Here's a question I have about the traditional Japanese Style of framing, and weather it's adaptable to modern construction.

First of all - for those that aren't familiar with it, the traditional Japanese technique seems to use a 'double girt' in place of the European 'knee brace' technique.

An example of what this might look like is here: http://www.f-lohmueller.de/pov/im_a71.htm

Please note that this is an ARTISTIC impression, and not an ARCHITECTUAL design - and is meant as an illustration only (and it's not my creation, either).

I'm wondering if any of you 'structural engineers' out there can comment on the structural stability impact of such a design?

In my current 'experimental design', I'm planning on swapping this 'span design', but boosting the post height to 11 feet (with a 2 foot, beam inclusive gap between the 'girts'), preseving an 8' 'head height' under the lower girt.

It is my understanding that the Japanese frame has more 'sway' in it, and that this is a deliberate design feature (due to Japan's tendancy to shake ), but this may not be desirable with modern building codes.

I'm also wondering what, if any, impact the double girt design would have on the number of "board feet" int the frame? While the 'brace girt' would have (roughly) the same number of board feet as the cap beam (maybe less, if it's thinner), BUT we are also 'freeing up' the board feet in the knee brace. Since, according to Ted Benson's books, the knee braces average 1/2 the length of the cap beam, this should be ROUGHLY equal.

Can anyone comment on this design? Has anyone designed/built such a frame style?

Please feel free to comment in forum, or email me.

- Charles Krause

Charles,
I have to agree with you that the type of frame you describe will have a lot of sway. I wonder if the infill material in a trditional Japanese frame is what provides the lateral stability. Other than full scale testing of actual joints, I do not know of any calculations that will yield meaning full numbers on the rigidity and strength of the frame you describe. In the 1995 earthquake that hit the city of Kobe, many of the deaths were the result of the collapse of traditionally built residences with heavy tile roofs. Many new western style homes (stick-framed w/ plywood) in the region suffered little or no damage. Somewhere in the evolution of traditional japanese housing there was an ommission in seismic resistance. Perhaps the events were few and far between.
I would recommend braces or plwood/SIPS to resist racking. When all else fails, there is always steel.