Free field Analysis using OpenSees

These TCL scripts present examples on the use of OpenSees to perform 1D nonlinear free field analysis. Total and effective stresses are considered. Two different constitutive models are used; i.e., Pressure Independent Multi Yield (PIMY) and Pressure Dependent Multi Yield (PDMY). The earthquake excitation is applied at the bottom of each model. To capture the compliance of the rock the earthquake excitation is input as a surface traction and the rock is represented as a dashpot. A 2% Rayleigh damping at 0.2 and 20 Hz is used to capture damping at small elastic strains. The Stabilized Single Point quad elements SSPQuad and SSPQuadUP are used to discretize the domain. The element discretization is done satisfying the criteria of 10 elements per wave length. Nodes at each elevation are constrained to move equal to represent the 1D condition. Each simulation has a simulation report describing the components of its constitutive model (simulation model, inputs and outputs, and analysis).