PASS/NOZZLE-FEM 3.5. Program Manual

3.9.2. Structure setting

The structure attachment model is specified by a junction type with a base element, by the dimensions and section parameters, by its placement way relative to the base element, etc.

The description of the base element is given in the section: Base element setting.

Table 3.19 shows key features of the base element (shell).

Table 3.19
Feature Description
Structure local coordinate system (LCS),
located on cylindrical or conical shells,
including tank and vertical vessel:

X-axis is directed along the local (longitudinal) Z-axis of the base element.

Y-axis is directed along the normal to the ZX-plane; it is calculated as $e_y = e_z \times e_x$.

Z-axis is directed along the longitudinal structure axis.

The cross-section rotation angle $\omega_t$ allowes to rotate the local X and Y axes around the local Z-axis,
to provide the specified orientation of a non-circular section relative to the base element.

Fig. 3.55. Structure LCS for stretch base element ($\omega_t$=-90°)
Structure local coordinate system (LCS),
located on heads:

X-axis is directed along a straight line in the head plane passing through the center of the head and the structure end, that is from C-point to A-point (fig. 3.56).

Y-axis is directed along the normal to the ZX-plane; it is calculated as $e_y = e_z \times e_x$.

Z-axis is directed along the longitudinal structure axis.

If the attachment is central (offset is not set), then X-axis coincides with the local X-axis of the head.

The cross-section rotation angle $\omega_t$ allowes to rotate the local X and Y axes around the local Z-axis,
to provide the specified orientation of a non-circular section relative to the base element.

Fig. 3.56. Structure LCS for head ($\omega_t$=-90°)
Structure local coordinate system (LCS),
located on elbow (bend):

X-axis is directed along the tangential axis of the central axial curve of the elbow (bend) element.

Y-axis is directed along the normal to the ZX-plane; it is calculated as $e_y = e_z \times e_x$.

Z-axis is directed along the longitudinal structure axis.

The cross-section rotation angle $\omega_t$ allowes to rotate the local X and Y axes around the local Z-axis,
to provide the specified orientation of a non-circular section relative to the base element.

Fig. 3.57. Structure LCS for elbow ($\omega_t$=0)
Structure local coordinate system (LCS),
located on rectangular plate:

It coincides with local CS of base element (plate).

Placement in LCS of base element:

For cylindrical or conical shells, including tank and vertical vessel, the structure placement can be specified by the following types:

Radial The longitudinal attachment axis is directed normal to the surface of the base element.
In section plane The longitudinal attachment axis is rotated at an angle from the normal to the surface of the base element.
The rotation is carried out in the cross section plane of the base element.
Offset The longitudinal attachment axis is shifted from the normal to the surface of the base element.
The offset is carried out in the plane of the cross section of the base element.
Tilted The longitudinal attachment axis is rotated by the deviation angle from the normal to the surface of the base element and by the angle around this normal.
Vector The longitudinal axis is defined by its projections in the local coordinate system of the base element.

For elbows (bends), the structure placement can be specified by the same types as for the cylindrical shell.
At the same time, additional types are introduced:

Trunnion offset The longitudinal attachment axis is perpendicular to the axis of the 1st leg and is shifted from the second end of the elbow (bend).
Trunnion offset from 1st leg axis The longitudinal attachment axis coincides with the longitudinal axis of the 1st bend leg (local Z-axis), while it can be offset relative to this axis.
Trunnion offset from 2st leg axis The longitudinal attachment axis coincides with the longitudinal axis of the 2st bend leg (local Z-axis), while it can be offset relative to this axis.

For heads or rectangular plates, the placement of the structure attachment can be specified by the following types:

Radial The longitudinal attachment axis is directed normal to the surface of the base element.
Offset The longitudinal attachment axis coincides with the local Z-axis of the base element.
Tilted The longitudinal attachment axis is rotated by the deviation angle from the normal to the surface of the base element and by the angle around this normal.
Vector The longitudinal axis is defined by its projections in the local coordinate system of the base element.
Constraints (dof):

Absent in the all calculation schemes.

Structure loads:

Thermal strains.

Concentrated loads in the juncture or on the structure end.

More information in the section: Setting model loads.

Shell loads:

Described in the section: Base element setting.

Special calculations:

Allowable loads;

Stiffness and flexibility factors;

Stress intensification factors;

Calculation as per WRC 537(107)/297 (only for circular and rectangular sections).

Structure junction types:

The structure design model corresponds to fig. 3.58.

Type 9: Trunnion
Type 10: Trunnion with reinforcement
Fig. 3.58. The design model of the structure junction

 

 

PASS/NOZZLE-FEM 3.5. Program Manual

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