Long-slotted holes as expansion joint 7

[zoparrat]

What is your opinion on the use of long-slotted holes to accommodate thermal/wind induced movements (not temporary but as a permanent expansion joint)? The long slot is in the horizontal direction; gravity load is normal to the direction of the slot. I'm looking for references that advise against this practice.

 

[connectegr]

zoparrat
Your best spec argument may be that there is no spec allowing it either. RCSC/AISC does not allow the use of finger tight bolts in a structural bearing connection. They also do not allow the use of a non-steel filler, which eliminates the use of Teflon between the plies. Thirdly, snug-tight, the least restrictive installation pretension, requires that all plies be pulled into firm contact.

It will be difficult to find a spec that specifically addresses the use of long slotted bearing connection as expansion joints. Especially when many of the parameters are already specifically rejected.

http://www.FerrellEngineering.com

 

[nutte]

nutte: "The spec doesn't make allowance for shear being tranferred through bolts in a joint that are not at least snug tight. "what is this spec you are referring to?

The 2005 AISC specification for steel buildings says in J3.1 (paraphrased): bolts must be pretensioned, except in certain cases where snug tight bolts are acceptable. Finger-tight bolts are neither pretensioned or snug tight, so they would appear to be prohibited.

The 2004 RCSC bolt specification (referenced by the AISC specification), section 4, says that joints with fasteners loaded in shear shall be snug-tightened, pretensioned, or slip critical. "Finger-tight" does not fall within any of these categories.

Not only is this detail a bad idea, it also violates the applicable specifications.

 

[ishvaaag]

What would be bringing us when finding any structural capacity for a slotted bolt connection as a buildability allowance?

 

[zoparrat]

connectegr: I'm looking at the 2009 RCSC spec and trying to find where it states that non-steel washers are not allowed. Do you know where this is stated? I found the following:

6.1.2. Slotted Hole: When a slotted hole occurs in an outer ply, an ASTM F436 washer or 5/16 in. thick common plate washer shall be used as required to completely cover the hole.

Can't a common plate washer be made of any type of material?

 

[zoparrat]

Also I couldn't find anything that rules out the use of a non-standard washer between plies for a slotted connection. The above section is a requirement for the outer ply only.

 

[nutte]

Look at section 3.1 (in the 2004 RCSC specification). It says anything between the head and nut must be steel.

You don't need washers between inner plies of a bolted joint.

 

[connectegr]

Refer to Bolted Parts 3.1
All connected plies that are within the grip of the bolt and any material that are used under the head or nut shall be steel...

http://www.FerrellEngineering.com

 

[connectegr]

Sorry for repeating nutte's reply. He types faster than me.

http://www.FerrellEngineering.com

 

[port125]

Modern Steel Construction magazine addressed this in the may issue (2011). A link is attached. The article essentially says don't use them.

http://www.modernsteel.com/Uploads/Issues/May_2011/052011_May11_steelwise_web.pdf