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*BEAMPRO2
Data format:
An arbitrary number of lines with 11 parameters each, as follows:
IPRO ITRUETENS AIRIN WT OD DBUOY XJ63 XJ36 DENDCAP CL DCONT
...
Status:
Optional
Purpose:
To define geometrical properties of a set of beam elements previously defined by global stiffnesses (*BEAMPRO)
Details :
| Parameter | Description |
|---|---|
| IPRO | Identification number referring to a keyword *BEAMPRO previously defined. |
| ITRUETENS | A flag to select whether the axial behavior of the line is defined with respect to the effective tension or to the true wall tension. ITRUETENS = 0 (default): The axial behavior of the riser is given with respect to the effective tension; ITRUETENS = 1 : The axial behavior of the riser is given with respect to its true tension; |
| AIRIN | Internal cross section of the riser (m2); |
| WT | Wall thickness of the riser (m); |
| OD | Outer diameter of the riser (m) |
| DBUOY | Buoyancy diameter (m) |
| XJ63 | = 0 (obsolete) |
| XJ36 | = 0 (obsolete) |
| DENDCAP | End cap diameter (m) |
| CL | Lift coefficient (used if contact and *LIFTOPTION is defined) |
| DCONT | Contact diameter (m) |
Note
Classically, the presence of a fluid inside and outside the riser is accounted for resorting to the effective tension concept. The true tension is linked to the effective tension by the following relationship :
\(T_{true} = T_eff - P_e S_e + P_i S_i\)
Where: - \(P_e\) is the external pressure due to sea water hydrostatic pressure, - \(P_i\) is the internal fluid pressure, - \(S_e\) is the external section of the pipe calculated from the hydraulic diameter : \(S_e = \pi * D_h^2/4\) - \(S_i\) is the internal cross section (AIRIN hereabove).
The same relation exists between the stresses. The true axial stress
\(\rho_{real}\) is deduced from the effective stress \(\rho_{eff}\) :
\(\rho_{real} = \rho_{eff} + \rho_{p}\) with \(\rho_p = \frac{P_i S_i - P_e S_e}{S_e - S_i}\)
The total apparent weight of the global system riser + fluid is used in the
calculations and the resulting effort is then the effective tension. A special
attention must be paid to the link between the axial strain of the riser and
the effective tension :
- When a multi-linear axial stiffness is defined, it is important to distinguish the effective tension from the true tension. When ITRUETENS=1, the axial behaviour is expressed in terms of the true tension;
- On the other hand, due to the Poissons coefficient, the fluid pressures change the axial strain. When ITRUETENS=1,the axial strain is corrected the pressures effect.
