In connection with simulation of the deformation of concrete beams with the computer code Autodyn-3D, we have made a couple of modifications of the material models in Autodyn by writing user subroutines in Fortran. In the crack softening model, which is used together with the RHT-model for concrete, we have introduced strain rate dependence and also introduced a bilinear damage evolution law. Furthermore, we have programmed a user implementation of the Johnson-Cook model for metals, which allows the user to select a reference strain rate different from 1 per second. This report describes the methods and serves as a user manual.