Conceptually, fabric composites have some structural advantages over conventional laminates. However, deformation and failure analyses become more complex with the additional anisotropy introduced by the weaving geometry. A micromechanistic deformation model, that could realistically be incorporated into structural finite element codes, is proposed where loading direction and weave parameters are allowed to vary. Comparisons are made to previous models and experimental results for woven materials, indicating that the proposed model provides improved estimates for the linear elastic stiffness. The model further provides predictions for internal stresses in the longitudinal, transverse, and interlace regions of the woven laminate which qualitatively correspond to the experimentally observed failure mechanisms. The experimental program investigates deformations behavior and failure mechanisms of 5-harness 0/90 weave Graphite/Epoxy laminates under tension, compression, and 3-point and 4-point bending loading. Under these conditions the woven laminates exhibit orientation dependent mechanical properties and strength.

Aker Maritime, Inc., J. J. Murray, Spars International, inc. Copyrwh! 1S9? OfMore l'eshrmlc+w Conference TMs Wprwasvovrcd fw@resemtilw arttw lF.9mi$~c Tetino!~y cotire.cehe!d m Hcuf.mn, TeKas, M Msy 1SW TFUSPWXI W,. s.ktod fo.~

Thia paper waa selected for presentation by lhe OTC Program Committee following revi_ of information con18ined in an abstract aubmlned by the authorIal. Conlenta of the paper, aa presented, have not bean reviewed by the OIIshore Technology Conference and are aubjact to correction by the euthor(a). The material, aa presented, does not _ r i l y reflect any poaition of the OIIshore Technology Conference or na oHlcera. Electronic reproduction, distribution, or storage ot any perl of thia paper tor commercial p\lfP088l without the written conaant oflhe OIIshore Technology Conference Is prohibited. Permiaalon 10 reproduce in print ia reatricted to an abatract of nof more than 300 words; iIIustrationa may nof be copied. The abstract must conlain conspicuoua acknowtedgmanl of where and by whom the paper waa presented. ABSTRACTComposite production riser (CPR) joints are being seriously considered in the development of deep water tension leg platforms (UPs), because of their inherent light weight, superior fatigue and corrosion resistance, and outstanding specific strength and stiffness properties. Current efforts on the development of CPR joints have been mainly focused on lowcost manufacturing and failure strength evaluation of CPR tube body and CPR joint connection. The important issue of system dynamics of UPs containing multiple CPR strings, has not been addressed.In this paper, system analysis of a UP containing 16 CPR strings and 12 tendons subjected to Gulf of Mexico environment loading have been conducted. The riser system is configured for 3,000 ft water depth with CPR joints, standard steel riser joints, splash zone joints, stress joint, and top tensioners. The study embraces several disciplines, including naval architecture, riser dynamics analysis, and composite failure mechanics to develop an iterative algorithm for evaluation of the top tension and stress joint requirement. Specifically, optimum top tension requirements have been determined based on riser dynamics and the failure envelope of the CPR joints. For comparison, the optimum top tension requirements are further used to size the UPs with all-steel riser and with CPR. For the 3,000 ft water depth case study, reduction in riser weight is magnified by 3.31 times in the UP size. It is demonstrated that the weight reduction in the riser string is nonlinearly related to the tensioner requirement and UP size.

Synthetic mooring ropes are among the several alternatives being developed for positioning deepwater floating platforms. These ropes are constructed from polymer fibers such as polyester, nylon, or aramid. Individual fibers are grouped in yarns and strands, and overlayed to yield ropes of different diameters. Synthetic mooring lines have shown to provide numerous advantages over steel cables, enabling deepwater exploration and production. Widespread utilization, however, entails addressing technical challenges in rope material characterization, dynamic response and mooring system design, installation, design life prediction, and reliability assessment. In this paper, a polymer mechanics based methodology is presented to address the long-term performance of mooring lines. The methodology provides an insight into the timetemperature dependent nature of synthetic rope deformation. A procedure for estimating damage evolution and the residual strength of a synthetic mooring line is also discussed. Failure of mooring terminations is beyond the scope of this study. However, outlined deformation and failure models can be used to design terminations, which are subjected to localized multiaxial stresses. INTRODUCTION In addition to obvious weight savings, characteristics such as neutral buoyancy, lower pretension requirements, improved fatigue performance, and better corrosion resistance make synthetic ropes an attractive replacement for steel cables as mooring lines for deepwater floating vessels. The potential advantages of polyester mooring lines have been successfully demonstrated in several feasibility studies [1,2] and pilot [3,4] projects. These projects clearly illustrate the operational and economic benefits of synthetic moorings and outlined the following technical challenges:special requirements during installation,complex loading history and associated time-dependent deformation during service,a multitude of long-term failure mechanisms due to combined creep and fatigue, andpotential strength degradation, in part, due to hysteresis effects, seawater exposure, and fiber abrasion. These challenges may be overcome with long-term testing and physical deformation and failure prediction model developments, and further field demonstration projects. In this paper, a polymeric mechanics based method is outlined to address deformation and failure of synthetic moorings. First, a review of mechanical characterization models of synthetic ropes is presented. Subsequently, a deformation model for synthetic moorings is described. Failure prediction methodologies for synthetic mooring ropes subjected to a marine environment are then discussed. LITERATURE REVIEW Single Fibers, Yarns, and Small Ropes A number of studies [5-12] have been reported in the open literature on mechanical properties of synthetic fibers, yarns, and small ropes. Cyclic and creep fatigue data were obtained [6,7] for Nylon 66 and single polyester fibers, yarns and ropes in air and sea water for load frequencies ranging from 0.1 Hz (typical in a marine environment) to 20 Hz. It was observed that the strain at failure under different loading (monotonic loading, static fatigue and cyclic fatigue) is the same (Fig. 1). It was postulated that the failure mode of fibers was mainly creep rupture, regardless of the loading cases. Using the cumulative time under load as a failure parameter, creep rupture models for fibers may predict the failure in cyclic tests at different frequencies in wet and dry conditions. The fatigue resistance of Nylon 66 and single polyester fibers, yarns, and small ropes are of similar nature at all frequencies, when the S-N curves are plotted in the S-time

Steel Catenary Risers (SCR) are critical dynamic structures with a complex fatigue response. The offshore industry lacks verification of analytical models with full-scale response measurements. Only a small number of installed SCRs have any instrumentation to monitor dynamic response. This paper describes an on-line monitoring system deployed on one of the Tahiti infield (production) SCRs. Tahiti is a Truss Spar Floater located in 4,000 ft water depth in the Gulf of Mexico. The system is configured with localized strain and motion measurement devices. Emphasis is placed on the selection of number and location of the monitoring devices to characterize vessel induced riser response, VIV induced riser response, riser-seabed interface, and discontinuities at the riser hang-off locations. Monitoring device sensitivity requirements and qualification programs are also discussed. The monitoring system configuration drivers are reviewed in detail such as; monitoring objectives, instrumentation requirements, specification and architecture, field development integration, and installation. Information provided in this paper would be helpful for configuration of complex monitoring systems for deepwater steel catenary rises.