Bridge Alignment Dialog Box

The Bridge Alignment dialog box allows you to define a bridge's alignment by creating, modifying, or deleting alignment tangents and/or curve segments. To open this dialog box, click the Alignment button on the Geometry tab.

CIP RC/PT Girder allows the user to input bridge geometry directly from the plans. The program uses the actual layout geometrics to assist the user in defining the analysis model. The designer must determine appropriate span lengths for the analysis. When bridges are on roadway curves and/or include skewed supports, the distance between supports can vary, thus making the analysis model difficult to define. CIP RC/PT Girder assists the designer by computing the distance between supports along the centerline of the bridge and, if desired, along the centerline of each girder. By default,CIP RC/PT Girder creates a straight alignment along a N 90 E bearing. When a segment is created, deleted, or modified, all ahead-station segments in the bridge layout line automatically adjust themselves, thus maintaining individual segment lengths and angles relative to their back-station neighbor.

Adding Tangents

This function adds a straight segment to the bridge alignment after the selected segment. The new segment is tangent to and equal in length to the preceding alignment segment.

Perform the following steps to add a straight segment after the selected segment:

In the grid, select the segment you want to add a tangent to by clicking anywhere in its row. A blue arrow displays on the left side of the grid to mark the selection.
Click the Add Tangent button.
Enter the tangent values in the grid. A definition for each parameter is available below.

Adding Curves

This function adds a curved segment to the bridge alignment after the selected segment. The new segment is tangent and equal in length to the preceding alignment segment. When creating a curve, note that spirals can only be used to connect tangent segments with a circular arc and vice-versa, i.e., one end of the spiral has an infinite radius (tangent) and the other uses the radius of the circular arc.

Note: CIP RC/PT Girder does not support spirals between compound curves but spirals between reversing curves, which pass through a point of infinite radius, can be modeled.

Perform the following steps to add a curve to the bridge alignment:

In the grid, select the segment you want to add a curve to by clicking anywhere in its row. A blue arrow displays on the left side of the grid to mark the selection.
Click the Add Curve button.
Enter the curve values in the grid. A definition for each parameter is available below.

Deleting Segments

This function deletes a segment from the bridge layout line and adjusts the starting direction of the following segment to create the effect of having progressively shortened the length of the deleted segment to zero.

Note: You will not be asked to confirm this delete command nor can this deletion be undone.

Perform the following steps to delete a segment from the bridge alignment:

In the grid, select the segment you want to delete by clicking anywhere in its row. A blue arrow displays on the left side of the grid to mark the selection.
Click the Delete Segment button to remove the selected segment.

Creating Alignment Ties

CIP RC/PT Girder can export/save plan view data to CAD formats. Users can choose to tie exported/saved data to the state plane coordinates by identifying a location along the alignment and specifying an appropriate coordinate value by clicking the Alignment Tie button to open the Alignment Tie dialog box.

Grid Definitions

Setting	Description
Beginning Station	Define the beginning station of the bridge alignment.
Offset to Bridge CL	Define the lateral offset from the alignment to the centerline of the bridge.
Segment	This noneditable field displays the segment number of the alignment.
Shape	This noneditable field lists whether the segment is a tangent or a curve.
Start Direction	Enter the starting direction of the segment. By default, the starting direction is equal to the direction of the end of the preceding segment
End Station	Enter the ending direction of the segment.
Radius	Enter the radius for a curve segment.
Spiral-In	Enter the spiral-in for a curve segment. Note: Spirals can only be used to connect tangent segments with a circular arc and vice-versa.
Spiral-Out	Enter the spiral-out length for a curve segment. Note: Spirals can only be used to connect tangent segments with a circular arc and vice-versa.
Sense	Select the curve sense (left or right) from the drop-down list.

Technical Discussion

The user can make use of CIP RC/PT Girder 's alignment to describe structures on complex layouts including offsets from the alignment to the centerline of the bridge. The user can then enter geometric data exactly as defined on the construction drawings and allow CIP RC/PT Girder to determine exact member distances and connection locations. By default, the alignment is defined as a tangent bearing N 90 E. The primary use of the alignment is to describe structures on curves or having skewed substructures, which will be analyzed using the Optional Girder Analysis option.