Cross-frame K Bot [SIG]

Location

Girders: Choose the two girders that are connected by the cross frame.

Skew Angle: A positive skew value rotates the cross frame in a clockwise direction, while a negative skew value rotates it in a counterclockwise direction. It is important to remember that the cross frames are positioned at the specified station along a line perpendicular to the PGL, which is then rotated according to the entered skew value.

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Station [Start/End]: Enter the station along the PGL. When dealing with curved girder bridges, collecting distance along the girder length can lead to different inputs for the right and left girder that are connected by cross frames, causing ambiguity. Therefore, collecting the station along the PGL is a more reliable solution to avoid such issues. Furthermore, since cross frames are typically continuous in the transverse direction, entering the same station for all cross frames ensures that their locations are consistent between each girder.

The same principle can be applied for skewed cross frames. If the user enters the same station and skew values for the cross frames between Girder 1-2, Girder 2-3, and Girder 3-4, it ensures continuity between the cross frames. It should also be noted that the cross frames are positioned along a line perpendicular to the PGL, which is rotated according to the entered skew value.

Inaccurate finite element models and disconnected nodes/elements in the cross frame can occur if the entered station values are not >= the girder start station or <= the girder end station. This can cause stability issues in the finite element model. To ensure correct station input, users should select the start/end options from the station input. This approach is especially recommended for cross frames located at the beginning or end of girders.

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Sections

Assign a section for the top, bottom, or diagonal chord, which can be imported from the AISC database by users. The section data will be utilized for the 3D model of the object and will directly influence the Finite Element Analysis (FEA) and Finite Element Model (FEM).

Top Chord Section: Assign a section for the top chord.

Bottom Chord Section: Assign a section for the bottom chord.

Diagonal Chord Section: Define a section for the diagonal chord.

Top Chord Orientation Angle: Specify an angle for the top chord to rotate around its longitudinal axis.

Bottom Chord Orientation Angle: Specify an angle for the bottom chord to rotate around its longitudinal axis.

Diagonal Chord Orientation Angle: Specify an angle for the diagonal chords to rotate around its longitudinal axis.

Gusset Plate

The parameters listed below are used for 3D representation. While gusset plates do not have finite element model (FEM) and do not provide additional stiffness to the elements, they can still be applied as weight loads and used for code checks, depending on user-defined settings and specifications. For visual representation of each parameter, refer to the figure below.

Top Gusset Plate: Gusset plates that exist under Superstructure > Connections can be assigned to the related column.

Bottom Gusset Plate: Gusset plates that exist under Superstructure > Connections can be assigned to the related column.

Center Gusset Plate: Gusset plates that exist under Superstructure > Connections can be assigned to the related column.

Top Plate - Vertical Offset from Top of Web: The location of the top gusset plate with respect to the top of the web along the vertical direction can be defined by this parameter. For visual representation, refer to the figure provided below.

Top Plate - Horizontal Offset from Edge of Web: The location of the top gusset plate with respect to the edge of the web along the horizontal direction can be defined by this parameter. For visual representation, refer to the figure provided below.

Bottom Plate - Vertical Offset from Bottom of Web: The location of the bottom gusset plate with respect to the bottom of the web along the vertical direction can be defined by this parameter. For visual representation, refer to the figure provided below.

Bottom Plate - Horizontal Offset from Edge of Web: The location of the bottom gusset plate with respect to the edge of the web along the horizontal direction can be defined by this parameter. For visual representation, refer to the figure provided below.

Center Plate - Vertical Offset from Bottom of Web: The location of the center gusset plate with respect to the bottom of the web along the vertical direction can be specified by this parameter. For visual representation, refer to the figure below.

Center Plate - Horizontal Offset from Center of Bay: The center distance between two girders, or in other words, the bay, can be used to specify the horizontal location of the center gusset plate, where a positive value offsets the center gusset plate to the right, and negative values offset the gusset plate to the left when looking upstation along the PGL.

Stiffener

The parameters listed below are used for 3D representation. While cross-frame stiffeners do not have finite element models (FEM) and do not provide additional stiffness to the elements, they can still be applied as weight loads, depending on user-defined settings and specifications.

Stiffener Used [YES/NO]: If this parameter is set to 'YES,' the user can define additional parameters for stiffeners. If it is set to 'NO,' the other parameters will be marked as not applicable (N/A).

Vertical Stiffener Thickness: For visual representation of vertical stiffener thickness, refer to the figure below.

Vertical Stiffener Width: For visual representation of vertical stiffener width, refer to the figure below.

Material: The material definition for the stiffener can be made using this parameter. Materials can either be imported or assigned from previously defined ones.

Geometry

These parameters are used for both computing the member end offset of cross frame truss elements in finite element analysis and 3D representation. For visual representation of each parameter, please refer to the figures below.

Top Chord - Vertical Distance of WP from Top of Web: This parameter can be used to specify the vertical distance of the Top Chord’s working point from the top of the web. The definition for this parameter affects both the 3D model and FEM of the crossframe.

Top Chord - Horizontal Distance of WP from Center of Web: This parameter can be used to specify the horizontal distance of the Top Chord’s working point from the center of the web. The definition for this parameter affects both the 3D model and FEM.

Top Chord - Inner Offset from WP: This parameter can be used to specify the inner offset of the Top Chord’s working point. The definition for this parameter affects both the 3D model and FEM.

Diagonal Chord - Vertical Offset from WP of Top Chord: This parameter can be used to specify the vertical offset of the Diagonal Chord's working point from the working point of the Top Chord. The definition of this parameter only affects the 3D model of the diagonal chords.

Diagonal Chord - Horizontal Offset from WP of Top Chord: This parameter can be used to specify the horizontal offset of the Diagonal Chord's working point from the working point of the Top Chord. The definition of this parameter affects both the 3D model and FEM.

Diagonal Chord - Vertical Offset from WP of Bottom Chord: This parameter can be used to specify the vertical offset of the Diagonal Chord's working point from the working point of the Bottom Chord. The definition for this parameter affects only the 3D model of the diagonal chords.

Diagonal Chord - TopSide Inner Offset from WP: This parameter can be used to specify the inner offset of the Diagonal Chord's working point on the top side. This parameter's definition affects both the 3D model and FEM.

Diagonal Chord - BottomSide Inner Offset from WP: This parameter can be used to specify the inner offset of the Diagonal Chord's working point on the bottom side. This parameter's definition affects both the 3D model and FEM.

Bottom Chord - Vertical Distance of WP from Bottom of Web: This parameter can be used to specify the vertical distance of the Bottom Chord’s working point from the bottom of the web. This parameter's definition affects both the 3D model and FEM.

Bottom Chord - Horizontal Distance of WP from Center of Web: This parameter can be used to specify the horizontal distance of the Bottom Chord’s working point from the center of the web. This parameter's definition affects both the 3D model and FEM.

Bottom Chord - Inner Offset from WP: This parameter can be used to specify the inner offset of the Bottom Chord’s working point. This parameter's definition affects both the 3D model and FEM.

FEA

For detailed explanations on axial rigidity coefficients, refer to the AASHTO excerpts below.

Top Chord Axial Rigidity Coefficient: This parameter specifies the axial rigidity coefficient of the top chord.

Bottom Chord Axial Rigidity Coefficient: This parameter specifies the axial rigidity coefficient of the bottom chord.

Diagonal Chord Axial Rigidity Coefficient: This parameter specifies the axial rigidity coefficient of the diagonal chord.