diff --git a/src/compute_state_dieterich_newmark.tex b/src/compute_state_dieterich_newmark.tex new file mode 100644 index 0000000000000000000000000000000000000000..242721bc62a7277340cfa96b2968a3e269bcb7d5 --- /dev/null +++ b/src/compute_state_dieterich_newmark.tex @@ -0,0 +1,34 @@ +\documentclass{scrartcl} +\usepackage{amsmath} +\begin{document} +\noindent The Newmark scheme in its classical form with $\gamma = 1/2$ +and $\beta = 1/4$ reads +\begin{align} + \label{eq:1} \dot \alpha_1 + &= \dot \alpha_0 + \frac \tau 2 (\ddot \alpha_0 + \ddot \alpha_1 )\\ + \label{eq:2} \alpha_1 + &= \alpha_0 + \tau \dot \alpha_0 + \frac {\tau^2}4 ( \ddot \alpha_0 + \ddot \alpha_1 )\text. + \intertext{We can also write \eqref{eq:2} as} + \nonumber \ddot \alpha_1 + \ddot \alpha_0 + &= \frac 4{\tau^2} ( \alpha_1 - \alpha_0 - \tau \dot \alpha_0) + \intertext{so that it yields} + \label{eq:3} \dot \alpha_1 + &= \dot \alpha_0 + \frac 2\tau ( \alpha_1 - \alpha_0 - \tau \dot \alpha_0) = \frac 2\tau ( \alpha_1 - \alpha_0) - \dot \alpha_0 +\end{align} +in conjunction with \eqref{eq:1}. The problem +\begin{align*} + -\dot \alpha_1 \in \partial \psi(\alpha_1) +\end{align*} +then becomes +\begin{align*} + \dot \alpha_0 -\frac 2\tau ( \alpha_1 - \alpha_0) + &\in \partial \psi(\alpha_1)\\ + \psi(\beta) - \psi(\alpha_1) + &\ge (\dot \alpha_0 -\frac 2\tau ( \alpha_1 - \alpha_0), \beta - \alpha_1) + \quad \forall \beta\\ + \frac 2\tau ( \alpha_1, \beta - \alpha_1) + \psi(\beta) - \psi(\alpha_1) + &\ge (\dot \alpha_0 + \frac 2\tau \alpha_0, \beta - \alpha_1) + \quad \forall \beta +\end{align*} +After which $\dot \alpha_1$ can be computed according to \eqref{eq:3}. +\end{document}