# Tie

Multipoint Constraint Implemented As Element

* Number of Nodes: varies
* Number of DoFs: varies

## Syntax

```
element Tie (1) (2) (3) [(4) (5) (6)...]
# (1) int, unique element tag
# (2) double, right hand side of the constraint equation, the constraint is homogeneous if this parameter is zero
# (3) double, penalty number, a relatively large number
# (4) int, node tag
# (5) int, dof tag
# (6) double, weight
```

## Example

Each `Tie` element can have multiple DoFs included. For example, to define the following constraint,

$$
5u\_2+6v\_4=9,
$$

where $$u\_2$$ and $$v\_4$$ are horizontal displacement of node `2` and vertical displacement of node `4` in a 2D model, then

```
element Tie 1 9. 1E8 2 1 5. 4 2 6.
```

In the above command, a large number `1E8` is used as penalty.

The `Tie` element does not care about the geometric implication. The tied DoFs can be of different types.

To tie a node to a line, consider the [`TranslationConnector`](https://tlcfem.gitbook.io/suanpan-manual/element/special/translationconnector) element.


---

# Agent Instructions: 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.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://tlcfem.gitbook.io/suanpan-manual/element/special/tie.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
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.