> 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/concrete-segmental-bridge-workflow/substructure-cbs/abutment-system-cbs/semi-integral-abutment-cbs.md). # Semi-Integral Abutment \[CBS] The Semi-Integral Abutment workflow item models an abutment whose backwall is cast with the superstructure and moves with it, while the seat below stays with the substructure. That is the defining feature of the detail: the superstructure frames into the backwall, the backwall bears on the seat through a joint, and — unlike a fully integral abutment — no moment continuity is forced across that joint. The object supports 3D visualization and optional finite-element meshing of the stem, backwall, and wing walls, and can be placed on any support line and referenced by approach slabs, piles, and stems. In the FE model the backwall is meshed as its own wall standing at the girder end station, with its own nodes, so the joint between it and the seat is a real separation rather than a shared boundary. The girders, cross frames, and deck picked in the FEM group tie into that wall; what crosses the joint below it is governed by **Backwall Connection to Seat**. The **Backwall** group, and the handful of backwall-related rows in **FEM General**, **Construction Joint**, and **Quantities**, are what distinguish this object from the Integral Abutment; every other parameter behaves identically. ### General **Location:** Support line on which the abutment is located. A single support line must be picked. **Front/Back \[Front/Back]:** Orientation of the abutment. Front (0) places the backwall facing upstation; Back (1) reverses that orientation so the backwall faces downstation. Choose the value that matches the bridge geometry at the picked support line. **Longitudinal Offset:** Offset of the abutment centerline along the PGL. Negative values shift the abutment downstation; positive values shift it upstation. **Transverse Offset:** Offset of the abutment centerline perpendicular to the PGL. Default matches the deck offset. Positive values place the abutment to the right of PGL when looking upstation; negative values place it to the left. **Material:** Concrete material assigned to the abutment stem, seat, backwall, and wing walls. Pick a previously defined material from *Properties > Materials*. ### Stem **Width (Perpendicular to pgl):** Width of the abutment stem in the transverse direction. Defaults to the deck width. Only required when Geometry Source is set to Parameters. **Length:** Length of the stem in the longitudinal direction (default 36 in). **Override Top Elevation \[No/Yes]:** When Yes, the stem top elevation is taken from the user-specified table below instead of the auto-computed PGL-based value. Only visible when Geometry Source is Section and a section point is defined. **Stem Top Elevation:** Station-based table defining the top elevation of the stem. Used when the top elevation is overridden or when the stem geometry is driven by parameters. The table's cell actions can populate the elevation from the deck or from the bearing elevations. **Override Bottom Elevation \[No/Yes]:** When Yes, the stem bottom elevation is taken from the user table instead of the default derived from the stem geometry. **Stem Bottom Elevation:** Station-based table defining the bottom elevation of the stem. Only visible when the bottom elevation is overridden or when the geometry is driven by parameters. **Bottom Elevation:** (Read-only) Computed bottom elevation of the front wall, shown for reference. **Left Plane Rotation:** In-plan rotation of the left face of the stem wall. Only enabled on the stepped-seat section variant. **Right Plane Rotation:** In-plan rotation of the right face of the stem wall. Same usage as Left Plane Rotation. **Geometry Source \[Parameters/Section]:** Selects how the stem cross-section is defined. Parameters (0) uses the Width and Length values above. Section (1) uses the picked Section below. **Section:** Section library object used when Geometry Source is Section. The section must expose a `_seatSection` parameter set. ### Backwall The backwall is the element that makes this abutment semi-integral: it is poured with the superstructure rather than with the stem, so it moves with the deck and is reported separately in the quantities. **Generate BackWall \[No/Yes]:** Enables the backwall. When No, the remaining backwall parameters are hidden and no backwall geometry, mesh, or volume is produced. Enabling it requires at least one girder in the FEM Girders list. **Thickness (Downstation w\.r.t. Support Line):** Backwall thickness measured downstation from the support line (default 0 in, i.e. the backwall sits entirely upstation of the line). **Thickness (Upstation w\.r.t. Support Line):** Backwall thickness measured upstation from the support line (default 18 in). The two thicknesses together define the backwall's longitudinal extent about the support line, letting the wall sit off-center — a real semi-integral backwall is cast against the girder ends with most of its body on the backfill side rather than centered on that line. The downstation/upstation labels are absolute, so they mean the same thing whether the abutment orientation is Front or Back. The split affects the 3D solid only: the FE panel is a zero-thickness shell that uses the total of the two values. **Backwall Top Elevation:** Station-based table defining the top elevation of the backwall. Defaults to the roadway surface at the abutment station. Cell actions can populate the elevation from the deck or from the bearing elevations. **Backwall Bottom Elevation:** Station-based table defining the bottom elevation of the backwall, i.e. the level at which the superstructure pour meets the stem. Defaults to 96 in below the roadway surface, which must clear the girder ends it encloses. Its cell actions write the same elevation the stem top is computed from, so the backwall starts where the stem ends and the two tables cannot drift apart. Note that computing the bottom sets the wall base rather than preserving the wall's current depth — the depth is whatever the top table says. **Show in 3D \[No/Yes]:** Controls whether the backwall solid is drawn. The solid still exists and is still counted in the Backwall Volume quantity when this is No — it is only hidden from the 3D view. ### Right Wing Wall **Wing Wall \[No/Yes]:** Enables or disables the right-hand wing wall. When No, the remaining right-wall parameters are hidden. **Section:** Section defining the right wing wall cross-section. The section must expose a `_wingwallSection` parameter set. **Wall Length:** Length of the wing wall along its own axis (default 360 in). **Longitudinal Offset:** Offset of the wing wall start from the abutment along the PGL direction. **Transverse Offset:** Offset of the wing wall start transverse to the PGL. **Angle of Start Face Plane:** Skew of the start face of the wing wall. **Angle of End Face Plane:** Skew of the end face of the wing wall. **Rotation Angle:** Rotation of the wing wall in plan around its start point. **Override Bottom Elevation \[No/Yes]:** When Yes, the wing-wall bottom elevation is taken from the input below instead of the default computed elevation. **Bottom Elevation:** User-specified bottom elevation of the right wing wall when override is enabled. **Top Vertical Offset:** Vertical offset of the top of the wing wall from the PGL-derived top elevation. **Bottom Elevation (readonly):** (Read-only) Auto-computed bottom elevation of the right wing wall shown for reference. ### Left Wing Wall Parameters mirror the Right Wing Wall group and control the left-hand wing wall: **Wing Wall \[No/Yes]:** Enables the left wing wall. **Section:** Section definition for the left wing wall. **Wall Length:** Length along the wing-wall axis. **Longitudinal Offset:** Offset from the abutment along the PGL. **Transverse Offset:** Offset transverse to the PGL. **Angle of Start Face Plane:** Skew of the start face. **Angle of End Face Plane:** Skew of the end face. **Rotation Angle:** In-plan rotation. **Override Bottom Elevation \[No/Yes]:** Toggle for user-input bottom elevation. **Bottom Elevation:** User-specified bottom elevation when override is enabled. **Top Vertical Offset:** Vertical offset of the wall top from the PGL-derived top elevation. **Bottom Elevation (readonly):** (Read-only) Auto-computed bottom elevation of the left wing wall shown for reference. ### 3D Visualization **Right Chamfer \[No/Yes]:** Enables a chamfer on the right end of the stem/backwall interface. When No, the remaining right-chamfer parameters are hidden. **Right Chamfer Width:** Chamfer width in the transverse direction. **Right Chamfer Length:** Chamfer length in the longitudinal direction. **Right Chamfer Depth:** Chamfer depth in the vertical direction. **Right Chamfer Vertical Offset:** Vertical offset of the chamfer from the top of the abutment. **Right Chamfer Transverse Offset:** Transverse offset of the chamfer from the wing-wall interior face. **Left Chamfer \[No/Yes]:** Enables a chamfer on the left end of the stem/backwall interface. **Left Chamfer Width:** Chamfer width in the transverse direction. **Left Chamfer Length:** Chamfer length in the longitudinal direction. **Left Chamfer Depth:** Chamfer depth in the vertical direction. **Left Chamfer Vertical Offset:** Vertical offset of the chamfer from the top of the abutment. **Left Chamfer Transverse Offset:** Transverse offset of the chamfer from the wing-wall interior face. ### FEM General **Generate FEM \[No/Yes]:** When Yes (default), a shell-element FE mesh is generated for the stem, backwall, and wing walls. When No, only the 3D visualization is produced. **Mesh Size:** Target element size used when meshing the abutment surfaces (default 120 in). **Rigid Material:** Rigid material used for stiff FE link elements inside the abutment mesh. Pick a Material defined under *Properties*. **Rigid Section:** Rigid section used for the same FE link elements. Pick a Section defined under *Properties*. **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 abutment and wing-wall surfaces. The default is MeshAdapt. **Match Top Elevation with Deck \[No/Yes]:** When Yes, the top of the abutment mesh is snapped to the deck elevation so the two meshes merge cleanly at the interface. **Override Right Wing Wall Thickness \[No/Yes]:** When Yes, the right wing wall thickness used by FEM is taken from the input below instead of the section's minimum width. **Override Left Wing Wall Thickness \[No/Yes]:** When Yes, the left wing wall thickness used by FEM is taken from the input below instead of the section's minimum width. **Right Wing Wall Thickness:** User-specified FE thickness for the right wing wall. Only enabled when the corresponding override is Yes. **Left Wing Wall Thickness:** User-specified FE thickness for the left wing wall. Only enabled when the corresponding override is Yes. **Backwall Connection to Seat \[Free/Rigid]:** How the backwall mesh ties to the seat below it. This governs only the seat tie — the joint that actually distinguishes the two details. Free (0), the default, models the real semi-integral detail: the backwall bears on the seat through a joint that transfers no moment, so nothing spans it. Rigid (1) adds a rigid tie to the seat, which is a deliberate simplification of a real connection rather than the connection itself — choose it knowingly. Only visible when a backwall is generated. **Girders:** Girders whose ends frame into this abutment. Picked from the model as a list. At least one girder is required when a backwall is generated. The girders are rigidly tied to the backwall regardless of the Backwall Connection setting — that tie is what makes the wall semi-integral, and it replaces the girder-to-seat link, which is switched off when a backwall carries the superstructure. **Cross Frames:** Cross frames connected to the abutment, picked as a list. Used to tie the cross-frame mesh into the abutment mesh. **Decks:** Decks connected to the abutment, picked as a list. Used to tie the deck mesh into the abutment mesh. **Backwall Soil Split Active (readonly):** (Read-only) Indicates whether the backfill pressure is split at the backwall. Active when a backwall is generated and girders frame into it. **Backwall Soil Split Elevation (readonly):** (Read-only) Elevation at which the backfill soil pressure is split between the backwall and the stem below. ### Bottom Fixity **Bottom Connection \[Substructure/Stiffness Matrix/Fixed/Custom DOF]:** How the base of the abutment is supported in the FE model. Substructure (0) connects it to the piles or footing modeled below. Stiffness Matrix (1) applies the 6x6 matrix below. Fixed (2) restrains all six degrees of freedom. Custom DOF (4) uses the individual fixity values below. **6x6 Stiffness Matrix:** Support stiffness matrix applied at the abutment base. Only visible when Bottom Connection is Stiffness Matrix. **Tx \[Free/Fixed]:** Translational fixity along the longitudinal axis. Enter 0 for free, -1 for fixed, or a stiffness value for a spring. Only visible when Bottom Connection is Custom DOF. **Ty \[Free/Fixed]:** Translational fixity along the transverse axis, entered the same way as Tx. **Tz \[Free/Fixed]:** Vertical translational fixity, entered the same way as Tx. **Rx \[Free/Fixed]:** Rotational fixity about the longitudinal axis. Enter 0 for free, -1 for fixed, or a rotational stiffness value. **Ry \[Free/Fixed]:** Rotational fixity about the transverse axis, entered the same way as Rx. **Rz \[Free/Fixed]:** Rotational fixity about the vertical axis, entered the same way as Rx. **Bottom Fixity UCS Rotation:** In-plan rotation of the local coordinate system in which the fixities above are applied. Only visible when Bottom Connection is not Substructure. ### Construction Joint Splits the abutment into two pours so staged-construction effects can be modeled. **Construction Joint \[No/Yes]:** Enables a horizontal construction joint in the abutment. When No, the remaining parameters in this group are hidden. **Joint Elevation:** Station-based table defining the elevation of the construction joint. The joint must lie between the wall bottom and wall top elevations shown below. It is allowed to sit below the bearing seat — on a two-pour abutment poured up to just under the seat, it deliberately does. **Wing Wall Joint \[No/Yes]:** Enables a separate construction joint in the wing walls. Only visible when Construction Joint is Yes. **Wing Wall Joint Elevation:** Station-based table defining the wing-wall joint elevation. Only visible when the wing wall joint is enabled; when left empty, the wing walls use the main joint elevation. **Wall Bottom Elevation (readonly):** (Read-only) Bottom elevation of the wall, shown as the lower bound for the joint elevation. **Wall Top Elevation (readonly):** (Read-only) Top elevation of the wall, shown as the upper bound for the joint elevation. **Bearing Seat Top Elevation (readonly):** (Read-only) Top elevation of the bearing seat, shown for reference. This is informational only and does not bound the joint. **Back Wall Bottom Elevation (readonly):** (Read-only) Bottom elevation of the backwall, shown for reference when placing the joint relative to the superstructure pour. ### Quantities All values in this group are derived from the generated geometry and are displayed for reference; they cannot be edited. **Total Top Face Area:** (Read-only) Combined top-face area of the stem, backwall, and wing walls. **Total Bottom Face Area:** (Read-only) Combined bottom-face area of the stem, backwall, and wing walls. **Total Surface Area:** (Read-only) Total exterior surface area of the abutment. **Max Height Left Wing Wall:** (Read-only) Maximum height of the left wing wall. Shown when the left wing wall is enabled and has a section. **Min Height Left Wing Wall:** (Read-only) Minimum height of the left wing wall. **Length Left Wing Wall:** (Read-only) Length of the left wing wall. **Thickness Left Wing Wall:** (Read-only) Thickness of the left wing wall. **Max Height Right Wing Wall:** (Read-only) Maximum height of the right wing wall. Shown when the right wing wall is enabled and has a section. **Min Height Right Wing Wall:** (Read-only) Minimum height of the right wing wall. **Length Right Wing Wall:** (Read-only) Length of the right wing wall. **Thickness Right Wing Wall:** (Read-only) Thickness of the right wing wall. **Seat Max Depth:** (Read-only) Maximum vertical depth of the seat. **Seat Min Depth:** (Read-only) Minimum vertical depth of the seat. **Seat Thickness:** (Read-only) Longitudinal thickness of the seat. **Seat Width:** (Read-only) Transverse width of the seat. **Volume:** (Read-only) Concrete volume of the abutment stem, seat, and wing walls. The backwall is reported separately below, since it belongs to the superstructure pour. **Filled Bottom Area Volume:** (Read-only) Volume of the filled region at the bottom of the abutment, used when the seat extends below the default footprint. **Backwall Volume (superstructure pour):** (Read-only) Concrete volume of the backwall. Reported apart from the main Volume because the backwall is cast with the superstructure rather than with the stem. Shown when a backwall is generated. **Rebar Density(per cubic foot):** Assumed rebar mass per unit volume used for quantity takeoff. **Rebar Weight:** (Read-only) Total rebar weight derived from Rebar Density and the abutment volume. Like Volume, it excludes the backwall. **Weight:** (Read-only) Total concrete weight derived from the material unit weight and the abutment volume. Like Volume, it excludes the backwall. **Material (Read-Only):** (Read-only) Name of the assigned concrete material, shown for verification. ### Referencing Objects These rows list the objects that reference this abutment — useful for checking which piles, approach slabs, foundations, and backfill soils are tied to it. **Piles:** (Read-only) List of Single Pile workflow items that reference this abutment. **Pile Groups:** (Read-only) List of Pile Layout workflow items that reference this abutment. **ApproachSlab:** (Read-only) List of Approach Slab workflow items that reference this abutment. **Foundations:** (Read-only) List of foundation objects that reference this abutment. **Supports Backfill Soil (readonly):** (Read-only) Indicates that this abutment accepts a Backfill Soil object. **Supports Abutment Top loads (readonly):** (Read-only) Indicates that this abutment accepts loads applied at its top. **Backfill Soils:** (Read-only) List of Backfill Soil workflow items that reference this abutment. **Backfill Soil Lifts (legacy):** (Read-only) Legacy list of backfill soil lifts, retained for models built before backfill soils became their own objects. ### IFC **Type \[IfcBridge/IfcBridgePart/IfcBeam/IfcColumn/IfcSlab/IfcFooting/IfcPile/IfcBearing/IfcReinforcingBar/IfcReinforcingMesh/IfcTendon/IfcMechanicalFastener/IfcAlignment/IfcPositioningElement/IfcKerb/IfcGuardrail/IfcSurfaceFeature/IfcElementAssembly/IfcCableSegment/IfcSensor/IfcDistributionElement/IfcPlate/IfcWall/IfcRail/IfcRoad/IfcDiscreteAccessory/IfcDistributionSystem/IfcMember/IfcBuildingElementProxy]:** IFC entity used when exporting this abutment. Default IfcBridge. **Predefined Type \[ABUTMENT/DECK/DECK\_SEGMENT/FOUNDATION/PIER/PIER\_SEGMENT/PYLON/SUBSTRUCTURE/SUPERSTRUCTURE/SURFACESTRUCTURE/USERDEFINED/NOTDEFINED]:** IFC predefined type. Default ABUTMENT. **Parent \[BRIDGE/SUPERSTRUCTURE/DECK/SUBSTRUCTURE/FOUNDATION/APPROACH\_STRUCTURE/RETAINING\_STRUCTURE]:** IFC parent container under which the abutment is exported. Default SUBSTRUCTURE. --- # 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 by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://docs.openbrim.org/templates/concrete-segmental-bridge-workflow/substructure-cbs/abutment-system-cbs/semi-integral-abutment-cbs.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. 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.