Slab on Metal Deck Construction Joint Spacing

[Galambos]

Does anyone have a reference for maximum pours for slab on metal deck?

I have seen drawings that seem to indicate 160ft or 10,000 sf.

An exhaustive google search doesnt turn up much.

We recently had a 350 ft building that was placed in one pour and seemed to exhibit cracking with "loud cracking sounds" according to a tenant. I'd like to make sure we are limiting our pours to a realistic amount based on something that can be backed up.

Thanks,
G

 

[Galambos]

perhaps, there is a reference that indicates construction joints are not required, too?

 

[SlideRuleEra]

G - Perhaps the Steel Deck Institute has recommendations. See this link:

http://www.sdi.org/

If not, doubt if there will be a documented, authoritative source.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[TopKnot]

They are typically not required, but sources vary. Depends on bracing location, temperature changes, etc.

NOT NEEDED:

http://www.concrete.org/FAQ/afmviewfaq.asp?faqid=65

http://www.eng-tips.com/viewthread.cfm?qid=65872

NEEDED:

http://www.vulcraft.com/products/catalogs/designing/document.pdf

(PAGE 25)

_________________________
Tony Krempin, PE
TopKnot Engineering

 

[JAE]

I've typically seen 400 c.y. of concrete in one day's placement as maximum.

TopKnot's last reference (the vulcraft link) only states that EXPANSION joints are needed between 200 to 250 ft. through the entire building....not construction or control joints in the slabs.

 

[haynewp]

I have never stipulated construction joint limits for slab on metal deck nor am I aware of loud cracking sounds. I am interested in others experience with this.

 

[WillisV]

Not needed. TopKnots first reference is correct. Also see ASCC position statement 23:

http://www.ascconline.org/PDF/PositionStmt_23_Web.pdf

 

[cliff234]

We don't specify construction joint spacings in our slabs-on-metal-deck. Regarding spacing of expansion joints, we have gone further than 250 feet. The spacing of expansion joints depends on building geometry, location of the lateral load resisting system, pinned versus fixed column bases, heated or un-heated building, expected temperature differential, etc. Refer to this publication: Building Research Advisory Board of the National Academy of Sciences (NAS, 1974) published Federal Construction Council Technical Report No. 65: Expansion Joints in Buildings.

Regarding the "loud cracking sounds", could this have been "banging bolts"? How do you know it was slab cracking that was making the noise?

 

[Galambos]

First, I am NOT looking to specify contraction or control joints. I am interested in determining if there are recommended limits on concrete placement volume.

I have several drawing sets from some high end structural companies that put limits on their pours. I want to determine the basis for these limits.

We are aware of bolt banging and the reports do not seem to match the 'shotgun blast' we read about. I hesitate mentioning this here, as to how preposterous this sounds, but the tenant said he saw cracks opening up while hearing the sound! In any case, the sounds have subsided and there have been no reports since.

I am not convinced that our long pour led to this, I just want to do my research to make sure we have our bases covered.

 

[cliff234]

I agree with you. I doubt that a large volume pour contributed to the cracks. The very nature of composite metal deck is going to tend to limit crack width due to shrinkage. The flutes and dimples in the deck will tend to prevent large sections of slab from sliding, thereby resulting in lots of very small cracks, versus fewer large cracks. We don't place limits on our slab pours - and we've never had any problems due to excessive shrinkage cracks.

 

[XR250]

I am currently working on a 10x60' suspended slab front porch. The deck spans the 10' direction and is temporarily shored. I can see how the decking provides crack control in the 10' direction. However, the deck has no resistance to forces perpendicular to the ribs (the 60' direction). As such, I am specifiying caulked control joints every 15' with the wire mesh stopping 3" short of each joint.