Week Seven // Grasshopper Trusses

This week I worked extensively in Grasshopper for Rhino to create a basic truss and then edit it to create different variations. I did all of the variations, with some nice results.

truss structure

To create the truss, we used different Grasshopper functions to create lines, and then subdivided them to create the cross braces. This involved a series of functions which can be followed in the Grasshopper web.

From there I created variations on the truss using different functions. The first one was the Catenary truss, with a curved bottom chord. To do so I used the Catenary function to change the geometry of the bottom chord and associate it with the top chord so that the system of cross bracing worked. I had some issues with this, as some of my strings got mixed up. By swapping the culling and item functions, I was able to sort some of the issues out. I tried to add a reverse function to fix it at first, but as you can see in the right photo, it didn’t help. I ended up having to swap how the functions attached to the Catenary function. To be perfectly honest, I’m not sure why it fixed it, but it did!

fuck up 1fuck up 2

Success!

success!

Next we did a trichordial structure, which was a breeze. I ended up not actually watching all of the tutorial and instead just followed the map, with good results. The main difference between this one and the basic truss was putting the top chord through a Move function with a multiplication attached to it. We also had to account for cross bars, which are seen in the picture below.

two top chords

Last but not least, the curved truss. This was the most complicated, but I had a relatively easy time with it because it involved a lot of pairing down. The main change was instead of a line I created with Grasshopper, I used a curve drawn in Rhino and then associated with a Grasshopper function. Using an Offset function to create the bottom chord, the cross bracing remained the same and I was then able to get rid of some of the extraneous stuff associated with the creating the bottom straight chord and it’s trim command. Here are my final results:

curved truss - slim down!

Yay! Overall I found this to be a good exercise, and I feel as though I could do a lot just following a Grasshopper map, with a  key of what some of the functions mean. I find it interesting how touchy the system can be, and am interested in learning more about why I may have gotten stuff mixed up in the first place.

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