Shouldn't you try Tensar first? The phone might be easier than the internet but I'm sure that they have e-mail on their web site

I remember using a 1-inch diameter Schedule 80 PVC Pipe. I believe this is what Tensar recommended, but this should be verified with Tensar. In general however, determine the max load in grid per amount of bar length equal to grid longitudinal strand spacing and analyze as a continuous beam with a series of point loads or more conservatively as a simple beam.Good luck.

It really depends on what you are asking the geogrid to do!  What kind of application is this?  Is it one where geogrid panels really do need to be spliced end to end such as in a landfill application, or is it one where the bodkin was specified mainly to showcase the "high junction strength" of Tensar geogrids (most other applications) which isn't really all that much of an asset when you take potential stress cracking at the junctions into consideration.  

Versaengine had a good suggestion, just don't forget shear; remember to consider creep, etc. on the bodkin material as well.

D. Bruce Nothdurft, MSCE, PE, PG, M.ASCE, etc, etc,...
Principal Engineer/Geologist
Atlantic Geoscience & Engineering
Charlotte, NC