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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>It is a good question as they say that earthquakes don’t kill people – buildings do. North American construction is built on 2x practice and we feel good because we are told that 2x buildings survive earthquakes because they have inherent elasticity. Unfortunately that presumption is so rampant that it affects code, common sense and reality and we impose the supposed elasticity of wood construction on layouts and floorplans that can’t support it. I see subdivisions with buildings that have poor building shape and then are so perforated with unsupported openings (windows, grand entrances, huge garage openings, etc) that they generally start to fail (lateral shifts, popped windows, etc.) even without an earthquake – and in an earthquake the ground floor is so soft the 2<sup>nd</sup> floors just collapse on it. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The issue is not so much how well they were built (as best practice in the assembly details) as that they are designed for failure. Building plans are not typically subject to engineering review and if they are as a ‘stock’ plan – are often significantly modified and compromised without any one really paying attention (other than proper header size or joist sizing). <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>When we talk about flexibility or stiffness we should really be talking about ductility and brittleness – as there is a range of ductility in all materials and how we design and join things together depends on that. A 2x building is really a combination of stiff and flexible elements. A pencil is flexible but becomes brittle and breaks when its ductility is exceeded. A shear wall is a good example of a stiff element in a building. A knee wall should be built as a shear wall, etc.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I wouldn’t say that simply bolting a woodframed building to a stiff foundation is state of the art for earthquake design but it is really all we have outside of complex dampening - so we might as well make that connection work well – but realistically it is the rest of the building from the roof down that needs to be equally well connected and also the foundation needs to have a good ground connection. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>As for the building foundation connection. We have concrete (stiff and strong but brittle) – we have steel bolts in the concrete (stiff but ductile – meaning it can bend and move before breaking) and we have the wood plate (ductile but can become brittle in compression or shear). Where is the failure going to occur? Typically even if the concrete cracks there is sufficient area to resist pullout or more commonly shear, especially if the bolts are deep enough. A 5/8 steel bolt has a lot of ductility for bending before breakage. A 2x wood plate is likely to become compressed and brittle against the washer area and fracture before a bolt will break or pull out of the concrete or the washer itself will fail in combination by bending. So a proper holdown connection to a foundation is really dependent upon the surface area of the washer(s). The use of a large square washer (not common) is probably more useful than doubling the number of connections. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>So the state of the art for foundation connections is actually making the common connection actually work. I use shearwalls and actual holdowns (hud) type and often use bolt connections that extend to top plates. I also employ an engineer to ensure that a design will work. I think employing engineers is the most progressive thing we can do to both use materials effectively and be conserving – as well as provide us with documented buildings which improve the knowledgebase as well as experience base for trades to base best practice on. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> greenbuilding-bounces@lists.bioenergylists.org [mailto:greenbuilding-bounces@lists.bioenergylists.org] <b>On Behalf Of </b>Alan Abrams<br><b>Sent:</b> June-05-11 10:33 AM<br><b>To:</b> Green Building<br><b>Subject:</b> Re: [Greenbuilding] rigid or flexible? are there any lessons from the Japan earthquake for fastening residential structures to their foundations?<o:p></o:p></span></p></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal style='margin-bottom:12.0pt'>Yoshihiro Takishita describes how the massive, timberframed "gassho zukuri" houses of Japan withstood tremors and storms--in which "the roof may become deformed or shift slightly, but...It resettles naturally, since the tenons are forced back into their mortises by the weight of the roof itself."* Major beams were often selected from twisted and crooked trunks, to take advantage of natural curves that were employed to enhance stability. This observation, however, hardly seems applicable to stud and joist construction.<br><br>Nevertheless, Hugh Newell Jacobsen, an architect with a long and carefully considered career in residential design, commented on how many vintage homes in South Carolina withstood Hurricane Hugo, while new ones "literally exploded." <br><br>"That is primarily because corners and rafters are just butt nailed, with little to hold them except good intentions. There's no diagonal, no strapping, nothing to firmly hold. And even with the technical design of plywood skin to reduce torque and rack, <u>you can't wrap corners with it.</u>"** [emphasis added]<br><br>By the same token, I recall photos of Galveston following the recent devastating hurricane--showing near complete destruction of block after block of residential neighborhoods, punctuated by the occasional surviving house--which uniformly looked like construction subsequent to adoption of wind resistant building codes. This tends to validate Jacobsen, in that connections between roof, floor, and wall assemblies had been taken into consideration, resolving the essential flaw he identified.<br><br>All this to say that there is no place for an intermediate position--that if we are building plywood skinned platform framed buildings--that we need to follow all the way through with best practices or engineering for our connections. <br><br>AA<br> <br>*Japanese Country Style: Putting New Life Into Old Houses/Kodansha<br>**The Wood Book 1990/Hatton Brown<br><br><br clear=all><b><span style='color:#006600'>Alan Abrams<br>Abrams Design Build LLC</span></b><span style='color:#006600'><br><i>A sustainable approach to beautiful space</i><br></span><span style='font-size:10.0pt;color:#006600'><br>6411 Orchard Avenue Suite 102<br>Takoma Park, MD 20912<br>office 301-270-NET- ZERO (301-270-6380) <br>fax 301-270-1466 <br>cell 202-437-8583<br><a href="mailto:alan@abramsdesignbuild.com" target="_blank"><span style='color:#3333FF'>alan@abramsdesignbuild.com</span></a></span><span style='font-size:10.0pt;color:#3333FF'><br></span><span style='font-size:10.0pt;color:#006600'><a href="http://www.abramsdesignbuild.com/" target="_blank"><span style='color:#3333FF'>www.abramsdesignbuild.com</span></a></span><br><br><br><o:p></o:p></p><div><p class=MsoNormal>On Sun, Jun 5, 2011 at 12:31 PM, Kat <<a href="mailto:molasses@q.com">molasses@q.com</a>> wrote:<o:p></o:p></p><div><p class=MsoNormal>I'd stick to the code. It was revised/became more stringent after the Kobe earthquake and will probably change again in a few years based on analysis of the most recent earthquake.<br><br>I've heard that ancient Chinese structures survived earthquakes because they were built without fasteners of any kind - my (non-engineer) understanding of that is the jiggling distributed itself throughout the structure at the joints, which were sort of lincoln-logged together. I think the key there is NO fasteners, though. None. I'm certain that if you build a house the way we do now (all full of nails) and neglect to attach it to the foundation and we get a big earthquake you'll end up with a house that slides off the foundation.<br><br>-Kat<o:p></o:p></p></div></div><p class=MsoNormal><o:p> </o:p></p></div></body></html>