# Elastic Joint Model In 3DEC

The Elastic model provides a linear representation of joint stiffness (normal and shear). There is no yield - and elastic joint is 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)