Old Concrete Joist System - F/A Joists 1

[ash060]

I have a renovation going on with a building from the '50s. The existing floor system using a precast joist system called F&A. It is an inverted tee concrete joist with a precast panel between them that is topped with concrete.

The drawings call out an 8" F/A Joist #867. I am trying to figure out the capacity of the joists. I was told that the first number is depth and the second number is allowable pounds per sq. foot. So the #867 would be 8" deep with an allowable load of 67 psf. I have no idea if this is true. If anyone can help that would be great. Thanks in advance.

 

[ash060]

I noticed an article in Structure Magazine and tired to contact the author, but the email was disconnected.

Any help would be great.

 

[concretemasonry]

There were and still are many F&A systems used. They varieties, materials and details vary with the location. Obviously the designations are different, so it would be imperative to research the general area of the project and possible suppliers for actual information.

Generally, most suppliers of the systems and the load ratings are firms that produce prestressed concrete products and molded concrete block (using unusual aggregates)or also sell clay block.

Typical applications are for shorter spans with the beam spacing depending on the size of specialized filler blocks. In Europe, the systems usually used a 2" thick concrete topping to carry a double loop (one for a spare) of hot water. The older systems usually used clay block as fillers, but the newer systems used concrete block with specialized aggregates.

In Hungary, very shallow beams (4" or 6") are used along with concrete block or block made from wood shavings/sand/cement mixture with a 2" topping for leveling and acceptance of hard floor finishes. This is also used for a beam system on roofs with 1:1 pitch.

Most western European and some U.S. systems were based on the German standards that are very detailed and specific. The same applies to system produced in parts of Africa.

Because it is a general construction method with local variations it is important to find the local details and since the beams are to common element, precasters in the region would be the best place to look for history and details. The 1950's was before the PCI plant certification program and requirements, many manufacturers still have good information, standards, designations and test information. - This would be the place to start your search.

Dick

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

 

[ash060]

Thanks I will start calling a couple precasters I know