Building expansion joint or not?
Building expansion joint or not?
(OP)
I'm designing a single story office/warehouse with a mezzanine in MN. Walls are precast panels. Roof is metal deck with beam and column lines. Building is approx. 165'x480'. Should I break up the 480' dimension with an expansion joint? Obviously for ease of design I'm trying to justify avoiding it. Thanks






RE: Building expansion joint or not?
RE: Building expansion joint or not?
Mike McCann
McCann Engineering
RE: Building expansion joint or not?
RE: Building expansion joint or not?
You wouldnt need a internal shearwall. You can still provide an exp joint at the middle, and transfer the shear across. The SDI diaphragm manual has a great example on this. The attached page from the manual shows to not provide the EJ continuous across the entire width and leave the middle connected. Shear will be smaller at the middle, so your decking should still work.
Or you could still provide the joint all the way across the building, and provide tensions ties on double beams (on on each side of the joint). This should be slotted to allow for movement in one axis, but transfer the shear parallel to the joint.
RE: Building expansion joint or not?
FWIW: We have done similiar warehouses ( Precast walls with columns and joist/joist girder roofs, some with full length mezzanine floors) with approximately 500 feet between expansion joints in the midwest (USA). Can't say it doesn't make me nervous every time, but we have had no reported problems with these buildings and several of them have been in place for many years.
If you can easily add an expansion joint, I would just to ease the mental stress, but it can be done otherwise.
If the internal layout allows, you can use a double row of columns with cable cross bracing for the lateral system. Very cheap and efficient lateral system inside a warehouse structure.
RE: Building expansion joint or not?
RE: Building expansion joint or not?
RE: Building expansion joint or not?
RE: Building expansion joint or not?
RE: Building expansion joint or not?
What's the problem with breaking the diaphragm in two. You can detail it so that the diaphragm still allows for shear transfer while allowing it to expand in the long direction.
Additionally, you are breaking the diaphragm in the middle, where the shear is negligible anyway.
RE: Building expansion joint or not?
RE: Building expansion joint or not?
I'm not sure I follow.
are you talking about the chord forces in the long direction? (i.e. perpendicular to the expansion joint at the edge of the deck, running the full length of the building?)
If so, I don't really think a building with a 3 to 1 aspect ratio would be that troublesome.
RE: Building expansion joint or not?
RE: Building expansion joint or not?
At the expansion joint/chord interface, you typically attach one side of the joint to the chord and allow the other one to move laterally; the chord itself is unbroken.
You are still able to transfer shear across the expansion joint (by, for example providing a 1" bolt across the joint, without allowing the bolt to move in the short direction.
I still fail to see where the problem lies.
RE: Building expansion joint or not?
Perhaps the reason we don't understand each other lies in the nomenclature we are using or that I just can't visualise your detail.
Fundamentally, the OP is trying to distribute the entire lateral load at roof level to the end walls which are 480' apart. He wants to do this by some type of diaphragm. Now if this diaphragm is broken in the middle and the two halves are prevented from moving differentially in the transverse direction but allowed to move in the longitudinal direction, you have a longitudinal expansion joint. But I fail to see how the chords on the two long sides can be unbroken and maintain a movement joint. Crossing the joint, they lock up the joint.
If there is an expansion joint and there is no bracing in the vicinity of the joint, the two ends of the building will behave like C sections, and a 240' wide channel flange is too much.
Perhaps someone else reading this thread can mediate the misunderstanding frv and I seem to have.
RE: Building expansion joint or not?
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