Energo Engineering

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Energo Engineering

Engineering, United States
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Ivanov L.D.,American Bureau of Shipping | Ku A.,Energo Engineering | Huang B.-Q.,Energo Engineering | Krzonkala V.C.S.,Abs Consulting
Ships and Offshore Structures | Year: 2011

The widespread practice for presentation of the still water loads acting on the hull structure of a floating production storage and offloading facility (FPSO) is to use the individual amplitude statistics. When the probability density function of the loads is built, its integration provides the probability of exceeding any given level of loads. Also, once it is available, one can apply the principles of extreme value statistics to obtain the highest value in any number of cycles. The individual amplitude statistics are used in fatigue strength calculations, while the extreme value statistics can be used in ultimate strength calculations. An example is given for the probability density functions of a sample FPSO when the two approaches are applied for assessment of the total hull girder load that can be applied for calculation of its ultimate strength. © 2011 Taylor & Francis.

Moslehy Y.,Energo Engineering | Kemp D.,Hess Corporation | Kitson M.,Energo Engineering | Litton R.,Energo Engineering | Sheppard R.,Energo Engineering
Proceedings of the Annual Offshore Technology Conference | Year: 2016

A Structural Integrity Management (SIM) program plays a substantial role in managing structural risks and reducing expensive deepwater in-situ repairs. Inspection and operating decisions and costs are significantly affected by what is defined in a SIM program. Baldpate compliant tower in particular features an innovative structural system and is among the tallest structures ever built. It is a valuable deepwater asset that needs a SIM program backed by a strong technical foundation to provide confidence that continued service and potentially expanded operations can be safely achieved. Earlier studies had shown that fatigue sensitivities at critical locations could potentially limit Baldpate's useful life beyond the original 20 year target. This was mainly due to the conservatism inherent in the spectral fatigue approach which did not capture the innovative and highly dynamic features of the Baldpate tower. In order to better understand the dynamic characteristics of this unique structure and accurately model the tower, a field measurement campaign using 3D accelerometers was carried out. The measurements were then used to benchmark and adjust the computer model. A time-domain rainflow fatigue analysis was utilized to capture the compliant response of the tower for both fatigue seastates and three large storms which have affected Baldpate. This showed that fatigue sensitivities are not limiting factors for continued service of Baldpate, and the areas of fatigue sensitivity were incorporated into a long term SIM plan to focus future inspection and monitoring efforts. This paper provides details on the study performed for the Baldpate structure using field measurement, a rainflow simulation and its contribution to the development of a long term, risk based SIM plan. The behaviors of several unique structural components, such as stress concentration factors at atypical connections, gap behavior and friction lock-up at the guided axial tubes, were also considered. SIM options for these unique structural components are discussed, including underwater inspection methods and on-site dynamic motion recording. These efforts resulted not only in a more promising range of fatigue lives than previously calculated, but also identified areas of focus in support of a risk based SIM and associated inspection plan to support continued service through the asset's viable economic life. This approach is enhanced by a real-time monitoring plan to measure the dynamic characteristics of the tower under different load conditions to indicate when certain unique structural characteristics (e.g., axial tube motion within the guides) would affect the fatigue life of critical joints in the Baldpate tower.

Younan A.H.,ExxonMobil | Puskar F.J.,Energo Engineering
Proceedings of the Annual Offshore Technology Conference | Year: 2010

This paper describes the updates of the API recommended practice for seismic design procedures and criteria for offshore structures. The updates are divided into two parts. The first part is a new API Recommended Practice (RP) called API RP 2EQ which contains the overall seismic design procedures and selection of seismic design criteria, applicable to all types of offshore structures. This is a modified version of ISO 19901-2 adjusted as necessary for the USA. The second part is an update to API RP 2A (RP2A) or seismic design practices for steel jackets, that follows a combination of prior RP2A practices as well as the guidance contained in ISO 19902 (steel jackets). This paper describes these updates and in particular discusses how the changes differ from prior API practice. The updated seismic documents are part of an overall API effort to update RP2A as well as merge and align with the worldwide ISO documents. Copyright 2010, Offshore Technology Conference.

Wisch D.J.,Chevron | Verret S.,Energo Engineering
Proceedings of the Annual Offshore Technology Conference | Year: 2014

The API Series 2 documents cover a wide range of offshore structures. Through evolution and borrowing from different documents, design margins and reliability levels indicate some inconsistency. An API Task Group is developing a strategy providing consistency across the various structures and components covered in the Series 2 Standards. This work will result in a new API standard providing guidance and high level design objectives. This work is parallel to and will feed into the third edition of ISO 19900, the overarching standard for the ISO 19900 Offshore Structures Series. Areas of discussion will include the background, usage and relative value of the use of a defined air gap, variance between structural factor of safety and mooring factors of safety approaches, the rationale for performance margins that may differ between new and existing facilities, the impact of the slope of the hazard curve and how the slope has created misunderstanding along with other topics critical in the performance of offshore structures. This paper will detail the results of a comprehensive audit of design practices and conditions in current Series 2 standards and provide a framework for future work providing consistency in margin approach and the logic for assessment of existing facilities relative to that for new facilities. This framework will provide an increased ability for owners and regulators to make conscious choices and have the ability to identify inconsistencies in design targets/margins that can easily occur in today's practice. Copyright 2014, Offshore Technology Conference.

Chen J.-Y.,Energo Engineering | Gilbert R.B.,University of Texas at Austin | Puskar F.J.,Energo Engineering | Verret S.,Energo Engineering
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2013

The objective of this paper is to document and study the failure of a driven, steel pipe pile foundation system supporting an offshore platform. The three-pile system failed in overturning because of a pull-out failure of the most critically loaded pile in a hurricane 5 years after installation. The calculated tensile capacity of this pile using the American Petroleum Institute (API) design method is close to the estimated load at failure. This case history is significant because it represents the failure of a large-diameter pile in service when loaded by a storm. Also, this case history generally affirms the current design methods and contradicts a widely held perception that offshore pile designs are significantly conservative. This case history highlights the opportunities to improve design practice by explicitly accounting for pile flexibility when dealing with strain-softening soils and by considering the capacity of the foundation system as well as the capacity of individual piles in design. © 2013 American Society of Civil Engineers.

Kong Q.,University of Houston | Robert R.H.,Energo Engineering | Silva P.,George Washington University | Song G.,University of Houston | Mo Y.L.,University of Houston
Transforming the Future of Infrastructure through Smarter Information - Proceedings of the International Conference on Smart Infrastructure and Construction, ICSIC 2016 | Year: 2016

Structural health monitoring of bridge columns in areas of high seismic activity is highly demanded. In this project, piezoce- ramic-based transducers known as smart aggregates (SA) were employed to detect the damage of a reinforced concrete (RC) bridge column subjected to pseudo-dynamic loading. The SA-based approach has been previously verified for static and dynamic loading but never pseudo-dynamic loading. An active sensing approach was developed to real-Time evaluate the health status of the RC column during the loading procedure. The existence of cracks attenuated the stress wave transmission energy during the loading procedure and reduced the amplitudes of the signal received by SA sensors. To detect the crack occurrence and evaluate the damage severity, a wavelet packet-based structural damage index was developed. Experimental results show that the values of the damage index increase with the increasing of the cracks in the RC column. In addition to monitoring the general severity of the damage, the local structural damage indices monitored the cyclic crack open-close phenomenon subjected to the pseudo-dynamic loading. © The authors and ICE Publishing: All rights reserved, 2016.

Puskar F.J.,Energo Engineering | Soong R.E.,Energo Engineering
Proceedings of the Annual Offshore Technology Conference | Year: 2010

Timely and cost effective inspection of offshore structures following a hurricane is critical in order to safely re-man the facilities and bring production back on-line. Recent hurricanes Ivan, Rita, Katrina and Ike in the Gulf of Mexico (GoM) resulted in thousands of above and below water structural inspections of offshore structures to determine if they sustained damage. Severa of the API Recommended Practices (RPs) for offshore structures provide guidance for such "special" inspections, but the guidance is limited and general in nature. API Bulletin 2HINS (2HINS, short for Hurricane [NSpection) complements those publications and provides additional guidance specific to structural inspection following hurricanes The document is applicable to permanent fixed and floating structures in the Gulf of Mexico. Copyright 2010, Offshore Technology Conference.

Spong R.,Energo Engineering | Gallagher D.,Energo Engineering
Proceedings of the Annual Offshore Technology Conference | Year: 2013

A well planned and executed Structural Integrity Management (SIM) program is the cornerstone of managing structural risks and it can greatly reduce unplanned, undesired and extremely costly in-situ structural repairs on floating offshore facilities. However, the level of effort, required resources and ultimately the operating costs to maintain offshore structures can be greatly influenced by decisions and assumptions made during design and construction. This is particularly the case for Floating Production Storage and Offloading (FPSO) units because of the added complexities and consequences related to the oil storage and offloading. Though, there are several examples of other floating facility types (e.g., Semisubmersibles, Spars, etc.) where decisions in design influenced the ease, or conversely the difficulty, maintaining the asset's structural integrity over the operating life. This paper provides general guidance on design and construction decisions that can help enhance the planning and execution of a SIM program while improving the long term structural integrity performance of offshore floating structures. Examples are also provided where design and construction decisions have been observed to positively or negatively influence the long term integrity of floating offshore structure hulls and marine systems during operation. The observations and examples are drawn directly from the authors' experiences supporting major oil and gas companies operating in Australia, West Africa and the Gulf of Mexico regions to develop, manage and execute offshore fleet SIM programs. Copyright 2013, Offshore Technology Conference.

Ku A.,Energo Engineering | Gallagher D.,Energo Engineering
Proceedings of the Annual Offshore Technology Conference | Year: 2013

The ability to maintain stationkeeping throughout severe environmental loading is critical to the safe operations of permanently moored floating facilities. Failures of forged mooring components have been observed on these facilities and noted by the issuance of multiple safety notices by United States regulatory bodies (U.S. Department of the Interior Safety Alerts No. 259 on 16 January 2008 and No. 296 on 12 May 2011). These alerts highlighted the need for Operators to remain vigilant in ensuring that the mooring components present are of sufficient quality and toughness to prevent the observed failures from occurring in the future. This paper describes a study which includes the following three main components: (1) a survey of existing facilities to determine the extent of forged low-toughness mooring connectors in service, (2) develop a high-level assessment procedure to assess such connectors, and (3) identify potential mitigation activities. The main findings of this paper confirm the existence of low fracture toughness connections. Operators, manufacturers and the classification societies have actively pursued improved manufacturing and certification processes which significantly improve the toughness values, which will be demonstrated in this paper. Assessment and mitigation processes are also summarized in this paper which can be employed by operators to reduce the risk exposure from the low toughness mooring components. Copyright 2013, Offshore Technology Conference.

Sheppard R.E.,Energo Engineering | Puskar F.J.,Energo Engineering | Waldhart C.,Energo Engineering
Offshore Technology Conference, Proceedings | Year: 2011

Blades form an integral part to the operations and structural response of wind turbine facilities and demonstrating their long- term integrity in an offshore environment is challenging. Current practice for blade inspections for land-based and offshore facilities is generally driven by knowledge of defects in similar blades or problems identified in the power performance of a particular turbine. In developing guidance for more proactive inspection and monitoring programs, it is useful to understand what mechanisms affect blade performance. A discussion covers the inspection guidance development; techniques capable of detecting blade damage; and various inspection techniques and their applicability to offshore blade inspections. This is an abstract of a paper presented at the Offshore Technology Conference 2011 (Houston, TX 5/2-5/2011).

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