> 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-u-girder-bridge-workflow/substructure-cug/pier-cug/steel-i-girder-bent-cap-cug/diaphragm-cug.md). # Diaphragm \[CUG] The Diaphragm object serves as a connection element between I-Girders. Both the FEM and 3D models are generated based on the parameter definitions listed below. ## Diaphragm **Girders**: Specify the girders for which the diaphragms will be generated. **Station on Girders (from Right End)**: Assume the right-hand side as the starting point for station definition when viewed up-station from the alignment. **Thickness**: This parameter is used to specify the thickness of the diaphragm in the bridge's transverse direction. **Material**: Assign a material to the diaphragm. Materials can be selected from previously defined options or imported as needed. **Top Offset (from Bottom of Top Flange)**: For a visual representation, refer to the figure below. **Bottom Offset (from Top of Bottom Flange)**: For a visual representation, refer to the figure below. ![image-20240913-125522.png](https://openbrim.atlassian.net/wiki/download/attachments/2575138834/image-20240913-125522.png?api=v2) ## FEA Settings **Girder Connection Release:** Defines how the diaphragm is connected to the straddle bent girders in the FE model. The diaphragm is modeled as a shell attached to each girder web at a top and a bottom node. Major moment is the in-plane bending of the diaphragm plate, minor moment is the bending about the vertical axis, and torsion is the twist about the diaphragm axis. * Fixed (default): all six degrees of freedom are connected at the four nodes. * Free Minor Moment: the rotation about the vertical axis (Rz) is released at the four nodes. Because each side stays connected at a top and a bottom node, torsion and the major moment are still transferred. * Free Minor and Most of Major Moment: the top nodes stay connected only vertically (horizontal translations and rotations released), and the bottom nodes release the rotation about the vertical axis. The major moment is no longer transferred as a top-bottom force couple, but the bottom nodes still hold torsion and transfer part of the major moment through the shell element (about 10 to 17 percent of the Fixed value in a three-girder straddle bent model). The axial force of the diaphragm passes at the bottom node, so an axial force also produces in-plane moment about the plate center. With this option the diaphragms share less load between the straddle girders, so check the girders again after selecting it. ## IFC **Type \[IfcBeam/IfcColumn/IfcSlab/IfcFooting/IfcPile/IfcMember/etc.]:** Specifies the IFC entity type for export. The diaphragm can be exported as various IFC types including 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, or IfcBuildingElementProxy. **Predefined Type \[ABUTMENT/ACCESSORY\_ASSEMBLY/ARCH/BEAM\_GRID/BRACED\_FRAME/CROSS\_BRACING/DECK/DILATATIONPANEL/ENTRANCEWORKS/GIRDER/GRID/MAST/PIER/PYLON/RAIL\_MECHANICAL\_EQUIPMENT\_ASSEMBLY/REINFORCEMENT\_UNIT/RIGID\_FRAME/SHELTER/SIGNALASSEMBLY/SLAB\_FIELD/SUMPBUSTER/SUPPORTINGASSEMBLY/SUSPENSIONASSEMBLY/TRACKPANEL/TRACTION\_SWITCHING\_ASSEMBLY/TRAFFIC\_CALMING\_DEVICE/TRUSS/TURNOUTPANEL/USERDEFINED/NOTDEFINED]:** Specifies the predefined type attribute for the IFC entity. Default value is CROSS\_BRACING. **Parent \[BRIDGE/SUPERSTRUCTURE/DECK/SUBSTRUCTURE/FOUNDATION/APPROACH\_STRUCTURE/RETAINING\_STRUCTURE]:** Specifies the parent structural hierarchy element in the IFC model. Default value is SUBSTRUCTURE. ## Quantities **Volume**: The total volume of the diaphragm based on the modeled element definitions. **Weight**: Based on the material and element definitions, the weight of the diaphragm is calculated. **Rebar Density(per cubic yard):** Estimated rebar weight per unit concrete volume for the diaphragm, used by downstream quantity takeoff reports to compute total rebar weight from the diaphragm's concrete volume. **Rebar Weight**: The calculated weight of reinforcement bars in the diaphragm based on the defined rebar density. --- # 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. 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