The German "Kehlbalkendach", literally Collar Beam Roof, is a roof system that relies on Collar ties to somehow strengthen or stiffen the roof structure. The simple Kehlbalkendach consist just of rafter pair joined with a collar somewhere between the mid point and top third of the rafters. The idea here is not that the ties will resist thrust at the plate, but rather create another triangle that stiffens the roof against live loads (triangles are immutable) essentially allowing them to get away with using smaller rafters.
The spans handled by this simple roof structure are surprising.
Variations of the Kehlbalkendach are perhaps the most prominent roof structure in German speaking countries. For larger spans purlins are used to support the collars.
a collar tie works well against live loading. This is because under wind loads, the tie transfers load to the other rafter in the pair, and so 2 pieces of wood can be used to share a single load in that way.