On the Design Considerations of New Offloading Hose Applied on a Turret Moored FPSO

2017 ◽  
Author(s):  
Decao Yin ◽  
Ivar Fylling ◽  
Halvor Lie ◽  
Rolf J. Baarholm ◽  
Timothy E. Kendon
Keyword(s):  
Limit State ◽  
Petroleum Products ◽  
Operating Conditions ◽  
Normal Operation ◽  
Ultimate Limit State ◽  
Operation Condition ◽  
Utilization Factor ◽  
Offshore Production ◽  
Axial Forces ◽  
Production Platform

Offloading hoses are used to transfer crude oil or liquid petroleum products from a fixed offshore production platform/floating production, storage and offloading (FPSO) unit to shuttle tankers. The hoses are subjected to environmental loads that are mainly waves, current, and vessel motions from both FPSO and the shuttle tanker. New offloading hoses were planned to be applied in a FPSO in harsh environment, and a design analysis was done in this connection. Numerical simulations were performed on ultimate limit state (ULS), serviceability limit state (SLS) and accidental limit state (ALS) by using the software RIFLEX [2]. Critical responses such as curvature and axial forces are checked. The following conditions are checked: 1. Normal operation condition with oil filled hose 2. Connect operation condition, floating gas filled hose 3. Emergency disconnect condition A SIMA [3] workflow was established to calculate accumulated fatigue damage of all the elements of the offloading hose model. For the new offloading hose, it is important to have a combined bending-tension loading capacity check. A utilization factor is proposed that possibly may be generalized. The results show that the specified hose has ample capacity for the considered operating conditions for the shuttle tanker to stay in any position within the 2nd emergency shut down sector (ESD2).

scholarly journals Non-deterministic Approach for Reliability Evaluation of Steel Portal Frame

2019 ◽  
Vol 5 (8) ◽  
pp. 1684-1697
Author(s):  
Hawraa Qasim Jebur ◽  
Salah Rohaima Al-Zaidee
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Structural Reliability ◽  
Limit State ◽  
Computational Cost ◽  
Probability Of Failure ◽  
Ultimate Limit State ◽  
Axial Forces ◽  
Portal Frame ◽  
Ultimate Limit

In recent years, more researches on structural reliability theory and methods have been carried out. In this study, a portal steel frame is considered. The reliability analysis for the frame is represented by the probability of failure, P_f, and the reliability index, β, that can be predicted based on the failure of the girders and columns. The probability of failure can be estimated dependent on the probability density function of two random variables, namely Capacity R, and Demand Q. The Monte Carlo simulation approach has been employed to consider the uncertainty the parameters of R, and Q. Matlab functions have been adopted to generate pseudo-random number for considered parameters. Although the Monte Carlo method is active and is widely used in reliability research, it has a disadvantage which represented by the requirement of large sample sizes to estimate the small probabilities of failure. This is leading to computational cost and time. Therefore, an Approximated Monte Carlo simulation method has been adopted for this issue. In this study, four performances have been considered include the serviceability deflection limit state, ultimate limit state for girder, ultimate limit state for the columns, and elastic stability. As the portal frame is a statically indeterminate structure, therefore bending moments, and axial forces cannot be determined based on static alone. A finite element parametric model has been prepared using Abaqus to deal with this aspect. The statistical analysis for the results samples show that all response data have lognormal distribution except of elastic critical buckling load which has a normal distribution.

scholarly journals ANALYSIS OF ULTIMATE LIMIT STATE OF SPHERICAL SHELL / SFERINIO KEVALO SAUGOS RIBINIO BŪVIO ANALIZĖ

2013 ◽  
Vol 5 (2) ◽  
pp. 69-75 ◽  
Author(s):  
Tomas Ulitinas ◽  
Stanislovas Kalanta ◽  
Juozas Atkočiūnas
Keyword(s):  
Mathematical Model ◽  
Spherical Shell ◽  
Limit State ◽  
Limit Load ◽  
Mathematical Programming Problem ◽  
Ultimate Limit State ◽  
Axial Forces ◽  
Internal Forces ◽  
The Mathematical Model ◽  
Ultimate Limit

The article presents ultimate limit state analysis and limit load problem of a symmetrically loaded flat spherical shell. Physical parameters (modulus of elasticity, Poisson's ratio), shape, dimensions of the construction, load and its adding position and orientation are known. The mathematical model of the problem is formulated by technically computing the shells theory. The bending moments and axial forces are described by the second and the first degree polynomials. The element's differential statics equations, describing the balance between the internal and external forces, are replaced with algebraic equilibrium equations presented by the Bubnov-Galerkin method. The mathematical model and the calculation algorithm of the internal forces and displacements in the shell analysis problem are developed and formulated using statics and geometry equations. The construction is divided into countable elements, which are composed into a computational network. It is necessary to take into account not only the geometric shape of the structure, but also the distribution of load when the computational network of spherical shell is composed. The spherical shells are considered in the cylindrical (ρ,φ,z) co-ordinate system. The begining of the coordinate system is the construction center. The internal forces and the displacements are independent of j coordinates, when the load is symmetrical, so it is enough to investigate only one radial of the shell. The circular shell elements are connected by boundary nodes in the main nodes of the discrete model. The second-order circular element with three nodal (calculation) points in the one radial is used for discretization (Fig. 1). The mathematical model of elastic-plastic problem is a nonlinear mathematical programming problem. Elastic internal forces S e and displacements u e are calculated by mathematical model (10)–(11). The values of internal forces and displacement of the main nodes are shown in Fig. 5. The values of nodal displacements are given up to the factor pR 0 / E, while the values of the internal forces are given up to the factor pR 0. The problem of limit load parameter p is calculated by mathematical model (15)–(16). The strength conditions are tested at all elements nodes. The value of limit load is p=2, 568 N 0/R 0. The Internal forces diagrams are shown Fig. 7. They are a corresponded plastic decomposition of flat spherical shell. Santrauka Darbe pateikiama simetriškai apkrauto lėkšto sferinio kevalo saugos ribinio būvio analizė. Konstrukcijos fizikiniai parametrai, forma, matmenys, apkrova ir jos pridėjimo vieta ir kryptis yra žinomi. Nagrinėjamas tamprusis ir idealiai tamprus plastinis kevalas, pasitelkiant ekstreminį energetinį principą randami tikrieji įtempių ir deformacijų būviai. Tampraus būvio analizės uždavinio matematinis modelis formuluojamas taikant virtualių jėgų principą, o ribinės apkrovos nustatymo uždavinio matematinis modelis formuluojamas kaip netiesinis matematinio programavimo uždavinys.

Building a Target Reliability Adaptive to China Onshore Natural Gas Pipeline

2014 ◽  
Author(s):  
Jinyuan Zhang ◽  
Zhenyong Zhang ◽  
Zhifeng Yu ◽  
Wen Wu ◽  
Yingshuai Chen
Keyword(s):  
Natural Gas ◽  
Population Density ◽  
Limit State ◽  
Operating Conditions ◽  
Risk Level ◽  
Ultimate Limit State ◽  
Gas Pipelines ◽  
Natural Gas Pipelines ◽  
Average Population Density ◽  
Average Population

To introduce and apply Reliability-Based Design and Assessment (RBDA) method to China’s onshore natural gas pipelines, China Petroleum Pipeline Engineering Corporation (CPPE) undertook a research project based on achievements from a series of researches sponsored by PRCI. RBDA method aims to maintain a consistent risk level throughout the lifecycle of pipelines by rational designs, professional operations and scientific maintenance. The basis of RBDA method is a set of risk-based reliability targets for pipelines, especially the target value of Ultimate Limit State (ULS). CPPE has developed a database for 37,000km natural gas pipelines in China and defined 148 operating conditions corresponding to various pressures, pipeline diameters, steel grades and pipeline lengths in different location classes. Failure calculation models are modified according to the corrosion and equipment impact under each specified operating condition. While calculating the failure consequences, 20,000 kilometers pipes from different locations classes were selected and statistics of average population density was made. Statistics of failure consequences were made again. Finally, the overall risk level of built natural gas pipelines was calculated. This paper introduces 148 operating conditions, failure probabilities, calculation method regarding failure consequences and average population density of all locations of different classes. Based on target reliability of pipelines set on country level, design and construction plan for newly-built pipelines are optimized by using RBDA method for rationally guiding subsequent operation and maintenance to reach the most optimal and cost-efficient plan in whole lifecycle of pipelines.

scholarly journals Experimental determination of longitudinal forces in front of braking train

2020 ◽  
Vol 78 (6) ◽  
pp. 358-365
Author(s):  
V. I. Matvetsov
Keyword(s):  
Thermal Stresses ◽  
Climatic Conditions ◽  
Axial Displacement ◽  
Operating Conditions ◽  
Normal Operation ◽  
Rolling Stock ◽  
Rail Track ◽  
Axial Forces ◽  
Continuously Welded Rail

The number of regularities detected in the experiments described by the author confirms that, despite of the differences in operating conditions between the middle of the 20th century and the present days, the methods of research and assessment of obtained results are still relevant.Features of the superstructure and track operation at the initial stage of introduction of the welded rails and continuously welded rail strings on the railways of the USSR are examined. It is demonstrated that axial displacement forces are occurred during the train movement, which are one of the most dangerous processes taking place in the track during the rolling stock movement. Axial displacement forces are manifested in the axial displacement of rails on the sleepers or displacement of rails with sleepers on the ballast. Knowledge of axial forces resulted from displacement of one rail line or the entire track is required for competent planning of installation and operation of the jointed rail track and continuously welded rail track, especially in the conditions of the Urals and Siberia. Methods and experimental results are provided for determination of additional axial forces acting in the track at the spike fastening and the individual intermediate fastening in front of braking train at the experimental sections of the continuously welded rail track in severe climatic conditions of the West-Siberian railway, where the annual fluctuations of therail temperature amount to 110°C.The following conclusions are made based on the analysis of the experiment results and experience of operation of the continuously welded rail strings: • no additional axial forces in front of braking train were detected in the continuously welded rail strings of the thermalstressed type without any release of thermal stresses on the independent fixation; • experiment confirmed possibility of installation and normal operation of continuously welded rail track on the entire network of railways of the Ministry of Transportation of the USSR; • recent wide introduction of trains of 7,100 t, combined trains of 12,600 and 14,200 tons require special attention to parameters of interaction of track and trains.

scholarly journals Fragility curves for Italian URM buildings based on a hybrid method

2021 ◽  
Author(s):  
A. Sandoli ◽  
G. P. Lignola ◽  
B. Calderoni ◽  
A. Prota
Keyword(s):  
Seismic Vulnerability ◽  
Fragility Curves ◽  
Limit State ◽  
Ultimate Limit State ◽  
Masonry Building ◽  
Masonry Buildings ◽  
Seismic Behaviour ◽  
Building Stock ◽  
Ground Acceleration ◽  
Damage Scenario

AbstractA hybrid seismic fragility model for territorial-scale seismic vulnerability assessment of masonry buildings is developed and presented in this paper. The method combines expert-judgment and mechanical approaches to derive typological fragility curves for Italian residential masonry building stock. The first classifies Italian masonry buildings in five different typological classes as function of age of construction, structural typology, and seismic behaviour and damaging of buildings observed following the most severe earthquakes occurred in Italy. The second, based on numerical analyses results conducted on building prototypes, provides all the parameters necessary for developing fragility functions. Peak-Ground Acceleration (PGA) at Ultimate Limit State attainable by each building’s class has been chosen as an Intensity Measure to represent fragility curves: three types of curve have been developed, each referred to mean, maximum and minimum value of PGAs defined for each building class. To represent the expected damage scenario for increasing earthquake intensities, a correlation between PGAs and Mercalli-Cancani-Sieber macroseismic intensity scale has been used and the corresponding fragility curves developed. Results show that the proposed building’s classes are representative of the Italian masonry building stock and that fragility curves are effective for predicting both seismic vulnerability and expected damage scenarios for seismic-prone areas. Finally, the fragility curves have been compared with empirical curves obtained through a macroseismic approach on Italian masonry buildings available in literature, underlining the differences between the methods.

scholarly journals A Diode-MMC AC/DC Hub for Connecting Offshore Wind Farm and Offshore Production Platform

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3759
Author(s):  
Kai Huang ◽  
Lie Xu ◽  
Guangchen Liu
Keyword(s):  
Wind Power ◽  
Wind Farm ◽  
Offshore Wind ◽  
System Control ◽  
Dc Voltage ◽  
Offshore Wind Power ◽  
Offshore Production ◽  
Production Platform ◽  
In Series ◽  
Dc Voltage Control

A diode rectifier-modular multilevel converter AC/DC hub (DR-MMC Hub) is proposed to integrate offshore wind power to the onshore DC network and offshore production platforms (e.g., oil/gas and hydrogen production plants) with different DC voltage levels. The DR and MMCs are connected in parallel at the offshore AC collection network to integrate offshore wind power, and in series at the DC terminals of the offshore production platform and the onshore DC network. Compared with conventional parallel-connected DR-MMC HVDC systems, the proposed DR-MMC hub reduces the required MMC converter rating, leading to lower investment cost and power loss. System control of the DR-MMC AC/DC hub is designed based on the operation requirements of the offshore production platform, considering different control modes (power control or DC voltage control). System behaviors and requirements during AC and DC faults are investigated, and hybrid MMCs with half-bridge and full-bridge sub-modules (HBSMs and FBSMs) are used for safe operation during DC faults. Simulation results based on PSCAD/EMTDC validate the operation of the DR-MMC hub.

scholarly journals Analysis of Turn-to-Turn Fault on Split-Winding Transformer Using Coupled Field-Circuit Approach

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1314
Author(s):  
Cunxiang Yang ◽  
Yiwei Ding ◽  
Hongbo Qiu ◽  
Bin Xiong
Keyword(s):  
Low Voltage ◽  
Short Circuit ◽  
Three Dimensional ◽  
Great Influence ◽  
Normal Operation ◽  
Transient Field ◽  
Axial Forces ◽  
Leakage Field ◽  
Characteristics Analysis ◽  
Split Winding

The turn-to-turn faults (TTF) are also inevitable in split-winding transformers. The distorted leakage field generated by the TTF current results in large axial forces and end thrusts in the fault windings as well as affecting other branch windings normal operation, so it is of significance to study TTF of split-winding transformers. In this paper, the characteristics analysis of the split-winding transformer under the TTFs of the low voltage winding at different positions are presented. A 3600 KVA four split-windings transformer is taken as an example. Then, a simplified three-dimensional simplified model is established, taking into account the forces of the per-turn coil. The nonlinear-transient field-circuit coupled finite element method is used for the model. The leakage field distribution under the TTFs of the low voltage winding at different positions is studied. The resultant force of the short-circuit winding and the force of the per-turn coil are obtained. Subsequently, the force and current relationship between the branch windings are analyzed. The results show that the TTF at the specific location has a great influence on the axial windings on the same core, and the distorted leakage magnetic field will cause excessive axial force and end thrust of the normal and short-circuit windings. These results can provide a basis for the short-circuit design of split-winding transformer.

Combined flexure and torsion of I-shaped steel beams

1989 ◽  
Vol 16 (2) ◽  
pp. 124-139 ◽  
Author(s):  
Robert G. Driver ◽  
D. J. Laurie Kennedy
Keyword(s):  
Limit State ◽  
Bending Moment ◽  
Phase Behaviour ◽  
Inelastic Interaction ◽  
Steel Beams ◽  
Ultimate Limit State ◽  
Second Phase ◽  
Design Standards ◽  
Limit States ◽  
Interaction Diagram

Design standards provide little information for the design of I-shaped steel beams not loaded through the shear centre and therefore subjected to combined flexure and torsion. In particular, methods for determining the ultimate capacity, as is required in limit states design standards, are not presented. The literature on elastic analysis is extensive, but only limited experimental and analytical work has been conducted in the inelastic region. No comprehensive design procedures, applicable to limit states design standards, have been developed.From four tests conducted on cantilever beams, with varying moment–torque ratios, it is established that the torsional behaviour has two distinct phases, with the second dominated by second-order geometric effects. This second phase is nonutilizable because the added torsional restraint developed is path dependent and, if deflections had been restricted, would not have been significant. Based on the first-phase behaviour, a normal and shearing stress distribution on the cross section is proposed. From this, a moment–torque ultimate strength interaction diagram is developed, applicable to a number of different end and loading conditions. This ultimate limit state interaction diagram and serviceability limit states, based on first yield and on distortion limitations, provide a comprehensive design approach for these members. Key words: beams, bending moment, flexure, inelastic, interaction diagram, I-shaped, limit states, serviceability, steel, torsion, torque, ultimate.

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