This clever and fairly mechanized scheme is an example of industrialized keyed beams. They are pre-cambered, and make highly efficient use of smaller and square timbers to assemble deeper beams. We would love to build a couple of these to fill your long span timber beam challenges. If you actually arrived at this page through a search for Derevygian Beams? You and I really ought to talk (my cell number is 603-381-3810); and you ought to understand that you may well be a very troubled individual. The illustration is from one of my Very Favorite timber tomes - Wooden Structures - a 1960's work translated from Russian and long out of print.