Daisy Chains and Gaffes

When analyzing rigid bodies with multi-point constraints, one potential problem with the Transformation constraint handler is the sequencing of primary and secondary, or retained and constrained, nodes across multiple constraints. Using OpenSees to solve Problem 9.39 from J.C. Smith’s Structural Analysis is a perfect opportunity to show how defining constraints in series, i.e., daisy chaining the constraints, can knock … Continue reading Daisy Chains and Gaffes →

Positive OpenSees Contact

Flipping through J.C. Smith’s Structural Analysis textbook, I’m confident OpenSees can handle every problem. Same goes for any other textbook on structural analysis. However, I totally paused on Problem 9.34 as it hinted at contact nonlinearity. The cantilever and the simple span have flexural stiffness EI=5120 kip-ft2, something in the ballpark of W6x12 steel members, but fudged to … Continue reading Positive OpenSees Contact →

The Three-Act Verification

Although I would like to write more posts on OpenSees verification examples, I believe a post still needs context, or a story, to not become a dull trope. “I found this example, here’s the OpenSees model and some assertions, and look, the assertions pass” is not a compelling three-act structure of setup, confrontation (or conflict), and resolution. … Continue reading The Three-Act Verification →