OpenSees Is Simple

OpenSees, and nonlinear structural analysis in general, is a simple endeavor. It's not complicated. It does not need to be complex. Although this clip from Bull Durham, the best baseball movie of all time, refers to throwing, hitting, and catching the ball, the simplicity translates to nonlinear structural analysis. You build the model. You … Continue reading OpenSees Is Simple

Stress Resultant Verification

Verifying material nonlinear frame element formulations is pretty difficult. There are only a handful of analytical solutions that do not rely on bilinear uniaxial constitutive response. You're much better off verifying geometric nonlinearity. However, an example based on a relatively straightforward biaxial stress resultant plasticity model has intrigued me over the years. The example, described … Continue reading Stress Resultant Verification

Plastic Rotation

Plastic rotations are a common damage measure for frame members and frequently define limit states of structural performance under seismic loading. The calculation of plastic rotations for frame elements in OpenSees is based on a decomposition of deformations in to elastic and plastic components. The elastic deformations are obtained by elastic unloading of the basic … Continue reading Plastic Rotation