# Pile Construction

This section defines the pile construction stage and soil-structure interaction.

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**Navigation:** Construction > Substructure Construction > Pile Construction

For detailed parameter explanations, see the [Pile Construction Reference](https://docs.openbrim.org/templates/steel-tub-girder-bridge-workflow/construction-stg/substructure-construction-stg/pile-construction-stg).
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## Overview

Nonlinear springs represent the stiffness of the soil around the foundation of the structure. The behavior of these springs is nonlinear because the stiffness of the soil changes as the load on the structure increases. The springs are typically placed at the base of the foundation and are connected to the foundation and the surrounding soil.

In OpenBrIM, nonlinear springs are used to model soil-structure interaction (SSI). These springs can be added to the model to simulate the behavior of the soil around the foundation. The stiffness of the springs can be adjusted based on the soil properties and the loading conditions, allowing the engineer to more accurately model the response of the structure to the soil and optimize the design accordingly.

## Steps

### Step 1: Navigate to Pile Construction

Navigate to **Loading > Construction > Substructure > Pile** in the tree view.

![Pile construction navigation](https://openbrim.atlassian.net/wiki/download/attachments/2175696899/image-20230223-115726.png?api=v2)

### Step 2: Select Construction Stage

Click the **three-dot icon** on the **Stage** cell and select **SubstrConstStage**.

![Stage selection](https://openbrim.atlassian.net/wiki/download/attachments/2175696899/image-20230223-115805.png?api=v2)

### Step 3: Pick Substructures Above

Click the **three-dot icon** on the **Substructures Above** cell and select **Pick**.

![Pick substructures](https://openbrim.atlassian.net/wiki/download/attachments/2175696899/image-20230223-120347.png?api=v2)

### Step 4: Select Foundations

Select all **Foundations** that were previously defined from the 3D View.

![Select foundations](https://openbrim.atlassian.net/wiki/download/attachments/2175696899/image-20230223-120654.png?api=v2)

### Step 5: Complete Selection

Click **Done** to complete the selection.

## Verification

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All piles should be assigned to the SubstrConstStage with their respective foundations.
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