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Roof Beam to Tilt up panel Connection

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civeng80

civeng80

Structural
Dec 21, 2007
745
This is a roof beam to tilt up concrete panel connection that I am proposing on a job. I thought this was a fairly typical connection detail at least in Australia.

Comments from checking engineers are that it will not act as a pin connection (even though it is designed as a pinned connection) and that significant moment will be transfered possibly damaging the panel. I always thought that this was the closest (or one of the closest) type of panel to beam connections to represent a pin.

Any ideas or suggestions or modifications on this would be appreciated.
 
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Who’s the design checker? I would tell them to stop wasting my time. The only moment it’s throwing into the wall panel is the eccentricity of the beam reaction which wouldn’t even exceed the cracking moment of the panel.

If that’s the detail the precaster and steel fabricator have been using for years then there would be no need to change it now. I generally to a similar detail with a seated angle bearing connection fixed to the panel with cast-in ferrules.
 
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I don't see a problem with the seat concept, as long as it is not at a panel joint. The checker may be concerned about the position of the girt, and the restraint by the girt as the rafter rotates.
 
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He's concerned that the connection will not act as a pin connection and that it will induce a moment on the panel which could be dangerous.
 
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With the girt located near the top of the rafter, I would share his concern. You might find that the trubolts nearest the rafter are failed by the rotation.
 
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This is a fairly standard detail in the precast industry.
The girt you refer to Hokie is in fact an eaves beam used to support the panels at the top and also forms the bottom chord for roof bracing.

Are you suggesting the channel should be placed lower to reduce the rotating moment ?
 
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Just a couple of questions, as I know Down Under you use a few systems that are not as popular in the USA.

What is the horizontal channel girt for? I know it braces the top of the roof beam against rotation. But you said it braces the panel, which makes me also wonder is the roof deck not a diaphragm? It would be more common in the USA to have a shelf angle that supports the roof deck, which is the diaphragm, and this braces the top of the roof panel and transfers in-plane and out-of-plane loads.

That aside, the bottom angle seat will put a moment into the panel, usually I would use about 2" of eccentricity for that connection and design the embed plate for that amount. However, your top rebar will take that up in tension so that looks OK.

The top channel girt COULD transfer some force into the panel when the roof beam is loaded and the top rotates slightly. However, I think using a bolted connection there prevents much restraint, and I think you could provide slotted holes that would allow the top of the beam to rotate (in-plane) but would provide lateral-torsional bracing.
 
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Why the need for the 200PFC at all?? What is it for?
 
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I'm located in the U.S. For roof beams to panels, we typically use a double-angle shear connection with horizontally slotted holes welded to an embedded plate in the panel. You already have the embedded plate in your detail, so you can easily do that. Either way, you only need to consider the load eccentricity of the connection for moment in the panel from the beam.
 
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civeng80,
Yes, placing the channel lower would reduce the tendency for the rafter rotation to place the trubolts in tension. But I realize that you have to coordinate that position with the bracing plane. Another reason for lowering the channel is that, at the lower end of the roof, it often interferes less with the gutter, sumps, and downpipes.

a2mfk and ztengguy,
The channel, as civeng80 said, is to support the panels at the top, and also to serve as a chord for a roof bracing system. We don't tend to use deck diaphragms here. We use steel roofing which is fastened either through the crowns or with a concealed fastener system, and the roofing is considered to have no diaphragm capacity. Rather, a horizontal truss system is employed.

steellion,
Double angle shear connections are another thing not typically used in Australia. Typical shear connections are end plates and fin plates.
 
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Spot on Hokie66 and thanks all for responses so far.

The guttering and sump and downpipes are not really a problem, but bracing further down would possibly mean putting in CHS struts/ties and not rely on the purlins for bracing. This is Ok as I dont really like using purlins (even double purlins) for bracing members.

The point is what is a safe moment arm from the angle seat to the girt cleat so that the moment transfered to the panel is safe.

Been thinking maybe a beam support with a spring with a stiffness equivalent to 2 cantilevers about .5m long (the distance from the centre of the beam to the first trubolt) woud give me an idea of the moment transfer to the panel, but this is statically indeterminate.

Even a ball park reasonable figure for the moment transfer to panel would be good.

Has anyone got a solution for this problem?
 
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I agree with you about using the purlins as struts. I know some people do it, but I never have.

The further you move the trubolts away from the rafter, the better.
 
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Thanks Hokie.

Any ideas about how to actually estimate the moment transfered to the panel with this (Semi rigid) connection?
 
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civeng80,

I have a detail very similar except one minor difference. Instead of the M16 Trubolt @ 1000 cts What you can get is a 'clip' type element which is fixed to the precast panel via a ferrule and it is not fixed to the PFC, however the flange of the PFC sits between this clip and the precast panel. This provides lateral restraint for the support of the top of the precast however does not connect the PFC to the wall beam. The exact name has slipped my mind! but they are common.

Regards,

"Structural Engineering is the Art of moulding materials we do not wholly understand into shapes we cannot precisely analyse, so as to withstand forces we cannot really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance." Dr. Dykes, 1976
 
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civeng,

further to my last post they are called 'fixing clamp'.

regards,

"Structural Engineering is the Art of moulding materials we do not wholly understand into shapes we cannot precisely analyse, so as to withstand forces we cannot really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance." Dr. Dykes, 1976
 
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Thanks aaronPTeng,

I think I know what your refering to.

A ferrule in the panel with a clamp plate bolted to the ferrule and welded to the flange of the channel.
Still fixes the panel to the eaves channel and also the eaves channel must still be fixed to the roof beam to achieve the roof bracing which is where the moment transfer occurs.

Either way because the eaves connects to the roof beam there is always some moment transfer so the aim is to minimize it.

Thanks again.
 
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aaronPTeng,
Clamping could take the normal wind force, but I would be dubious of that type connection for taking the strut force into the shear walls. I think there would have to be at least intermittent positive connections to transfer the in plane force.
 
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Civeng,

I miss typed one part sorry, I do fix the wall beam to the roof beam, However Is there a need to weld the clamp plate to the flange of the PFC?

Regards,

"Structural Engineering is the Art of moulding materials we do not wholly understand into shapes we cannot precisely analyse, so as to withstand forces we cannot really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance." Dr. Dykes, 1976
 
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