PCI Handbook - 48"wide DBT's

[vandede427]

I'm looking for span tables for 48" wide - 14" double tees. I've got all the PCI Handbooks dating back to the 3rd Edition (pub 1985) and none of them have 48" wide dbt's.

I'm doing some work to an existing roof, and the drawings are probably 70's-ish.

Would anybody with a PCI Handbook older than the 3rd Edition please look up the following:

48"wide x 14"deep dbltee w/ 27S strand pattern spanning 30'.

thanks

 

[JedClampett]

They were probably made from 8 ft. or 10 ft. wide double tees.
My 2nd Edition PCA Handbook has no capacity for 30 ft. long double tees with a 27 strand pattern. For a 8'-0" wide double tee with 28 strands, the longest span is 26 ft. For that span the capacity is 33 psf. You could work backward and figure out the allowable based on that.

 

[vandede427]

how would the 4' section have two webs if it was made from an 8' section??? that means an 8' section would have been cast with 4 flanges. they don't do that.

 

[JD2]

I am looking thru a 2nd edition PCI book. The reinforcing nomenclature indicates the first number is the number of strands, the second number is the diameter of the strand in 16ths, the letter and number after that indicate whether the strands are depressed and how many depressed points there are. The charts are set up for 1/2" strand. Your number of 27, based upon this nomenclature would indicate 2 strands (probably straight) and a 7/16" strand.

You don't indicate whether the double tee is topped or not, the actual geometry of the tee, whether it is lightweight or normal weight concrete, whether the strands were 270 ksi, 250 ksi, stress relieved or low relaxation strand. If it is 4' between legs then most likely it was cast in an 8' wide tee bed with the outer flanges blocked out. The 8' wide tees had the legs 4'-0"o.c., the 10' wide tee would have the legs 5'-0" apart.

That having been said, when I worked for a pre-cast manufacturer (back in the early 80's), we had our own design program and produced our own strand pattern designs which had no relationship at all to the patterns shown in the PCI book. We designed it and laid it out however we needed it and however it was required to be to fit the casting beds out in the casting yard. It's possible the nomenclature could be particular to a specific manufacturer and not as per the PCI nomenclature in the handbook.

You might be careful assuming that it is a PCI design. Just a thought.

 

[JedClampett]

They cast them without the overhangs on each side. What is the spacing between the webs?

 

[vandede427]

look guys, all I've got is some shaded, old, crusty, scanned, barely legible pdf of a roof plan that was produced in the early 70's. all it says is 4'-0" x 14" double tees - strand pattern 27S.

let's assume normal weight concrete and untopped.

 

[rcd445]

I have the first edition. It has the doubletees you describe. The load table does not list a value for thirty feet. The safe superimposed live load at 28 feet is listed as 29 psf and is governed by ultimate strength. The table is based on 5000 psi concrete, 3500 psi release strength and 270000 psi strands. Information preceeding the load table say tha higher concrete strengths utilized in many prestressing plants will result in an increase in load and span capacity. The designation 27S implies two parallel strands of 7/16" diameter.