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*Nonlinear Stiffener

Purpose

To define a stress-strain curve for a non-linear bend stiffener.

Theory

Refer to Bend Stiffeners for further information on this feature.

Keyword Format

A block of lines that define a stress-strain curve repeated as often as necessary. The block begins with a line defining the curve name. It is followed by as many lines as necessary to define each point on the curve.

Line defining the curve name:

CURVE=Curve Name

Line defining a point on a curve:

Stress, Strain

Each curve must have at least two points defined

Table Input

Notes

(a)The stress inputs are direct (longitudinal) stresses, and likewise direct strain. You do not specify a moment-curvature relation; rather Flexcom transforms the stress-strain data you specify here into moment-curvature curves for each element of the stiffener, based on the element properties.

(b)Use as many lines as you need to completely define a particular stress-strain curve. Simply leave Column 1 blank for second and subsequent lines. For subsequent stress-strain curves, put the curve name in Column 1 and specify the stress-strain data in the same way.

(c)The points defining the non-linear stress-strain curve may be specified in any order. Flexcom subsequently sorts the data pairs into ascending order of strain.

(d)If the strain in the non-linear bend stiffener element lies between the specified stress-strain data points, Flexcom uses linear interpolation to determine the relevant stiffness of the element.

(e)If the strain in the non-linear bend stiffener element lies outside the specified range of the stress-strain curve, then Flexcom simply extrapolates from the first or last section of the curve as appropriate.

(f)If none of the specified strain terms have a negative value, the curve is assumed to be symmetrical about the origin (i.e. the behaviour of the bend stiffener is the same for both positive and negative strains).