The New Offset dialog has 2 tabs:
On the Absolute tab, an offset value is defined by specifying a value of the shift in the direction of selected axes. This offset value does not change regardless of the operations performed on the elements on which the offset was defined.
On the Relative tab, an offset value is defined in relation to other existing objects. A basic feature of this offset type is automatically fitting an object to objects that already exist. (Fitting the length of a selected object to other defined objects, that is, the length increases or decreases as well as changing the position of one object with respect to another).
The difference between the absolute (manual) and relative (automatic) offset is shown in the following 2 examples:
Changing a section of a column adjoining to a beam
After the geometry of the beam-column connection is defined, an offset equal to one-half the height of the column section is defined.
After changing the column section, the offset is not updated. The offset value still equals one-half the height of the previous section.
After the geometry of the beam-column connection has been defined, an offset equal to one-half the height of the column section is defined.
After changing the column section, the offset is updated to the new column section. Elements adjust to each other.
Changing the position of an object with respect to a selected object
A beam-beam connection.
After changing the beam section, the offset is not updated. The offset value does not change.
A beam-beam connection.
After changing the beam section, the offset is updated to the new section of the second beam. Elements adjust to each other.
Description of the Absolute tab:
UX - Beginning , UX - End, UY - Beginning, UY - End, UZ - Beginning, and UZ - End.
The Relative tab has 2 parts: Cross-section and Member length.
Automatically defines an offset for structure bars. The offset is defined by a shift of a bar axis to extreme section dimensions (only). An automatic offset is defined in thedialog that opens after clicking Section position.
You can find information about the section shift with respect to the axis (vz,vpz,vy,vpy,0) under the Section position button.
Automatically defines an offset for structure bars. The offset is defined by selecting an object to which the offset additionally refers. This object can be both a bar and a panel defined in a structure. This offset type is defined in thedialog that opens after clicking Axis offset.
For this offset type, you must give the number of a reference object. The object (bar or panel) number can be entered in the field or the object can be selected in the drawing area.
You can find information about the reference object (section) and the shift value: vy, vpy, vz, vpz, 0 under the Axis offset button.
Member length has 2 selection lists. The first list refers to the beginning of the member; whereas, the other list refers to the member end. The list comprises the following positions: in the axis, reduce length, and increase length.
Operation of the relative offset:
The relative offset (length increase/reduction) is calculated automatically. Its value is the greatest cross dimension of all the elements adjoining to a given node. When an element is set at an angle, the projection of dimensions on the X axis of the adjoining element is considered and the element length is reduced or increased to fit the dimension resulting from the projection.
Similarly to shifting the section with respect to an axis, you specify the point on the reference object, with which to associate the axis of the element that is assigned an offset. This offset is intended for typical cases, such as, purlins supported by a spandrel beam.