Existing HollowCore Plank Openings

[GBMRAO]

Dear Friends,
I am working on a project where we have 6" hollow core planks with 2" topping. This building is built in 1985 south of Georgia. The planks are nontypical width of 40" and 36" wide. I was trying to find any load tables and am unsuccessful. Do any of you have historic hollow-core plank tables that match the criteria? I contacted Spancrete and am waiting for their response.

i have few other questions.
1. I was not able to located or find how many strands are there in the plank. I want to assume 3 - 3/8"Dia strands. Does anyone know if this the least number of strands in the industry? Gatecore people said back in the days they used 3/8" minimum.
2. Since this is a roof plan and they have roof trusses not bearing on the plank the only load is dead load. + some live load for HVAC repairs if people are up there.
3. Is it reasonable to consider a concentrated load will be acting at the end of the opening and review the existing plan for the load capacity? if the rest of the plank has the required capacity then i should be ok. Given the load is transferred to the next strand after the opening.
4. Do I have to consider torsion in the slab too?

I may have asked some silly questions. please let me know if am doing something wrong in my assumptions. I am new to the precast hollow core. as it was always a delegated design.

Thanks

 

[GBMRAO]

Is there any other manufacturer other than spancrete who does 40" planks?

 

[JLNJ]

I'm guessing that the industry has forced out the inefficient and that there is more uniformity between precasters now. Flexicore used to make their own, more narrow, planks, but they have gone the way of the dinosaur.

My PCI manual 3rd Edition shows decks from 6 different manufacturers, but Spancrete is the only one with a 40" wide plank. Unfortunately it doesn't have load tables or strand patterns. "Spancrete is also available in 48" and 60" widths. All sections not available from all producers."

My 20-year-old Spancrete binder shows all 48" widths.

 

[Ingenuity]

GBMRAO

Spancrete on their manufacturers website have a great resource library for all-things-hollowcore: Link

For example:

Other topics:

PCI also has the old PCI Manual load charts for precast elements (from 1st Ed to 7th Ed): Link. I am not sure if they have 40" wide hollowcore planks.

Unless you have definitive info on the actual panel used and its strand arrangement, I would get the plank soffit GPR scanned to determine the number of strands. To determine the strand dia you will have to arrange for a soffit invasive probe - this will give you bottom concrete cover too. We have done this a bunch of times - we have even removed strand segment lengths and had load tested to failure to determine their mechanical properties (needed to verify if grade 250 or 270 ksi).

 

[GBMRAO]

Thank you so much Ingenuity

 

[structSU10]

I have span tables for 40" wide plank, and a diagram for layout. The load tables I have are for 8" plank with 2" topping though.

I had asked my local precast plant that produces hollowcore for this information, and he even produced new span tables for some of the plank layouts he didnt have a 'historic' version of. Might be worth a check with a local guy to see if they can attempt to reproduce load tables or have something handy.

I have attached the tendon pattern for the 40" planks that were used.

 

[MOJOJOHN]

I would design the hollow core by 1985 standards, get the number of tendons and check by ground penetrating radar then modify my assumptions accordingly.

 

[MOJOJOHN]

Please allow me to correct my previous post. Should GPR first to determine drape if any.

 

[jayrod12]

I don't know if I've ever seen draped (or harped as you may prefer) strands in a hollowcore slab.

 

[GBMRAO]

thanks for all ur suggestions. We are waiting for the contractor to do some demo radar testing to figure out the existing options.

 

[MOJOJOHN]

I don’t remember seeing any drapes either, but gpr will tell.