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OWSJ Bridging Furnish and Install

OWSJ Bridging Furnish and Install

OWSJ Bridging Furnish and Install

(OP)
OWSJ = Open Web Steel Joists

Being July 4, here in the U.S., I cannot consult with steel joist vendors.

Over the past years, I've come to understand that, other than special requirements by the EOR, all steel joist bridging requirements and bridging termination requirements are per SJI requirements, are to be furnished by steel joist supplier and installed by steel joist erector.

One concern I have is, how much horizontal force is applied to the bridging termination connection which is to occur at the ends of each bridging line and applied to the wall or other structure at that location?

I used to show a detailed bridging termination connection to solid grouted concrete masonry. But, several years ago, since both joist vendors, that I deal with, agreed that they provide the material, which the erectors will install, I have not been concerned with it. Is this a mistake? I've understood that, since I have determined the lateral diaphragm force(s) are to transfer out through the perimeter, or other load path, therefore, there is no significant force transferred at bridging termination.

Any thoughts? Please advise...

Thank you!

RE: OWSJ Bridging Furnish and Install

Luckily there are Canadians on hand and working today. My thoughts:

- I don't see any diaphragm forces needing to travel through the bridging.

- For long runs of joists without intermittent cross bridging, the bridging and terminations will collect some meaningful force along the run. 2% of chord force X #OWSJ etc. Not exactly that but something along those lines. By the book, it's a real load with real consequences and it should be considered at the bridging termination connection and support structure.

- The forces aren't all that big relative to the typical capacities of the things that the bridging is normally connected to and I've never heard of anything ever going awry at the connections in service. I consider my time better spent elsewhere unless it's a very exotic condition. Bridging terminating at tensile fabric or something.

Much of my workload is WI based these days. Perhaps we'll cross paths on something...

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: OWSJ Bridging Furnish and Install

(OP)
Thanks Koot!

RE: OWSJ Bridging Furnish and Install

I have not done one in a few years but when I did, I would always calculate the force and termination connection or just add a bunch of X's to bring the load up to the roof deck.
This brings up a similar issue that I have never really thought about... When designing a roof diaphragm, should we add the 2% bracing force accumulated from the bar joist or truss top chords to the overall shear? I guess statistically, many of them will cancel each other out.

RE: OWSJ Bridging Furnish and Install

A detailed look at the fabrication processes for many of these products will reveal that the imperfections producing instability are systematic in nature and tend to aggregate rather than cancel out. Still though, I'm all for ignoring it in most cases. Structural engineering is a very rough science; some things need to be allowed to fly under the radar or we'll all go quite mad.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: OWSJ Bridging Furnish and Install

Quote (KootK)

Structural engineering is a very rough science; some things need to be allowed to fly under the radar or we'll all go quite mad.

Well said!

RE: OWSJ Bridging Furnish and Install

SJI (Vulcraft and New Millenium) provide the bridging force that the structure has to handle based on the Joist size. Let me see if i can find a link. It is published though

RE: OWSJ Bridging Furnish and Install

Here is info for LH

Table 104.5-1
LH-DLH Section Number, Spacing of bridging, then the force lbs (N)
lbs (N)
02,03,04........11'-0" (3352 mm) .......... 400 (1779)
05,06..........12'-0" (3657 mm) .......... 500 (2224)
07,08..........13'-0" (3962 mm) .......... 650 (2891)
09,10..........14'-0" (4267 mm) .......... 800 (3558)
11,12..........16'-0" (4876 mm) .......... 1000 (4448)
13,14..........16'-0" (4876 mm) .......... 1200 (5337)
15,16..........21'-0" (6400 mm) .......... 1600 (7117)
17..........21'-0" (6400 mm) .......... 1800 (8006)
18,19..........26'-0" (7924 mm) .......... 2000 (8896)
Number of lines of bridging is based on joist clear span dimensions.
* Last two digits of joist designation shown in load table.
** Nominal bracing force is unfactored


http://bechtel.colorado.edu/~willam/4830%20Vulcraf...
See page 60

(Formatting that table sucked!)

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