Alberto Omar Vazquez-Hernandez

A Reliability-Based Comparative Study for Mooring Lines Design Criteria

The characteristic load effect for the design of mooring systems can be defined by means of three procedures: 1) an extreme sea state with a given return period, 2) a set of sea states on a contour line associated to a return period or 3) extreme response (tension) statistics for a long-term period. This work presents the result of a reliability-based partial safety factor calibration study for a LRFD mooring line design criteria considering the three approaches mentioned above. The calibration exercise is applied to three FPSOs considering North Sea environmental conditions and different water depths: 200m, 800m and 3000m. The mooring systems investigated take into account lines made up of chains and polyester ropes. It is shown that the design procedure based on the long-term response, among all water depths investigated, is the one that presents less scattered reliability indices around the target level.Copyright

On the Extreme Analysis Applied to Moored Floating Platforms

This paper presents an insight into some different methods for prediction of extreme response values of slender structures belonging to moored floating units. The methods investigated are: Weibull-tail fitting, SRSS, SRSS modified, LS and LS modified (API). All these methods are based on a single time series sample of the response parameter. The statistical uncertainty associated to each method is assessed by means of analyzing several independent simulations of the response parameter. Numerical examples include the top tension response analysis of two mooring lines: one connected to an FPSO in deepwater and the other to an FPSO in shallow water.Copyright

Influence of Ultra-Short Mooring Radius in Torsional Behavior of FPSO-Turret in Ultra Deepwater

This paper discusses the effect of the torsional (yaw) stiffness of the mooring system of an FPSO turret in its mooring radius. This study was developed to determine the minimum mooring radius of a FPSOs turret mooring system in ultra-deep waters (3,000 meters) in Campos Basin, offshore Brazil. The paper shows that the mooring system torsional stiffness can limit the minimum mooring radius.Copyright

Solitary wave collisions by double-dam-broken simulations with the MPS method

Purpose The paper aims to apply a modified version of the MPS method to a double dam-breaking test, in which high dispersion zones and as well high natural clusterization zones are present, such as when the water column collapses into two sides and the two solitary waves collide respectively. Design/methodology/approach The work takes advantage of the mixed source term from the cheaper computational version of the Moving Particle Semi-implicit (MPS) method to reduce one step from the MPS classical algorithm, also applying modifications to the variance parameter in the Laplacian operator and gradient model we can succsesfully simulate the proposed test. Findings The results show stable behavior in dispersion and clusterization zones, also the colision and merging produced by solitary waves was succsessfully simulated. Research limitations/implications The main limitation in this work was compare the obtained results with the original cheaper computational version of the Moving Particle Semi-implicit becaus...

FPSO Conceptual Design System Tools Considering Hurricane Data Base and Production Requirements

The conceptual design is an important stage of the engineering process of any floating production system. This design stage takes into account the specific site conditions and production requirements to find a feasible technical alternative of the system characteristics, from which in the next engineering stage the structure is improved. Among the basic characteristics of a floating production system are the hull main dimensions, which have to meet the production and stability requirements, as well as the mooring system characteristic. The mooring system definition mainly depends on the water depth, hull dimensions and the environmental site conditions. The environmental conditions are different from site to site, where in some sites around the world harsh conditions like hurricanes or typhoons may occur. Therefore, in the dimensioning of the mooring system such environmental conditions have to be considered. In the case of Gulf of Mexico, hurricane conditiones have presented a risk to the oil and gas existing facilities as it is evident on the severe damages and failures they have provoked in some cases. The present study aims to consider a computational tool that takes into account in the conceptual design stage a data base of hurricane conditions in Gulf of Mexico, as well as the production and site requirements so that to carry out the basic sizing of hull and mooring systems. The tool also considers a data base considering different hull sizes (wave force coefficients) and mooring materials to estimate the environmental loads and the mooring system design.Copyright