> For the complete documentation index, see [llms.txt](https://alpaca4d.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://alpaca4d.gitbook.io/docs/basics/results/brick-stresses.md).

# Brick Stresses

The full stress tensor at every solid element, plus the Von Mises equivalent stress.

## 🔧 Grasshopper component

`Brick Stresses (Alpaca4d)` — **Alpaca4d ▸ 08\_NumericalOutput**

Applies to [SSP Brick](/docs/basics/elements/brick.md) and [Four Node Tetrahedron](/docs/basics/elements/four-node-tetrahedron.md) elements.

### Inputs

| Name        | Nick          | Type    | Default | Description                                                                                                                              |
| ----------- | ------------- | ------- | ------- | ---------------------------------------------------------------------------------------------------------------------------------------- |
| AlpacaModel | `AlpacaModel` | Model   | —       | The analysed model.                                                                                                                      |
| History     | `History`     | Boolean | `false` | Read every recorded step instead of one. Each output becomes a tree `{step}` holding that step's value per element. **Step** is ignored. |
| Step        | `Step`        | Integer | `0`     | Analysis step.                                                                                                                           |

### Outputs

One value per element, in the element's local axes. Both element types have a single integration point, so there is nothing to sample along the element — the outputs are flat lists, ordered by element tag.

| Name     | Nick       | Type          | Description                              |
| -------- | ---------- | ------------- | ---------------------------------------- |
| Sigma11  | `σ₁₁`      | Number (list) | Normal stress along axis 1, in `kN/m²`.  |
| Sigma22  | `σ₂₂`      | Number (list) | Normal stress along axis 2.              |
| Sigma33  | `σ₃₃`      | Number (list) | Normal stress along axis 3.              |
| Sigma12  | `σ₁₂`      | Number (list) | Shear stress in the 1–2 plane.           |
| Sigma23  | `σ₂₃`      | Number (list) | Shear stress in the 2–3 plane.           |
| Sigma13  | `σ₁₃`      | Number (list) | Shear stress in the 1–3 plane.           |
| VonMises | `VonMises` | Number (list) | Von Mises equivalent stress, in `kN/m²`. |

With **History** on, each of them becomes a tree with one branch per step, `{step}`, holding that step's value per element.

## 📈 When to use it

**Use it when**

* You are checking a solid region against a strength criterion — Von Mises for a ductile material, the principal stresses for a brittle one.
* You need the stress state at a detail: a bearing, an anchorage, a stress concentration.

**Do not use it when**

* You want a contour → [View Results](/docs/basics/visualisation/view-results.md), with *Brick stresses* picked as the result, which colours the mesh by any of the seven quantities.

{% hint style="info" %}
An [SSP Brick](/docs/basics/elements/brick.md) has a **single integration point**, at the centroid. Each branch therefore holds one value per element, and the stress you get is an element average — fine for a global picture, coarse near a concentration. Refine the mesh where the gradient is steep.
{% endhint %}