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Re: Strap hold down detailing
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- Subject: Re: Strap hold down detailing
- From: John Turner <jdkjt(--nospam--at)pacbell.net>
- Date: Sat, 01 Jan 2005 20:14:36 -0800
could be, I was doing the EE work, and the structural engineer says the ends of the garage had these things for the shear wall. I was concerned as need a 14" elec. box to go in there. John Turner, EE Ted Ryan wrote: > Are you referring to Hardy Frames? Never heard of Harvey Walls... > > Ted Ryan > > ----- Original Message ----- > From: "John Turner" <jdkjt(--nospam--at)pacbell.net> > To: <seaint(--nospam--at)seaint.org> > Sent: Saturday, January 01, 2005 5:56 AM > Subject: Re: Strap hold down detailing > > > When you say wall frames, have you any info on "Harvey Walls"? They are > > proposed on the 2'5" end walls for townhouses at the double garage doors! > > > > John Turner, PE > > > > "Bill Allen, S.E." wrote: > > > > > Chuck - > > > > > > FWIW, my question was general in nature and was relative to all coil > straps > > > up to and including CMST12s. > > > > > > Regarding the 2nd question, I try to provide a hold down for all > calculated > > > uplift forces >0. Sometimes I go to wall frames to eliminate uplift > forces. > > > > > > Regards, > > > > > > T. William (Bill) Allen, S.E. (CA #2607) > > > ALLEN DESIGNS > > > Consulting Structural Engineers > > > http://www.AllenDesigns.com > > > V (949) 248-8588 . F (949) 209-2509 > > > > > > -----Original Message----- > > > From: chuck utzman [mailto:chuckuc(--nospam--at)pacbell.net] > > > Sent: Tuesday, December 28, 2004 11:41 PM > > > To: seaint(--nospam--at)seaint.org > > > Subject: Re: Strap hold down detailing > > > > > > Bill's post implied a "lightly" loaded shearwall, say 1/2" CDX w/ 10d@6" > > > loaded at about 100 to maybe 140 plf. On an 8' post that's 800 to 1100 > > > #. These days I'm using more & more engineered joists (to eliminate the > > > shrinkage problem) & on an upper floor CS16 x 4' seem about right with > > > nails at every other hole. Since the shear is in the plywood, the strap > > > nails suck it out before it gets into the post. The nailing above the > > > strap are the only ones lifting the post (which is why Simpson's > > > Strongwall tiedowns are set kind of high on their corner posts IIRC). > > > > > > That does bring up another question. Where are you guys setting your > > > cut-off value for tiedowns? After talking to Ed Diekmann & some other > > > S.E.'s with a lot of wood-frame design experience, I decided on 800#. I > > > just had a big dispute with a young, outside plan checker who thought > > > the number should be 0. (My calculated net uplift was 300# & this > > > particular location was very difficult to access, so I said no.) > > > > > > I don't see the straps as any more susceptible to shrinkage than PHD's. > > > Around here we're framing with green D.F. which dries very slowly (until > > > the the building is closed-in & the occupants turn on the heat). With > > > green, sawn 2x12 joists the only way I can see to address shrinkage is > > > with a tensioning coupler like Simpson's TUD. At $50 each that seems a > > > little pricey but YMMV > > > > > > Chuck Utzman,P.E. > > > > > > Ed Tornberg wrote: > > > > > > > This is a subjective response - sorry, no numbers. > > > > > > > > "How much is enough?" is fairly straightforward with respect to > > > > gravity loads. > > > > > > > > "How much is enough?" is complex, sometimes vague, esoteric, and > > > > sometimes mind-numbing with respect to lateral design. > > > > > > > > For the majority of wood-frame buildings, because of the many > > > > unaccounted and redundant, lateral force resisting mechanisms, as well > > > > as the multiple factors of safety, I'm more and more inclined to not > > > > subject the inner workings of holdown detailing to thesis-level > > > > scrutiny. Especially for wind-governed elements. > > > > > > > > But for a structure that doesn't have the redundancies, say a large > > > > commerical shell building, or a "high liability risk" structure, like > > > > multilevel multifamily, I'd "do more". > > > > > > > > I agree with the other posts approving of straps over sheathing, > > > > especially if it's a lightly loaded shearwall. > > > > > > > > Ed Tornberg > > > > > > > > Tornberg Consulting, LLC > > > > > > > > 503-551-4165 > > > > > > > > -----Original Message----- > > > > *From:* Bill Allen, S.E. [mailto:T.W.Allen(--nospam--at)cox.net] > > > > *Sent:* Thursday, December 23, 2004 10:34 AM > > > > *To:* seaint(--nospam--at)seaint.org > > > > *Subject:* Strap hold down detailing > > > > > > > > Now that I'm just relaxing (just waiting for USC to show OU exactly > > > > what an "average" offense is like), I thought I would throw out a > > > > question to find out how others do things. > > > > > > > > Currently, I detail straps to be installed over the plywood (oops, > > > > Wood Structural Panel) sheathing. Otherwise, it would be difficult to > > > > install the SW edge nailing. Simpson has load tested this condition > > > > and they believe it is O.K. to install it like this. I know there may > > > > be some who don't like this installation, but for the purposes of this > > > > topic, let's assume it's O.K. > > > > > > > > For CS straps, which are 1-1/4" wide, a single 2X stud may be adequate > > > > for anchorage. Similarly, for CMST straps which are 3" wide, double 2X > > > > studs would be a mimumum and may be adequate for anchorage (both for > > > > tension and compression). Let's assume that they are for the purposes > > > > of this topic. With this scenario, how do you address the stud which > > > > has the shear wall edge nailing as well as the strap nails? I've heard > > > > where some folks omit the edge nailing at the strap. For short straps, > > > > this doesn't seem to be much of a problem. A CS16 has an end length of > > > > 11" with 10d nails and 14" with 8d nails. However, with a CMST12, the > > > > strap is more than half the height of the shear wall. I'm having > > > > trouble reconciling forces with a FBD (load transfers from the SW into > > > > the end post back through the SW into the strap). > > > > > > > > Of course, one could make the end post wider to allow the edge nailing > > > > to run past the strap. For a CS, that would require a double stud. For > > > > a CMST, that would require 3-2Xs. I don't have so much of a problem > > > > with the larger strap (of course, all of the multiple studs would have > > > > to be face nailed to transfer the load from the edge nailing to the > > > > hold down strap), but it seems to me that this **might** be "overkill" > > > > for a lightly loaded CS strap. After all, CS20, CS18 and CS16 straps > > > > have capacities of 1,030 lbs, 1,370 lbs and 1,705 lbs respectively. > > > > > > > > Opinions and comments are welcome. > > > > > > > > Regards, > > > > > > > > T. William (Bill) Allen, S.E. (CA #2607) > > > > > > > > *_ALLEN DESIGNS_* > > > > > > > > Consulting Structural Engineers > > > > > > > > http://www.AllenDesigns.com <http://www.allendesigns.com/> > > > > > > > > V (949) 248-8588 > > > > > > > > > > > > > > > > . > > > > > > > > > > > > > > > > F (949) 209-2509 > > > > > > > > > > ******* ****** ******* ******** ******* ******* ******* *** > > > * 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 > > > ******* ****** ****** ****** ******* ****** ****** ******** > > > > > > ******* ****** ******* ******** ******* ******* ******* *** > > > * 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. 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- RE: Strap hold down detailing
- From: Bill Allen, S.E.
- Re: Strap hold down detailing
- From: John Turner
- Re: Strap hold down detailing
- From: Ted Ryan
- RE: Strap hold down detailing
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