> For the complete documentation index, see [llms.txt](https://docs.openbrim.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.openbrim.org/templates/truss-bridge-workflow/substructure-tb/foundation-tb/custom-abutment-only-tb.md). # Custom (Abutment only) \[TB] A custom footing that sits under an abutment. In addition to the footing geometry it carries the wing-wall and back-wall thicknesses of the abutment above, so the footing plan follows the abutment footprint (including its wing walls and end extensions). Use it when an abutment needs a footing whose outline is driven by the abutment geometry rather than a simple rectangle. ## General **Abutment:** The abutment this footing is placed under. The footing is positioned and shaped from the selected abutment's geometry. The user must provide a value. **Longitudinal Offset:** Longitudinal position of the footing along the Projected Grade Line (PGL), where 0 refers to the reference point of the abutment above. A negative value shifts the footing down-station; a positive value shifts it up-station. **Transverse Offset:** Transverse position of the footing center relative to the abutment. A value of 0 places it at the abutment center; a positive value offsets it to the right when looking up-station along the PGL. **Material:** Material assigned to the footing. (Read-only) **Bottom Elevation Calculation Method \[Constant Elevation/Constant Depth]:** Chooses how the bottom of the footing is located. 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. **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. ## Geometry **Right Wing Wall Inside Thickness:** Thickness of the right wing wall on its inside face, used to shape the footing outline under the wing wall. **Right Wing Wall Outside Thickness:** Thickness of the right wing wall on its outside face. **Back Wall Inside Thickness:** Thickness of the abutment back wall on its inside face. **Back Wall Outside Thickness:** Thickness of the abutment back wall on its outside face. **Left Wing Wall Inside Thickness:** Thickness of the left wing wall on its inside face. **Left Wing Wall Outside Thickness:** Thickness of the left wing wall on its outside face. **Right End Extend:** Length by which the footing extends beyond the abutment at the right end (transverse direction, looking up-station). **Left End Extend:** Length by which the footing extends beyond the abutment at the left end. **Right End Skew:** Skew angle applied to the right end face of the footing. **Left End Skew:** Skew angle applied to the left end face of the footing. ## FEM **Generate FEM? \[Yes/No]:** Setting this to No disables the analytical (finite-element) representation of the footing. **Rigid Section:** When enabled, the footing is treated as a rigid section in the analytical model. **FEM Type \[Shell/Stiffness Matrix]:** Selects how the footing is modeled: Shell meshes the footing into shell elements; Stiffness Matrix represents it with a user-supplied 6x6 stiffness matrix. **Mesh Size:** Sets the maximum distance for a single finite-element line when meshing the footing. **Min. # of Strips in Long. Dir.:** Minimum number of mesh strips generated along the longitudinal direction. **Min. # of Strips in Trans. Dir.:** Minimum number of mesh strips generated along the transverse direction. **6x6 Stiffness Matrix:** The user-supplied stiffness matrix used when FEM Type is Stiffness Matrix. **Additional Result Extraction Point in Long. Dir.:** Adds an extra result-extraction location along the longitudinal direction. **Additional Result Extraction Point in Trans. Dir.:** Adds an extra result-extraction location along the transverse direction. **Mesh Algorithm \[GridMesh/MeshAdapt/Automatic/Initial mesh only/Delaunay/Frontal Delaunay/Frontal Delaunay for Quads/Packing of Parallelograms/Quasi structured Quad]:** Selects the meshing algorithm used to generate the footing's finite-element mesh. ## FEM and Display **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. ## Quantities The following are computed automatically from the footing geometry and reinforcement inputs and are reported for take-off. (Read-only) **Bottom Surface Area:** Area of the footing's bottom face. (Read-only) **Top Surface Area:** Area of the footing's top face. (Read-only) **Total Pile Surface Area:** Combined surface area of the piles under the footing. (Read-only) **Net Bottom Surface Area(excluding piles):** Bottom face area with the pile footprints removed. (Read-only) **Side Surface Area:** Area of the footing's side (edge) faces. (Read-only) **Top Surface Perimeter:** Perimeter of the footing's top face. (Read-only) **Depth:** Depth of the footing as reported for quantities. (Read-only) **Top Surface Width:** Width of the footing's top face. (Read-only) **Top Surface Height:** Height (longitudinal extent) of the footing's top face. (Read-only) **Rebar Calculation Method \[By Density/By Length]:** Chooses how reinforcement quantities are estimated: By Density uses a rebar density per unit volume; By Length sums explicit reinforcement lengths. **Rebar Density(per cubic yard):** Reinforcement weight per cubic yard, used when Rebar Calculation Method is By Density. **Rebar Weight (By Density):** Total reinforcement weight computed from the density. (Read-only) **Longitudinal Reinforcement Length:** Total length of longitudinal reinforcement, used when Rebar Calculation Method is By Length. (Read-only) **Transverse Reinforcement Length:** Total length of transverse reinforcement. (Read-only) **Longitudinal Reinforcement Weight:** Weight of the longitudinal reinforcement. (Read-only) **Transverse Reinforcement Weight:** Weight of the transverse reinforcement. (Read-only) **Total Rebar Weight (By Length):** Total reinforcement weight computed from explicit lengths. (Read-only) **Volume:** Concrete volume of the footing. (Read-only) **Weight:** Concrete weight of the footing. (Read-only) --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## 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. 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