# Creation of Geometric Axes and Geometric Parameters#

## Organization of the dialog#

The dialog for creation of axis elements is divided into two main areas, a graphical view and a table view.

The graphical view is to check the system. The table view has many possibilities to be edited in a comfortable way.

In the header of the table view one can find some basic buttons. Another possibility is to insert a whole table with copy and paste. In this case the number of lines in the table is completed as needed.

## General#

The User can generate bridge axes using the following available context menu options:

• New Axis: Alignment elements in plan and elevation are defined graphically using the corresponding tasks. Geometric parameters can be defined for this axis.

• Axis from 3D AutoCAD curves: The axis geometry is created directly from the selected AutoCAD geometry. Geometric parameters can be defined for the axis.

• Import axis from the SOFiSTiK database: Axis and geometric parameters are imported from an existing database, and can then be further processed. Linked structural elements will lose the access.

Definition of the Horizontal Alignment

Using the Geometric Axis Horizontal Alignment task, the alignment elements of an axis can be defined in plan.

An axis is always based on a starting point (coordinates x,y) and a tangential direction. The user can define the lengths and curvatures of each section, from which the values of the tangents are then calculated. For the radii values, positive values indicate a curve to the right and negative values indicate a curve to the left.

The following alignment elements are available:

• Straight lines

• Circular arcs

• Transition curves

Depending on the characteristics of the curvature progression over the curve’s length ‘s’, there are different sub-types of transition curves/curve sequences:

• Clothoide: The curvature varies linearly along ‘s’

• Bloss Curve Transition: The curvature proceeds with a cubic function

• Sinusoidal form: The curvature proceeds with a sinusoidal form

• Cosinusoidal form: The curvature proceeds with a cosinusoidal form

• Biquadratic form: The curvature proceeds with a biquadratic spiral as transition curve type

Definition of the Vertical Alignment

The height development is independent of the alignment in plan, and is given with the input of z-coordinates of the tangential intersection points and the radii of curvature along the axis at the preset station positions. The curves follow a quadratic parabolic curve.

The level is always interpreted as a height above z = 0.0. For the height, positive values correspond with the negative self-weight direction.

Placements define the geometry of important intersections or points for the alignment. For each of these placements a local working plane (see Cross Members Editor) can be automatically created for the structural elements (substructures, etc.). The working planes are aligned perpendicular to the axis and additional rotations can be specified.

The following types of placement are available for selection:

• Support axis

• Construction point (joint)

• Excess at the beginning

• Excess at the end

• Connection point (cable)

Placements are, in principle, defined on the main axis by specifying angles, which are then transferred to the secondary axis. The global rotation rotates clockwise from the y-axis around the selfweight direction. The local rotations refere to the local coordinate system of the main axis.

New placements are defined via the little buttons in the header. They can be defined with a offset to the neighbored placement or `Automatic` in the middle between the placements.

It is also possible to define placements with reference to other placements. In that case, the ID of an already existing placement is entered as a reference placement in column `Ref. ID`. In column `Ref. Offset` a fixed distance is given to the reference placement. If the station of the reference placement changes, the dependent placement also moves.

Note

Placements refered on an axis out of the task take the station out of the projected length. Placements refered on an drawn axis take the station out of the real length.

Definition of Axis Based Variables

Variable progression for any alignment elements can be defined along a geometric axis. These variables can be used, for example, to control the cross section variation along the axis.

Depending on the type of supports, linear, quadratic or cubic Splines can be created (i.e. in the progression column, a selection of pre-defined progression types for the support positions are available to choose from). Stepped variations are also possible.

For a better orientation, the existing placements are displayed as vertical bars in the graphics area. In the upper-right corner of the graphics area there is a menu to control the visibility of placement types.

New stations for the variables are defined via the little buttons in the header. They can be defined with a offset to the neighbored station or `Automatic` in the middle between two existing stations.

It is also possible to define variables with reference to existing placements. In that case, the ID of the placement is entered in column `Placement`. If the station of the placement changes, the dependent variable also moves.

Secondary axis can be defined via the contextmenu. The following options are available:

• Create with Offset: A secondary axis dependent on the main axis is created. The values are given and modified with the help of the `Offset Parameters` dialog.

• Y and Z Offset: A secondary axis parallel to the main axis is created. The values Y and Z define a fixed offset.

• Y and Z Offset from Variable: A secondary axis with variable distance to the main axis is created. The values Y and Z are taken from a variable assigned to the main axis.

• Create from 3D AutoCAD curves: The secondary axis geometry is created directly from the selected AutoCAD geometry. The startpoint and endpoint of the secondary axis is customized to the length of the axis.

Note

The AutoCAD geometry used for a drawn secondary axis should be longer as the axis itself.