The Influence of Tension, Pressure and Weight on Pipe and Riser Deformations and Stresses

Abstract

The influence of tension, pressure, and weight on different aspects of pipe and riser behavior has already been the subject of many articles (see references). In spite of this it has frequently been misunderstood, sometimes with serious consequences. The object of this paper is to explain the subject clearly and the approach is therefore deliberately very elementary. The principal problems of bending, buckling, yielding and strains, usually treated in separated papers, are here treated homogeneously. The widely used concepts of “effective tension” and “effective stress” are given interpretations, easy to visualise, which are related to analogous concepts in other engineering fields. Finally, eight diverse particular examples of the influence of tension, pressure and weight on pipe and riser behavior, are discussed.

Linear Vibration Characteristics of Cable–buoy Systems

“…Note that Archimedes' principle is not applicable to the in"nitesimal cable element since the hydrostatic pressure "eld is not closed [12]. To account for this, the force due to hydrostatic pressure is added to the cross-sectional area of the cable element and then subtracted from the equilibrium tension.…”

The Magic of Buoyancy and Hydrostatics –Buoyancy and Effective Forces

“…Sparks introduced the term effective tension in 1984 and formulated the relation between true and effective tension (Sparks, 1984): T e = w(e) -p bottom A + pA = w(e) -B(e) (4) This shows that Archimedian tension and the effective tension are identical as defined by line BD in Fig 1. Note that the effective tension at a certain level can be derived by using equation (2) directly, thus not needing to go via the true tension of equation (3). mas.ccsenet.org Modern Applied Science Vol. 11, No.…”

“…The hydro-mechanical model and understanding that supports the equation is presented in his publications (Sparks 1984(Sparks , 2005. The explanation is based on the acceptance of hydrostatic pressure 'invading' solid material and representing a force internally in the same manner as at the external flat.…”

Free Vibrations of Catenary Risers with Internal Fluid

“…The strain energy stored at the riser due to the axial deformation is due to the axial tension on the linear elastic riser and due to the axial stress resulting from enclosing external and internal hydrostatic pressures [6]. The axial tension is defined by T and the axial stress due to the enclosing hydrostatic pressures is defined by 2 (2) where E is the modulus of elasticity.…”