interior truss heel sheathing 1

[struct_eeyore]

I have a series of wood trusses terminating on the interior of the building which have some very tall heels (13'+)
There is no shear transfer by design here - although some might occur in reality.
I'm leaning towards sheathing this section full height, but am wondering if that might be overkill - in lieu of X-bracing.
(truss profile is hatched in figure below)

 

[RWW0002]

OP started this thread by proposing sheathing the truss verticals over the interior bearing, specifically not for VLFRS. And several of our friends here have expressed support for that. Is sheathing that surface not functionally identical to installing full height blocking? I feel that it is.

I agree with you here, and was trying to make that exact point. The sheathing in OP is similar to blocking at interior bearing, yet I would imagine that few of those who expressed support for the sheathing would also be in favor of blocking at interior supports (but could be wrong).
Personally, I do not feel like the sheathing is needed, nor blocking at interior bearings (provided adequate chord/web bracing are provided) unless part of LFRS.

 

[KootK]

Are there any other meaningful examples of deep wood framed members that either do require some sort of "rollover" or torsional bracing @ bearing, or do not that come to mind?

The most common one that I know of is so close to OP's case as to, probably, be uninteresting. Light frame unit/corridor setups. Here, full depth blocking is usually considered impractical. So you're relying on lateral restraint of the bottom chord coming from the corridor wall top plates. Those, in turn, are themselves laterally restrained by the corridor walls -- intentionally or incidentally -- behaving as shear walls.

Another example is floor trusses at interior supports (multi-span, not continuous). There you will typically just have the ribbon which, in my opinion, is only there for vertical load distribution, not rollover resistance (no doubt it provides some).

I've looked at a number of wood beam over girder industrial building where the beams were set up Gerber style with no rollover bracing. This is kind of ambiguous though because the beams are usually so stocky that they probably benefit from pretty decent "bracing" just by virtue of their own geometry.

 

[KootK]

Major significant question. Why does KootK's logo only show Kot?

Kot?? Damn it. It is supposed to be as shown below. My quick and dirty, lame attempt at a phone readable avatar the day that the forum upgrade launched. 'Twas the same day that I watched the gloriously gratuitous Motley Crue documentary on Netflix (The Dirt).

V1.0 was [Koot]. But you can't see that at phone size.

V2.0 was [KK]. Unfortunately that felt a little too close to clansman territory.

V3.0 was [Special K]. My daughter felt that some might find that offensive.

So here we are... I suck at branding.

 

[XR250]

V3.0 was {Special K]. My daughter felt that some might find that offensive.

Because Ketamine?

 

[KootK]

Because Ketamine?

Ha! Because "special" might suggest being on the spectrum in some fashion (I may well be).

This may be before your time but I once got into a fair bit of a dust up here for referring to myself as a "spaz". It seems that, in some parts of the world that are not north America, being spastic is a rather serious developmental condition not to be made light of. People have family members who are spazzes and it's not funny.

So... yeah. I'm in no hurry to relive the kind of beating that I took over spaz-gate.

At worst, I'm mocking Germans and arena rock. And, really, who's going to come running to their defence?

 

[XR250]

I mean, what is not offensive nowadays?
My kids, who I consider to be the "PC Police" will still use the "R" and "G" words though.

 

[Flotsam7018]

There's still a little life left in this horse, at least for me - not sure about the OP, but I've been meaning to get back to it.

3) My hunch is that the "lateral restraint" bit eliminated from the NDS was originally expressed as it was precisely because they were assuming that most members have automatic lateral restraint at the bottom coming from the sheathed walls that support them. Where that is true, top restraint = rotational restraint. But, then, assumptions are dangerous so it's best to avoid them if you're a code writer.

The statement from the commentary says that "lateral displacement does not necessarily prevent rotation". If they were assuming there was not a VLFRS capable of providing the required stability, then prevention of lateral displacement also wouldn't be provided. But then, they must be getting at something else...

The sheathing in OP is similar to blocking at interior bearing, yet I would imagine that few of those who expressed support for the sheathing would also be in favor of blocking at interior supports (but could be wrong).

I have always required blocking between joists at interior points of bearing. Some relevant ICC sections below:

IBC:



IRC:


The provisions above are for prescriptive design and do leave room for alternative solutions, however they highlight the point that blocking at points of bearing is quite ordinary. I've never gotten pushback from the contractors I work for this item, and they are generally not shy.

The reasons previously stated are all that I have to support specifying blocking in these scenarios, and they are not hills I would die on. However, I do feel the benefits are worth the cost in regard to blocking (not sheathing an entire truss heel). The cost of 2x blocking will be minimal and is often substantially made up of cutoffs.

 

[RWW0002]

I have always required blocking between joists at interior points of bearing. Some relevant ICC sections below:

The blocking I was referring to is truss blocking between trussed at interior bearing (No LFRS). Lets say a 50' span truss @ 8:12 with a bearing right at midspan. Are you planning on 16'-8" tall x 2' blocking panels between each truss? That may be a big ask, and not commonplace in my experience.

 

[Flotsam7018]

@RWW0002 so you are in support for blocking conventional framing at interior bearing (not shear) walls? If so, why wouldn't you support doing that for a trussed system? Don't say the lever arm....

That may be a big ask, and not commonplace in my experience.

I agree. Through this discussion, I have settled on solid blocking matching the chord depth at top and bottom in addition to proper CLBs for the webs, this I feel addresses the concerns I have and any exorbitant expense. This of course isn't my project, so no idea what @struct_eeyore has/will do.

 

[KootK]

There's still a little life left in this horse, at least for me - not sure about the OP, but I've been meaning to get back to it.

Hell yes, count me in. In my opinion, OP's lose ownership of their threads as conversations evolve. @struct_eeyore has been well served here already.

If they were assuming there was not a VLFRS capable of providing the required stability, then prevention of lateral displacement also wouldn't be provided.

I don't feel that is the case. Historically, we've relied on diaphragms to brace our framing members regardless of whether or not those diaphragms received explicit stabilization from a designated VLFRS. That diaphragms are themselves laterally stabilized has always been assumed. And rightly so as diaphragm participation has always been in important part of what makes conventional building stable, whether that aspect received explicit attention or not.

In short, I would not read anything into the code's not explicitly mentioning the need for diaphragms to be stabilized by a VLFRS. When it comes to laterally bracing members connected to diaphragm, the codes implicitly assume that the diaphragms stay put.

 

[KootK]

I've never gotten pushback from the contractors I work for this item, and they are generally not shy.

To be clear, I do not object to the use of blocking as rotational member restraint for shallow depth members like 2x framing, TJI, etc. I agree that such blocking, in those situations, is rational and represents a healthy ROI. Moreover, such blocking tends to be good for erection stability. load transfer coming in from above, etc.

What I object to is taking the practice of -- and sometimes requirement for -- shallow depth member blocking and using that as justification for requiring similar blocking in tall systems like OP's truss end scenario. There are similarities, of course. But there also important differences.

 

[KootK]

so you are in support for blocking conventional framing at interior bearing (not shear) walls? If so, why wouldn't you support doing that for a trussed system?

Through this discussion, I have settled on solid blocking matching the chord depth at top and bottom

So you do not trust the moment connection shown below then? I've not shown any eccentricities but acknowledge their presence.

In this sense, it is the OOP flexural stiffness of the truss web that rotationally braces the chord.

 

[KootK]

I have settled on solid blocking matching the chord depth at top and bottom

I have some measure of sympathy for that approach at the truss bearing (bottom). I would argue that it is not a rational approach at the truss top chord however.

From a stability perspective, I fail to see how the condition is any different at the end web joint of the truss top chord than it is at any other web joint along the truss top chord. And surely you are not proposing such blocking at all of the top chord panel points?

 

[RWW0002]

@RWW0002 so you are in support for blocking conventional framing at interior bearing (not shear) walls? If so, why wouldn't you support doing that for a trussed system?

I am in support of blocking in the following locations:
1. Where necessary for LTB.
2. Where explicitly required by NDS (prescriptively or otherwise).
3. Where it may not quite be needed for 1 or 2 but can be easily provided and is fairly cheap.
(*4. Where required for stability of a beam/column joint. For now I am assuming the case of a gyp-sheathed wall low and diaphragm high, and am tabling this one for this portion current discussion and leaving that part up to you and KootK for now.)

For Conventional Framing
at end bearing (simple supported) - 2 and 3 might apply for blocking of conventional framing
at interior bearing (continuous) - 1 and 3 might apply for blocking of conventional framing

For trussed system
at end bearing (simple supported) - 3 might apply for shallow heels
@ interior bearing - 1 might apply but there are likely better ways to restrain against LTB