Convergence of a solution algorithm typically means your model satisfies equilibrium and compatibility for the current applied loads and any nonlinear response. But there are pathological cases where the algorithm converges while the model remains in a state that violates equilibrium or compatibility. A simple case (brought to my attention by Chen Fei) involves a … Continue reading Pathological Convergence
Tag: Distributed load
Partial-Span Uniform Loads
Although no one is going to use OpenSees to compute tributary loads for one-way floor systems, it’s still satisfying to analyze the resulting beam models. A common example is a beam that frames around one side of a floor opening. On the side of the beam with no opening, tributary area calculations produce a uniform … Continue reading Partial-Span Uniform Loads
Rotated Local Axes
OpenSeesing through the SeismoStruct Verification Report (v2025), I expected smooth sailing across Chapter 2, Comparison with Independent Hand-Calcs, where “hand-calcs” means SAP2000 analysis results. But light storm clouds set in on Example 2, Rotated Local Axes. The model is a W12x106 cantilever rotated 30 degrees about its longitudinal axis. A uniform distributed load (roughly the member self-weight) is … Continue reading Rotated Local Axes
Distributed Moments
I have often posited that we can use OpenSees to solve every reasonable problem from any textbook on structural analysis, dynamics, or mechanics. I even put together a few posts, e.g., here and here, on how OpenSees can solve rigid body dynamics problems, the ones that torment every civil engineering sophomore. But a seemingly easy structural analysis problem that OpenSees … Continue reading Distributed Moments