# Custom Diaphragm \[SPIG]

### Bracing

**Girders:** Choose the two girders that are connected by the bracing member.

**Skew Angle:** A positive skew value rotates the bracing in a clockwise direction, while a negative skew value rotates it in a counterclockwise direction. The bracing is positioned at the specified station along a line perpendicular to the PGL, which is then rotated according to the entered skew value.

![](https://openbrim.atlassian.net/wiki/download/attachments/2122776694/image-20230307-082442.png?api=v2)

**Station \[Start/End]:** Enter the station along the PGL, or select the **Start** / **End** option. Using the PGL station keeps the bracing continuous transversely across the bridge and avoids ambiguity from different along-girder distances on curved bridges. Use the Start/End options for bracings located at the beginning or end of the girder span to prevent disconnected nodes in the FEM.

**Section:** Assign a section for the bracing member, imported from the AISC database or defined as a custom section.

**Horizontal Offset from Edge of Web:** Horizontal offset of the bracing member in the transverse direction, measured from the edge of the girder web.

**Vertical Offset from Top of Web:** Vertical offset of the bracing member from the top of the girder web.

**Type \[Truss/Beam]:** Selects the finite-element representation of the bracing member. Truss provides only axial stiffness; Beam adds flexural and torsional stiffness.

**Orientation Angle \[0/90/180/270]:** Specify a rotation angle around the longitudinal axis of the bracing.

**Chord Flipping Side \[Back Station/Ahead Station]:** Controls which side of the perpendicular line the bracing and gusset plates are oriented. Flip this value when the default layout places the members opposite to the detailing drawings.

**Top Chord Section:** Section assigned to the bracing (Read-only; mirrors **Section** above).

**Top Chord Material:** Material assigned to the bracing, derived from the assigned section (Read-only).

**Bottom Chord Section:** Present for consistency with cross-frame objects; not used by Custom Bracing (Read-only).

**Bottom Chord Material:** Present for consistency with cross-frame objects; not used by Custom Bracing (Read-only).

**Diagonal Chord Section:** Present for consistency with cross-frame objects; not used by Custom Bracing (Read-only).

**Diagonal Chord Material:** Present for consistency with cross-frame objects; not used by Custom Bracing (Read-only).

### Gusset Plate

**Top Gusset Plate:** Assign a Gusset Plate defined under Superstructure > Connections.

**Top Plate - Vert. Offset from Top of Web:** Vertical offset of the top gusset plate from the top of the girder web.

**Top Plate - Horz. Offset from Edge of Web:** Horizontal offset of the top gusset plate from the edge of the girder web.

**Show Gusset Plate \[YES/NO]:** Controls whether the gusset plate is rendered in the 3D view.

### Stiffener

The parameters below are used for 3D representation. Stiffeners do not contribute stiffness to the FEM by default but can be included as weight loads.

**Stiffener Used \[YES/NO]:** When YES, the stiffener sub-parameters become editable; when NO, they are not applicable.

**Vertical Stiffener Thickness:** Thickness of the stiffener plate.

**Vertical Stiffener Width:** Width of the stiffener plate.

**Distance from Top of Web:** Clear distance between the top of the stiffener and the top of the girder web.

**Distance from Bottom of Web:** Clear distance between the bottom of the stiffener and the bottom of the girder web.

**Vertical Clip Height:** Vertical dimension of the corner clip trimmed from the stiffener.

**Horizontal Clip Width:** Horizontal dimension of the corner clip trimmed from the stiffener.

**Material:** Material assigned to the stiffener plate. Import or pick a previously defined material.

**Show Stiffener \[YES/NO]:** Controls whether the stiffener is rendered in the 3D view.

**Generate FEM \[YES/NO]:** When NO, the bracing's analytical member is not generated. Use this to visualize the geometry without contributing stiffness to the analysis.

### FEA

**Axial Rigidity Coefficient:** Multiplier applied to the axial rigidity (EA) of the bracing member in the FEM. Default 1.0.

### 3D Detailing

**Align Ends Parallel to Web \[YES/NO]:** When YES, the ends of the bracing member are rotated so that they align parallel to each girder's web. Useful for skewed bracing arrangements.


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