Holdfast Training Services Trial Blog

Yesterday on site we had an interesting discussion about an issue which has been in the background for a while, which everyone has been ignoring until it’s actually preventing concrete being laid.

Issue: The pavement thickness of the client has been specified as 150mm + 20mm. The precast secondary elements they are resting on are designed to deflect up to 40mm, the primary beams 6mm and the piles to settle up to 20mm. Whilst we haven’t actually been given FPLs (finished pavement level) by the designer yet, they are coming and we will have to be within +/-6mm to be compliant with the spec.

This is a similar problem to on Joe Murrows site, we can’t however back prop to limit deflection as it is over water!

This has raised the following questions:

1. At which point does out liability end? FPL which change over time therefore so long as it’s less than 20mm is that okay?
2. We have raised RFIs regarding which is the overriding factor, pavement thickness or FPL. We think it is going to be FPL, but if it is do we risk overloading the planks to get this? Atkins have designed for the concrete to be up to 45mm thicker to account for this, it is likely to be tight at midspan though…. This also doesn’t take into account the as built levels being lower that design.
3. How do we monitor this settlement?
   • Currently we are monitoring the levels at the four stages highlighted below. What we have suggested is that monitor selected areas, these include areas under the most loading and where the piles might be bearing on different boundarys to those it was designed for. These are being monitored weekly at top of plank level, point 3.
   • At the moment it all comes down to resources, it is isn’t in the spec that we have to monitor it, therefore there is no money for it. A very shortsighted viewpoint I think as the elements listed below are intrinsically linked to knowing how much movement there is!

Areas where we are recording levels

Any ideas on how we could:

1. Cheaply and easily monitor settlement accurately?

2. Accurately measure Deflection?