tag:blogger.com,1999:blog-6261993076995357307.post3618040555038294436..comments2023-11-05T06:16:56.961-05:00Comments on the Carpentry Way: Shaken, not StirredAnonymoushttp://www.blogger.com/profile/14328401081765407624noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-6261993076995357307.post-47479417581640081082012-09-24T19:09:09.464-04:002012-09-24T19:09:09.464-04:00Jay,
great to hear from you. I think if you are ...Jay, <br /><br />great to hear from you. I think if you are going to propose non-Western structural systems to Western engineers, you are going to have to convince them with empirical data for starters, and there's virtually none of that in the English language. So, uphill is your path. You face the same problem as those who wish to be proponents for cob, light clay straw, hemp-crete, etc. - engineers are not going to sign off on it unless they can be confident about performance. With next-to-no data to go on, the only recourse is modelling and finite element analysis, building model walls and testing them with a simulator, etc. That costs money and time of course. If, as an engineer, your professional license was on the line, and a lawsuit could sink your business permanently, you would be prudent about where you placed your stamp. Trying to convince them with metaphors about Eastern martial arts are generally going to be a waste of time I'm afraid.<br /><br />The irony here is that engineers will not sign off on western timber-framed structures either, regardless of bracing, as they cannot be made adequately rigid enough. The pegs will always allow too much movement at the joints. For a barn or utility structure, a little building sway in the wind is not much of an issue, however for modern houses with their expensive triple-glazed sealed windows and carefully controlled air exchanges such wall movements cannot be allowed. The primary way in which the timber frame structure can exist in such an situation is as a temporary scaffold and then a largely decorative element, as seen in the usual timber-framed, SIP-wrapped structural system we have grown to know and, uh, love (ahem!).<br /><br />I don't quite agree with your conclusion about oblique bracing. Oblique bracing IS tunable for flex. Yes, short and thick braces - the typical knee brace - are rigid, and can act as fulcrums to lever nearby joints apart if subject to shearing loads. They are also notoriously weak at their connection points. A 'strut', by definition, is subject to compression alone (a 'tie' being designed to resist tension alone), and a strut is how a wooden brace functions in most timber frame designs. Wood is most suited to functioning in that manner in a structure, unless the connections are to rely upon metal and/or adhesives.<br /><br />If a more flexible bracing arrangement was desired, then the braces can be lengthened, slimmed, curved, etc. Again though, the idea of a flexible brace is not going to fly with structural engineers if a primary goal is to keep the building from moving under shear loads so as to preserve the integrity of doors and windows. I've always liked longer braces myself, such as you see in German traditional wall framing.<br /><br />I also like nuki, however it is most critical that the joins between nuki and posts be tight for good structural performance; that tightness in fit however makes assembly difficult. <br /><br />Japanese framing has employed diagonal bracing and trusses for the past 150 years to one extent or another, and the vast majority of Japanese timber frames done in the post-war period, residences and temples alike, make use of diagonal reinforcement. Most of that is concealed in the structure, in the walls and up in the roof, as are the metal reinforcements. There's no need to be completely avoidant of diagonal bracing in an Japanese/Chinese timber frame - a point of harmony can be achieved.<br /><br />So, if you want to bring these sorts of Asian framing systems, which have great virtues, into the 21st century Western context, then you are going to have to adapt them in ways which work within this context, including oversight by the structural engineering community. One way is enclosing the timber structure with SIPs, however I believe there are better solutions than that which give adequate rigidity and good thermal performance.<br /><br />~Chris<br />Anonymoushttps://www.blogger.com/profile/14328401081765407624noreply@blogger.comtag:blogger.com,1999:blog-6261993076995357307.post-71902062576681365842012-09-24T18:38:37.637-04:002012-09-24T18:38:37.637-04:00Dennis,
yes, the hikiya daiku has exactly the sam...Dennis,<br /><br />yes, the hikiya daiku has exactly the same problem as many doing traditional work - demand drying up.<br /><br />I think heavy roofs are fine so long as the structure is designed for them. Heavy roofs and 'sukiya', with its tendency towards overly-slender structural elements is, to my way of thinking, an odd and ill-suited combination. If you want the sukiya look, then keep the structure to one floor, and use a metal roof.<br /><br />Heavy tile roofs in Japan have posed problems for centuries due to their weight. On massive structures, the weight of the roof will deform structural members over time, especially hip rafters. One solution has been to redesign tiles to be lighter. Another has been to beef up the structure using a lot of metal, even metal columns with concrete filling, etc.<br /><br />In the end though, while you can design and brace a structure with a heavy tile roof to perform adequately in a high-frequency earthquake region, it makes far more sense to me to use a lighter roof and try and keep things to one floor. I really like copper-shingled roofs myself. Much lighter than the tile, and with comparable lifespan. There are other metals used for roofing as well of course, most cheaper than copper (terne, steel) and some more costly (titanium).<br /><br />~C<br /><br />Anonymoushttps://www.blogger.com/profile/14328401081765407624noreply@blogger.comtag:blogger.com,1999:blog-6261993076995357307.post-86912589487778972342012-09-24T02:57:47.540-04:002012-09-24T02:57:47.540-04:00Hi Chris,
Thanks for a wonderful post. It is rat...Hi Chris,<br /><br />Thanks for a wonderful post. It is rather serendipitous as well, as I have been having several conversations of late with engineers, architects, and G.C. about the true realities of Asian architecture. There is so much miss information and misinterpretation, that I am routinely dispelling myths of building methodologies East to West.<br /><br />Your fourth photo down is one I will be keeping for educational purposes. It clearly shows what I have been stating for decades about the simple reality of “horizontal” versus “oblique” bracing systems. Often I am confronted with the statement, “this design you are submitting has no proper bracing,” or “the building is not rigid enough to be safe.” This often comes from architects or engineers that are only indoctrinated into Western thinking modalities. I try to use the metaphor of Martial Arts, which seems to help them understand. Eastern combat styles are much more deflecting and flexible; while the Western fighting styles tend to be more ridged and braced, often with the back leg in and oblique position to the body.<br /><br />I have also noted through observation that oblique bracing, (which only works in compress unless it is designed as a “strut”) is truly too ridged, often acting as a fulcrum weakening a frame, and when it fails, it does so catastrophically. Unlike horizontal bracing, (see fourth photo,) which is flexible and forgiving, often allowing occupants time to respond to a seismic or metrological occurrences and further allocate the buildings repair. <br /><br />From a construction approach, the placement of Nuki 貫 beams (a pass through horizontal member for those not familiar with Japanese design,) facilitates design flexibility and ease of assembly. When assembling a timber frame, I would much rather deal with 貫 than all the different bracing assemblies within bent systems of Western frames.<br /><br />I could go one but would rather wait to see what others have to say. Thanks once again for your wonderful efforts on this blog.<br /><br />Regards,<br /><br />Jay<br />Jay C. White Cloudhttps://www.blogger.com/profile/16327164403578757417noreply@blogger.comtag:blogger.com,1999:blog-6261993076995357307.post-67952652784122747532012-09-23T22:58:03.379-04:002012-09-23T22:58:03.379-04:00I have a friend that is Hikiya Daiku, and he also...I have a friend that is Hikiya Daiku, and he also supplemented his skills to also be what is referred to as a "Tobi", or a person that specializes in doing work above ground level, sometimes well above ground level! I met this interesting man when removing tree tops. I believe that he must be the only Hikiya Daiku in the area, and there doesn't seem to be much demand for their work any longer, probably both in part due to the expense, and also the difficulty in finding such specialists, to the point that there work seems to have been largely forgotten.<br /><br />Living in earthquake central here, especially after the latest big one in Northern Japan, there seems to be more and more concern about living in houses with the traditional heavy tiled roofs. As mentioned in your post, cited as one cause for very negative earthquake consequences. Though they still can be seen everywhere, possibly now some movement away from them. Of course there is already the strong movement away from timber frame itself, though more often than not it is for dubious reasons. Chris, apart from ''officialdom'' what are your own thoughts on the heavy roofs? In a high frequency earthquake region, can timber frame houses be built to counter the possible negative consequences of the heavy roofs in the event of a big shaker coming along, as they certainly will do? I'm wondering what construction plan you would advise? During the Northern quake, i was far enough away to not experience damage, but standing outside of my shop at the time, I suddenly felt sick to my stomach. You do get a very odd combination of movements with the quakes.djyhttps://www.blogger.com/profile/08985330530360767281noreply@blogger.comtag:blogger.com,1999:blog-6261993076995357307.post-38651519185819514612012-09-23T22:38:12.266-04:002012-09-23T22:38:12.266-04:00Tom,
pleased to receive your comment. Besides the...Tom,<br /><br />pleased to receive your comment. Besides the issue of whether the building holds together or not, there is the matter of people being killed and crushed not by the structure, but by things inside the structure that come loose during the seismic event. Chandeliers, large bookcases, etc., can become deadly when thrown about rapidly. And if the building is ultra rigid, then the seismic shocks will be transmitted even more directly to occupants. It's interesting to observe in videos of other tests at E-Defense (not shown above) how the behavior of furnishings inside the houses can cause danger.<br /><br />And a lot of people think it is safest to stand under a doorway or similar, but if the building collapses, these locations are not actually so safe. Apparently it is better to position yourself next to an object which will provide some adjacent space if the ceiling comes crashing down. Better to be next to a car than under a car, that sort of thing.<br /><br />~CAnonymoushttps://www.blogger.com/profile/14328401081765407624noreply@blogger.comtag:blogger.com,1999:blog-6261993076995357307.post-65761073285811029592012-09-23T16:56:34.854-04:002012-09-23T16:56:34.854-04:00Chris
How odd to see those apartment buildings st...Chris<br /><br />How odd to see those apartment buildings still perfectly square, but so desperately out of plumb! There may be such a thing as too much diagonal reinforcement!<br /><br />Tomtomausmichigannoreply@blogger.com