The present paper...

The paper presents a combined experimental and numerical investigation of cyclic loading response of an internally pressurized steel piping system. The piping system comprises three elbows and is subjected to quasi-static end-displacement excitation. Global deformation and local strain measurements are obtained, indicating significant strain ratche...

To prepare modern societies for major breakdowns of Critical Energy Infrastructures in Europe, resilience concepts need to be developed, tested and validated to make sure proper planning, preparation, response and recovery is made and achieved in the event critical situations occur. Critical Energy Infrastructures, such as the gas & power smart gr...

The paper reports the development of an implicit numerical scheme for plane stress cyclic elasto-plasticity, capable of integrating a wide range of hardening rules, and simulating multi-axial ratcheting in metal structural components. Constitutive relations account for von Mises yielding in combination with mixed hardening. Emphasis is given to the...

The present paper describes the numerical implementation of the bounding-surface cyclic-plasticity model in a finite element environment, suitable for simulating the structural behavior of metal components subjected to strong cyclic loading. The model is based on the Dafalias-Popov “bounding surface” concept, equipped with appropriate enhancements...

A coupled cyclic plasticity-damage model is implemented for simulating low-cycle fatigue in metal components. Constitutive relations account for J 2-flow theory with nonlinear kinematic/isotropic hardening, coupled with isotropic continuum damage mechanics. The damage potential is written in a general form, allowing for implementing different damag...

Cold forming induces significant plastic deformation at corner locations of structural steel members, resulting in both material strain hardening and the development of residual stresses, which influence the fatigue resistance of the steel members. Reliable fatigue assessment at such critical locations requires knowledge of the influence of pre‐exi...

The framework of pipeline design in geohazard areas is presented in this Chapter. Following a brief overview of relevant design standards and recommendations, the main procedures for pipeline design against geohazards is outlined and a flowchart is presented. The concept of importance factor is introduced and pipeline classification is presented an...

The experimental results of the GIPIPE project are presented in this chapter, supported by numerical simulations from rigorous finite element models. In the first part of the chapter, the experiments conducted at CSM facilities, in Sardinia, are described in detail. They comprise 3 tests on axially-loaded buried pipes, 3 tests on transversely-loade...

The main types of ground-induced actions on buried pipelines are presented. Seismic actions are presented first and a distinction is made between transient actions, associated with seismic wave propagation and permanent actions, e.g. tectonic fault movement, liquefaction and lateral spreading. Subsequently, landslide actions are described. In all t...

A set of simplified pipeline design methodologies are outlined for the strain analysis and design of pipelines under ground-induced actions from tectonic faults and landslides. The methodologies refer mainly to “strain demand”, as alternatives to the more elaborate finite element methodologies presented in Chap. 7. These simplified methodologies ha...

Numerical results for strike-slip (horizontal) fault crossings are presented, using advanced three-dimensional finite element models. The model consists of a soil prism and employs shell elements for the pipeline and “brick” continuum elements for the soil. Appropriate boundary conditions are imposed, so that continuity of the pipeline outside the...

The present chapter focuses on the important issue of “strain demand”, which is the first stage of “strain-based” design methodology of pipelines. Sometimes, this stage is referred to as “stress analysis” or “structural analysis” of the pipeline. The chapter describes efficient numerical methodologies for the analysis of buried pipelines subjected...

The present study focuses on the mechanical behavior of fillet-welded steel plated joints and the development of a strain-based fatigue assessment procedure, motivated by the seismic response of unanchored steel tanks that exhibit repeated uplifting, leading to low-cycle fatigue failure of the base plate connection with the tank shell, due to cycli...

This book presents state-of-the-art methodologies for the design and analysis of buried steel pipelines subjected to severe ground-induced action, including tectonic (quasi-static) effects, slope movements (landslides), liquefaction-induced actions or excavation-induced settlements. The text is an amended version of the final deliverables of the GI...

The paper presents a combined experimental and numerical investigation of the bending response of lap welded joints in pressurized steel water pipelines. It is motivated by the structural performance of large-diameter steel pipelines used for water transmission in seismic and geohazard areas, where the pipeline may be subjected to severe permanent...

The present study uses advanced numerical tools to examine the mechanical behavior of steel pipe bends (elbows), subjected to strong cyclic loading, associated with repeated plastic deformations of alternate sign. The elbows are modeled with finite elements, accounting for the measured elbow geometry and the actual properties of steel elbow materia...

High-cycle fatigue experiments are performed on welded tubular steel X-joints, with braces and chord of equal diameter. They are scaled-down joints, used extensively in offshore wind platforms. Three different welding procedures are considered in specimen fabrication: manual, fully-automatic and manual with HFMI post-weld treatment. Τwo possible lo...

Motivated by the seismic response of unanchored liquid storage tanks, their uplift mechanism under strong lateral loading is examined. Using three-dimensional finite element models, nonlinear static analysis is conducted to define the moment-rotation relationship of uplifting tanks resting on rigid foundation and describe the evolution of critical...

The mechanical performance of lap welded joints is essential for safeguarding the structural integrity of steel water pipelines, after a severe earthquake or other geohazard loadings. Over the past four years, an extensive experimental project was launched to determine the structural performance of lap welded joints under the most severe ground def...

Welded lap joints are commonly used in large-diameter steel pipelines for water transmission. Their structural performance constitutes a key consideration for safeguarding pipeline integrity with no loss of pressure containment, required after a severe seismic or geohazard event. Full-scale experiments are presented, which are part of an extensive...

The present work investigates the response of industrial steel pipe elbows subjected to severe cyclic loading (e.g. seismic or shutdown/startup conditions), associated with the development of significant inelastic strain amplitudes of alternate sign, which may lead to low-cycle fatigue. To model this response, three cyclic-plasticity hardening mode...

The effects of manufacturing process on mechanically lined pipe structural performance are investigated. Alternative manufacturing processes are considered, associated with either purely hydraulic or thermo-hydraulic expansion. The problem is solved numerically, accounting for geometric nonlinearities, local buckling phenomena, inelastic material b...

The goal of this paper is to examine a generalized designing procedure for spur gears and achieve verification by using a finite elements analysis software. In the beginning it is crucial that the basic characteristics of the spur gears are clarified, as well as the AGMA criterion, so the reader would be able to understand the procedure that is goi...

The present work is motivated by the increasing need for cost-efficient solutions in offshore structural systems for wind energy production and for improvement of their structural performance. The structural behavior and design of high-strength steel welded tubular connections (yield strength higher than 700 MPa) subjected to monotonic and strong...

The present work is motivated by the increasing need for cost-efficient solutions in offshore structural systems for wind energy production and for improvement of their structural performance. The structural behavior and design of high-strength steel welded tubular connections (yield strength higher than 700 MPa) subjected to monotonic and strong c...

Σκοπός της παρούσας μελέτης είναι η παρουσίαση μιας εις βάθος διερεύνησης της μηχανικής απόκρισης των ελεύθερα εδραζόμενων δεξαμενών αποθήκευσης υγρών υπό πλευρικά σεισμικά φορτία, καθώς και την επακόλουθη επιρροή του ανασηκώματος σε παραμέτρους όπως η τάση του τοιχώματος. Επιδιώκει επίσης να προσφέρει πληροφορίες σχετικά με την υστερητική απόκρισή...

Mild steel and high-strength steel welded connections are compared in terms of their fatigue performance. There is also literature review of experimental fatigue data of geometrically identical welded T-joint specimens made of high-strength steel (S690 Q) and mild steel (S355 JR). It is experimentally verified that high-strength steel might not be...

The present study is motivated by the need for improving the fatigue performance of offshore wind energy structural systems. In particular, the ultra low-cycle fatigue performance of welded tubular X-joints is examined, motivated by the need of safeguarding the integrity of offshore platforms under extreme loading conditions. The welded specimens a...

Joint “efficiency” factors are proposed for pressure vessels, piping, and pipelines by ASME standards. For the particular case of non-radiographically-tested lap-welded joints, a low value of joint “efficiency” is proposed. This low value has raised some concerns regarding the use of welded lap joints in geohazard or seismic areas, where significan...

Unanchored steel tanks, subjected to strong seismic loading, may exhibit base plate uplifting. Under repeated uplifting, the welded connection of the tank base plate with the tank shell (a fillet-welded connection) is subjected to strong cyclic deformation, involving reverse plastic loading, and this could lead to failure of the welded connection i...

Industrial steel piping components are often subjected to severe cyclic loading conditions which introduce large inelastic strains and can lead to low-cycle fatigue. Modeling of their structural response requires the simulation of material behavior under strong repeated loading, associated with large strain amplitudes of alternate sign. Accurate nu...

The present paper describes a numerical investigation of the mechanical response of externally-pressurized dented stainless-steel pipes, subjected to reverse cyclic axial loading. This is the first part of a large-scale project, between The University of Edinburgh and Tianjin University, and is motivated by the mechanical response of offshore pipel...

The paper is part of European research program JABACO (2015-2018), on the optimization of design and construction of offshore jacket platforms for supporting large wind turbines (5 - 10 MW) in water depths ranging from 30m to 80m. In particular, the paper describes an experimental investigation on the high-cycle fatigue performance of welded tubula...

An economical method to protect offshore pipelines against corrosive ingredients of hydrocarbons is a double-walled (also called "lined" or "bi-metallic") pipe, in which a thick-walled low-alloy carbon steel ("outer pipe") is lined internally with a thin layer ("liner pipe") from a corrosion resistant alloy material. During the deep-water installat...

This paper explores the performance of a 10 MW offshore wind turbine (OWT) supported either on a large diameter monopile or a 4-legged jacket emphasizing on the nonlinear response of its belowseabed foundation. The seabed foundation alternatives, a monopile and a multipod foundation, are compared under monotonic, cyclic, and seismic loading. For al...

The paper is part of European research program JABACO (2015-2018), on the optimization of design and construction of offshore jacket platforms for supporting large wind turbines (5-10 MW) in water depths ranging from 30m to 80m. In particular, the paper describes an experimental investigation on the high-cycle fatigue performance of welded tubular...

The presence of dents on steel pipeline wall may constitute a threat for pipeline structural safety. Experimental testing results supported by numerical simulations are reported, in an attempt to assess the structural integrity of smoothly dented (nongauged) steel pipes. Ten experiments on 6 in diameter X52 steel pipes are reported, where dented st...

Large-diameter steel pipes, fabricated through the spiral-welding manufacturing process, are extensively used in onshore pipelines for the transmission of energy (hydrocarbon) and water resources. However, their use in demanding applications, such as geohazard areas or in offshore applications has been very limited. Safeguarding the structural inte...

During offshore installation, steel lined pipes are subjected to severe plastic bending, resulting in detachment of the thin-walled liner pipe from the outer pipe and eventually, the formation of local buckling in the form of shortwave wrinkles that menace the structural integrity of the pipeline. The paper focuses on the mechanical behaviour of me...

The present paper reports numerical calculations which complement experimental work reported in the companion paper entitled “Experimental Results of Steel Lap Welded Joints in Seismic Conditions”, also presented in ASCE 2018 Pipelines Conference. Nonlinear finite element simulation tools are employed to investigate the bending capacity of internal...

Welded lap joints are commonly used in large-diameter steel pipelines for water transmission. Their structural performance constitutes a key issue for safeguarding pipeline structural integrity with no loss of pressure containment, required even after a severe seismic event. Full-scale experiments are presented herein, and are part of an extensive...

Welded lap joints are commonly used in large-diameter steel pipelines for water transmission. Their structural performance constitutes a key issue for safeguarding pipeline structural integrity with no loss of pressure containment, required even after a severe seismic event. Full-scale experiments are presented herein, and are part of an extensive...

Large-diameter thick-walled steel pipes during their installation in deep-water are subjected to external pressure, which may trigger structural instability due to pipe ovalization, with detrimental effects. The resistance of offshore pipes against this instability is affected by local geometric deviations and residual stresses, introduced by the l...

The mechanical behavior of spiral-welded large-diameter steel pipes is simulated, with the purpose of defining their bending deformation capacity against local buckling. The steel pipes are candidates for hydrocarbon onshore pipeline applications with diameter-to-thickness ratio D/t equal to 53 and 69, and are subjected to longitudinal bending unde...

The present paper reports numerical calculations which complement experimental work reported in the companion paper entitled “Experimental Results of Steel Lap Welded Joints in Seismic Conditions”, also presented in ASCE 2018 Pipelines Conference. Nonlinear finite element simulation tools are employed to investigate the bending capacity of internal...

Buried pipelines are often constructed in seismic and other geohazard areas, where severe ground deformations may induce severe strains in the pipeline. Calculation of those strains is essential for assessing pipeline integrity, and therefore, the development of efficient models accounting for soil-pipe interaction is required. The present paper is...

The present paper offers an overview of available methodologies and provisions for the structural analysis and mechanical design of buried welded steel water pipelines subjected to earthquake action. Both transient (wave shaking) and permanent ground actions (from tectonic faults, soil subsidence, landslides and liquefaction-induced lateral spreadi...

Pipe bends, often referred to as “elbows”, are special pipeline components, widely used in onshore buried steel pipelines. They are sensitive to imposed deformations and their structural behavior is quite flexible and associated with the development of significant stress and strain, which may lead to failure. In the present paper, the mechanical pe...

Pipelines and piping components when subjected to extreme loading conditions (e.g. earthquakes, hurricanes, support settlements, industrial plant shutdown) undergo large plastic deformations, associated with widespread yielding, leading to fracture, either due to monotonic loading or ultra-low-cycle fatigue (ULCF) or extreme low cycle fatigue. ULCF...

A matlab file for the calculation of the induced strains in a buried pipeline subjected to permanent ground deformations.

The work presented in this paper is part of an extensive European research project on horizontal seismic links subjected to strong full-reversing cyclic loading. Both experimental testing and numerical simulations were conducted. The link specimens were subjected to combined shear and bending, representing the actual conditions acting on a seismic...

Steel tubes can be applied for many applications, structural as well as in pipelines. They may be loaded by combinations of internal or external pressure, soil load, bending moment and normal force. Important failure modes are local buckling, severe ovalisation (flattening of the cross section) and rupture of the pipe wall at local buckles or welds...

In geohazard areas, buried pipelines are subjected to permanent ground-induced deformations, which constitute major threats for their structural safety. Geohazards include seismic fault movement, liquefaction-induced lateral spreading, slope instability or soil subsidence, and are associated with the development of severe strains in the pipeline. C...

Nonlinear finite element simulation tools are employed to investigate the bending capacity of internally-pressurized double-welded lap pipeline joints for a typical steel, with D | t value equal to 191.5. The study constitutes the first part of a comprehensive investigation on welded lap joints, which comprises both numerical simulations and experi...

Ground-supported unanchored liquid-storage cylindrical tanks, when subjected to strong seismic loading may exhibit uplifting of their bottom plate, which may have significant effects on their dynamic behavior and structural integrity. In particular, due to uplifting, a substantial amount of plastic deformation develops at the vicinity of the welded...