Create Girders

This command lets you create alignments that define the girders. The exterior girders may be computed first according to the placement method, placement criteria, and the minimum and maximum overhang values. The interior girders then may be computed according to the placement method, placement criteria, and the minimum and maximum spacing values.

All girders must be sensed in the same direction. The start of the girder is at the back abutment/pier and the end of the girder is at the ahead abutment/pier.

All computed bridge components (for example, slab fascia, abutments, pier lines, girders, pedestals, and footings) must fall within the extents of the controlling horizontal alignment and within the extents of the surface model that represents the existing ground.

Before Using This Command

Dialog Box Options

Method

specifies how the software creates the girders. The following methods are available:

Seed Name

specifies the name that the software assigns to the alignment. The software automatically increments the numeric portion of the name each time an alignment of this style is created. It is recommended that you use the default seed name.

Description

lets you key in a brief description of the alignments. This is an optional field.

This field will be used by the Create Vertical command to retain type of girder. The user should not use this field.

Style

specifies the style of the alignment. It is recommended that you use the girder style. However, you may also use the beam style.

Placement Criteria

Span Type

specifies whether or not girders are divided into individual units abutments/piers. A simple-span bridge is divided into individual units between each abutment and pier. A continuous-span bridge has one undivided unit between the first and last selected abutments/piers.

Method

defines how the software places the girders. There are three methods available: Chord, Mid-Tangent, or Curved. Each placement criteria method may be affected by the controlling overhang, which is specified in the Use Overhang field.

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To create curved girders using the Number of Girders, Maximum Spacing, or Distances to Exterior Girders methods, the selected longitudinal lines must be parallel with the active horizontal alignment.

Use Overhang

specifies whether the software uses the minimum overhang line or the maximum overhang line as the control for placement of the exterior girders.

Number of Girders

when Number of Girders is the selected method, specifies how many girders to place.

Spacing

when Maximum Spacing is the selected method, specifies the maximum amount of spacing allowed between girders. The distance between the selected longitudinal lines is divided by this number and the result is rounded up to determine how many girders are placed, taking into consideration the minimum and maximum spacing and overhang specifications.

You can key in the distance, or you can click the Input button to define the distance with your cursor.

Overhang

when Overhang Chord is the selected method, specifies the distance between the girder and the selected longitudinal line. You can key in the distance, or you can click the Input button to define the distance with your cursor.

Offset

when Random Longitudinal Line is the selected method and Curved is the selected Placement Criteria method, specifies the distance between the selected longitudinal line and the girder. A negative number places the girder left of the longitudinal line and a positive number places the girder right of the longitudinal line.

You can key in the offset, or you can click the Input button to define the offset with your cursor.

Fixed Spacing

when turned on, forces the girders to be parallel to the girder created from the first selected longitudinal line.

Placement Checking

Minimum Spacing

specifies the minimum distance between girders. You can key in the distance, or you can click the Input button to define the distance with your cursor.

Maximum Spacing

specifies the maximum distance between girders. You can key in the distance, or you can click the Input button to define the distance with your cursor.

Minimum Overhang

specifies the minimum distance between the selected longitudinal lines and the exterior girders. You can key in the overhang, or you can click the Input button to define the overhang with your cursor.

Maximum Overhang

specifies the maximum distance between the selected longitudinal lines and the exterior girders. You can key in the overhang, or you can click the Input button to define the overhang with your cursor.

Measure Offsets

Along Abutment

The offsets are measured along the transverse (that is, abutment/pier lines).

Along Bearing Line

The offsets are measured along the bearing line.

Perpendicular to Longitudinal Axis

The offsets are measured radial to the longitudinal lines (that is, typically slab fascia lines).

Left Back

specifies the left back distance (offset) that is applied to the back transverse line and the left longitudinal line. You can key in the distance, or you can click the Input button to define the distance with your cursor.

Right Back

specifies the right back distance (offset) that is applied to the back transverse line and the right longitudinal line. You can key in the distance, or you can click the Input button to define the distance with your cursor.

Left Ahead

specifies the left ahead distance (offset) that is applied to the ahead transverse line and the left longitudinal line. You can key in the distance, or you can click the Input button to define the distance with your cursor.

Right Ahead

specifies the right back distance (offset) that is applied to the ahead transverse line and the right longitudinal line. You can key in the distance, or you can click the Input button to define the distance with your cursor.

This applies to the previous four fields.

When you select two different longitudinal lines, the software automatically determines the sign of the offsets, so keying in a negative or positive value is immaterial. However, when the longitudinal lines are the same (that is, selecting the centerline of the roadway) the software honors the signs that you define.

Apply

executes the command using the information defined in the dialog box. The dialog box remains active after you click Apply.

Close

dismisses the dialog box and exits the command.

Help

displays help.