Determination of Concrete Plank Tendons
Determination of Concrete Plank Tendons
(OP)
A Client of mine want to add load to a concrete plank floor system. No one has plans of the existing planks. Has anyone ever exposed the tendons and measured the diameter and used that info to estimate the strength of the planks. Then grout the hole back up?






RE: Determination of Concrete Plank Tendons
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Determination of Concrete Plank Tendons
We always SPR (radar) scan the work area first. In your case of a plank, you will need to gain access to the bottom of the plank, and scan with radar or even a pachometer to locate the strands, then you know where to undertake the chipping. Whilst radar or a pachometer can locate strands (and tendons) non-destructively, they are not accurate in determining diameter of strand (or rebar either), hence why invasive proving is necessary.
Use the scanning to locate the center spacing of the strands within the planks and use invasive probing to determine strand diameter AND measured concrete clear cover. All do a visual check on the condition of the strand whilst you are there. The number of probes required will depend on the number of different planks in the structural system (spans etc), but we usually go for a 3 probe minimum, and check for consistency/variability amongst the results of the probing.
Overhead chipping lends itself to the use of lightweight electric chipping hammers, and caution must be exercised in NOT damaging the strands, even the individual wires should be damage-free.
In my work region, older precast structural products were manufactured from either 3/8" or 1/2" diameter 7-wire strands, so it is 'never a given' that they will be 1/2" ∅, which is prevalent today in 99% of precast products.
The attached photo is one of a precast I-joist that we had to expose the strand configuration to calculate the capacities given no existing drawings were available.
Patching of the bottom of plank, in your case, if best done with a quick-setting, per-manufactured, overhead cementitious repair mortar.
RE: Determination of Concrete Plank Tendons
RE: Determination of Concrete Plank Tendons
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Determination of Concrete Plank Tendons
You are a geek...but so too am I...
RE: Determination of Concrete Plank Tendons
Also, by using SPR scanning first, you can often detect any plank voids (assuming hollow-core) before concrete chipping.
RE: Determination of Concrete Plank Tendons