# Soil Structure Interaction \[TB]

Analyzing a pile under lateral loading is a complex procedure because the soil's reaction at any point on the pile depends on the pile's deflection. Conversely, the pile's deflection relies on the soil's resistance. As a result, determining the response of a pile under lateral loading falls into a category of soil-structure interaction issues. It is essential to meet the conditions of compatibility and equilibrium between the pile and the soil, as well as between the pile and the superstructure. Therefore, in order to meet this equilibrium condition and properly analyze a pile foundation, a nonlinear relationship needs to be applied.

{% hint style="info" %}
To perform nonlinear analysis in stage construction, click 'Construction > Construction Stage' in the navigation tree view, then activate the Nonlinear option.
{% endhint %}

Lateral soil-structure interaction is modeled with nonlinear *p-y* curves. Axial interactions are modeled with nonlinear *t-z* curves for soil skin-friction and *q-z* curves for soil end bearing (tip) resistance.


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