Fun With Wood X-bridging

Gus Dering

If he had a woman willing to play erector set out in the cold night, on a Friday night, he would have a ring on that finger so fast he would be the Notloneframer.

Oh wait, we aren't much different playing with him on a Friday night are we?

Nevermind, as you were

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loneframer

Here is the deflection caused by 220 lbs.

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"Walking the fine line between production and perfection"



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tgeb

So....maybe you got bored with adding weight and ran into it with the truck parked outside??

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Tom

www.gebcon.com

jkfox624

I tried to show my wife how to lay out a stair stringer the other night out of boredom. She went upstairs before i got my framing square out of the truck. And yes the suspense is killing me.

naptown CR

Methinks you misunderstand the purpose of bridging

jkfox624

Why is that?

DrewD

Do the joist have end bearing or simply end nailed through the 2x? I guess I'm just no clear on what it is your exactly trying to prove. Do you want to see how much weight the system can support by transferring the load through the x-bracing and into the the saw horses or something else?

jkfox624

Unless im mistaken hes trying to prove how x bracing makes a floor system act as 1 unit instead of individual pieces. Taking it to the point that the x bracing can support joists sitting on nothing.

Gus Dering

I'm thinking he is seeing if his scaffolding planks and pump poles can handle about 300 lbs falling about 4 feet straight down on them.

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Every parent who has walked barefoot into their child's room late at night hates Legos

loneframer

Exactly. All the weight is being carried by the bridging essentially, transfered to the end joists. The field joists are not attached to the box or supported in any other way.

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"Walking the fine line between production and perfection"



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Warren

Upon further review, I think this "test" is flawed. In the real application, the joist would be supported on both ends as well as being tied together. How about a side by side test. Build 2 mini floor systems out of 2x4's and install bridging in one system. Then add the weight and see how much differently they perform.

loneframer

Then what is it's purpose if it's not to unify the floor and force weight loading to be shared by adjacent joists?

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"Walking the fine line between production and perfection"



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naptown CR

Bridging would be much stonger if there were a bottom chord tying the joists together.
None of the codes allow a reduction in joist size because of the addition of bridging.
Bridging is used primarily for the STIFFINING of a floor structure by partially transferring the load on one joist onto the two on either side.
If a properly attached bottom cord were added then each row of bridging would become in effect a floor truss and would add to the structure.
Although The theory behind the experiment is valid the lack of a bottom chord invalidates the prescribed system strength.

loneframer

That is exactly what I'm getting at.

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"Walking the fine line between production and perfection"



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loneframer

Which is the point of the test, taken to an extreme. The bridging is the structure in this case. Centerloading the model and transfering the load to adjacent joists. It's really not about the science as much as it is the destruction.

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"Walking the fine line between production and perfection"



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loneframer

Here is 270 lbs.

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"Walking the fine line between production and perfection"



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oldfrt

Very impressive!

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JonM

FYI According to code, bridging is not required until you use a 2 x 14

R502.7.1 Bridging. Joists exceeding a nominal 2 inches by
12 inches (51 mm by 305 mm) shall be supported laterally by solid
blocking, diagonal bridging (wood or metal), or a continuous 1-inchby-
3-inch (25.4 mm by 76 mm) strip nailed across the bottom of joists
perpendicular to joists at intervals not exceeding 8 feet

BuiltByMAC

This is a cool experiment, Lone! I'm gonna go off the deep end and say you could drive a Smart or a Metro up onto that thing. you got enough weight plates?
I'd say easy more than 1,000 maybe not more than 2.

Mac

jkfox624

Damnit its taking you soooo long to add more weight. I got a kid that wants me to take him hunting in the morning lets speed this up.