Eigenvalue analysis is often a necessary step before starting a dynamic response history analysis in OpenSees. You may want natural frequencies in order to compute Rayleigh damping coefficients, to apply modal damping, to compute modal properties, or to perform a response spectrum or modal superposition analysis. However, eigenvalue analysis can fail, indicating a problem with … Continue reading Why Your Eigenvalue Analysis Failed
Tag: Mass
Inerters Everywhere
Vibration control devices based on relative acceleration, or inerters, are all the rage these days. So it's no surprise that inerter models are making their way into OpenSees. As far as I know, two inerter elements are available: InertiaTruss and Inerter. There has also been a third attempt at inerters, but via a material model. … Continue reading Inerters Everywhere
Mass and Weight
Many structural analysis software programs will automatically define mass based on the input gravity loads. OpenSees is not one of those programs. You have to define mass and weight separately. Fortunately, using variables for units makes the mass and weight definitions easy. Plus, if using customary units, you won't have to waste time Googling the … Continue reading Mass and Weight
Portwood Digital 