Stress Estimation of Offshore Structures

2020 ◽  
Author(s):  
◽  
Marius Tarpø
Keyword(s):  
Design Process ◽  
Offshore Structures ◽  
Structural Failure ◽  
Stress Strain ◽  
Actual Structure ◽  
Existing Structures ◽  
The North ◽  
Strain Estimation ◽  
Industry Standards ◽  
Virtual Sensing

Offshore structures are subjected to a harsh environment where the fluctuating waves continuously strain the structures and these forces cause the initiation and propagation of cracks in the structures. In other words, the structures accumulate fatigue damage, which eventually leads to structural failure. To avoid fatigue failure, the operational lifetime of a structure is limited to a design lifetime in which the structure is safe for operation. This design process is based on precautious stochastic assessments, norms, and industry standards that simplify the actual structure and environment in such a manner that it involves little risk of structural failure. As many structures in the North Sea approach the end of their design lifetime, the owners are faced with a dilemma: either abandon the field or replace the structures. Another option is the lifetime extension of the existing structures. This requires a reduction of the uncertainties in the design process - such as the stress history in fatigue-critical location. Unfortunately, these locations are often inaccessible or directly harmful to the sensors due to the hostile environment of the ocean. This thesis focuses on virtual sensing to estimate the stress/strain response of offshore structures by indirect measurements. The thesis addresses the state of the art and maps some essential issues within stress/strain estimation. In this thesis, stress/strain estimation is applied to different test specimens to address certain scientific issues. Parts of the thesis relate to the calibration of the system model for virtual sensing by operational modal analysis.

Integrity Management System for Fixed Offshore Structures Inspection Strategy

2004 ◽  
Author(s):  
Mohamed A. El-Reedy
Keyword(s):  
Management System ◽  
Offshore Structures ◽  
Assessment Method ◽  
Offshore Platforms ◽  
Offshore Structure ◽  
Structure Comparison ◽  
Actual Structure ◽  
Existing Structures ◽  
Integrity Management

The GUPCO offshore structure management system was developed as a part of an integrated infrastructure management system. This paper presents a case study of providing an integrity management system for inspection, evaluation and repair of the fixed offshore platforms in Gulf of Suez. The management system procedure is presented focusing on the first step for defining the highly risky weight to the lower risky weight structure based on API criteria for assessment of the existing structures. The risk analysis methodology for developing design and assessment criteria for fixed offshore structure based on consequence of failure is illustrated. In our case study the assessment method is applied for a number of fixed offshore structures. The above methodology is performed after theoretical assessment and then verifying by using ROV subsea inspection for the fixed offshore structure. Comparison between the actual structure performance and the predicting risk assessment for the structure from the model will be studied. The overall management system will be illustrated in scope of predictive maintenance philosophy and reliability for all offshore structures.

The Evolution of Lazy-S Flexible Riser Configuration Design for Harsh Environments

2012 ◽  
Author(s):  
Keith Anderson ◽  
Mark O’Connor
Keyword(s):  
System Design ◽  
Return Period ◽  
Original System ◽  
Life Extension ◽  
Harsh Environments ◽  
Flexible Riser ◽  
Traditional System ◽  
Existing Structures ◽  
The North ◽  
Industry Standards

Flexible riser configurations in harsh environments require riser buoyancy in order to decouple vessel induced motions from the seabed interface. This is achieved through either wave (distributed buoyancy) or S (subsea buoy) solutions. In the UK sector of the North Sea circa 30% of all floating production system field developments utilise subsea buoys in Lazy-S configurations. The majority of these fields have been in service for many years and designed prior to the widespread adoption of current industry standards, the analytical rigour available today, and better characterisation of the metocean environment. In many cases original system design has also been for 50yr return period conditions, compared to the specified 100yr return period events required in todays codes and standards, e.g. ISO 13628-2 [1]. Therefore, when replacement riser or life extension work is performed on existing structures or new developments are being designed there can be significant challenges in confirming the applicability of traditional system configuration designs. The principal challenges with these configurations is minimising sag bend compressions driven by differential buoy vs. vessel motions and maintaining the riser or umbilical minimum curvature and compression criteria at the seabed touch down. The latter point is a particular problem for umbilicals routed via Lazy-S configurations owing to their relatively low weight and stiffness, and constraining MBR criteria. This paper considers the applicability of Lazy-S configurations as a solution to modern harsh environment field developments and the evolution in Lazy-S system design to address the design challenges with particular emphasis on the TDP response.

CREDO RADON UA – INFORMATION MODEL FOR CALCULATION OF ROAD CONSTRACTION

2019 ◽  
pp. 34-42
Author(s):  
Volodymyr Karedin ◽  
Nadiya Pavlenko
Keyword(s):  
Design Process ◽  
Static Loading ◽  
Computer Aided Design ◽  
Experimental Studies ◽  
Construction Materials ◽  
Residual Deformation ◽  
Road Construction ◽  
Information Support ◽  
Existing Structures ◽  
Road Pavement

CREDO RADON UA software provides an automated calculation of the strength of the pavement structures of non-rigid and rigid types, as well as the calculation of the strengthening of existing structures. In the article, one can see the main features and functionality of the CREDO RADON UA software, the main points in the calculations according to the new regulations. Information support of the design process includes necessary databases, informational and helping materials that make up the full support of the pavement design process. The concept of CREDO RADON UA 1.0 software is made on the use of elasticity theory methods in calculations of initial information models of pavements. Performing optimization calculations, the roadwear in CREDO RADON UA is designed in such a way that no unacceptable residual deformation occurs under the influence of short-term dynamic or static loading in the working layer of the earth bed and in the structural layers during the lifetime of the structure. The calculation algorithms were made in accordance with the current regulatory documents of Ukraine. CREDO RADON UA software allows user to create information bases on road construction materials and vehicles as part of the traffic flow for calculations. The presented system of automated modeling makes it easier for the customer to control the quality of design solutions, to reasonably assign designs to layers of reinforcement, to quickly make comparisons of calculations of different designs for the optimal use of allocated funds. Prospects for further improvement of the program should be the results of theoretical and experimental studies on filling the databases, which are used as information support for automated design of road structures. Keywords: CREDO RADON UA, road, computer-aided design, repair project, road pavement, strengthening, construction, rigid pavement, elasticity module, a transport stream, calculation method, information support, dynamic or static loading.

Designing an Indigenous Voice that empowers: How constitutional recognition could strengthen First Nations sovereignty

2021 ◽  
pp. 1037969X2110096
Author(s):  
Jason O’Neil
Keyword(s):  
First Nations ◽  
Design Process ◽  
Interim Report ◽  
Role Of Government ◽  
Existing Structures ◽  
First Peoples ◽  
Indigenous Voice

This article considers how a First Nations Voice to Parliament, if carefully designed, could strengthen the land-based sovereignty and autonomy of First Peoples in Australia. It critiques the proposals presented in the Indigenous Voice Co-design Process' Interim Report released January 2021 for its emphasis on the role of government and existing structures. It responds to Indigenous critiques of the Uluru Statement from the Heart, while arguing for a constitutionally enshrined Voice to Parliament that respects and defers to First Nations' Country-based authority.

scholarly journals Horizontal Movement of Fast Ice in the North Water Area

1977 ◽  
Vol 19 (81) ◽  
pp. 547-554 ◽  
Author(s):  
Hajime Ito ◽  
Fritz Müller
Keyword(s):  
Sea Ice ◽  
Water Area ◽  
Physical Characteristics ◽  
Stress Strain ◽  
Horizontal Movement ◽  
The North ◽  
North Water ◽  
Fast Ice ◽  
External Forces

AbstractThe understanding of the horizontal movement of fast ice is important for applied sea-ice mechanics. A case study, carried out in conjunction with a polynya known as North Water, is presented in this paper. The displacements of the fast-ire arches which separate the polynya from the surrounding ice-covered sea, were measured and found to be small. It is, therefore, confirmed that these arches prevent the influx of large quantities of sea ice into the polynya. The results are then explained in terms of the external forces (wind and current), the stress- strain situations and some physical characteristics (temperature and thickness) which were measured simultaneously.

Developing an integrated framework for optimization of spatial requirements of construction equipment

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
S. Hemalattha ◽  
R. Vidjeapriya
Keyword(s):  
Construction Projects ◽  
Indoor Environment ◽  
Outdoor Environment ◽  
Building Information Modelling ◽  
Actual Structure ◽  
Content Type ◽  
Space Planning ◽  
Existing Structures ◽  
Building Information

PurposeThis study aims to develop a framework for optimizing the spatial requirements of the equipment in a construction site using a geographic information system (GIS).Design/methodology/approachAn ongoing construction project, an existing thermal powerplant in India, is considered to be the case study, and the corresponding construction activities were scheduled. The equipment spaces were defined for the scheduled activities in building information modelling (BIM), which was further imported to GIS to define the topology rules, validate and optimize the spatial requirements. The BIM simulates the indoor environment, which includes the actual structure being constructed, and the GIS helps in modelling the outdoor environment, which includes the existing structures, temporary facilitates, topography of the site, etc.; thus, this study incorporates the knowledge of BIM in a geospatial environment to obtain optimized equipment spaces for various activities.FindingsSpace in construction projects is to be considered as a resource as well as a constraint, which is to be modelled and planned according to the requirements. The integration of BIM and GIS for equipment space planning will enable precise identification of the errors in the equipment spaces defined and also result in fewer errors as possible. The integration has also eased the process of assigning the topology rules and validating the same, which otherwise is a tedious process.Originality/valueThe workspace for each activity will include the space of the equipment. But, in most of the previous works of workspace planning, only the labour space is considered, and the conflicts and congestions occurring due to the equipment were neglected. The planning of equipment spaces cannot be done based only on the indoor environment; it has to be carried out by considering the surroundings and topography of the site, which have not been researched extensively despite its importance.

scholarly journals Hybrid Finite Element Method Development for Offshore Structures’ Calculation with the Implementation of Industry Standards

2019 ◽  
Vol 26 (4) ◽  
pp. 90-100
Author(s):  
Jacek Łubiński ◽  
Henryk Olszewski
Keyword(s):  
Finite Element ◽  
Method Development ◽  
Structural Model ◽  
Model Development ◽  
Steel Structures ◽  
Cost Effective ◽  
Offshore Structures ◽  
Wind Loading ◽  
Hybrid Finite Element Method ◽  
Industry Standards

Abstract In the design process of offshore steel structures, it is typical to employ commercial calculation codes in which simulation and evaluation of results are performed on the basis of the available standards (e.g. API, DNV, Lloyds). The modeling and solution rely on finite element methods and cover the simulation of the structure’s properties along with the influence of the marine environment – sea currents, wave and wind loading, as well as the influence of vibrations, buoyancy and accompanying mass of water. Both commercial and open source mathematical modeling software which is available nowadays allows for cost effective and flexible implementation of advanced models for offshore industrial structures with high level of credibility and safety. The models can be built to suit task-specific requirements and evaluated on the basis of the selected criterial system best suited to the needs of the customer. Examples of methodology for environmental and structural model development are presented, along with simulation results covering a wide scope of data, ranging from stress and deformation to resonant characteristics and issues of technological feasibility.

Strain Based Failure Assessment for Offshore Structures Under Seismic Loading

2008 ◽  
Author(s):  
Wangwen Zhao ◽  
Richard Turner ◽  
Jian Liang
Keyword(s):  
Hot Spots ◽  
Low Cycle Fatigue ◽  
Inelastic Strain ◽  
Seismic Loading ◽  
Offshore Structures ◽  
Fortran Program ◽  
Strain History ◽  
Stress Strain ◽  
Failure Assessment ◽  
Stress Reversals

Under seismic loading, structural hot spots can experience very high levels of stress and many random stress reversals. Conventional stress based methods cannot assess the failure state in detail when stress is beyond the elastic limit and nominal stress reversals are more than double the yield stress. A method has been created to fully reproduce the true stress/ strain history by using 1) generalised Masing’s rule with equivalent cyclic energy dissipation to model cyclic stress/strain relation, 2) Neuber’s method to calculate inelastic strain concentration factor, and 3) relative effective notch factor determined from comparing S-N curves of different joint classes. From this reproduced strain history, strain cycles can be counted and low cycle fatigue analysis can be conducted by using Miner’s rule and by estimating damage from the strain based failure criteria such as Coffin-Mason method. This method has been implemented in a numeric procedure and coded in a FORTRAN program called CYSTRA (as for CYclic STRain Analysis). It takes input of “nominal” random stress history directly from general structural software, linear or non-linear, local or global, and calculates extreme strain and strain cycles at multiple hot spots for the whole structure efficiently. Thus it greatly facilitates failure assessment for offshore structures which can have a large number of hot spots within the structure, unlike mechanical devices commonly assessed in strain based analysis where detailed FE based methods can be used.

Composite Sleeve Repair in the North American Regulatory Environment

2020 ◽  
Author(s):  
Xavier Ortiz ◽  
Dan Jungwirth ◽  
Yashar Behnamian ◽  
Hossein Jiryaei Sharahi
Keyword(s):  
Maximum Stress ◽  
Oil And Gas ◽  
Hazardous Materials ◽  
Regulatory Environment ◽  
Department Of Transportation ◽  
Regulatory Requirements ◽  
The North ◽  
Industry Standards ◽  
American Society ◽  
The U.S

Abstract Composite sleeve repairs have been used in the pipeline industry for the last 25+ years. Fiberglass sleeves (e.g., Clock Spring®) were initially introduced in the market and are still being used as a proven pipeline repair method. For the last 15+ years, new composite materials have been introduced in the industry to provide a wider variety of repair options depending on the type of imperfections being repaired. Regulations in the U.S.A. and Canada share some requirements regarding design, installation, testing, and assessment of composite sleeve repairs. The U.S. Department of Transportation (DOT) through the Pipeline and Hazardous Materials Safety Administration (PHMSA) recommends the use of repair methods consistent with industry standards. The 2019 version of the Canadian CSA Z662 Oil and Gas Pipeline Standard includes requirements for testing and qualification according to the American Society of Mechanical Engineers (ASME) regulation PCC-2 or ISO/TS 24817, and requirements for conducting an engineering assessment to determine the subsequent maximum stress on the pipe sleeve. This paper compares the regulatory requirements for pipeline composite sleeve repairs in the U.S.A. and Canada; it describes some of the options for composite sleeve repair, and reviews engineering assessments of methodologies for composite sleeve repair.

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