Fibre rope cross section wizard

The wizard will generate a Fibre Rope cross-section_.

The different options are

  • Default : This will create the default Fibre Rope cross section with no additional input

  • Syrope model: Polyester rope

Input:

  • Rope diameter in [mm]: d

1. Cross-section properties

  • Mass coefficient: \(m_{coeff}=m_{air}\)

  • Weight in air (dry mass):

    • The mass is calculated based on the regression line equation fitted to Bridon Superline Polyester for Permanent Mooring (Bridon fibre rope catalogue).

\[m_{air}=0.0007 d^2-0.0088d+0.489 [kg/m]\]

  • External cross sectional area:

\[A_{ext}=\frac{1}{\rho_{sw}} m_{air} (1-r_{air}^{sub})\\ \rho_{sw}= 1025 kg/m^3\\ r^{sub}_{air}=\frac{m_{sub}}{m_{air}}=0.25\\\]

where \(r^{sub}_{air}\) is the ratio between submerged weight to weight in air (dry mass).

2. Capacity properties

The MBL is calculated based on the regression line equation fitted to Bridon Superline Polyester for Permanent Mooring (Bridon fibre rope catalogue).

  • Tension capacity:

\[MBL=0.2658d^2+4.9392d-654.74\]

3. Hydrodynamic force coefficients

  • Load formulation is Morison

  • Input code: Nondimensional coefficients

Quadratic drag coefficient with respect to d

\(C_{Qx}^ {fiber}\)

\(C_{Qy}^ {fiber}\)

Fiber rope

0.1

1.6

  • Added mass in tangential direction: \(C_{Ax}=0.0\)

  • Added mass in normal direction: \(C_{Ay}=1.0\)

  • Linear drag coefficient in tangential direction: \(C_{Lx}=0.0\)

  • Linear drag coefficient in normal direction: \(C_{Ly}=0.0\)

4. Polyester rope

4.1. Syrope model

Using Fiber rope cross-section and Fiber Rope Model

  • \(t_{max}=0.4*MBL\)

In the Syrope model, the static stiffness for new rope (i.e., original working curve stiffness) as well as aged rope (i.e., working curve stiffness) are chosen to be 8 and 14, respectively. The values are chosen based on quasi-static stiffness values for preliminary design in ABS. The stiffness for a new rope is assumed to be smaller than the post-installation rope address in ABS.

Simplified dynamic stiffness model based on mean tension: \(K_rd=A+BT_{mean}\) A and B coefficients are based on BV standard.

  • DynamicStiffnessCoefficient [N]: A = \(18.5* MBL\)

  • DynamicStiffnessCoefficient [-]: B = \(0.33*100\)

5. Reference

  • ABS. Guidance Notes on the Application of Fiber Rope for Offshore Mooring. (2021).