Parapet upstand/stringcourse/edge beam
Parapet upstand/stringcourse/edge beam
(OP)
Hi,
I am doing a parapet replacement job in the UK, which involves breaking out the existing edge cantilever and recasting it with more rebar to increase the capacity. On the deck this is not a problem as the new rebar can just be lapped onto the existing bars to tie it into the rest of the structure. However, the parapet continues onto mass concrete wing walls.
My problem is this - As I have no reinforcement in the wingwall to lap the new bars onto, how much of the wingwall do I have to reconstruct as reinforced concrete?
I am doing a parapet replacement job in the UK, which involves breaking out the existing edge cantilever and recasting it with more rebar to increase the capacity. On the deck this is not a problem as the new rebar can just be lapped onto the existing bars to tie it into the rest of the structure. However, the parapet continues onto mass concrete wing walls.
My problem is this - As I have no reinforcement in the wingwall to lap the new bars onto, how much of the wingwall do I have to reconstruct as reinforced concrete?





RE: Parapet upstand/stringcourse/edge beam
If that is the case, you might want to consider stopping at the existing mass concrete wingwalls and not extending the rebar into them. As long as the existing wingwall is adequate to serve the purpose of containing traffic and the new parapet you are building does not depend on the wingwall for strength you shouldn't have to do anything to it. The new condition should be no less than the existing.
RE: Parapet upstand/stringcourse/edge beam
I've had to deal with this problem previously (when working in the UK) and didn't find any answer that I was completely happy with.
RE: Parapet upstand/stringcourse/edge beam
The solution we have eventually come up with invovles determining the point on the wingwall where the tensile stress in the mass concrete is <1N/mm2. This was done using a combination of pucher charts and 45 degrees distribtion with depth. We then propose to reconstruct the wingwall above this point with reinforced concrete and resin anchor some starter bars into the existing concrete to tie the new and the old together.
If anyone wants to comment on this solution, then I'm interested to hear other views.
RE: Parapet upstand/stringcourse/edge beam
I am working on a job exactly the same as the one you had. Could you share your experience and how you deal with the problem in the end?
Thanks.
RE: Parapet upstand/stringcourse/edge beam
A grillage model of the same wall produced worse results as the load didn't distribute very welll
RE: Parapet upstand/stringcourse/edge beam
I think in principle your approach seems OK, but wondered how you arrived at the value of 1N/mm2 for tensile resistance of concrete ?
It is suggested within clause 4.2.3.4.1 of BS 8002 that the allowable stresses on mass concrete should be limited to 0.28N/mm2 and 0.55N/mm2 in tension and shear respectively.
VB