Precast/prestressed hollow concrete planks? 1

[jim57]

Trying to determine design data on these precast, prestressed hollow concrete planks. the building is pre 1954. The planks are 16" wide, 8" tall with a 2" concrete top. There are two 6" diameter holes and four rebars along the bottom. One on each end and two in the middle. See photos. They look like Flexicore, but can't find any data with two center rebars.
Thanks

 

[JedClampett]

It's very, very likely that the manufacturer changed names, got absorbed or went out of business. And even more likely that they don't have 65 year old records.
I would call the local precaster and ask if they knew from the date who made those. Sometimes you get lucky and find an oldtimer who remembers. Since the planks are heavy to ship, it's probable that they're from not that far away. From a name, maybe you can find out who they are now.
And are you sure those are reinforcing bars, not prestressed tendons?
Another source is the Prestressed Concrete Institute (PCI). But expect a very conservative guess on any capacity, if any.

 

[Ingenuity]

From 1954 Flexicore datasheet for - 6" deep NOT 8" deep - they had 2, 3 & 4 bottom steel combinations, which I presume to be prestressing strand NOT rebar:

 

[Ingenuity]

Here is 1957 Flexicore tables for 8" deep - they don't show the bottom steel configurations but based upon the area of steel you may be able to find your situation.

See attached file for better resolution.

 

[dik]

Thanks Ingenuity... more stuff for my hard drive... it's not filling up fast enough.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[jim57]

Thanks for the input. Do you have the back sheet to the submitted documents as that describes how to use the table. I need to know if it includes the 2" top course.
Thanks.

 

[bones206]

Just below the table it says: "Includes the live load plus any dead load that is additional to the weight of the bare grouted slabs in place".

More links:

thread507-432122

http://www.slideruleera.net/Flexicore 8x16 Hollow Slabs - Load Tables - 1957.pdf

https://files.engineering.com/downl...e=FLEXICORE_SAFE_LOAD_TABLES_1954_to_1978.pdf

https://patents.google.com/patent/US2956375A/en

 

[jim57]

Thank you for all your help[

 

[jim57]

Is there any information on drilling holes thru the fleicore. Ned to drill 3.5" diameter from top

 

[Ingenuity]

Is there any information on drilling holes thru the fleicore. Ned to drill 3.5" diameter from top

Yes, do NOT hit the pre-tensioned strands! But you knew that already, right.

GPR scan the plank - this will locate the strand and also the void - pilot drill, then once you have determined you are in the middle of the HC void, wet core from top of slab.

I know that your planks are not SPANCRETE units but the attached files has relevant info on coring/drilling holes.

Also, if you need any tech additional info related to Spancrete-type HC panels see here: Link

 

[msquared48]

@ ingenuity...

Need to send those tables to sliderule to post on his site...

Mike McCann, PE, SE (WA, HI)

 

[Ingenuity]

Need to send those tables to sliderule to post on his site...

Mike, I did sometime back and it is there, along with other plank data too:

 

[hokie66]

Those Flexicore tables are not for prestressed hollow core. They state the allowable steel stress is 20000 psi.

 

[Ingenuity]

hokie66 - thanks, I shall contact SRE and get him to add my prestressed HC Flexicore data.

 

[jim57]

Thank you for the quick response.