Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: Log Strucutres - IS-LOG document

[Subject Prev][Subject Next][Thread Prev][Thread Next]
There is a good reason for the standard - try to get a building permit for a type of structure that is not mentioned in the building code because you have to respond to the same comments over and over again.  It can be a royal pain in the butt.
 
Also what do you use for design bending stress, compressive stress and modulus of elasticity for your logs.  Try to get a building permit in a place that does an actual structural plan review with assuming these values.  Even if the code says you don't need to design some log homes for lateral forces if the wall grids are laid out a certain way - you need to design log beams, columns and wall headers.
 


From: Jordan Truesdell, PE [mailto:seaint1(--nospam--at)truesdellengineering.com]
Sent: Wednesday, June 28, 2006 8:20 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Log Strucutres - IS-LOG document

I hate to belabor this, but why is a standard necessary for log structures that tells us (in five pages instead of a sentence) that we should design it properly?  I'm not surprised that certain type of log structures would perform well under seismic loading, especially if interlocking joinery and full logs were involved. Since most of the US falls in design category C or lower, it's not surprising that that would be the limit for prescriptive design (you know, the one that's not in the standard).

I was sort of hoping, by making faces at the document and process, to needle someone "in the know" who lurks in this list to stand up and defend the standard. Someone to tell me I am utterly misguided on this point, and that there is a perfectly good prescriptive standard that shows the "framing" details and connections for all the common log-building styles that the code will adopt or adapt with mandatory language. Either that person doesn't exist, or he/she does, and knows the document is a useless waste of time intended to show inclusion by the ICC without actually having to provide any useful result for local inspectors or those actually building log homes.

Oh well, guess this thread can die now.
Jordan
(PS: just to be clear, my rants aren't aimed at you, Scott, and I appreciate your replies.)

Haan, Scott M POA wrote:
Log structures are like any other building, you have to design each part in a chain of connections to get the loads where they are supposed to go.  The way I've seen the interconnection between logs done is with single shear between each log with threaded rod connections using yield limit equations and overturning being checked with full height threaded rods in tension.  The walls have to be held at the top and bottom by floors, foundation, roof or girts or from side to side with side walls - and they seem to be working.  I know log home kit manufacturer who has a bunch of structures that made it through the 7.9 Mentasta earthquake without an issue.
 
I don't have the draft standard at work but I thought I remember there are prescriptive limits on the layout but it does not get into any detail on connections etc...  Also I thought I remember there being limits on where engineering is not required like Seismic Design Category C or lower.  If it has to be designed in seismic design category D then it would be useful  to have a response modification factor so you can determine the seismic forces.


******* ****** ******* ******** ******* ******* ******* *** * Read list FAQ at: http://www.seaint.org/list_FAQ.asp * * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to: * * http://www.seaint.org/sealist1.asp * * Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ********