ESTIMATING EXTREME TENDON RESPONSE USING ENVIRONMENTAL CONTOURS

The environmental contour technique was used to estimate the extreme i n-line responses of deep-water TLP tendons designed for the Gulf of Me xico. The simulated response estimates were then used to estimate fail ure probabilities and reliabilities utilizing a deterministic displace ment limit state. The reliability of individual tendons and tendon sys tems is directly associated with their respective probabilities of fai lure. By designing for environmental contours identified using this te chnique the resulting design will be more likely to approach the inten ded target reliability. In this article the environmental contour theo ry is explained and then used to estimate the extreme tendon responses in two examples reflecting practical design uncertainties. Experiment al data from large scale model tendon experiments was introduced in or der to assess the numerical prediction. In the first example the probl em of uncertainty associated with pretensioning of the individual tend ons is investigated. Although the amount of uncertainty due to the cha nge in tension is not known the use of contour inflation is illustrate d as a means to compare the numerical prediction with the experimental data. The second example addresses the uncertainties associated with the fluid/structure interaction. The placement of tendons in close pro ximity results in the amplification of the tendon motions. At present, no adequate hydrodynamic model exists which can be used with confiden ce in design practice, Again contour inflation is explored as a means to compensate for this phenomena and to quantify in a global sense the impact of this uncertainty on design. (C) 1998 Elsevier Science Ltd.