Asymptotic Analysis of TLP Tendons and Risers

Abstract

Except for the presence of highly localized bending stresses near the supports, the behavior of a slender tendon or riser under axial tension is essentially similar to that of a stretched string. From the viewpoint of analysis, however, a tendon or riser is neither a string nor a conventional beam, thus suggesting the exploration of more suitable analytical techniques. The relative significance of the flexural stiffness of such a slender member can be expressed conveniently in terms of two perturbation parameters, one for each end of the member. Closed-form asymptotic formulas are developed to depict, in an explicit and quantitative manner, the extent to which static or dynamic behavior of a tendon or riser may be affected by localized bending stresses near the supports. These formulas include, in particular, closed-form expressions for distribution of localized bending stresses, effect of rotational springs at the supports, lateral vibration frequencies of tendon or riser, and corresponding mode shapes.