Opinion on Building Expansion Joint

[mmodfr2013]

Hello,

I am looking for opinions on the need for an expansion joint in a building in the early design stages, there's a quick sketch attached. It is 7-stories, load bearing cold formed stud walls supporting concrete on metal deck with composite joists. Ordinary concrete shear walls are located around stair and elevators cores, with a single striaght wall located as shown on the sketch. Seismic Design Category is B.

My intuition tells me me to put an expansion joint roughly at the elbow and make two rectangles. AISC Fig 2-6 put me right on the line of needing a joint for 'other materials' but that table was developed for beam-and-column construction, and I have metal stud walls. The Architect is asking if one is really needed, and I have been looking for any other resources/etc that had more solid recommendations for this construction type.

 

[dik]

Not sure of the effectiveness of your shear walls, but can you locate the joint at the re-entrant corner? Alternatively can you locate the joint at right angles and break the 350' length into two parts?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[hokie66]

Not conversant with the system of cold formed stud bearing walls for a 7 story building, but I think that plan definitely needs a movement joint, at the reentrant corner. Two rectangles, 280 x 70 and 240 x 70.

 

[mmodfr2013]

dik,

We are early on in the design, everything right now is very preliminary, the dashed line is more or less at the corner, just a few feet off, lined up on a party wall. This is a rough sketch.

Hokie66,

Agree, but the cold formed design is delegated to someone who I assure you knows what they are doing. The whole project was reprogrammed due to timber costs. Aside from that, I agree there needs to be a joint, because there does. Bbut is there anything you're basing that on, other than your experience as an engineer? I'm trying to avoid going back to a meeting and leaning on the AISC guidelines for beam and column building in structural steel.

 

[MSUK90]

Aren't the 240' and 280'(350'-70') lengths also require expansion joint besides a joint at re-entrant corner?

 

[hokie66]

mmodfr2013,

There would doubtless be numerous papers I have read on movement joints, but after doing structural design for lots of years, I generally lean on my own experience these days. You may have cold formed bearing walls, but you have concrete floors. IMHO, the concrete dictates that you need a movement joint.

 

[HTURKAK]

My suggestion will be , providing two E.J's . The EJ locations and block sizes in this case dictated by RC composite slab.
The block sizes will be ≅ 70 X 175 ft.

 

[haynewp]

The building can experience movement at the elbow and I would put a vertical joint there if you can make the building stable with your shear wall arrangement and if there was not a need for an add'l joint based on AISC criteria. I have always put a joint at such intersections and there is a guidance from National Roofing Contractor's Association manual on this also.

 

[To Madeira]

I would look at where fire walls are located by the architect and see if they would make logical placed to also have a expansion/movement joint.

At 7 stories, can you use strap bracing instead of concrete shear walls? That would allow you to place them to distribute over the floor plates more uniformly.

 

[dik]

hturkak... great. That's what I was trying to describe. Steel studs can have an impact on the energy efficiency.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[XR250]

I really hope the designer and installers know what they are doing.
I used to design LGMF almost full-time and would never attempt a building of that height.
Waaay too many design and construction details to pay attention to.

 

[dik]

I've not done one, but not a problem... they're doing twice that height in wood...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[haynewp]

I wouldn't think an additional joint other than at the corner would be necessary based on what has been stated so far about the building. An essentially steel building with a concrete topping slab that may be only at the floors. The additional joint creates more construction cost, and more work for structural, mech, and arch to deal with another full height joint in a 7 story building.

 

[jayrod12]

They are doing tall buildings in wood, but framed entirely different. Those buildings use post and frame construction and the lateral system is not the wood framing generally.

For stick framed wood buildings that exceed 4 storeys, the requirements for hold-downs and shrinkage compensating systems get quite ridiculous. I can only imagine the requirements for light gauge at those heights to be equally as complicated and onerous. But I've never done a load-bearing steel stud building.

 

[hokie66]

The higher wood buildings that are being built in some places don't have concrete floors, as far as I know.

 

[dik]

CLT as I recall... and yes, no concrete.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[haynewp]

A five story Hampton Inn had buckled studs at the first floor during construction down the road from me. A simplification to say it buckled without knowing more, but I remember the permitted height with load bearing studs was highly questioned at the time. Not my project or company involved.