# Custom Footing \[SIG] ## Footing **Substructure:** Choose the substructure element associated with the footing, such as columns. The center of the selected element will be utilized for positioning the footing. **Geometry Option \[Section/Point List]:** Selects how the footing polygon is defined. Section uses a named cross-section profile; Point List uses the longitudinal/transverse coordinate list in **Footing Points** below. **Footing Points:** Users can define custom polygons by providing the longitudinal and transverse locations of the points comprising them. * **Longitudinal Distance From Reference Point:** The longitudinal distance from the center of the substructure above is determined by a positive or negative value. A negative value shifts the point down-station along the PGL, while a positive value moves it up-station. * **Transverse Offset From Reference Point:** The transverse distance from the center of the substructure above is determined by a positive or negative value. ![](https://openbrim.atlassian.net/wiki/download/attachments/2123595789/image-20230322-112305.png?api=v2) **Thickness:** The thickness of the footing is also employed to define the shell element thicknesses in the analytical model. **Longitudinal Offset:** Employed to determine the position of the footing. Longitudinal offset along the Projected Grade Line (PGL), where 0 refers to the center point of the substructure above. **Transverse Offset:** This parameter can be used to specify the location of the footing's center, where a value of 0 places it at the center of the chosen substructure. A positive value will offset the footing to the right, and a negative value will offset it to the left when looking up-station along the PGL. {% hint style="info" %} The positive direction of the Y-axis will be to the left when looking upstream along the PGL. However, based on the requests of engineers who have been using OpenBrIM for their bridge projects, positive transverse offset values will indicate the right-hand side when looking upstream along the PGL. This distinction should be taken into account when defining the location of bridge elements using transverse offset values (where positive transverse offset indicates the right side), as well as when making definitions related to FEM and loading (where positive Fy indicates the left side along the PGL). {% endhint %} **Material:** Material of the footing **Rotation:** This parameter is utilized to rotate the rectangular footing, with 0 indicating that it is perpendicular to the PGL. **Bottom Elevation Calculation Method \[Constant Elevation/Constant Depth]:** Chooses how the bottom of the footing is located when placed under an abutment. Constant Elevation fixes the footing bottom at the specified Bottom Elevation; Constant Depth keeps the footing a fixed Depth below the abutment bottom. **Depth:** The thickness of the footing measured from its top to its bottom. Used when Bottom Elevation Calculation Method is Constant Depth, or for foundations that sit below standalone substructure elements (no abutment above). **Bottom Elevation:** The elevation of the footing's bottom face with respect to the Global Coordinate System. Used when Bottom Elevation Calculation Method is Constant Elevation. **Footing Top Slope(Outside Abutment Region)\[Match Abutment Slope/Flat]:** Controls the top surface of the portion of the footing that extends beyond the abutment footprint. Match Abutment Slope continues the abutment's top slope across the full footing; Flat keeps the top horizontal outside the abutment region. ## FEM **Generate FEM? \[Yes=1/No=0]:** Setting the "Generate FEM" parameter to "No" can disable the analytical representation of the pile. **Rigid Section:** A rigid section is employed to establish rigid line elements that connect the footing to pier columns or piles. Column connections are established using five rigid elements to distribute pier forces to the footing from five distinct locations (center, top right, top left, bottom left, and bottom right) rather than a single point, which would result in unrealistic high stress concentrations. When the user assigns different sections, the locations of the rigid lines and the footing mesh adapt accordingly. **FEM Type \[Shell=0/Stiffness Matrix=1]:** This parameter is used to determine the FEM type preference. **Mesh Size:** The maximum length of the shell elements representing the footing. **Min. # of Strips in Long. Dir.:** The longitudinal direction corresponds to the direction that is along the length of the footing. The number of strips is employed to extract major axis bending moment results from shell elements using the fecomposite approach for design purposes. Essentially, it consolidates the forces of shell elements at their centers of gravity. If 1 is selected, the design will utilize the combined forces of all shell elements. **Min. # of Strips in Trans. Dir.:** The longitudinal direction corresponds to the direction that is along the width of the footing. The number of strips is employed to extract major axis bending moment results from shell elements using the fecomposite approach for design purposes. Essentially, it consolidates the forces of shell elements at their centers of gravity. If 1 is selected, the design will utilize the combined forces of all shell elements. * As per AASHTO C5.12.8.4, the moment of the forces acting on one side of the vertical plane passing through the entire section should be used; therefore, **using one strip is suggested** ![image-20241104-234759.png](https://openbrim.atlassian.net/wiki/download/attachments/2123595789/image-20241104-234759.png?api=v2) **6x6 Stiffness Matrix:** If the **Stiffness Matrix** option is chosen, the 6x6 stiffness matrix can be specified. This matrix defines the resistance in three translational and three rotational degrees of freedom. **Additional Result Extraction Point in Long. Dir.:** Enter the distance from the back end of the footing to view results at that specific location. This does not alter the FEA model or introduce new nodes; the software simply interpolates between existing end forces. These station settings only affect how composite FEA results are displayed in the spreadsheet or FEA view, and do not impact standard analysis results like member end forces, displacements, or reactions. **Additional Result Extraction Point in Trans. Dir.:** Enter the distance from the right end of the footing to view results at that specific location. This does not alter the FEA model or introduce new nodes; the software simply interpolates between existing end forces. These station settings only affect how composite FEA results are displayed in the spreadsheet or FEA view, and do not impact standard analysis results like member end forces, displacements, or reactions. ![image-20250522-120435.png](https://openbrim.atlassian.net/wiki/download/attachments/2123595789/image-20250522-120435.png?api=v2) ## Quantities **Bottom Surface Area:** The surface area of the section assigned to the bottom of the custom footing is calculated and displayed to the user in this column. **Top Surface Area:** The surface area of the section assigned to the top of the custom footing is calculated and displayed to the user in this column. **Total Pile Surface Area:** The total pile surface area of the custom footing is presented to the user in this column. **Net Bottom Surface Area(excluding piles):** The net bottom surface area of the custom footing, excluding piles, is presented to the user in this column. **Side Surface Area:** The side surface area of the custom footing is presented to the user in this column. **Top Surface Perimeter:** The top surface perimeter of the custom footing is presented to the user in this column. **Volume:** The volume of the custom footing, based on the definitions provided by the user, is calculated and displayed to the user in this column. **Weight:** Based on the defined geometry and material properties of the element, the weight of the modeled element is calculated and presented to the user in this column. **Height:** The height of the custom footing is presented to the user in this column. **Top Surface Width:** The top surface width of the custom footing is presented to the user in this column. **Top Surface Height:** The top surface height of the custom footing is presented to the user in this column. ## Strip Settings **Min. # of Strips in Long. Dir.:** Minimum number of result-extraction strips in the longitudinal direction (perpendicular to PGL is transverse; this is along-PGL). **Min. # of Strips in Trans. Dir.:** Minimum number of result-extraction strips in the transverse direction. **Additional Result Extraction Point in Long. Dir.:** Additional longitudinal result-extraction points on top of the auto-generated strip grid. **Additional Result Extraction Point in Trans. Dir.:** Additional transverse result-extraction points on top of the auto-generated strip grid. ## FEM and Display **Mesh Algorithm \[GridMesh/MeshAdapt/Automatic/Initial mesh only/Delaunay/Frontal Delaunay/Frontal Delaunay for Quads/Packing of Parallelograms/Quasi structured Quad]:** Meshing algorithm applied to the footing surface. Default MeshAdapt. **Show 3D \[No/Yes]:** When Yes, the footing is visible in the 3D view. ## Flexural Reinforcement **Longitudinal Direction Reinforcements:** Tabular list of longitudinal (along-PGL) rebar layers in the footing. **Transverse Direction Reinforcements:** Tabular list of transverse (perpendicular-to-PGL) rebar layers in the footing. ## Shear Reinforcement **Shear Reinforcement \[Include/Ignore]:** Enables or disables shear reinforcement modeling in the footing. **Shear Reinforcement Profile in Longitudinal Direction:** Rebar profile used for longitudinal shear reinforcement. **Shear Reinforcement Profile in Transverse Direction:** Rebar profile used for transverse shear reinforcement. **Shear Reinforcement Material:** Material assigned to shear reinforcement. **Spacing in Longitudinal Direction:** Spacing of shear reinforcement in the longitudinal direction. **Spacing in Transverse Direction:** Spacing of shear reinforcement in the transverse direction. **Distance Between Legs in Longitudinal Direction:** Spacing between legs of shear reinforcement in the longitudinal direction (center-to-center). **Distance Between Legs in Transverse Direction:** Spacing between legs of shear reinforcement in the transverse direction (center-to-center). ## Side Reinforcement **Longitudinal Direction Side Reinforcements:** Tabular list of longitudinal side-face reinforcement rows. **Transverse Direction Side Reinforcements:** Tabular list of transverse side-face reinforcement rows. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.openbrim.org/templates/steel-i-girder-bridge-workflow/substructure-sig/foundation-sig/custom-footing-sig.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.