SHEAR TRANSFER TO DIAPHAM 2

[dwaine]

I have a wood frame 24' by 44' building with an interior shear wall in the middle & parallel to the trusses. The load is 12,000 #'s. What's the best way to transfer into diapham?

 

[SperlingPE]

How tall is the building?
1. Build wall (typically one lower wall with another wall on top) to underside of roof deck/diaphragm. Install sheathing as required.
2. Build typical wall, install gable end truss on top of wall. Gable end truss with verticals at required spacing. Sheath wall. Install shaething as required.

Both examples above require attention to details and load path (i.e. attaching the truss to the wall, hold downs, footing size, attaching the upper wall to the lower wall, noting diaphragm boundaries and nailing them as required).

 

[cap4000]

If I understand your problem, your trusses span the 24ft direction and the interior shear wall is 24ft long. The diaphragm load per foot would = 12000/24 or 273# per foot. Clarify your structural conditions and the Code you are using. What are the wall and diaphragm details??

 

[cap4000]

Correction on the grocery store math 12000/24=500#/ft.

 

[dwaine]

the code is IBC 2000 , IRC 2000 , it's a residence, single story , wood trusses. The shear wall that I have is in the middle of the middle. I was thinking ladder bracing betwen two trusses & have trusses designer design to transfer load to diapham but I'm not confortable with that? Connections are a concern

 

[nrguades]

I agree with sperlingPe that in that particular case you need to provide an extra truss on top of the shearwall with proper connection to the diaphragm and into the shearwall, with both the wall and the truss properly sheathed.

 

[cap4000]

Assuming the shear wall diaphram load = to 500#/ft. I think you should have your wall attached directly to the plywood roof sheathing. IBC 2000 pgs 564 & 565 gives you the plywood options and nail sizes and spacings required. REF: "Panels Applied Direct to Framing" with fastner spacings. If necessary, I can provide you the formulas for the lateral nail loads and plywood in plane shear stress Fv if necessary. Good Luck.

 

[dwaine]

Thank you SterlingPE, Nrguades & cap4000. I feel alot better about my project with your advise. But what about getting 12,000 #'s into diaphram? Remember "Middle wall in middle of building". I'm thinking fully sheathing dedicated gabel truss over wall with heavy nailing but what type of procedure & arithmetic will I use to feel secure? Thanks again I very much appreiciate the help

 

[cap4000]

Show me in the IBC Code where a Truss is sheathed in a Shear Wall with an allowable diaphragm load table? To many stud pieces,angles and perhaps "toe nail city". I believe you have to stick to your typical plywood and (ONE PIECE) full height stud framing wall all the way up to the roof underside. IBC page 563 gives you the 6 panel arrangement types you can use. You can easily transfer 500#/ft with the correct nail size and spacing, stud size and spacing and plywood type.The procedures and math is already done for you by the IBC. Once you have selected a plywood type and nail size, I can prove for you the tables correct. Finally,how high if your roof and what configuration with dimensions is your truss??

 

[dwaine]

cap4000 my roof pitch is 3/12 & available shear wall is all on one side of peak. Conditions could be that with zero nailing of top of truss to diapham there would be zero resistance. So total resistance force is by nailing connection to sheating of diaphram. I see the IBC charts as unit load capablities of a diaphram not the connection to it???? The nails in the top of my truss could experience more of a pullout force than shear? I'm trying but keep seeing a really kool vertial wall with a Nebraska barn liening against it?

 

[cap4000]

Don't worry about the wall liening any further. Trusses must be 24 inches c/c as a max.(See note "b" on pg 565.) See IBC pg. 564 Using Structural 1 Sheathing 15/32 thick and a 10 penny common nail at 4 inches c/c (3 every foot required, but I recommend 4 nails per foot) gives a value 510#/ft fasten into 1.5inch (use 2 Plates=3 inches) thick top plate of the Shear Wall, NOT THE TRUSS!!. I assume you have this roof and shear wall diapragm designed and the shear wall anchored properly at the slab to prevent overturning as you have a pretty high 12,000# Shear Force. Now, take 2 Tylenol and call me in the morning,if you can afford it, after designing probably the most expensive barn in the country. Good Luck.

 

[dwaine]

cap4000 Thank you. I'm Norwegian so will have to let my mind work on this for a while. I'm confortable with pg 564 "the wall" the transfer to floor , overturning, soil interchange. I see these charts as giving strengths of horizontal & vertical beams. Somewhat frail beams that need some care when concentrated loads come to town? Their connection & force transfer make's a Mom worry. I can just follow the nailing pattern for the wall or roof diaphram design for the force tranfer?? Ever been to Nebraska?

 

[SperlingPE]

dwaine
I am in Lincoln.
If this is an existing structure, I agree about building a full height wall (from floor to roof sheathing). Anchoring the wall to the floor/foundation will require some sort of hold down detail as well as enough weight to counteract the uplift.

 

[dwaine]

SperlingPE, Project is actually a very expensive, complex home. The barn thing was an attempt to figuratively explain my concern. I grew up in Nebraska, born in Hastings. I saw a lot of liening barns back then. " improper lateral design" I have one concern which is the proper connection of an interior shear wall to the roof. I can't intuitively see how a large load could definitedly be tranfered to wall under my conditions. My wall is not full width & is on one side of peak. Therfore on opposite front loading the tranfer would be to some degree the pull out strength of the nailing of the shear wall to diaghram. I'm think now that the dedicated truss fully sheared & tied to shear wall & nailed to roof per IBC chart number will work? How would you connect to roof? Connect the dedicated truss to top plates?

 

[SperlingPE]

If I am understanding this correctly, you have a interior shear wall that is not the full iwdth of the house. You have calculated 12,000# that must be transferred from the roof diaphragm to the shear wall. The load must then go from the shear wall to the foundation/slab. Wind from the wall side will transfer into the wall. Wind from the opposite side will also transfer into the wall. I would have some concern, however since the wall is not full width. A drag strut or another wall would be worth considering. When looking at the nailing tables in the code books, shear walls mark the boundary of horizontal diaphragms. A 12000# load sounds pretty high for a residential lateral load. A 100' long house with a wind load of 20 psf would indicate 24' tall walls [(100/2)*(24/2)*20].

 

[SperlingPE]

In the previous post I was thinking a flat roof building. I forgot that this is a pitched roof structure. Achieving a 12' (or more) tributary height is possible with a high pitched roof.

 

[cap4000]

Your Mom has a valid "worry". Are you sure of the very high 12,000# Force.?? I assumed the wall was 24 foot long?? As far as fastening tne wall: 4-10d commons/foot of wall will get 500#/foot into the structural roof sheathing. PS:Never been to Nebraska,have you ever been to New Jersey? Good Luck!