Diaphragm [STG]

Location

Girders: Choose the two girders that are connected by the diaphragm.

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.

Section

The data related to this section is used for both the 3D model and the Finite Element Model (FEM) of the object. For visual representation of each parameter, refer to the figure below.

Top Flange Width: The top flange’s width can be specified using this parameter along the longitudinal direction.

Top Flange Thickness: The thickness of the top flange along the Z-axis can be defined by this parameter.

Web Depth: The web depth along the Z-axis can be defined using this parameter.

Web Thickness: Web thickness along the longitudinal direction can be specified by defining this parameter.

Bottom Flange Width: Bottom flange's width in the longitudinal direction can be specified using this parameter.

Bottom Flange Thickness: Bottom flange's thickness along the Z-axis can be defined by this parameter.

Top Flange Material: The material definition for the top flange of the diaphragm can be made using this parameter. Materials can either be imported or assigned from previously defined ones.

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

Bottom Flange Material: The material definition for the bottom flange of the diaphragm can be made using this parameter. Materials can either be imported or assigned from previously defined ones.

3D Details

Top Offset from Top of Web: The top offset of the diaphragm from the top of the girder's web.

Gap between Diaphragm and Stiffener: For visual representation, refer to the figure below.

FEA Setting

FE Model[Two Beam+Shell/Single Beam]:If the 'Two Beam + Shell' option is selected, the top and bottom flanges will be modeled as beam elements, while the remaining portion will be modeled as a shell element. In the absence of this option, a complete section will be defined as a single beam and connected to both bottom and top flange nodes using rigid elements, based on the user's selected preferences.

If you choose two beam and shell elements, the rigid definitions below become not applicable (N/A).

Rigid Section Top: A diaphragm can be linked to the top flange node using a rigid beam element. Please designate a section for this purpose.

Disable Bottom Rigid Line [NO/YES]: Choose "Yes" if you prefer not to generate a rigid beam element between the diaphragm and the bottom flange node.

Rigid Section Bot: A diaphragm can be linked to the bottom flange node using a rigid beam element. Please designate a section for this purpose.

Girder Connection Type [Fixed/Pin]: The girder connection type can be defined as either Fixed or Free for diaphragms when the FE model is set to Two Beam + Shell. Based on this definition, the four nodes can have their rotational degrees of freedom (Rx, Ry, Rz) set to either Fixed or Free.

Axial Rigidity Coefficient: This parameter can be used to specify the axial rigidity coefficient of the diaphragm. For further details, refer to AASHTO Chapter 4.6.3.3.4

Stiffeners

The parameters listed below are used for 3D representation. While 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.

Stiffeners Thickness: For visual representation, refer to the figure below.

Stiffeners Width: For visual representation, refer to the figure below.

Gusset Plate

Gusset Width: The width of the gusset plates can be specified using this parameter. For visual representation, refer to the figure below.

Gusset Height: The height of the plates can be specified using this parameter. For visual representation, refer to the figure below.

Number of Bolt Columns at Gusset: For visual representation, refer to the figure below.

Number of Bolt Rows at Gusset: For visual representation, refer to the figure below.

Bolt Horizontal Spacing at Gusset: For visual representation, refer to the figure below.

Bolt Vertical Spacing at Gusset: For visual representation, refer to the figure below.

Gusset Plate Thickness: The thickness of the gusset plates along the longitudinal direction can be defined by this parameter.

Bolt Property: Assign a previously defined bolt property

Bolt to Gusset Plate Edge Distance: The distance between the edges of the plates and the bolts.

Show Bolts (Detailing) [NO/YES]: If this parameter is set to 'NO,' the bolts will not be displayed. Otherwise, the bolts will be shown within the model.However, enabling this option increases the triangulation number, leading to slower performance. To reduce compile time, disabling the detailing option can be helpful.