• Journal of Advanced Research in Ocean Engineering
• /
• v.4 no.1
• /
• pp.35-46
• /
• 2018

In this paper, safety analysis of the process of installing offshore structures such as manifolds and jacket-type substructures using floating cranes and barges in waves is performed. The safety analysis consists of three components. First, the dynamic responses of the offshore structure, cranes, and barge, all of which are moored and connected using wire ropes, are analyzed. Second, tensions in the wire ropes connecting the cranes and the offshore structures are calculated. Finally, any collision between the offshore structure and the cranes or the barge that transports the offshore structure is detected. Equations of motion of the offshore structure, cranes, and barge are formulated based on multibody dynamics, as well as considering the hydrostatic, hydrodynamic, and mooring forces. Additionally, proportional-derivative control of the tagline between the cranes and the offshore structure is performed to verify the safety of the installation process, as well as for reducing the dynamic response and collisions among them.

• Steel and Composite Structures
• /
• v.42 no.2
• /
• pp.209-219
• /
• 2022

Offshore platforms in seismically active areas must be designed to survive in the face of intense earthquakes without a global structural collapse. This paper scrutinizes the seismic performance of a newly designed and established jacket type offshore platform situated in the entrance of the Gulf of Suez region based on the API-RP2A normalized response spectra during seismic events. A nonlinear finite element model of a typical jacket type offshore platform is constructed taking into consideration the effect of structure-soil-interaction. Soil properties at the site were manipulated to generate the pile lateral soil properties in the form of load deflection curves, based on API-RP2A recommendations. Dynamic characteristics of the offshore platform, the response function, output power spectral density and transfer functions for different elements of the platform are discussed. The joints deflection and acceleration responses demands are presented. It is generally concluded that consideration of the interaction between structure, piles and soil leads to higher deflections and less stresses in platform elements due to soil elasticity, nonlinearity, and damping and leads to a more realistic platform design. The earthquake-based analysis for offshore platform structure is essential for the safe design and operation of offshore platforms.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2007.09a
• /
• pp.639-653
• /
• 2007

Offshore geotechnical site investigation of the seabed ground has been a key factor of the successful construction of various types of offshore structures like as sea-crossing bridges, submerged tunnels, and other marine facilities. Offshore investigations are not easy tasks because of the wave, wind, tidal ebb and flows, and others. Recent developments of offshore equipment including platforms and testing devices like as maine cone penetrator have inspired us to get more reliable characteristics of the seafloor. General information on the offshore site investigations and technical trends concerned are introduced.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.8 no.3
• /
• pp.31-41
• /
• 1988

Recently, the offshore structures are increasingly constructed to explore the natural resources. These offshore structures are to be designed to resist the repetitive wave forces. A probabilistic method for the fatigue analysis of offshore concrete structures is presented in this study. The present spectral fatigue analysis calculates wave forces first and then the transfer functions for unit waves from which stress spectra are determined. The calculated fatigue stresses may then be used to evaluate the fatigue damage of concrete structures. A simplified model for the estimation of fatigue damage of the structures, which employs only the probabilistic moments of the peak stress distribution without direct integration, is also proposed. The present study allows more realistic fatigue analysis of offshore concrete structures.

• International Journal of CAD/CAM
• /
• v.6 no.1
• /
• pp.29-40
• /
• 2006

The paper presents an optimization system which integrates a parametric design tool, 3D diffraction-radiation analysis and hydrodynamic performance assessment based on short and long term wave statistics. Controlled by formal optimization strategies the system is able to design offshore structure hulls with superior seakeeping qualities. The parametric modeling tool enables the designer to specify the geometric characteristics of the design from displacement over principal dimensions down to local shape properties. The computer generates the hull form and passes it on to the hydrodynamic analysis, which computes response amplitude operators (RAOs) for forces and motions. Combining the RAOs with short and long-term wave statistics provides a realistic assessment of the quality of the design. The optimization algorithm changes selected shape parameters in order to minimize forces and motions, thus increasing availability and safety of the system. Constraints ensure that only feasible designs with sufficient stability in operation and survival condition are generated. As an example the optimization study of a semisubmersible is discussed. It illustrates how offshore structures can be optimized for a specific target area of operation.

• Ocean Systems Engineering
• /
• v.13 no.2
• /
• pp.97-121
• /
• 2023

Through-the-thickness stress distribution in a tubular member has a profound effect on the fatigue behavior of tubular joints commonly found in steel offshore structures. This stress distribution can be characterized by the degree of bending (DoB). Although multi-planar joints are an intrinsic feature of offshore tubular structures and the multi-planarity usually has a considerable effect on the DoB values at the brace-to-chord intersection, few investigations have been reported on the DoB in multi-planar joints due to the complexity of the problem and high cost involved. In the present research, data extracted from the stress analysis of 243 finite element (FE) models, verified based on available parametric equations, was used to study the effects of geometrical parameters on the DoB values in two-planar tubular DYT-joints. Parametric FE study was followed by a set of nonlinear regression analyses to develop six new DoB parametric equations for the fatigue analysis and design of axially loaded two-planar DYT-joints.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
• /
• 1996.10a
• /
• pp.19-22
• /
• 1996

Extreme sea statistics and combinations of environmental events or response for structures are very important problem in performance evaluation and design of coastal and Offshore structures. A probabilistic method is developed that leads to the combination of Typhoon (Hurricane) or winter storm induces winds, waves, currents and surge for a generic site. The traditional recommendation for the fixed structures is a combination of the 100 years maximum wave height with the 100 years wind and current. (omitted)

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.466-472
• /
• 2009

Offshore wind energy is gaining more and more attention during this decade. For the countries with coast sites, the water depth is significantly large. This causes attention to the floating wind turbine. Offshore wind turbines are designed and analyzed using comprehensive simulation codes that account for the coupled dynamics of the wind inflow, aerodynamics, elasticity and controls of the wind turbine, along with the incident waves, sea current, hydrodynamics, and foundation dynamics of the support structures. In this work, a three-bladed 5MW upwind wind turbine installed on a floating spar buoy in 320m of water is studied by using of fully coupled aero-hydro-servo-elastic simulation tool. Specifications of the structures are chosen from the OC3 (Offshore Code Comparison Collaboration) under "IEA Wind Annex XXIII-subtask2". The primary external conditions due to wind and waves are simulated. Certain design load case is investigated.

• Journal of Power System Engineering
• /
• v.18 no.2
• /
• pp.19-24
• /
• 2014

This research conducts CAE analysis of fire damper and design of damper controlling system. The prediction of the design heat transfer was done the answer of fire damper could be obtained by using continuity equation of damper controlling and orthogonal array. Through the design analysis of optimal offshore construction, new fire damper of H-120 class was designed. Accordingly, this equipment will be tested in actual offshore construction. Finally, we could obtain fire damper of optimal design with orthogonal array. With the CAE results of this research, The offshore plant will obtain eco-friendly fire damper with a method to select optimal condition of fire damper with orthogonal array.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.11 no.1
• /
• pp.44-51
• /
• 1991

This paper describes the practical difficulties experienced with ultrasonic testing during site fabrication of the offshore structures, and indicates some of the problems when UT indications are evaluated according to written procedure which is prepared to the requirements of the applicable code (standard) and/or specification.