Tub Girder [STG]
Girder Parameters
Girder Layout: Select a layout previously defined during the stages of Bridge Geometry -> Girder Layouts for this column.
For visual representation of the parameters used to define the tub girder's geometry, refer to the image below.
Top Flange Width: Users can specify the width of the top flanges using this parameter.
Top Flange Thickness: Users can specify the thickness of the top flanges using this parameter.
Web Depth Projected to CL of Box: The vertical measurement of web depth is obtained by projecting the depth to the tub girder's centerline, which can be defined by this parameter.
Web Thickness: This parameter can be used to specify the web thickness.
Bottom Flange Width: The width of the bottom flange can be specified using this parameter.
Bottom Flange Thickness: The thickness of the bottom flange can be specified by this parameter.
Spacing between Top Flanges: The spacing of top flanges—measured from the centerline of each—can be specified by this parameter.
Distance between Bottom Flange Edge and Web Centerline: The distance between the outer edge of the bottom flange and the centerline of the web can be specified using this parameter.
Users have the option to specify changes in the plate girder section dimensions either along the PGL or along the length of the girder. To access the editor, click on the three dots and choose "Edit (Spreadsheet)." If the user enters the length along the girder, the end station will be calculated automatically. Conversely, if the user enters the end station, the length data will be calculated automatically.
Girder webs can have nonprismatic variations, which are supported. To access the variation features, the user can click on the three dots and select "Variation" to open the pop-up window. From there, the user can define variations using linear, parabolic, circular, polynomial, or custom functions. The finite element mesh takes into account the locations of section changes and various other mesh quality parameters such as aspect ratio, mesh element size, orthogonality, and skewness.
Haunch Thickness: The haunch thickness is defined as the measurement between the bottom of the deck and the bottom of the top flange. Like plate girder dimensions, nonprismatic variations and various haunch values can be added by selecting "Edit (Spreadsheet)" from the three dots menu. Additionally, nonprismatic variations can be entered using the "Variation" pop-up window.
Additional Haunch Width: The additional haunch width is measured from both the right and left extensions of the top flange. During deck construction, the automatic haunch load computation is impacted by both the haunch thickness and additional haunch width.
Hybrid girders are supported, allowing the assignment of different materials to the top flange, bottom flange, and web. Furthermore, it is possible to use varying steel materials between different stations through station-dependent material definitions.
Top Flange Material: The material definition for the top flange 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 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 can be made using this parameter. Materials can either be imported or assigned from previously defined ones.
Web Slope (readonly): This column displays the calculated slope of the web, derived from the input parameters provided by the user.
FEA Settings
Supports: This input is used when multiple bearings need to be placed at a specific location on a girder.
When this input is not used, all bearings are automatically generated at the center of the bottom plate of a tub girder when a fixity value is set on the insertion points of the Girder Layout.
When a cross slope is present, the Girder Layout does not pass through the center of the bottom flange. However, if the FEA Settings → Support input is not used, OpenBrIM automatically generates bearings at the center of the bottom flange, provided that a bearing fixity is set on the insertion points in the Girder Layout. 
To have more than one bearing for a Tub Girder: As shown in the screenshot, the bearing is generated at the center of the bottom plate of the tub girder, not at the location of insertion point. If two or more bearings are needed for the bottom plate of the tub girder at a specific station, the steps should be as follows. The bearings will be generated at the exact location of the insertion points as defined:
Define new insertion points at Bridge Geometry -> Insertion Points.
Define those insertion points as bearings at Superstructure -> FEA Bearings.
The third and final step is assigning the required bearings to girders. This must be done in Superstructure -> Steel Girders -> Tub Girder FEA Settings Tab by using the Supports column and selecting the 'Pick...' option. This step overrides the data related to the bearing generation parameters, resulting in the proper formation of bearings ,as shown in the screenshots below.
Mesh Size (Longitudinal): The maximum distance between nodes in the longitudinal direction is specified using the longitudinal mesh size. In most cases, a smaller mesh size can be generated based on the bracing locations, deck pouring or deconstruction definitions, or section change locations.
# of Result Extraction St.: The result extraction station settings are solely for viewing FEA composite results in either the spreadsheet or FEA view, and do not impact standard finite element analysis results like member end forces, node displacement, and node reactions. For girder code checks, exact code check stations will be utilized for FEA composite results.
Rigid Section: This parameter's definition is only used when there are two or more bearings at the same station. Rigid beams are employed to link the bottom nodes of tub girders with bearing locations/supports as seen in the screenshot below. Please refer to the following documentation to understand how to define rigid sections.
Additional Result Extraction St.: The results of FEComposite elements are generated for stations by default. If additional results are needed at a specific station, this parameter can be used. The FEA will not be affected; only the “Composite Element Forces” and “Composite Element Stresses” are calculated based on the “Additional Result Extraction Station” inputs.
Quantities
The quantities obtained from parameter definitions are presented to the user as read-only values under this tab.
Min Section Area: For varying sections in the row defined, the minimum cross-section area will be displayed under this column.
Max Section Area: For varying sections in the row defined, the maximum cross-section area will be displayed under this column.
Total Surface Area: The combined surface area of all elements is summed up and presented under this column. Each side of the element’s surfaces is accounted for in the calculations.
Min Cross-Section Perimeter: For varying cross-sections, the minimum perimeter obtained from the smallest cross-section is presented under this column.
Max Cross-Section Perimeter: For varying cross-sections, the maximum perimeter obtained from the largest cross-section is presented under this column.
Volume: The total volume of the entire girder is presented under this column.
Min Length Path: The shortest vertical length of the girder is presented under this column.
Length @ COG Path: The length of the girder along its center of gravity (COG) axis is presented under this column.
Max Length Path: The longest vertical length of the girder is presented under this column.
Weight: The weight of the girder is calculated based on its properties and assigned materials.
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