diaphragm capacity 1

[nrguades]

0-------------------------0 xxxxxxxxxxxxx (shearwall line)
(load bearing steel frame) (wooden shearwall)
(not braced)
greetings..

Is it ok if the beam in the load bearing steel frame(not braced)will not be connected to the wooden shearwall supposing the lateral nailing requirement of diaphragm to shearwall is already satisfied in the shearwall portion.Is the wooden diaphragm at the gap between the load bearing steel frame and wooden shearwall is critical for tearing off.( if is critical.. how will check the diaphragm tensile and shearing capacity in this case?)

 

[SperlingPE]

I have been involved in a investigation where I have seen this done. I could not verify in the field that the specified nailing and details were followed. I did see on the cotract drawings that the wood shear wall was designed to take the entire shear load. The reason for the investigation was that the drywall bridged the gap between the steel and the wood. Drywall cracks were continually happening. There is some inherent stiffness in a vertical load bearing steel frame. By attaching the diaphragm to the frame you will transfer load to the steel framing. In order for this load to transfer to the shear wall, there will have to be some deflection (may be very small) and a load transfer mechanism at the gap between the steel and wood wall. Verify the stiffness [deflection] of each assemble [steel framing & wood shear wall] and detail accordingly.

 

[nrguades]

thanks SperlingPE for the inputs... I have some additional question, would it be ok if the frame will carry a wooden shearwall above and the lateral movement will be transfered to the shearwall below with the use of this transfer mechanism at the gap between the steel and the wood wall. How about if the diaphragm(flexible-t&g plywood) will be the the one that will be used to transfer this lateral loads,how will we check the diaphram capacity?

 

[SperlingPE]

Correct me if I don't understand.
You have steel framing and wood shear wall side by side. You want to put a wood wall on top of the steel framing that will bridge the gap between the steel and wood. If I am picturing this correctly, the horizontal diaphragm will be connected to shear wall [spacer boards, top plate, nails, truss ties, etc.]. At this point the shear load is transferred to your vertical diaphragm. I believe this would minimize any shear load going into the steel framing. Calculate the horizontal shear that is distributed to this wall. Divide this load by the length of your shear wall (steel + wood). This is the load that would have to be resisted by your vertical diaphragm. Another way is to desing an angle that is attached to your steel framing and wood shear wall (at the top). This would be like a short drag strut. With this configuration you would have a wood shear wall with a line load at the top and a point load where the steel frame attaches to the wood shear wall.

 

[nrguades]

I would like to clarify on the statement "calculate the horizontal shear that is distributed to this wall. Divide this load by the length of your shearwall (steel + wood)".
Im bit confused on on (steel + wood) part. Will it not be right to just divide the load by the length of the wood only? Or this is done in order to computed the shear to be transfered by the drag strut as point load to the wooden shearwall. thanks again

 

[SperlingPE]

You must use the entire length of wall to be able to calculate the point load from the drag strut. If you just want the shear load that is to be resisted by the shear wall, divide by the length of the shear wall.

 

[nrguades]

thanks for the help...