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Brick

The Brick element in Alpaca4d is a 3D solid (hexahedral) element based on the OpenSees SSPbrick formulation (Stabilized Single-Point brick). It is suitable for modelling volumetric behaviour such as foundations, cores, massive walls or blocks where a full three‑dimensional stress state is important.

🔧 Grasshopper component

The SSP Brick (Alpaca4d) component constructs a single brick element from a hexahedral mesh and a 3D material.

  • Inputs

    • Mesh: Hexahedral mesh representing the brick geometry.

      • Type: Mesh with exactly 8 vertices (one per corner).

      • The component internally cleans/sanitises the mesh (CleanHexahedron), but it is still good practice to use well‑formed bricks.

    • Material: 3D material assigned to the brick.

      • Type: Alpaca4d multi‑dimensional material (e.g. concrete, soil, etc.).

      • Controls the constitutive law in 3D (stress–strain behaviour).

    • Colour (optional): Display colour of the brick in Grasshopper/Rhino.

  • Outputs

    • Element: Alpaca4d SSPbrick element that can be passed to the assemble/model component.

📈 When to use a brick element

  • Use it when

    • You need full 3D stress state (e.g. confinement, triaxial behaviour, contact with soil or massive concrete).

    • The structure or sub‑structure cannot be represented accurately by beams or shells alone.

    • You are performing solid mechanics studies (e.g. stress concentrations inside a block).

  • Do not use it when

    • The structure is thin compared to its in‑plane dimensions → use Shell elements instead.

    • Member behaviour is beam‑like (bending dominated) → use Force Beam Column or other frame elements.

🔗 Relation to OpenSees

Alpaca4d’s brick element writes the OpenSees SSPbrick command:

element SSPbrick $eleTag $node1 $node2 $node3 $node4 $node5 $node6 $node7 $node8 $matTag $bx $by $bz

where:

  • the 8 mesh vertices map to the node tags $node1 ... $node8,

  • the Material input provides matTag,

  • the optional body forces $bx, $by, $bz are set based on the BodyForce property inside Alpaca4d.

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