Portal Frame

A simple exploration of a portal frame utilising the Grasshopper plugin Karamba. Exploring the behaviour and parameters of a basic model and utilising the optimisation tool Galapagos within Grasshopper.

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Comment by Joshua Seskis on October 24, 2011 at 6:37pm: Yeah there is a component called modify beam in Karamba which lets you set wether or not the member will experience moments. Whenever I have been using Karamba it is always set to true so truss modelling has been tricky to get to work right.

The connections behave like moment connections in that they maintain their geometry and transfer the moment to the strut members and I verified the model in Space Gass so I am pretty confident this is representative.

Comment by Steve Lewis on October 24, 2011 at 5:30pm: Cool, but portal frames are usually governed by flexural capacity and I wasnt aware karamba yet had the ability to model flexural members and it was currently limited to only axial members. However your deflected shape does appear to be showing a flexural type member......

Comment by Joshua Seskis on October 24, 2011 at 6:07am: Hi Mateusz, Thanks for commenting.

Typically the height and width of a portal frame will be fixed in most engineering problems. If I were to design a factory I will be constrained by the physical volume that it can occupy and other constraints such as head height availability, maximum unsupported span etc. etc.

I used Galapagos not to find a definite solution but to optimise a better solution. I have adopted a fitness function focused on how much the structure deflects and how much it weighs where I can review the genomes to find a solution that is preferred. Also this was more of an exercise in exploring the value of optimisation than something that is designed to converge on a solution. It was made as part of my final year exploration into the usefulness of Grasshopper in Structural Analysis.

If you want to play with the file you can find it here.

Comment by Mateusz Zwierzycki on October 24, 2011 at 5:56am: If you let galapagos decide which section profile would be best, it won't manage to do it. IMO would be better to manualy select profile, and then modify with galapagos it's x an y dimensions.