End Cross-Frame [SIG]
- Umut Nuhat Sevinc
- Omer Faruk Ozkan
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.
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.
Chord Flipping Side [Back Station/Ahead Station]: The Chord Flipping Side can be specified using this parameter.
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.
Second Top Node: An additional node is added to the top chord, dividing it into three parts.
Vertical Strut: A vertical strut is added between the top chord and the bottom chord.
Vertical Strut Section: Assign a section for the vertical strut.
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.
Vertical Strut Orientation Angle: Specify an angle for the vertical strut to rotate around its longitudinal axis.
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 specifies the vertical distance between the working point (WP) of the Top Chord and the top of the web. The definition for this parameter affects both 3D and FEM of the crossframe.
Top Chord - Horizontal Distance of WP Center of Web: This parameter specifies the horizontal distance between the working point (WP) of the Top Chord and the center of the web. The definition for this parameter affects both 3D and FEM of the crossframe.
Top Chord - Inner Offset from WP: This parameter specifies the inner offset distance of the Top Chord’s working point. The definition for this parameter affects both 3D and FEM of the crossframe.
Diagonal Chord - Top Vertical Offset from WP of Top Chord: This parameter specifies the vertical offset between the working point (WP) of the Diagonal Chord and the working point of the Top Chord. This parameter's definition only affects 3D models of diagonal chords.
Diagonal Chord - Top Inner Offset from WP: This parameter specifies the inner offset of the Diagonal Chord’s working point along the top side. The definition for this parameter affects both 3D models and FEM.
Diagonal Chord - Bottom Vertical Offset from WP of Bottom Chord: This parameter specifies the vertical offset between the working point (WP) of the Diagonal Chord and the working point of the Bottom Chord. This parameter's definition only affects 3D models of diagonal chords.
Diagonal Chord - Bottom Horizontal Offset from WP of Bottom Chord: This parameter specifies the horizontal offset between the working point (WP) of the Diagonal Chord and the working point of the Bottom Chord. The definition for this parameter affects both 3D models and FEM.
Diagonal Chord - Bottom Inner Offset from WP: This parameter specifies the inner offset of the Diagonal Chord’s working point along the bottom side. The definition for this parameter affects both 3D models and FEM.
Bottom Chord - Vertical Distance of WP from Bottom of Web: This parameter specifies the vertical distance between the working point (WP) of the Bottom Chord and the bottom of the web. The definition for this parameter affects both 3D models and FEM.
Bottom Chord - Horizontal Distance of WP from Center of Web: This parameter specifies the horizontal distance between the working point (WP) of the Bottom Chord and the center of the web. The definition for this parameter affects both 3D models and FEM.
Bottom Chord - Inner Offset from WP: This parameter specifies the inner offset distance of the Bottom Chord’s working point, measured along the inner edge. The definition for this parameter affects both 3D models and FEM.
Top Node Horizontal Offset: This parameter applies a horizontal offset to the nodes of the top chord.
Strut Top Vertical Offset from CL of Top Chord: This parameter specifies the vertical distance between the top chord and the top side of the vertical strut.
Strut Bottom Vertical Offset from CL of Bottom Chord: This parameter specifies the vertical distance between the bottom chord and the bottom side of the vertical strut.
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.
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-Top Gusset Plate: Gusset plates that exist under Superstructure > Connections can be assigned to the related column.
Center-Bottom Gusset Plate: Gusset plates that exist under Superstructure > Connections can be assigned to the related column.
Strut Top 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 Top Plate - Vertical Offset from Top of Web: The location of the center gusset plate with respect to the top of the web along the vertical direction can be specified by this parameter. For visual representation, refer to the figure below.
Center Top 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.
Center Bottom Plate - Vertical Offset from Top of Web: The location of the center gusset plate with respect to the top of the web along the vertical direction can be specified by this parameter. For visual representation, refer to the figure below.
Center Bottom 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.
Show Gusset Plate[YES/NO]: The Gusset Plate object can be activated using this parameter.
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.
Distance from Top: This parameter allows adjustment of the distance to the top of the web.
Distance from Bottom: This parameter allows adjustment of the distance to the bottom of the web.
Vertical Clip Height: For a visual representation of the vertical clip height, refer to the figure below.
Horizontal Clip Width: For a visual representation of the horizontal clip 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.
Show Stiffener [YES/NO]: The Stiffener object can be activated using this parameter.
Generate FEM [YES/NO]: Setting the "Generate FEM" parameter to "No" can disable the analytical representation of the cross frame.
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.
