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RE: Horizontal Cold Joint in Concrete Beam

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Steve –

 

I’m just not comfortable not connecting the two sections together. The way I’m looking at it, if there is no shear transfer mechanism between the two sections, the top two bars won’t get any load.

 

T. William (Bill) Allen, S.E.

ALLEN DESIGNS

Consulting Structural Engineers

-----Original Message-----
From: S. Gordin [mailto:mailbox(--nospam--at)sgeconsulting.com]
Sent: Tuesday, February 21, 2006 7:55 AM
To: Seaint@Seaint. Org
Subject: Re: Horizontal Cold Joint in Concrete Beam

 

Bill,

 

Just out of curiosity - why do you need to develop additional shear strength through bonding or mechanical means when the shear capacity of the "bottom" portion of the beam is sufficient?

 

Steve Gordin SE
Irvine CA

----- Original Message -----

From: Bill Allen

Sent: Tuesday, February 21, 2006 7:36 AM

Subject: Horizontal Cold Joint in Concrete Beam

 

I’ve got a concrete grade beam with a horizontal cold joint in it. Please, don’t ask me why. The beam is 16” deep, 24” wide has 2-#5 bars T&B and f’c=3,000 psi. The cold joint varies between 8” above the bottom of the beam to 10” above the bottom of the beam.

 

I determined the shear capacity of the beam based on concrete only (2 x √(f’c) x b x d) which is much greater than the design load on the beam. I then translated that load into a VQ/I load in order to look at a shear friction model. I soon realized I don’t have the room to develop the “L” bars projecting out of the first pour and hooking into the second pour which are intended to transfer the shear across the cold joint. I then thought about embedded or drilling headed studs into the first pour, but the ACI code refers the PCI handbook (reference 11.18 from the commentary R11.7.8) for the anchorage of headed studs. I don’t have the PCI handbook. Are there any other, more generic, references which would serve as a guide to the design of the headed studs? I’ve already proposed a bonding agent (Sikadur HiMod 32), but the contractor would rather use mechanical means.

 

Thanks in advance,

 

T. William (Bill) Allen, S.E.

ALLEN DESIGNS

Consulting Structural Engineers