# Elastic Joint Model In 3DEC

The Elastic model provides a linear representation of joint stiffness (normal and shear). There is no yield. Elastic joints are infinitely strong.

Formulations

The Elastic joint model in 3DEC calculates the incremental normal and shear stresses on a joint from normal and shear displacements multiplied by normal and shear stiffnesses as follows.

(1)$\begin{split}\Delta \sigma_n = k_n \Delta u_n \\ \Delta \sigma_s = k_s \Delta u_s\end{split}$
 where $$\Delta \sigma_n$$ and $$\Delta \sigma_s$$ are the change in normal and shear stress, $$k_n$$ and $$k_s$$ are the normal and shear stiffnesses (in units of STRESS/LENGTH), and $$\Delta u_n$$ and $$\Delta u_s$$ are the incremental normal and shear displacements.

## Properties

elastic
stiffness-normal f

Set joint normal stiffness (stress / distance)

stiffness-shear f

Set joint shear stiffness (stress / distance)