Support leg setting

PASS/NOZZLE-FEM 3.6. Program Manual

3.9.3. Support leg setting

The support leg model is specified by a trunnion 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.

The program allows to insert a support legs on all types of base elements, except for vertical cylindrical vessels and bends.

Table 3.20 shows key features of the base element (shell).

Table 3.20

Feature

Description

Support local coordinate system (LCS),
located on cylindrical or conical shells:

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 support 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. 3.61. Support LCS for stretch base element ($\omega_t$=-90^°)

Support 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 support end, that is from C-point to A-point (fig. 3.62).

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 support axis.

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

Fig. 3.62. Support LCS for head ($\omega_t$=-90^°)

Support 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 support placement can be specified by the following types:

Radial	The longitudinal support axis is directed normal to the surface of the base element.
In section plane	The longitudinal support 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 support 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 support 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 support 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 support 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 support 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 support 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 support support can be specified by the following types:

Radial	The longitudinal support axis is directed normal to the surface of the base element.
Offset	The longitudinal support axis coincides with the local Z-axis of the base element.
Tilted	The longitudinal support 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.