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*PIP Stiffness

Purpose

To define force-deflection curves for non-linear pipe-in-pipe connection stiffnesses.

Theory

Refer to Non-Linear Power-Law Connections for further information on this feature.

Keyword Format

A block of lines that define a force-deflection curve repeated as often as necessary. There are two possible types of force-deflection curves: explicit pairs of force-deflection values and power-law curves. The keyword formats are slightly different in each case, so each one is described separately.

Explicit Data Pairs

The first line defines the curve name, and optionally the curve type. This is followed by as many lines as necessary to define each point on the curve.

CURVE=Curve Name [, TYPE=DATA PAIRS]

Deflection, Force

Each force-deflection curve must contain at least two points, and deflection values should not be negative.

Power Law

The first line defines the curve name, the curve type, and the configuration in which is curve is to be used. The second line contains the maximum contact force, the exponent.

CURVE=Curve Name, TYPE=POWER LAW [, CONFIGURATION=Configuration Type]

Maximum Contact Force [, Exponent] 

Configuration Type may be PIP (default) or POP. Exponent defaults to 5.

pipe-in-pipe stiffness - Data Pairs

Purpose

To define force-deflection curves (using explicit data pairs) for non-linear pipe-in-pipe connection stiffnesses.

Table Input

Notes

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

(b)The points defining the non-linear force-deflection curve may be specified in any order. Flexcom subsequently sorts the data pairs into ascending order.

(c)If the deflection in the non-linear connection lies between the specified force-deflection data points, Flexcom uses linear interpolation to determine the relevant stiffness of the connection.

(d)If the deflection in the non-linear connection lies outside the specified range of the force-deflection curve, then Flexcom simply extrapolates from the first or last section of the curve as appropriate.

(e)The nonlinear stiffness of a connection does not depend on the direction of relative displacement of the connected nodes, because of the inherent symmetry of a pipe cross-section. Mathematically, this means the nonlinear stiffness curves should be symmetric about the origin, so you should not specify negative displacement values.

pipe-in-pipe stiffness - Power Law

Purpose

To define force-deflection curves (using a power-law approach) for non-linear pipe-in-pipe connection stiffnesses.

Table Input

Notes

(a)Refer to Non-Linear Power-Law Connections for further information on this feature.: