We needed a cylinder going horizontal for cyclic loading for one of the test projects for testing asphalt pavement. They determined a diameter that they wanted to use. We had some structural tubing laying around the lab that fit the loading criteria that they wanted. They were worried about deflection of the cylinder. I drilled and tapped a hole in the center horizontally. Then I made an adapter using 2 inch rod and drilled and tapped both ends with a lathe. Then a set screw was placed on one end of the rod and screwed into the structural tubing. Concrete was poured in to limit deflection along the horizontal axis.
This was used in K-TRAN: KU-08-3 ▪ FINAL REPORT ▪ January 2013: Tolerable Strains for Hot Mix Asphalt Overlays over Concrete Pavements