Flexible Riser Top Connection Analysis With I-Tube Interface and Bending Hysteresis Effect

2019 ◽  
Author(s):  
Yangye He ◽  
Hailong Lu ◽  
Murilo Augusto Vaz ◽  
Marcelo Caire
Keyword(s):  
Kinematic Hardening ◽  
Bending Moment ◽  
Element Model ◽  
Beam Model ◽  
Flexible Riser ◽  
Nonlinear Bending ◽  
Cross Sectional ◽  
Irregular Wave ◽  
Global Dynamic ◽  
Curvature Distribution

Abstract The flexible riser top connection to the floating production platform is a critical region for fatigue lifetime (re)assessment. The interface with the I-tube and its curved sleeve combined with the gap between the riser and bend stiffener may lead to different curvature distribution when compared to the traditional modeling approach that considers the bend stiffener attached to the pipe. For a more accurate top connection assessment, the flexible riser bending hysteresis can also be directly incorporated in the global dynamic analysis helping to reduce curvature amplitude and lifetime prediction conservatism. This work investigates a 7” flexible riser-bend stiffener top connection with I-tube interface by performing irregular wave global dynamic analyses with the OrcaFlex package and considering a nonlinear bending moment vs curvature riser behavior obtained from a detailed cross sectional model developed in Abaqus. OrcaFlex curvature distribution results are also compared with a quasi-static finite element model that uses an elasto-plastic formulation with kinematic hardening to represent riser hysteresis through an equivalent beam model. A good curvature distribution correlation is observed for both top connection models (OrcaFlex x Abaqus) in the bend stiffener area with reduced amplitudes when riser bending hysteresis is considered.

Flexible Riser Bending Hysteresis Influence on Bend Stiffener Response

2014 ◽  
Author(s):  
Marcelo Caire
Keyword(s):  
Dynamic Analysis ◽  
Segment Length ◽  
Analysis Tool ◽  
Flexible Riser ◽  
Element Analysis ◽  
Irregular Wave ◽  
Global Dynamic ◽  
Flexible Risers ◽  
Curvature Distribution ◽  
Internal Pressures

The bending stiffness response is an important parameter in the lifetime assessment of unbounded flexible risers. Its behavior is governed by interlayer friction mechanisms leading to a non-linear moment x curvature relationship that is highly dependent on the internal pressure. In order to investigate its influence on the critical bend stiffener hang-off region response, a detailed finite element analysis is carried out using a specialized tool for a short segment length of a selected 2.5″ ID riser cross section. Different internal pressures are numerically analyzed and the resulting local hysteretic bending response is then adjusted and directly incorporated into a global dynamic analysis tool that uses an equivalent elasto-plastic formulation with a hardening parameter that controls the behavior of the slippage mechanism. A fully coupled irregular wave dynamic analysis is then carried out and the flexible riser curvature distribution response in the bend stiffener region compared for different bending hysteresis models adopted.

Fully coupled seakeeping, slamming, and whipping calculations

2009 ◽  
Vol 223 (3) ◽  
pp. 439-456 ◽  
Author(s):  
J T Tuitman ◽  
Š Malenica
Keyword(s):  
Linear Time ◽  
Three Dimensional ◽  
Bending Moment ◽  
Fatigue Loading ◽  
Element Model ◽  
Beam Model ◽  
Full Wave ◽  
Elastic Modes ◽  
Large Container ◽  
Fully Coupled

This paper presents a methodology to solve the seakeeping, slamming, and whipping problems coupled within a single calculation. The coupled problem is solved within a partly non-linear time domain seakeeping program. The elastic modes used in this hydroelastic problem can be calculated using a beam model or full three-dimensional (3D) finite element model of the ship structure. The slamming loading is calculated by a two-dimensional (2D) method. The main focus of this paper is the creation of an accurate and consistent coupling between the 3D seakeeping program and the 2D slamming calculation. Differences in timescale and integration methods make this coupling complex. A large container ship is used to illustrate the application of the presented methodology. The contribution of the non-linearities and the whipping response to the expected maximum bending moment and fatigue damage of this ship for a full-wave scatter diagram is calculated. The results show that the slamming-induced whipping response has a significant contribution to both the ultimate bending moment and the fatigue loading of the ship.

Effect of Reeling on Pipeline Structural Performance

2016 ◽  
Author(s):  
Yafei Liu ◽  
Stelios Kyriakides
Keyword(s):  
Kinematic Hardening ◽  
Element Model ◽  
External Pressure ◽  
Structural Performance ◽  
Loading History ◽  
Cross Sectional ◽  
Collapse Pressure ◽  
Comparison Of The Results ◽  
Tension Loading ◽  
D Model

The winding and unwinding of a pipeline in the reeling installation process involves repeated excursions into the plastic range of the material, which induce ovality and changes to the mechanical properties. We present two modeling schemes for simulating reeling/unreeling capable of capturing these changes and can be used to assess their impact on the structural performance of the pipeline in deeper waters. In the first model, the complete 3-D reeling process is simulated through a finite element model that includes proper treatment of contact and nonlinear kinematic hardening for plasticity. The second model includes the pipe geometric cross sectional nonlinearities, contact, and nonlinear kinematic hardening, but variations along the length of the line are neglected. Instead, an axially uniform curvature/tension loading history is applied that corresponds to that experienced by a point of the line during the process. The two models are used to simulate a set of experiments in which tubes were wound and unwound on a model reel at different values of tension. Both models are shown to reproduce the induced ovality and elongation very well. Several of the reeled tubes were subsequently tested under external pressure demonstrating the effect of the reeling cycle on structural performance. The two models are shown to also reproduce the decrease in collapse pressure as a function of the applied back tension. Comparison of the results of such simulations highlight when a fully 3-D model is required and when the simpler 2-D model is adequate for evaluating the structural performance of a reeled pipe.

scholarly journals Ratcheting Simulation of a Steel Pipe with Assembly Parts under Internal Pressure and a Cyclic Bending Load

2019 ◽  
Vol 9 (23) ◽  
pp. 5025
Author(s):  
Yang ◽  
Dai ◽  
He
Keyword(s):  
Internal Pressure ◽  
Kinematic Hardening ◽  
Three Dimensional ◽  
Bending Moment ◽  
Element Model ◽  
Steel Pipe ◽  
Cyclic Bending ◽  
Ratcheting Strain ◽  
Bending Load ◽  
Transition Points

The ratcheting behavior of a steel pipe with assembly parts was examined under internal pressure and a cyclic bending load, which has not been seen in previous research. An experimentally validated and three dimensional (3D) elastic-plastic finite element model (FEM)—with a nonlinear isotropic/kinematic hardening model—was used for the pipe’s ratcheting simulation and considered the assembly contact effects outlined in this paper. A comparison of the ratcheting response of pipes with and without assembly parts showed that assembly contact between the sleeve and pipe suppressed the ratcheting response by changing its trend. In this work, the assembly contact effect on the ratcheting response of the pipe with assembly parts is discussed. Both the assembly contact and bending moment were found to control the ratcheting response, and the valley and peak values of the hoop ratcheting strain were the transition points of the two control modes. Finally, while the clearance between the sleeve and the pipe had an effect on the ratcheting response when it was not large, it had no effect when it reached a certain value.

scholarly journals Coupled Bending-Bending-Torsion Vibration of a Rotating Pre-Twisted Beam with Aerofoil Cross-Section and Flexible Root by Finite Element Method

2004 ◽  
Vol 11 (5-6) ◽  
pp. 637-646 ◽  
Author(s):  
Bulent Yardimoglu ◽  
Daniel J. Inman
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Cross Section ◽  
Centrifugal Force ◽  
Axial Stress ◽  
Element Model ◽  
Torsional Stiffness ◽  
Extended Model ◽  
Beam Model ◽  
Cross Sectional

The purpose of this paper is to extend a previously published beam model of a turbine blade including the centrifugal force field and root flexibility effects on a finite element model and to demonstrate the performance, accuracy and efficiency of the extended model for computing the natural frequencies. Therefore, only the modifications due to rotation and elastic root are presented in great detail. Considering the shear center effect on the transverse displacements, the geometric stiffness matrix due to the centrifugal force is developed from the geometric strain energy expression based on the large deflections and the increase of torsional stiffness because of the axial stress. In this work, the root flexibility of the blade is idealized by a continuum model unlike the discrete model approach of a combination of translational and rotational elastic springs, as used by other researchers. The cross-section properties of the fir-tree root of the blade considered as an example are expressed by assigning proper order polynomial functions similar to cross-sectional properties of a tapered blade. The correctness of the present extended finite element model is confirmed by the experimental and calculated results available in the literature. Comparisons of the present model results with those in the literature indicate excellent agreement.

Response of guyed tower to irregular waves for linear and nonlinear behaviour of mooring cables

1985 ◽  
Vol 12 (1) ◽  
pp. 200-212 ◽  
Author(s):  
Momen A. Wishahy ◽  
M. Arockiasamy
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Time History ◽  
Element Model ◽  
Irregular Waves ◽  
Wave Forces ◽  
Beam Model ◽  
Nonlinear Behaviour ◽  
Irregular Wave ◽  
Linear And Nonlinear

The dynamic response of a guyed tower to irregular waves has been studied by the finite element method. Hydrodynamic interaction is taken into account by the added water mass concept, and the fundamental frequencies are determined using (i) a lumped-parameter two-dimensional beam model and (ii) a three-dimensional truss finite element model. The effect of the mooring guy lines is simulated using one-dimensional boundary elements. The example structure analyzed is the Exxon test guyed tower erected in water of 89.3 m depth in the Gulf of Mexico. The measured wave height – time history reported by Exxon is used to determine the wave forces. Irregular wave forces are computed using the linearized Morison's equation. The nonlinearity of the mooring system is computed using an iterative technique in which the cable configuration is corrected using successive solutions. The tower response in terms of offset-time history to wave forces is determined for both linear and nonlinear cable behaviour. The computed frequencies and the responses agree reasonably well with the available measured values. Key words: guyed tower, irregular wave forces, linear and nonlinear mooring cable stiffness, dynamic response.

scholarly journals Numerical Simulations and Experimental Study on the Reeling Process of Submarine Pipeline by R-Lay Method

2021 ◽  
Vol 9 (6) ◽  
pp. 579
Author(s):  
Ming Ju ◽  
Xiaodong Xing ◽  
Liquan Wang ◽  
Feihong Yun ◽  
Xiangyu Wang ◽  
...  
Keyword(s):  
Finite Element ◽  
Kinematic Hardening ◽  
Bending Moment ◽  
Material Model ◽  
Element Model ◽  
Structural Instability ◽  
Thickness Ratio ◽  
Combined Loading ◽  
Obvious Effect ◽  
Von Mises Plasticity

During the reeling process of the reel-lay method, the pipe will be subjected to combined loading of tension and bending. Excessive ovalization of the pipe will affect the structural performance and even lead to structural instability of the pipe. In this paper, a numerical simulation model of the pipe-reeling process is established by finite element tools. The Ramberg–Osgood material model is used to study the ovalization and bending moment of the pipe cross-section during the pipe-reeling process based on the Von Mises plasticity and nonlinear kinematic hardening rules. The results show that the ovalization and bending moment of the pipe section will change significantly during the pipe-reeling process. Subsequently, one set of 6-inch pipe-reeling experimental setups was designed to conduct a full-scale experiment. Compared with the experimental results, the feasibility of the finite element model is verified. Finally, the effects of diameter-to-thickness ratio, the material parameters of the pipe, and the pipe axial tension on the ovalization and bending moment changes are studied. Research shows that each parameter has a certain influence on the pipe of the reeling process, and the diameter-to-thickness ratio of the pipe has the most obvious effect. When the diameter-to-thickness ratio decreases, the bearing capacity for bending moments and the ability to resist ovalization of pipe are enhanced. At the same time, each parameter has a significant impact on the reeling process of the pipeline.

scholarly journals Near-Fault Seismic Response Analysis of Bridges Considering Girder Impact and Pier Size

Mathematics ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 704
Author(s):  
Wenjun An ◽  
Guquan Song ◽  
Shutong Chen
Keyword(s):  
Seismic Response ◽  
Bending Moment ◽  
Expansion Method ◽  
Response Analysis ◽  
Seismic Action ◽  
Transient Wave ◽  
Cross Sectional ◽  
Displacement Response ◽  
Near Fault ◽  
Continuous Girder Bridge

Given the influence of near-fault vertical seismic action, we established a girder-spring-damping-rod model of a double-span continuous girder bridge and used the transient wave function expansion method and indirect modal function method to calculate the seismic response of the bridge. We deduced the theoretical solution for the vertical and longitudinal contact force and displacement response of the bridge structure under the action of the near-fault vertical seismic excitation, and we analyzed the influence of the vertical separation of the bridge on the bending failure of the pier. Our results show that under the action of a near-fault vertical earthquake, pier-girder separation will significantly alter the bridge’s longitudinal displacement response, and that neglecting this separation may lead to the underestimation of the pier’s bending damage. Calculations of the bending moment at the bottom of the pier under different pier heights and cross-sectional diameters showed that the separation of the pier and the girder increases the bending moment at the pier’s base. Therefore, the reasonable design of the pier size and tensile support bearing in near-fault areas may help to reduce longitudinal damage to bridges.

scholarly journals Internal Force on and Deformation of Steel Assembled Supporting Structure of Foundation Pit under Thermal Stress

2021 ◽  
Vol 11 (5) ◽  
pp. 2225
Author(s):  
Fu Wang ◽  
Guijun Shi ◽  
Wenbo Zhai ◽  
Bin Li ◽  
Chao Zhang ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Bending Moment ◽  
High Strength ◽  
Element Model ◽  
Internal Force ◽  
Foundation Pit ◽  
Dimensional Finite Element ◽  
Influence Of Temperature On ◽  
Scale Experiment ◽  
Three Dimensional Finite Element

The steel assembled support structure of a foundation pit can be assembled easily with high strength and recycling value. Steel’s performance is significantly affected by the surrounding temperature due to its temperature sensitivity. Here, a full-scale experiment was conducted to study the influence of temperature on the internal force and deformation of supporting structures, and a three-dimensional finite element model was established for comparative analysis. The test results showed that under the temperature effect, the deformation of the central retaining pile was composed of rigid rotation and flexural deformation, while the adjacent pile of central retaining pile only experienced flexural deformation. The stress on the retaining pile crown changed little, while more stress accumulated at the bottom. Compared with the crown beam and waist beam 2, the stress on waist beam 1 was significantly affected by the temperature and increased by about 0.70 MPa/°C. Meanwhile, the stress of the rigid panel was greatly affected by the temperature, increasing 78% and 82% when the temperature increased by 15 °C on rigid panel 1 and rigid panel 2, respectively. The comparative simulation results indicated that the bending moment and shear strength of pile 1 were markedly affected by the temperature, but pile 2 and pile 3 were basically stable. Lastly, as the temperature varied, waist beam 2 had the largest change in the deflection, followed by waist beam 1; the crown beam experienced the smallest change in the deflection.

Investigation on the free vibration behavior of sandwich conical shells with reinforced cores

2021 ◽  
pp. 109963622110204
Author(s):  
Mehdi Zarei ◽  
Gholamhossien Rahimi ◽  
Davoud Shahgholian-Ghahfarokhi
Keyword(s):  
Free Vibration ◽  
Orientation Angle ◽  
Element Model ◽  
Filament Winding ◽  
Vertex Angle ◽  
Sandwich Shell ◽  
Cross Sectional ◽  
Conical Shells ◽  
Vibration Behavior ◽  
Axial Forces

The free vibration behavior of sandwich conical shells with reinforced cores is investigated in the present study using experimental, analytical, and numerical methods. A new effective smeared method is employed to superimpose the stiffness contribution of skins with those of the stiffener in order to achieve equivalent stiffness of the whole structure. The stiffeners are also considered as a beam to support shear forces and bending moments in addition to the axial forces. Using Donnell’s shell theory and Galerkin method, the natural frequencies of the sandwich shell are subsequently derived. To validate analytical results, experimental modal analysis (EMA) is further conducted on the conical sandwich shell. For this purpose, a method is designed for manufacturing specimens through the filament winding process. For more validation, a finite element model (FEM) is built. The results revealed that all the validations were in good agreement with each other. Based on these analyses, the influence of the cross-sectional area of the stiffeners, the semi-vertex angle of the cone, stiffener orientation angle, and the number of stiffeners are investigated as well. The results achieved are novel and can be thus employed as a benchmark for further studies.

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