Bolting into a precast double-tee plank
My company manufactures vehicle security barriers. Typically these barriers are secured with bolts. We drill 7/8 †diameter holes, vacuum them out, and then use an epoxy. We then insert the 7/8†x 6†bolts, wait for the epoxy to cure, then tighten the nuts down.
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I am researching for some upcoming parking garage projects where our barriers will be utilized. It is my understanding that these parking garages will be comprised of parking decks made of precast double-tee planks.
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Anyone familiar with thes double-tee planks they’ll be using for the parking decks? Is there a particular manner you would recommend to secure our barriers for these projects?
I’ve attached a photo of the type of barrier that will be used in these particular projects.
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Replies
Make sure you get a good layout of the steel reinforcing strands that run through the plank. Hitting one will dramatically weaken the plank.
Depending on the plank's makeup, you're probably going to be looking at a through-bolted connection.
Is there someone who made them locally? Usually there is one nearby that made them.
Or some way to detect the steel in them. There might be companies that can come out and spray paint over the steel. Locating company? Like the ones that come out before you dig.
Will Rogers
Edited 6/24/2009 5:55 pm by popawheelie
The critical strands will be in the ribs below where it appears you will be working. You will find some mesh or rebar in the skins. If this is an existing structure, I suspect a through bolt will be necessary as the top slab may be too thin for typical Hilti Bolts. If this is a proposed facility you might want them to provide embed plats set in some to weld to or threaded inserts.
In any event, I recommend you have an engineer provide you a design for this element. If not, should any component ever fail you could wind up with a lot of liability on your shoulders.
Brad
as long as you bolt thru the top of the "T" and not the rib you should be fine. the double tees are either 10 or 12 feet wide so there is plenty of room to miss the rib.
No engineer, eh? We need to revise the laws in this country... if you cannot afford a structural engineer, one will be provided for you.
Thanks for your input.
This happens to involve projects that are months away. I had gotten an email from our customer's architect a few minutes before I posted the thread. What she had said was that in the past,they've had structural engineers forbid any drilling into precast concrete double-tee planks. That did not sound right to me. In addition to posting the thread I also contacted the plank manufacturer and the precast institute in Chicago.
IMHO, one can never acquire too much knowledge, and I happen to really value the input of the knowledgable folks at breaktime.
"Preach the Gospel at all times; if necessary, use words." - St. Francis of Assisi
No, I didn't vote for him; but he IS my president. I pray for the his safety, and the safety of his family every day. And I pray that he makes wise decisions.
Hilti HY-20 or HY-150. Installation is identical to your existing use of threaded rod/ bolt and epoxy.
I am sure the manufacturer of the T planks can advise you regarding the rebar grid and orientation.
My guess is you don't need enough planks or have enough identical registrations to warrant an insert/ sleeve as part of the fabrication process.
Frankie
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I would suggest contacting the precast company who makes the tees. They might just install what you need in the concrete.
These TTs, as I recall, are typically something like F'c=7,000-10,000 psi concrete. Hope you have a big drill ;o)
Are you sure there would be no slab topping?
What about having the manufacturer cast in welding plates at approximate locations? You could then field-weld threaded rod to the plates for field-bolting (they're certainly used to casting plates into them).
Your typical installation method will likely be OK - IF it is permitted by the manufacturer. You can probably get shop drawings of the standard reinforcing bars to know what areas to avoid and/or use/rent a pachometer to field-locate steel:
http://www.ndtjames.com/catalog/rebarLocators/r-meterMKIIIpachometer.htm
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Used one years ago to avoid bars in concrete beams when core-drilling for sprinkers - only hit one bar in 150 holes.
Hope you have a *big* drill -
Jeff
Edited 6/25/2009 1:47 am ET by Jeff_Clarke