Peter,
The traditional Japanese timberframe is essentially "unbraced" in the Western sense of the word. The entire structure of a Japanese house is designed to roll with seismic activity resulting in a minimal amount of damage. This was achieved through time tested stategies such as "post on stone" foundations, the use of flexible softwood timbers, elaborate and very tight joinery, and numerous smaller constituent components, to name a few. Also keep in mind that the infill "wattle and daub" wall system is what truly keeps things rigid. I've been told that it acts like a shock absorber of sorts. Within the mud wall, between posts and beams, exists an armature "wattle" of both verticle and horizonal studs that are mortised with wedged and dovetailed tennons. Attached to this is an intricate grid of succesivley smaller bands, lashed together and mortised into the frame. In areas with really heavy snowfall a component like a girt called a "dosashi" is added, sometimes in many tiers and usually accompanied by a dense network of layered interlocking log beams running both transverse and longitudinaly. All this said, I should point out that because the traditional design approaches can not be qauntified or explained in the context of modern engineering, todays' "traditional" Japanese house sits on a continuous foundation, contains a plethora of hidden supplamental metal fastners, and uses shear walls and or hidden diaganol braces. Recently a carpenter friend from Japan lamented on how we were building structures that could last for many centuries had we not placed them on concrete foundations. The prevailing thought among several Japanese carpenters I've spoken with is that concrete exposed to oxygen starts to deteriorate after sixty or so years. Food for thought
