Use of slotted holes in purlins for roof movement? 4

[IJR]

Friends

There is this practice: A roof is elevated from a group of RC blocks by steel frames. To facilitate movement of the roof, some designers simply use slotted holes at purlin connections, instead of actually
isolating the roof supporting frame at the RC joint. This is usually done to avoid placing two columns side by side at the interface between neighboring RC blocks. And some even slot the roof bracing.

I find this disturbing. I dont trust slotted holes except for erection purposes. What is your opinion?

Thanks in advance.

respects
IJR

 

[Galambos]

I share your concern, and so do the people of pittsburgh: Link

 

[hokie66]

Slotted holes are no substitute for a movement joint in gravity loaded members.

 

[rowingengineer]

I see this the other way, a correctly detailed slotted movement joint will perform just as well as two frames in a roof situation if the loads are minor under gravity loads. However I may have this wrong as this may not be a light weight roof, if not my view would be different, I have attached a discussion by Fisher.

As for slotting bracing I don't see how this would work and seems like it could be handled better.

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[IJR]

Let me add: The reason I dont trust slotted connections for sliding is they usually use conventional nuts and snug-tighten them at site even if drawings specify adjusted nut clearance.

respects
ijr