PCI Handbook load tables for Hollowcore Plank

[cmbyrd77]

Can anyone tell me if the safe superimposed service loads tables in the PCI Handbook are based off of a 1 ft width of section or the 4ft width of section shown? Obviously there would be a big difference in the section properties, and in return a difference in the allowable safe superimposed load. If it is based off of the 4ft width, is there a quick and easy way to reduce the value. I can't see it as being as easy as dividing by 4.
My other question is regarding the f'c. I am checking an existing building, and I don't know the f'c of the precast used. I can assume 3000 psi, but the values in the PCI Handbook are based off of 5000 psi. I looked in the Handbook to see if there was a way to reduce the values, but I didn't see anything.

Thank you for the help.

 

[JAE]

The safe superimposed load tables in the PCI Handbook are in PSF terms so the width doesn't enter into the issue.

Most precast, over the years, has been generally 5,000 psi minimum.

 

[UcfSE]

Look at the Key in the upper left area. The loads are in psf.

 

[JedClampett]

The edition I have (2nd) gives hollowcore superimposed loads in psf, so it's basically a one foot section of hollowcore.
As far as the concrete strength, why do you want to reduce it? Do you know that it's 3000 psi? Precasters have been using high strength concrete for a long time. Plus for bending capacity, concrete strength has a small effect. I think you're safe in using the table values.

 

[JAE]

Wow - great minds think alike! And at the same time!

 

[cmbyrd77]

The building was built in 1970, so I wasn't really sure what strength precasters were using back then. I assumed it wouldn't have been less than 3000psi. I've tried finding something on the drawings, but nothing shows up, and I don't have the existing specs or shop drawings. Thank you all very much for you help.

 

[concretemasonry]

Precasters of flat slabs cannot afford to go much below 5000 psi because they need the higher strength to turn the plant around daily, which requires cutting the 400' to 600' long planks from the setting beds on a fast schedule.

One strength advantage they have is that they are in a planned facility with inside aggregate and cement storage plus heated beds, (if required). Having a uniform supply of aggregate and an in-house lab helps to maintain uniformity.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.