Handle Your Constraints with Care

Manipulating the nodal equilibrium equations is necessary to enforce constraints between degrees of freedom (DOFs) at two or more nodes in a structural model. These multi-point constraints arise from assumptions of axial and flexural rigidity of frame elements, e.g., rigid diaphragms, and also between two nodes at the same location where some of the DOFs … Continue reading Handle Your Constraints with Care

Be Careful with Modal Damping

Modal damping is kind of the it-spell in the dark art that is modeling viscous damping in structures. Although modal damping is pretty straightforward, you should be aware of an important aspect of its implementation in OpenSees. The issue is that OpenSees assembles the dynamic tangent in to the matrix storage scheme you choose via … Continue reading Be Careful with Modal Damping