Shear connectors with partial depth precast deck panels

[71corvette]

Hi All,

I’m working on digging up some information regarding the use of shear connectors on steel girder bridges where partial depth precast deck panels are used. Specifically, when shear connectors are used in combination with partial depth precast concrete deck panels, how far do the shear connectors need to project into the CIP portion of the deck slab (if at all)?

AASHTO LRFD requires that shear connectors project a minimum of 2" into the deck slab, but the code is silent on whether the partial depth precast panels count toward this requirement. Separately, PCI New England has a standard detail that requires the shear studs extend at least to the top of the precast deck panel. Other than these two sources, I've been able to dig up only a small amount of guidance on how to approach this issue.

The issue is that having the studs extend up into the CIP portion of the deck slab creates clear cover issues at the top of the stud as haunch height varies. Coversely, not having the studs project into the CIP deck slab creates questions about whether full composite action is being developed.

So, what have your experiences been with this situation? What guidance do your state/local agencies provide when dealing with these situations? I’ve heard some interesting approaches on the topic so far and am interested to hear some of the approaches used by other agencies.

Thanks!

 

[bridgebuster]

1"

I think this is will help:

https://www.nysdot.gov/portal/page/.../bridge-detail-sheets/ss-superstructure-slabs

Click on BD SS8-R1

 

[Qshake]

Aside from AASHTO you'll likely find many different opinions depending on where this bridge is located. I recommend visiting that state's or agency's website for guidance.

Also for large haunches #4 hairpin bars are used to further reinforce the haunch.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[71corvette]

Thanks for the NYDOT link, I had actaully looked through their drawings but didn't come across that detail.

I've been looking at various DOT websites and browsing their standards, but I've only found a few that have definitive guidance on this issue. Here in the Northeast the only agencies that have set standards (that I've come across) are MaineDOT and MassHighway...

 

[crossframe]

Also in the Northeast is New Hampshire, who specifies that shear studs "shall extend to the top of the deck panels (min)."

 

[71corvette]

Thanks crossframe, do you have a specific reference for that NHDOT requirement? I tried finding it in their manuals but have been unsuccessful so far.

I'm still surprised at how few agencies address this issue. I've still only found a handful that address it.

 

[crossframe]

It's shown on a standard details sheet, PRECAST CONCRETE DECK PANEL DETAILS, produced by NHDOT. My revision is dated 4/02. It should be obtained from NHDOT, as it isn't available from their website.

 

[edward1]

I worked 20 years with VDOT and we had so many problems with precast deck slab panels in the early 1980's that they were banned by this DOT.

 

[Qshake]

edward1, what kind of problems? A lot of DOT's cite reflective cracking, are there others?

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[edward1]

The deicing sand and salt that was spread on bridge deck got into the precast panels and caused spalling and cracking in these. Also we weren't get a good bond between the panels and the 4" poured deck on top. When repairs are needed in decks with precast panels we had to remove the 4" top slab and the 4" panels completely.

 

[71corvette]

Edward1-

That's interesting. Do you recall if the DOT required any corrosion inhibiting admixtures (e.g. Calcium Nitrate Solution) in the precast panel mix design? What kind of surface were the panels given during fabrication? We use a raked finish to produce a +/- 1/4" profile.

So the expected to be able to re-use the panels when the redecked the bridge? Interesting, I always thought they would just remove them in their entirety.

 

[edward1]

I don't know if any corrosion inhibiting admixtures were required. No surface finish was specified. I recommended both the panels and poured in place deck be removed for deck repairs. VDOT only removed portion of poured in place deck for repairs.