Dynamic response sensitivity analysis by the direct differentiation method (DDM) works pretty well in OpenSees, minus a couple limitations. First, not all element and material models implement the methods necessary to compute response sensitivity with respect to model parameters. And second, even fewer element and material models implement the methods necessary to compute the sensitivity … Continue reading Damping Is a Sensitive Subject
Tag: Direct differentiation
The Sensitivity Is in the Details
Although the Hardening and Steel01 uniaxial materials can be calibrated to give the same response, the DDM response sensitivity with respect to the same parameter can be different due to how the material models are implemented. Consider the truss model from a previous post on minimal DDM examples. The stress-strain response shows the elastoplastic tangent … Continue reading The Sensitivity Is in the Details
Rectangular Hollow Structural Sections
A hollow structural section (HSS) is manufactured from steel and is either rectangular, square, or circular. This post will address rectangular HSS, inclusive of square HSS. Round HSS is a little easier to define and will be the subject of another post. There are a couple options in OpenSees for defining material nonlinear rectangular HSS … Continue reading Rectangular Hollow Structural Sections
Section Integration
If we can use procedures in Tcl or Python to lay out fiber patches and layers for standard section types, e.g., doubly-reinforced RC sections and wide flange steel sections, then why do we need the SectionIntegration class? You cannot say that it is not useful to have commands that define fibers in terms of basic … Continue reading Section Integration
You Never Forget
My first journal article was not without some minor drama. Another group of researchers was also in pursuit of the direct differentiation method (DDM) formulation for force-based frame elements. Mutually aware of the parallel efforts, one of those researchers went so far as to call me on a public landline in Davis Hall with a … Continue reading You Never Forget
Minimal DDM Examples
Although it was the subject of my first journal article and has been a welcome diversion since, other than one post, the direct differentiation method (DDM) has not seen much action on the blog. With the DDM, you can compute accurate and efficient derivatives of the structural response with respect to various model and load … Continue reading Minimal DDM Examples
Sensitivity Training
Sensitivity of structural response with respect to modeling parameters provides search directions for gradient-based algorithms in reliability analysis, optimization, and system identification. In addition to these applications, stand-alone sensitivity analysis gives useful information about the effect of parameters on the structural response. There are three methods to compute response sensitivity for nonlinear, path-dependent analysis of … Continue reading Sensitivity Training
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