OpenSees offers three types of transformations between the basic system and global system for frame (beam-column) elements: Linear - small displacement assumptions for compatibility and equilibrium PDelta - small displacement assumption for compatibility with the $latex P-\Delta$ term included in equilibrium Corotational - large displacement assumption for compatibility and equilibrium Use the geomTransf command to … Continue reading Geometric Transformation
Tag: Corotational
Cable Analysis
Analyzing cables subject to transverse loads is straightforward in OpenSees. Use a mesh of corotational truss elements with elastic uniaxial material. Of course, you can use any uniaxial material you like. The only trick is you have to scramble the nodes up a little bit--if you try to analyze a perfectly straight cable, you'll get … Continue reading Cable Analysis
Stability Challenge Results
I posted a modeling challenge for the famous, perhaps now infamous, three member truss example of OpenSees. The members are very slender, so I wanted to see how well we can account for geometric nonlinearity. First, the results. There were five entries--three reported a load factor of about 0.47 and two gave a load factor … Continue reading Stability Challenge Results
Meshing for Column Loads
For material nonlinear analysis of frame models, you can improve the computed response by using more displacement-based elements or more integration points in a force-based element. The material nonlinearity occurs inside the basic system, also known as the natural system or the kernel. To capture geometric nonlinearity due to large displacements, you have to go … Continue reading Meshing for Column Loads
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