Foundation tie beams - monolithic or separate placement?

[tngolfer]

I've usually detailed the tie beam to be cast monolithically with the slab on grade. My rationale was that one concrete placement would be cheaper. The owner of the building I'm currently working on has required us to provide contraction joints on 45-60 degree angles to the column lines so fork lift traffic crosses the joints on an individual wheel basis and not per axle. The more I think about it though, no crack is going to cross that large of a section due to path of least resistance.

Do you see any issues if I place the tie beam with the t/beam at my b/slab elevation and run the vapor retarder continuous between the two to act as a bond breaker? Or alternately, drop the tie beam the depth of my granular sub-base so other disciplines can run piping and conduit without interfering with my tie beams.

 

[BAretired]

Provide a sketch.

BA

 

[hokie66]

Not sure of the purpose or layout of your tie beams, but restraint by monolithic beams will certainly be a factor in slab on ground shrinkage cracking.

The owner's approach is novel in my experience, but at least he's thinking.